Recanalized Coronary Thrombus: Role of OCT in Identifying a Slow-Evolving and Underestimated Coronary Lesion

Pathological studies have revealed spontaneous recanalized coronary thrombi as a frequent evolution of coronary occlusions; however, they are poorly recognized on coronary angiography, and the optimal therapeutic strategy for clinical evolution is unknown. We report the role of optical coherence tomography in identifying a recanalized coronary thrombus causing myocardial ischemia after 11 years of follow-up. (Level of Difficulty: Intermediate.)

Long-term efficacy and safety of newer generation ultrathin strut drug-eluting stents: a systematic review and meta-analysis

Background

Recent trials have demonstrated that short-term efficacy and safety of ultrathin strut drug-eluting stents (DES) were non-inferior to contemporary stents but long-term benefit remains uncertain.

Purpose

The main objective of this meta-analysis was to evaluate efficacy and safety of ultrathin strut DES with an extended follow-up in comparison to 2nd and 3rd generations DES.

Methods

A double-blind review of randomized controlled trials (RCT) comparing ultrathin strut DES to contemporary DES was performed from MEDLINE and CENTRAL databases and from cardiological congresses. The primary efficacy endpoint was target vessel failure (TLF) defined as a composite of cardiac death, target vessel myocardial infarction (TV-MI) and target lesion revascularization (TLR) and the primary safety endpoint was occurrence of stent thrombosis (ST). Short (1 year) and long term (≥2 years) effects were estimated separately. This analysis was pre-specified in PROSPERO (CRD42019142206).

Results

The meta-analysis included 13 RCT including 19,490 patients. In short term, we found TLF decrease with ultrathin strut DES (RR 0.85, CI [0.75–0.97], p=0.01), driven by lower TV-MI (RR 0.83, CI [0.66–1.03], p=0.1) and TLR (RR 0.77, CI [0.58–1.01], p=0.1) rates, and a non-significant downward trend in ST (RR 0.85 CI [0.64–1.14]).

In long term, from the 5 trials with extended follow-up, there was no significant difference between ultrathin strut DES and thicker strut stents in rate of TLF at the longest available follow-up (RR 0.90, CI [0.76–1.06], p=0.2), despite a numerically reduction of TV-MI (RR 0.81, CI [0.61–1.08], p=0.05) and TLR (RR 0.85, CI [0.69–1.04], p=0.1) in favor of ultrathin strut stents. However, we observed a persistent numerically reduction in ST (RR 0.79, CI [0.61–1.02], p=0.01).

Conclusion

Ultrathin strut DES was associated with a lower target lesion failure rate at one year but not beyond 2-years follow-up. Nevertheless, the safety of the ultrathin strut stents was sustained over time with a numerically reduction of ST.

Funding Acknowledgement

Type of funding source: None

Post resuscitation electrocardiogram for coronary angiography indication after out-of-hospital cardiac arrest

BACKGROUND

Coronary angiography is the standard of care after Out-of-Hospital Cardiac Arrest (OHCA), but its benefit for patients without persistent ST-segment elevation (STE) remains controversial.

METHODS

All patients admitted for coronary angiography after a resuscitated OHCA were consecutively included in this prospective study. Three patient groups were defined according to post-resuscitation ECG: STE or new left bundle branch block (LBBB) (group 1); other ST/T repolarization disorders (group 2) and no repolarisation disorders (group 3). The proportion and predictive factors of an acute coronary lesion, defined by acute coronary occlusion or thrombotic lesion or lesion associated with flow impairment, were evaluated according to different groups as well as thirty-day mortality.

RESULTS

Among 129 consecutive patients: 62 (48.1%), 30 (23.3%) and 30 (23.3%) patients were included in groups 1, 2 and 3 respectively. An acute coronary lesion was observed in 43% (n = 55) of patients, mainly in group 1 (n = 44, 70.9%). Initial coronary TIMI 0/1 flow was more frequently observed in group 1 than in group 2 (n = 25, 40.3% vs n = 1, 3.3%) and never in group 3. Chest pain and STE or new LBBB were independently associated with an acute coronary lesion (adj. OR = 7.14 [1.85-25.00]; p = 0.004 and adj. OR = 11.10 [3.70-33.33]; p < 0.001 respectively). In absence of any repolarization disorders, acute coronary lesion or occlusion were excluded with negative predictive values of 93.3% and 100% respectively. The one-month survival rate was 38.8% and was better in patients among the group 1 compared to those from the 2 other groups (n = 28, 45.2% vs n = 21, 35%, respectively; p = 0.014).

CONCLUSION

Considering the high negative predictive value of post-resuscitation ECG to exclude acute coronary lesion and occlusion after OHCA, a delayed coronary angiography appears a reliable alternative for patients without repolarization disorders.

[Severe bleeding with antiplatelet therapy: What to do?]

Antiplatelet therapy is the cornerstone of coronary artery disease treatment and prevention. Combination of aspirin and P2Y₁₂ inhibitor is recommended after acute coronary syndrome and after elective percutaneous coronary intervention. The optimal duration of dual antiplatelet therapy depends on the individual ischemic and bleeding risk of the patient. Bleeding on dual anti platelet therapy remains the most frequent complication of antiplatelet therapy even is mostly minimal or moderate. Beyond individualized evaluation of patients' bleeding risk, management of patients with severe bleeding complications is a challenging situation and requires general and specific recommendations with interruption of the dual antiplatelet therapy in the vast majority of the cases.

Safety of Percutaneous Coronary Intervention Without P2Y12 Inhibitor Pretreatment From a Cohort of Unselected Patients

OBJECTIVES

Recent studies have challenged systematic pretreatment with a P2Y12 inhibitor before percutaneous coronary intervention (PCI) in elective and non-ST segment elevation myocardial infarction (NSTEMI) patients. The aim of this study was to assess outcomes after performing PCI immediately after coronary angiography with an exclusive "on-the-table" P2Y12 inhibitor loading dose, by evaluating ischemic and bleeding complications in unselected patients.

METHODS

Consecutive patients admitted for elective PCI or NSTEMI were included in this two-center, prospective, observational study, and received a P2Y12 inhibitor after coronary angiography when PCI was decided. The primary composite endpoint was first occurrence of cardiovascular death, myocardial infarction, stroke, urgent revascularization, or use of bail-out glycoprotein IIb/IIIa inhibitors at 30 days after PCI. Stent thrombosis and bleeding criteria (Bleeding Academic Research Consortium [BARC]) were evaluated.

RESULTS

Among 299 included patients, a total of 188 were admitted for elective PCI and 111 for NSTEMI. The incidence of the primary endpoint was 8.5% (95% confidence interval [CI], 5.7-12.4). No definite stent thrombosis occurred. Three independent predictive factors were associated with the primary endpoint: NSTEMI setting (odds ratio [OR], 5.61; 95% CI, 1.75-17.98), thrombotic coronary lesion (OR, 4.26; 95% CI, 1.45-12.54), and longer procedure duration (OR, 1.06; 95% CI, 1.03-1.09). Clinically relevant bleedings (BARC 2, 3, or 5) occurred in 5.4% of patients.

CONCLUSIONS

In an unselected population admitted for elective PCI or NSTEMI in real-world clinical practice, administration of a P2Y12 inhibitor only after coronary angiography is associated with a low rate of ischemic and bleeding events at 30 days.

[New oral anticoagulants in coronary artery disease]

Antiplatelet therapy is essential for the prevention of recurrent cardiovascular events in stable and unstable coronary artery disease. Oral anticoagulants have been rarely used for treatment of coronary artery disease. The new direct oral anticoagulants offer various molecules and dosages and may be used in coronary artery disease. Dedicated studies are currently being conducted to confirm the optimal doses and the ideal association of antithrombotic drugs in different settings of coronary artery disease.

Assessment of Patient's Peak Skin Dose Using Gafchromic Films During Interventional Cardiology Procedures: Routine Experience Feedback

To assess the interest of Gafchromic films in detection of patient's peak skin dose (PSD) in interventional cardiology. A prospective study of 112 patients was conducted (July-December 2015). Three diagnostic and therapeutic procedures were evaluated: coronary angiography (CA), coronary angiography and coronary angioplasty for one or two vessels disease (CA-PTCA) and coronary angioplasty of complex chronic total occlusion (CTO). Dosimetric indicators (DIs) were collected and PSD were measured with Gafchromic films. Dose distribution was evaluated within 10 'Thorax Body-zone' defined by the system. Correlations between PSD and DI or dose distribution were computed. Delivered dose increased in complex procedures. The PSD were 0.121 ± 0.063 Gy for CA, 0.256 ± 0.142 Gy for CA-PTCA and 1.116 ± 0.721 Gy for CTO. High correlations were observed for PSD and DI as well for dose distribution within the 'Thorax Body-zone'. Film dosimetry is suggested for CTO procedures since the threshold of 2 Gy for skin injuries is likely to be exceeded.

[What is the place of bioresorbable vascular scaffolds in setting of ST-segment elevation myocardial infarction?]

A 50-year-old woman was admitted for an inferior ST-segment elevation myocardial infarction; immediate coronary angiogram revealed a subocclusive stenosis of the right coronary artery. After optimal antithrombotic treatment, the type of stent could be discussed. The latest generation of drug-eluting stents showed excellent efficacy and safety in the long-term but has limitations such as potential chronic inflammation of the arterial wall and no recovery of vasoactive function. Bioresorbable vascular scaffolds, with complete resorption within several months, may reduce these limitations. Implantation of bioresorbable scaffold in the context of myocardial infarction may be interesting. However, very few studies are currently available in this setting. Preliminary results and perspectives are presented in this review.

[Are there any contraindications to the transradial approach?]

The transradial approach is the most frequent access used in France for coronarography and percutaneous coronary intervention. This access permits a reduction of local complications in comparison with femoral access. There are very few real contraindications of transradial approach. The use of Allen's test before coronarography remains controversial in the transradial catheterization community. It remains a standard practice in some institutions, however many centers have stopped using Allen's test considering that there is no evidence supporting its use.

[Diagnostic and prognostic significance of CK-MB, troponins, CRP, BNP and/or NT-proBNP in coronary angioplasty. Elevation mechanisms and clinical implications]

The recommendations from respected bodies concerning the treatment and follow up of patients undergoing coronary angioplasty for stable angina or acute coronary syndrome (ACS) are essential for reducing the risks related to the procedure, and for preventing the occurrence of long term complications. Measuring the levels of troponin and CK-MB is part of the diagnostic and prognostic strategy during the coronary angioplasty procedure. In this context, the frequent elevation of markers following uncomplicated angioplasty is a sign of minor irreversible myocardial damage, the prognostic significance of which remains under discussion. Recent data suggest that only a basal troponin elevation (more so than CK-MB) prior to angioplasty has a long term prognostic value in ACS ST- patients, and that troponin elevation occurring after the procedure in the presence of normal basal concentrations, is only associated with in-hospital complications. Determining the basal level of troponin would appear to be essential for interpreting any elevation in concentrations following angioplasty. The recommendations should integrate this fundamental point, if it is confirmed. On the other hand, the question has been raised whether other markers (CRP, BNP and/or NT-proBNP) should be systematically measured as a routine prior to angioplasty. An elevation of CRP before and/or after angioplasty is an unfavourable short and long term prognostic factor. Elevation of NT-proBNP before angioplasty is also an unfavourable long term prognostic factor. Recommending a multi-marker strategy might represent a future direction for identifying at risk patients prior to coronary angioplasty, thus enabling specific treatment to be proposed.

A systems model of training for patients in phase 2 cardiac rehabilitation

BACKGROUND

The aim of this study was to apply a systems model of training for athletes in patients with coronary artery disease (CAD) undergoing phase 2 cardiac rehabilitation.

METHODS

Data from six patients with CAD undergoing 20 conventional training sessions were used to test this model. The method required daily training quantification using heart rate, and regular assessment of real exercise tolerance using a constant-duration test. Convolution of training quantity with real exercise tolerance was provided for every patient model exercise tolerance, by minimizing the residual sum of squares.

RESULTS

The results showed that application of the systems model of training to the six patients resulted in a strong fit between real and model exercise tolerances: r(2) = 0.77, 0.79, 0.83, 0.84, 0.85 and 0.92, respectively (P < 0.05).

DISCUSSION

Moreover, the systems model admitted for all patients corresponded to one first-order transfer function, which was fitness. This result was in contrast with the systems models reported in athletes and in a patient with CAD undergoing phase 3 cardiac rehabilitation which were found to include two first-order transfer functions: fitness and fatigue, simultaneously.

CONCLUSION

The systems model of training of patients with CAD undergoing phase 2 suggested two practical consequences: first, the improvement of exercise tolerance is directly related to training, and consequently second, patients who enter immediately phase 3 training may prevent a decrease in their exercise tolerance.

High versus low training frequency in cardiac rehabilitation using a systems model of training

No study has reported the long term effects of cardiac rehabilitation, concerning the duration of beneficial effects of training program. The present study analyzed the influence of training session frequency on long-term beneficial effects in patients with coronary artery disease (CAD) undergoing phase 2 cardiac rehabilitation. Four patients with CAD completed 20 training sessions. Two patients were assigned to low training frequency (LTF) and two to high training frequency (HTF): three and five sessions per week(-1), respectively. The method was based on the systems model of training and required training quantification and the assessment of real exercise tolerance. Convolution of training quantity with real exercise tolerance provided the model exercise tolerance for every patient. The model parameters, the magnitude factor (k), and the time constant of decay (tau), were fitted from real and model exercise tolerances by the least squares method. LTF and HTF resulted in similar increases in exercise tolerance (12-14%). A model with one-component (fitness) allowed fitting exercise tolerance in all patients with r (2) = 0.77, 0.79, 0.84, and 0.91, respectively (p < 0.05). The addition of a second component did not improve the fit in any patient (p > 0.05). The k value was about twice as high with LTF (0.13 and 0.16 AU) than with HTF (0.05 AU for the two patients), whereas the tau value was about twice as low with LTF (37 and 41 days) than with HTF (72 and 89 days). The long term beneficial effects estimated by 4tau, were twice as long with HTF (288 and 356 days) than with LTF (148 and 164 days). We concluded that exercise tolerance was similarly increased with HTF and LTF but HTF training induced beneficial effects which were sustained twice as long.

Prognostic value of cardiac troponin T in patients with both acute and chronic stable congestive heart failure: comparison with atrial natriuretic peptide, brain natriuretic peptide and plasma norepinephrine

BACKGROUND

The prognostic value of cardiac troponin T (cTn-T) in a mixture of patients with both acute and chronic congestive heart failure (CHF), simultaneously assessed and compared with neurohormonal factors, has not yet been thoroughly evaluated. Thus, we focused on the prognostic value of cTn-T in comparison with atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and plasma norepinephrine (PNE) in this population.

METHODS

Prognostic correlates of elevation of cTn-T, ANP, BNP, PNE were analyzed in 63 acute and chronic CHF patients followed up to record worsening CHF and cardiac death.

RESULTS

cTn-T (> or =0.03 microg/L) was found in 17.4% (11 of 63) of patients. cTn-T correlated with ANP, BNP, PNE. Acute CHF patients were more positive for cTn-T and BNP. In our cohort, neither cTn-T (> or =0.03 microg/L) nor PNE were associated with increased mortality and worsening HF in CHF patients. After adjustment, BNP was the only independent predictor of cardiac events (RR, 3.23; p=0.01).

CONCLUSIONS

BNP emerged as the only independent predictor of cardiac events in a mixture of patients with both acute and chronic CHF, suggesting that it is the analyte that best reflects long-term prognosis in a diverse population enrolled to mirror the "real world" situation.

Applying a Systems Model of Training to a Patient with Coronary Artery Disease

PURPOSE

The aim of the present study was to apply a systems model of training for athletes to a patient with coronary artery disease (CAD) undergoing phase 3 rehabilitation.

METHODS

A patient with CAD underwent 14 wk of training during which exercise was quantified using intensity and duration. Real exercise tolerance was assessed twice a week during this period using a constant-load test. The model exercise tolerance was obtained by convolving the quantified training to real exercise tolerance. The model parameters were obtained by fitting the real exercise tolerance to model exercise tolerance by the least square method. These parameters were then used to calculate the time needed after a training impulse to reach maximal tolerance (tg) and then to return to the pretraining level of tolerance (ti).

RESULTS

The results showed that: 1) the fit between real and model exercise tolerances was significant (r = 0.73, P < 0.05), and 2) tg and ti were predicted 17 and 120 d posttraining, respectively.

CONCLUSIONS

The application of a systems model of training for athletes to a patient with CAD was successful. We were able to predict the maximal exercise tolerance and the duration of increased tolerance subsequent to the training period.

[Is it necessary to rehabilitate coronary artery disease patients based on ventilatory threshold?]

PURPOSE

To compare the efficiency of two programs of exercise-based rehabilitation that are different for heart rate (HR) training in patients with coronary artery disease: heart rate (HR) according to Karvonen formula (HR training =70% (max HR -rest HR) +rest HR) or HR recorded at the gas exchange ventilatory threshold (VT). TYPE: Controlled randomised clinical trial.

SETTING

Cardiovascular rehabilitation unit.

METHOD

Twenty-four male patients (54 +/-9.5 years old) with coronary artery disease were allocated at random to one of the two groups: KHR group (n =13) according to Karvonen formula (n =11), and VTHR group according to VT determined by exertion test (n =13). The exercised-based program was similar for all the patients, differing only in HR training (five daily sessions a week for four weeks). Assessment tests were performed at D1 and D28 and included: - an exercise test with measure of HR and double product (HR x blood pressure) at rest, submaximal and maximal intensity, with measure of oxygen consumption and gas exchanges at rest and at maximum exercise; - specific functional tests based on daily life activities; - dyspnea assessment at maximal intensity; - quality of life measurement by SF36. It was taken notice of the drugs taken by the patients, specially betablockers.

RESULTS

At inclusion, the two groups were not different for parametric (age, body mass index) and non parametric values (medical or surgical treatment, comorbidity). Even though HR training was significantly different (p <10(-6)), at the end of the program there was a significant increase of power and oxygen consumption at VT (+42.6%, p <10(-6); +18.6%, p <10(-5)) and at maximal intensity (+18.7 %, p <10(-6); 14.2 %, p <10(-5)), but differences between the two groups were not significant; double product was significantly lower at rest (-13.9 %, p <10(-5)) and at submaximal exertion (-10.6 %, p < 10(-3)). Yet, the two groups differed in HR, and HR increased in VTHR group and decreased in KHR, the difference being significant at VT (p =0.05), at submaximal (p =0.037) and maximal exercise (p = 0.05). Dyspnea at maximal intensity was higher in VTHR but SF36 values were not different.

DISCUSSION AND CONCLUSION

These results confirm the efficiency of cardiac training program according to Karvonen formula as to ventilatory threshold. However, there is a negative chronotropic effect of cardiac training according to Karvonen formula with a higher intensity, which corresponds to a less cardiac work for a same activity.

Islet-brain1/JNK-interacting protein-1 is required for early embryogenesis in mice

Islet-brain1/JNK-interacting protein-1 (IB1/JIP-1) is a scaffold protein that organizes the JNK, MKK7, and MLK1 to allow signaling specificity. Targeted disruption of the gene MAPK8IP1 encoding IB1/JIP-1 in mice led to embryonic death prior to blastocyst implantation. In culture, no IB1/JIP-1(-/-) embryos were identified indicating that accelerated cell death occurred during the first cell cycles. IB1/JIP-1 expression was detected in unfertilized oocytes, in spermatozoa, and in different stages of embryo development. Thus, despite the maternal and paternal transmission of the IB1/JIP-1 protein, early transcription of the MAPK8IP1 gene is required for the survival of the fertilized oocytes.

Embryonic stem cells and gene targeting

The development of gene targeting technology, the exchange of an endogenous allele of a target gene for a mutated copy via homologous recombination, and the application of this technique to murine embryonic stem cells has made it possible to alter the germ-line of mice in a predetermined way. Gene targeting has enabled researchers to generate mouse strains with defined mutations in their genome allowing the analysis of gene function in vivo. This review presents the essential tools and methodologies used for gene targeting that have been developed over the past decade. Special emphasis has been laid on the available embryonic stem cell lines and the importance of the genetic background. Also, the state-of-the art of gene targeting approaches in species other than mice will be discussed.

Trophoblast cell-specific carcinoembryonic antigen cell adhesion molecule 9 is not required for placental development or a positive outcome of allotypic pregnancies

The carcinoembryonic antigen (CEA) family consists of a large group of evolutionarily divergent glycoproteins. The secreted pregnancy-specific glycoproteins constitute a subgroup within the CEA family. They are predominantly expressed in trophoblast cells throughout placental development and are essential for a positive outcome of pregnancy, possibly by protecting the semiallotypic fetus from the maternal immune system. The murine CEA gene family member CEA cell adhesion molecule 9 (Ceacam9) also exhibits a trophoblast-specific expression pattern. However, its mRNA is found only in certain populations of trophoblast giant cells during early stages of placental development. It is exceptionally well conserved in the rat (over 90% identity on the amino acid level) but is absent from humans. To determine its role during murine development, Ceacam9 was inactivated by homologous recombination. Ceacam9(-/-) mice on both BALB/c and 129/Sv backgrounds developed indistinguishably from heterozygous or wild-type littermates with respect to sex ratio, weight gain, and fertility. Furthermore, the placental morphology and the expression pattern of trophoblast marker genes in the placentae of Ceacam9(-/-) females exhibited no differences. Both backcross analyses and transfer of BALB/c Ceacam9(-/-) blastocysts into pseudopregnant C57BL/6 foster mothers indicated that Ceacam9 is not needed for the protection of the embryo in a semiallogeneic or allogeneic situation. Taken together, Ceacam9 is dispensable for murine placental and embryonic development despite being highly conserved within rodents.

Comparison of the diagnostic value of cardiac troponin I and T determinations for detecting early myocardial damage and the relationship with histological findings after isoprenaline-induced cardiac injury in rats

Cardiac troponins I (cTnI) and T (cTnT) have been shown to be highly sensitive and specific markers of myocardial cell injury. The purpose of this study was to investigate the diagnostic value of cTnI and cTnT with regard to creatine kinase (CK) and lactate dehydrogenase (LD) and to determine whether they can be used for early diagnosis of myocardial damage in rats, and to examine the relationship between cTnl and cTnT release with histological examinations, using isoprenaline-induced cardiac muscle damage as an experimental model in the rat. Eighteen Wistar rats per group were treated with a single dose of either isoprenaline (iso) or with normal saline as a control group. The anti-cTnI and cTnT monoclonal antibodies (mAbs) employed in the cTnI (Access) and cTnT (Elecsys) assays cross-react with cTnI and cTnT of the rat. A highly significant rise of cTnl or cTnT was found already 2 h after iso. The time-courses of cTnI and cTnT were monophasic in form. The highest cTnI (mean+/-S.D., 1.1+/-2.3 ng/ml) and cTnT (mean+/-S.D. 3.6+/-30 ng/ml) were found 4 h after iso. cTnI and cTnT significantly increased in iso-treated rats in comparison with controls whether the differences between 2-, 4- and 6-h levels and basal levels were considered or not. The areas under cTnl and cTnT curves (AUC) (0-6 h) and the maximal cTnI and cTnT (0-6 h) after iso were significantly different from the controls. For CK and LD, no elevation in comparison with controls could be detected (except a trend for LD whether or not the difference between 6-h levels and basal levels were considered (P=0.08) and for LD AUC (0-6 h) (P=0. 059)). Correlations between maximal cTnI and cTnT and AUC were 0.69 (P=0.0001) and 0.60 (P=0.0066), respectively. Histological examinations of iso-treated rats revealed acute focal or multifocal myofibrillar degeneration of the myocardial tissue in ten out of 14 rats and showed the earliest alterations 4 h after iso in one treated rat. Only four of the controls exhibited evidence of mild changes and slight mononuclear cell infiltration. cTnl and cTnT peak values to at least 0.35 and 1.3 ng/ml, respectively, were necessary to detect histological myocardial cell injury after iso. cTnI and cTnT were found to be early markers for diagnosing iso-induced myocardial damage in comparison with CK and LD. Elevations of cTnI and cTnT appeared to relate to the severity of histologic changes after myocardial injury. Although there was a difference in the absolute concentration of results between cTnI and cTnT assays, due to a lack of standardization and heterogeneity in the cross-reactivities of mAbs to various troponin I and T forms, cTnI and cTnT can be used as easily measurable target parameters for detection of cardiotoxic and/or cardiodegenerative effects in rats.

Proliferation, but not growth, blocked by conditional deletion of 40S ribosomal protein S6

Because ribosome biogenesis plays an essential role in cell proliferation, control mechanisms may have evolved to recognize lesions in this critical anabolic process. To test this possibility, we conditionally deleted the gene encoding 40S ribosomal protein S6 in the liver of adult mice. Unexpectedly, livers from fasted animals deficient in S6 grew in response to nutrients even though biogenesis of 40S ribosomes was abolished. However, liver cells failed to proliferate or induce cyclin E expression after partial hepatectomy, despite formation of active cyclin D-CDK4 complexes. These results imply that abrogation of 40S ribosome biogenesis may induce a checkpoint control that prevents cell cycle progression.

Evaluation of incidence, clinical significance, and prognostic value of circulating cardiac troponin I and T elevation in hemodynamically stable patients with suspected myocardial contusion after blunt chest trauma

BACKGROUND

The frequency and prognostic influence of myocardial injury in patients with blunt chest trauma is controversial. We investigated the value of cardiac troponin I (cTn-I) and cardiac troponin T (cTn-T), highly specific markers of myocardial injury, to determine whether their measurement would improve the ability to detect myocardial contusion in stable patients with blunt chest trauma in comparison with conventional markers and whether they were associated with significantly worse late clinical outcome.

METHODS AND RESULTS

Over an 18-month period, myocardial contusion was diagnosed in 26 of 94 patients (27.6%) with acute blunt chest trauma (motor vehicle crash; 81%), because of echocardiographic abnormalities (n = 12), electrocardiographic abnormalities (n = 29), or both. Patients with myocardial contusion had a significantly higher Injury Severity Score at the time of admission (p = 0.001) and a significantly longer hospital stay (p = 0.0008). All patients survived admission to hospital and were hemodynamically stable. None of the patients died or had severe in-hospital cardiac complications. The percentage of patients with elevated CK, (CK-MB/total CK) ratio, or CK-MB mass concentration was not significantly different between patients with or without myocardial contusion. However, there were significant differences between the two groups when we applied the commonly used threshold levels of CK-MB activity and myoglobin. The percentage of patients with elevated circulating cTn-I and cTn-T (> or = 0.1 microg/L) was significantly higher in patients with myocardial contusion (23% vs. 3%; p = 0.01 and 12% vs. 0%; p = 0.03, respectively). Complete changes in cTn-I and cTn-T correlated well (r = 0.91, p = 0.0001). Sensitivity, specificity, and negative and positive predictive values of cTn-I and cTn-T in predicting a myocardial contusion in blunt trauma patients were 23%, 97%, and 77%, 75%, and 12%, 100%, and 74%, 100%, respectively. Clinical follow-up was available in 83 patients (88%) (mean, 16 +/- 7.5 months). There were no deaths in either group directly attributed to cardiac complications. None of the patients had any long-term cardiac complications or myocardial failure related to blunt chest trauma.

CONCLUSION

Although improved specificity of cTn-I and cTn-T compared with conventional markers, it should be emphasized that the main problem with cTn-I and cTn-T is low sensitivity as well as low predictive values in diagnosing myocardial contusion. cTn-I and cTn-T measurement is currently not an improved method in diagnosing blunt cardiac injury in hemodynamically stable patients. Moreover, there was no association of postmyocardial contusion cell injury and late outcome in these patients when cTn-I and cTn-T and other conventional markers were considered.

CK-MB mass test in ischemic myocardial injury. Comparison of two tests: BioMerieux Vidas and sanofi access immunoassays

The analytical and clinical performances of the new fluorescent immunoassay (CK-MB mass Vidas-BioMerieux) were examined and compared to the chemiluminescent test (CK-MB mass Access-Sanofi-Pasteur). Assay precisions of the CK-MB Vidas test within-assay or between-assay were less than 5.4 and 5.3%, respectively. Linearity was tested up to 214 microg/L. The CK-MB Vidas test was free of interference with CK-BB, CK-MM, and macro-CK. One hundred nineteen blood samples from patients with ischemic myocardial injury (IMI): acute myocardial infarction (AMI), suspected myocardial contusion (SMC), and unstable angina pectoris (UA), were tested using both immunoassays. In AMI, a good correlation was found (Y [CK-MB Access] = 1.1372 x [CK-MB Vidas] - 6.3902; r(2) = 0.96). In UA and SMC, low values were observed and both methods were well correlated (Y [CK-MB Access] = 1.3662 x [CK-MB Vidas] + 0.0671; r(2) = 0.97). Clinical data were in good agreement with both immunoassays. ROC analysis performed in AMI demonstrated that the clinical performances of the two assays were similar.

Release kinetics of cardiac troponin I and cardiac troponin T in effluents from isolated perfused rabbit hearts after graded experimental myocardial contusion

BACKGROUND

Few experimental studies report effects of direct contusion on cardiac enzyme release. Cardiac troponins I (cTnI) and T (cTnT) have been shown to be highly sensitive and specific markers of myocardial cell injury. This investigation was designed to determine and compare the acute effects of quantified magnitudes of blunt cardiac trauma upon release of cTnI and cTnT in comparison with creatine kinase (CK) and lactate dehydrogenase (LD).

METHODS

In 24 rabbit hearts prepared on a standard Langendorff apparatus, myocardial contusion (MC) was produced by a single blow with a ball falling from a predefined height, delivered directly to the surface of the heart. Hearts were divided into control (n = 6) and various quantified impacts: 75 mJoules (mJ) (n = 6), 100 mJ (n = 6), 200 mJ (n = 6). Coronary effluent samples for cTnI, cTnT, CK, and LD were collected at baseline, immediately after MC and 5, 15, 30, 45, and 60 minutes after MC. At the end of experiment, histologic condition was evaluated.

RESULTS

The anti-cTnI and cTnT MAbs used in the cTnI (Access) and cTnT (Elecsys) assays cross-react with cTnI and cTnT of the rabbit. The time-courses of cTnI, cTnT, CK, and LD were monophasic in form. After MC, all parameters rose significantly compared with baseline and with control group. The maximal release occurred immediately after MC. The area under the cTnI curve and the maximal cTnI concentration were linked to the contusion energy when increased at 200 mJ. Maximal concentrations and areas under cTnT, CK, LD time activity curve were not linked to the contusion energy level and showed no between-energy group differences. The correlation found between maximal cTnI and maximal cTnT concentrations was 0.70 (p = 0.0001). Histologic examination showed cellular disruption and after the more severe impact, the extent of pathologic changes was more extensive.

CONCLUSION

After graded experimental MC, maximal cTnI concentration and area under cTnI curve increase with the power of impact kinetic energy. Levels of cTnI allow a much higher accuracy in detecting the extent of myocardial injury postMC in comparison with cTnT, CK, and LD in this experimental study. These results should be consistent with the more extensive cTnI release with more severe impact in patients with blunt chest trauma. Furthermore, because specificity and time-course of release, both cTnI and cTnT should have a role in the diagnosis and evaluation of such patients.

Relation of minor cardiac troponin I elevation to late cardiac events after uncomplicated elective successful percutaneous transluminal coronary angioplasty for angina pectoris

There is little information about the relation between mild cardiac troponin I (cTn-I) increase after coronary interventions and late outcome. We therefore focused on the long-term outcome and the clinical, morphologic, and procedural correlates of elevation of cTn-I compared with cardiac troponin T, creatine kinase (CK), CK-MB activity and mass, and myoglobin in 105 patients with successful elective percutaneous transluminal coronary angioplasty (PTCA) for stable or unstable angina. Patients with myocardial infarction and those with unstable angina who had a detectable increase in serum markers before PTCA were excluded. Markers were measured before and after the procedure and for 2 days. Patients were followed up to record recurrent angina, myocardial infarction, cardiac death, repeat PTCA, or elective coronary artery bypass graft surgery. Procedure success was achieved in all cases. Elevation in cTn-I (> or =0.1 microg/L) was observed in 23 of 105 patients (22%) (median peak: 0.25 microg/L); 18% had cardiac troponin T (cTn-T) release (> or = 0.1 microg/L, median peak 0.21); 11.4% CK-MB mass (> or =5 microg/L), and 7.6% myoglobin (> or =90 microg/L) release. Five and 2 patients had elevated CK and CK-MB activity, respectively. Fourteen of 18 patients with cTn-T elevation had a corresponding elevation in cTn-I (kappa 0.68; p = 0.001). Patients positive for cTn-I had more unstable angina (p = 0.042) and heparin before PTCA (p = 0.046), and had longest total time (p = 0.004) and single inflation (p = 0.01). By multivariate logistic regression, predictors of postprocedure cTnI elevation were maximum time of each inflation (odds ratio 9.2; p = 0.0012), type B lesions (odds ratio 6.6; p = 0.013), unstable angina (p = 0.041), and age > or =60 years (p = 0.032). Clinical follow-up was available in 103 patients (98%) (mean 19+/-10 months). Kaplan-Meier survival analysis showed that cTn-I elevation was not an important correlate of cardiac events (p = 0.34, by log-rank analysis). The incidence of recurrent angina, myocardial infarction, cardiac death, and repeat revascularization after 12 months was not different in patients positive or negative for cTn-I. We conclude that cTn-I elevation after successful PTCA is not associated with significantly worse late clinical outcome. Levels of cTn-I allow a much higher diagnostic accuracy in detecting minor myocardial injury after PTCA compared with other markers, but there is no association with periprocedural myocardial cell injury and late outcome when cTn-I and other markers are considered.

Differences between IL-4- and IL-4 receptor alpha-deficient mice in chronic leishmaniasis reveal a protective role for IL-13 receptor signaling

IL-4 receptor alpha-chain-deficient (IL-4Ralpha-/-) mice were generated by homologous and site-specific recombination, using the Cre/loxP system in BALB/c-derived embryonic stem cells. In vitro analysis of cells from these mice revealed impaired IL-4- and IL-13-mediated functions, demonstrating that the IL-4Ralpha-chain is an essential component of both the IL-4 and the IL-13 receptor. Whereas Leishmania major-infected BALB/c mice developed fatal progressive disease with type 2 Ab responses within 3 mo, both IL-4Ralpha-/- and IL-4-/- BALB/c mice contained infection with reduced footpad swelling, parasite load, moderate histopathology, and type 1 Ab responses during this time period. Conclusively, these results demonstrate an IL-4-dependent mechanism of susceptibility in BALB/c mice. Nevertheless, in contrast to mutant mice, infected C57BL/6 mice healed completely within 3 mo, indicating that additional factors are necessary for subsequent healing and elimination of the pathogen. During the further course of infection, IL-4Ralpha-/- mice developed progressive disease with massive footpad swelling. Lesions became ulcerative and necrotic with subsequent destruction of connective tissue and bones, as well as dissemination into organs and consequent mortality within the monitored 6 mo of chronic infection. In striking contrast, IL-4-/- mice maintained control of infection on a moderate level, but were unable to clear the pathogen. The distinct phenotypes of the BALB/c embryonic stem cell-derived IL-4-/- and IL-4Ralpha-/- mouse strains identify previously unsuspected mechanisms for maintaining host immunity to chronic infection with L. major, mediated by a functional IL-13 receptor.

Efficient generation of transgenic BALB/c mice using BALB/c embryonic stem cells

BALB/c is one of the most widely used and best characterized mouse strains in immunology. For various applications, it is necessary to generate BALB/c transgenic mice. However, using the conventional microinjection technique it is extremely inefficient to produce transgenic BALB/c mice since the one-cell stage BALB/c embryos are highly vulnerable to pronuclear DNA microinjection. To overcome this problem, we have investigated the generation of Egr-1 (early growth response gene) transgenic mice via the transfection of BALB/c embryonic stem cells. Transfectants carrying Egr-1 constructs comprising either the immunoglobulin heavy chain or the MHC class II promoter/enhancer system were injected into C57BL/6 host blastocysts resulting in chimeric mice. For both type of expression vectors, transgenic offspring of the germline chimeras expressed recombinant Egr-1 in lymphoid tissues containing B cells. This demonstrates the successful generation of Egr-1 transgenic BALB/c mice using transfected ES cell.

Permissive role of thrombopoietin and granulocyte colony-stimulating factor receptors in hematopoietic cell fate decisions in vivo

The question of whether extracellular signals influence hematopoiesis by instructing stem cells to commit to a specific hematopoietic lineage (instructive model) or solely by permitting the survival and proliferation of predetermined progenitors (permissive model) has been controversial since the discovery of lineage-dominant hematopoietic cytokines. To study the potential role of cytokines and their receptors in hematopoietic cell fate decisions, we used homologous recombination to replace the thrombopoietin receptor gene (mpl) with a chimeric construct encoding the extracellular domain of mpl and the cytoplasmic domain of the granulocyte colony-stimulating factor receptor (G-CSFR). This chimeric receptor binds thrombopoietin but signals through the G-CSFR intracellular domain. We found that, despite the absence of a functional mpl signaling domain, homozygous knock-in mice had a normal platelet count, indicating that in vivo the cytoplasmic domain of G-CSFR can functionally replace mpl signaling to support normal megakaryopoiesis and platelet formation. This finding is compatible with the permissive model, according to which cytokine receptors provide a nonspecific survival or proliferation signal, and argues against an instructive role of mpl or G-CSFR in hematopoietic cell fate decisions.

The transcription factor early growth response 1 (Egr-1) advances differentiation of pre-B and immature B cells

In mature B lymphocytes, the zinc finger transcription factor early growth response 1 (Egr-1) is one of the many immediate-early genes induced upon B cell antigen receptor engagement. However, its role during earlier stages of lymphopoiesis has remained unclear. By examining bone marrow B cell subsets, we found Egr-1 transcripts in pro/pre-B and immature B lymphocytes, and Egr-1 protein in pro/pre-B-I cells cultivated on stroma cells in the presence of interleukin (IL)-7. In recombinase-activating gene (RAG)-2-deficient mice overexpressing an Egr-1 transgene in the B lymphocyte lineage, pro/pre-B-I cells could differentiate past a developmental block at the B220(low) BP-1(-) stage to the stage of B220(low) BP-1(+) pre-B-I cells, but not further to the B220(low) BP-1(+) CD25(+) stage of pre-B-II cells. Therefore, during early B lymphopoiesis progression from the B220(low) BP-1(-) IL-2R- pro/pre-B-I stage to the B220(low) BP-1(+) IL-2R+ pre-B-II stage seems to occur in at least two distinct steps, and the first step to the stage of B220(low) BP-1(+) pre-B-I cells can be promoted by the overexpression of Egr-1 alone. Wild-type mice expressing an Egr-1 transgene had increased proportions of mature immunoglobulin (Ig)M+ B220(high) and decreased proportions of immature IgM+ B220(low) bone marrow B cells. Since transgenic and control precursor B cells show comparable proliferation patterns, overexpression of Egr-1 seems also to promote entry into the mature B cell stage. Analysis of changes in the expression pattern of potential Egr-1 target genes revealed that Egr-1 enhances the expression of the aminopeptidase BP-1/6C3 in pre-B and immature B cells and upregulates expression of the orphan nuclear receptor nur77 in IgM+ B cells.

The bHLH protein PTF1-p48 is essential for the formation of the exocrine and the correct spatial organization of the endocrine pancreas

We have generated a mouse bearing a null allele of the gene encoding basic helix-loop-helix (bHLH) protein p48, the cell-specific DNA-binding subunit of hetero-oligomeric transcription factor PTF1 that directs the expression of genes in the exocrine pancreas. The null mutation, which establishes a lethal condition shortly after birth, leads to a complete absence of exocrine pancreatic tissue and its specific products, indicating that p48 is required for differentiation and/or proliferation of the exocrine cell lineage. p48 is so far the only developmental regulator known to be required exclusively for committing cells to an exocrine fate. The hormone secreting cells of all four endocrine lineages are present in the mesentery that normally harbors the pancreatic organ until day 16 of gestation. Toward the end of embryonic life, cells expressing endocrine functions are no longer detected at their original location but are now found to colonize the spleen, where they persist in a functional state until postnatal death of the organism occurs. These findings suggest that the presence of the exocrine pancreas is required for the correct spatial assembly of the endocrine pancreas and that, in its absence, endocrine cells are directed by default to the spleen, a site that, in some reptiles, harbors part of this particular cellular compartment.

Resistance of Fc receptor- deficient mice to fatal glomerulonephritis

Immune complex-mediated inflammation is a common mechanism of various autoimmune diseases. Glomerulonephritis (GN) is one of these diseases, and the main mechanism of the induction of GN has been unclear. We examined the contribution of Fc receptors in the induction of nephrotoxic GN by establishing and analyzing mice deficient in the Fc receptor gamma chain (FcRgamma). Whereas all wild-type mice died from severe glomerulonephritis with hypernitremia by administration of anti-glomerular basement membrane (GBM) antibodies, all FcRgamma-deficient mice survived. Histologically, wild-type mice showed glomerular hypercellularity and thrombotic changes, whereas the renal tissue in FcRgamma-deficient mice was almost intact. Deposition of anti-GBM antibody as well as complement components in the GBM were equally observed in both wild-type and knockout mice. These results demonstrate that the triggering of this type of glomerulonephritis is completely dependent on FcR+ cells.

IgD can largely substitute for loss of IgM function in B cells

The mu and delta heavy chains of IgM and IgD, the first antibody isotypes expressed during bone-marrow B-cell development, are encoded by a common transcription unit. Expression of the mu chain on the surface of late pre-B cells allows their further development to immature B cells. Coexpression of the delta chain and emigration of the immature B cells to the periphery eventually leads to the development of naive mature IgM/IgD double-positive cells. Although IgM is important in driving B-cell development, the contribution of IgD is not clear. Here we investigate the function of IgD. We generated mice deficient in IgM (IgM-/- mice) by deleting the mu region in embryonic stem cells. IgM-/- mice showed normal B-cell development and maturation, with IgD replacing membrane-bound and secretory IgM. Moreover, specific B-cell responses and isotype class switches occurred during immunization or infection. In contrast to mice deficient in B cells, IgM-/- mice survived infection with vesicular stomatitis virus by developing neutralizing immunoglobulins, but they were more susceptible than wild-type controls with delayed specific immunoglobulin responses. These data lead us to conclude that IgD is largely able to substitute for IgM functions.

[Prognostic significance of early raised cardiac troponine I in unstable angina. Contribution to the identification of a high-risk sub-group]

The authors compared the clinical and angiographic characteristics of 44 patients with unstable angina according to cardiac Troponine I concentrations (TnIc) during early blood sampling and then tried to determine a threshold value to predic the occurrence of cardiac events during the hospital period and after 12 months. Tnlc, creatinine-kinase (CK), CK-MB activity and CK-MB mass were sampled over 48 hours. Forty-five per cent of patients had TnIc > or = 0.1 microgram/L; CK-MB activity and CK-MB mass were detected in 16 and 32% of patients. Age, gender, classification and recurrence of angina, previous cardiac history, risk factors, coronary angiographic appearances were comparable in patients with and without raised TnIc. No major cardiac events occurred during the hospital period in either group. The number of angioplasties and coronary bypass procedures was also comparable. At one year, the incidence of myocardial infarction (N = 4) and death (N = 5) was significantly different in patients with raised Tnlc (33% versus 0% in patients without increased TnIc). However, betablocker therapy was less prescribed in the group with the poorest outcomes and left ventricular dysfunction was also significantly more common in this group. Early elevation of Tnlc could contribute to the identification of a high risk subgroup of patients with unstable angina.

Two amyloid precursor protein transgenic mouse models with Alzheimer disease-like pathology

Mutations in the amyloid precursor protein (APP) gene cause early-onset familial Alzheimer disease (AD) by affecting the formation of the amyloid beta (A beta) peptide, the major constituent of AD plaques. We expressed human APP751 containing these mutations in the brains of transgenic mice. Two transgenic mouse lines develop pathological features reminiscent of AD. The degree of pathology depends on expression levels and specific mutations. A 2-fold overexpression of human APP with the Swedish double mutation at positions 670/671 combined with the V717I mutation causes A beta deposition in neocortex and hippocampus of 18-month-old transgenic mice. The deposits are mostly of the diffuse type; however, some congophilic plaques can be detected. In mice with 7-fold overexpression of human APP harboring the Swedish mutation alone, typical plaques appear at 6 months, which increase with age and are Congo Red-positive at first detection. These congophilic plaques are accompanied by neuritic changes and dystrophic cholinergic fibers. Furthermore, inflammatory processes indicated by a massive glial reaction are apparent. Most notably, plaques are immunoreactive for hyperphosphorylated tau, reminiscent of early tau pathology. The immunoreactivity is exclusively found in congophilic senile plaques of both lines. In the higher expressing line, elevated tau phosphorylation can be demonstrated biochemically in 6-month-old animals and increases with age. These mice resemble major features of AD pathology and suggest a central role of A beta in the pathogenesis of the disease.

Distinct roles for lymphotoxin-alpha and tumor necrosis factor in organogenesis and spatial organization of lymphoid tissue

Specialized roles for the pro-inflammatory cytokines tumor necrosis factor (TNF) and lymphotoxin (LT) were characterized in TNF/LT alpha -/- and TNF -/- mice established by direct gene targeting of C57BL/6 ES cells. The requirement for LT early in lymphoid tissue organogenesis is shown to be distinct from the more subtle and varied role of TNF in promoting correct microarchitectural organization of leukocytes in LN and spleen. Development of normal Peyer's patch (PP) structure, in contrast, is substantially dependent on TNF. Only mice lacking LT exhibit retarded B cell maturation in vivo and serum immunoglobulin deficiencies. A temporal hierarchy in lymphoid tissue development can now be defined, with LT being an essential participant in general lymphoid tissue organogenesis, developmentally preceeding TNF that has a more varied and subtle role in promotion of correct spatial organization of leukocytes in LN and spleen PP development in TNF -/- mice is unusual, indicating that TNF is a more critical participant for this structure than it is for other lymphoid tissues.

Release kinetics of serum cardiac troponin I in ischemic myocardial injury

OBJECTIVES

The study was undertaken to evaluate the release kinetics of cardiac troponin I (cTn-I) in ischemic myocardial injury.

DESIGN AND METHODS

The reference range for cTn-I was established by determination of cTn-I in sera and plasma obtained from 622 healthy volunteers (Group 1). cTn-I was compared to: (a) Creatine kinase (CK) MB mass and myoglobin in 12 patients with severe skeletal muscle damage (Group 2); (b) CK-MB activity in 48 patients with myocardial infarction (MI) receiving intravenous thrombolysis (Group 3) (in this group, an additional 43 patients with MI were analyzed separately to characterize cTn-I patterns in thrombolyzed and nonthrombolyzed populations): and in 44 patients with unstable angina (Group 4).

RESULTS

In Groups 1 and 2, no positive results (> or = 0.1 microgram/L) were obtained. In Group 3, the time-courses of cTn-I were mostly monophasic in form. A pathologic increase occurred earlier in cTn-I than in CK-MB activity (p = 0.0002); the period with increased cTn-I was longer (p = 0.001), the overall sensitivity of cTn-I (93.9%) was higher than that of CK-MB activity (p = 0.00001). cTn-I was more sensitive at admission (p = 0.0004). In additional patients, the cTn-I peak occurred and cTn-I disappeared significantly later in nonthrombolyzed than in the thrombolyzed group. In Group 4, positive tests results were detected in 45% of patients for cTn-I, 16% for CK-MB activity, and 32% for CK-MB mass.

CONCLUSIONS

The cTn-I assay appears to be ideally suited for the detection of ischemic myocardial injury in complex clinical situations because of its high specificity; cTn-I indicates myocardial tissue damage in patients with unstable angina and is superior to CK-MB activity and mass in this respect.

Efficient targeting of the IL-4 gene in a BALB/c embryonic stem cell line

Embryonic stem (ES) cell lines have been derived from the inner cell mass of day 3.5 blastocysts of the inbred mouse strain BALB/cJ. Twenty-three lines were karyotyped and three were selected for injection into C57BL/6J host blastocysts. Two of the three lines, BALB/c-I and BALB/c-IV, produced germ-line chimaeras. The suitability of the BALB/c-I line for gene targeting experiments was tested by transfecting a targeting construct for the interleukin-4 (IL-4) gene. Transfected BALB/c-I cells exhibited efficient homologous recombination of the targeting vector and transmitted the induced mutation through the germline. This newly-characterized BALB/c-ES cell line thus provides an alternative to the traditional 129-derived and the recently described C57BL/6 embryonic stem cell lines, and will be useful in disrupting genes involved in the immune system. Furthermore, the genetically pure BALB/c IL-4 deficient mice will aid in studying the role of IL-4 in several infectious disease models in which the BALB/c mouse is a susceptible strain.

Targeted mutation of plakoglobin in mice reveals essential functions of desmosomes in the embryonic heart

Plakoglobin (gamma-catenin), a member of the armadillo family of proteins, is a constituent of the cytoplasmic plaque of desmosomes as well as of other adhering cell junctions, and is involved in anchorage of cytoskeletal filaments to specific cadherins. We have generated a null mutation of the plakoglobin gene in mice. Homozygous -/- mutant animals die between days 12-16 of embryogenesis due to defects in heart function. Often, heart ventricles burst and blood floods the pericard. This tissue instability correlates with the absence of desmosomes in heart, but not in epithelia organs. Instead, extended adherens junctions are formed in the heart, which contain desmosomal proteins, i.e., desmoplakin. Thus, plakoglobin is an essential component of myocardiac desmosomes and seems to play a crucial role in the sorting out of desmosomal and adherens junction components, and consequently in the architecture of intercalated discs and the stabilization of heart tissue.

IL-4-deficient Balb/c mice resist infection with Leishmania major

Mice with a genetically engineered deficiency for either IL-4 or IFN-gamma R1 (single mutants), and IL-4/IFN-gamma R1 (double mutants) on the Balb/c and 129Sv background were used to study the course of infection with Leishmania major. In contrast to genetically resistant 129Sv wildtype mice, IL-4/IFN-gamma R1 double mutant mice developed fetal disease with parasite dissemination to visceral organs similar to mice lacking IFN-gamma R1 only. Balb/c mice, which are exquisitely susceptible to L. major, were rendered resistant to infection by disruption of the IL-4 gene. As compared to homozygous IL-4+/- mice, heterozygous IL-4+/- mice, heterozygous IL-4+/- animals consistently developed smaller lesions with less ulceration and necrosis, indicating the likelihood of gene-dosage effects. This implicates that the magnitude of the IL-4 response determines the severity of disease. CD4+ T cells of IL-4-deficient mice showed impaired Th2 cell development, as assessed by quantitative RT-PCR of characteristic cytokines. Development of resistance is not explained by default Th1 development, because this was observed only at very late stages of infection. Moreover, the induction of inflammatory cytokines (e.g., IL-1 alpha, IL-1 beta, TNF-alpha, IL-12) together with iNOS in the lesion and draining lymph nodes was not altered in the absence of IL-4.

Molecular mechanisms of lymphocyte-mediated cytotoxicity and their role in immunological protection and pathogenesis in vivo

Studies with perforin-deficient mice have demonstrated that two independent mechanisms account for T cell-mediated cytotoxicity: A main pathway is mediated by the secretion of the pore-forming protein perforin by the cytotoxic T cell, whereas an alternative nonsecretory pathway relies on the interaction of the Fas ligand that is upregulated during T cell activation with the apoptosis-inducing Fas molecule on the target cell. NK cells use the former pathway exclusively. The protective role of the perforin-dependent pathway has been shown for infection with the noncytopathic lymphocytic choriomeningitis virus, for infection with Listeria monocytogenes, and for the elimination of tumor cells by T cells and NK cells. In contrast, perforin-dependent cytotoxicity is not involved in protection against the cytopathic vaccinia virus and vesicular stomatitis virus. LCMV-induced immunopathology and autoimmune diabetes have been found to require perforin-expression. A contribution of perforin-dependent cytotoxicity to the rejection of MHC class I-disparate heart grafts has also been observed. Its absence is efficiently compensated in rejection of fully allogeneic organ or skin grafts. So far, evidence for a role of Fas-dependent cytotoxicity as a T cell effector mechanism in vivo is lacking. Current data suggest that the main function of Fas may be in regulation of the immune response and apparently less at the level of an effector mechanism in host defense. Further analysis is necessary, however, to settle this point finally.

Porphobilinogen deaminase deficiency in mice causes a neuropathy resembling that of human hepatic porphyria

Acute intermittent porphyria (AIP) is a human disease resulting from a dominantly inherited partial deficiency of the heme biosynthetic enzyme, porphobilinogen deaminase (PBGD). The frequency of the trait for AIP is 1/10,000 in most populations, but may be markedly higher (1/500) in psychiatric patients. The clinical expression of the disease is characterized by acute, life-threatening attacks of 'porphyric neuropathy' that include abdominal pain, motor and sensory neurological deficits and psychiatric symptoms. Attacks are frequently precipitated by drugs, alcohol and low caloric intake. Identical symptoms occur in other hepatic porphyrias. To study the pathogenesis of the neurologic symptoms of AIP we have generated Pbgd-deficient mice by gene targeting. These mice exhibit the typical biochemical characteristics of human AIP, notably, decreased hepatic Pbgd activity, increased delta-aminolevulinic acid synthase activity and massively increased urinary excretion of the heme precursor, delta-aminolevulinic acid after treatment with drugs such as phenobarbital. Behavioural tests reveal decreased motor function and histopathological findings include axonal neuropathy and neurologic muscle atrophy.