Impacts of additional cycles of neoadjuvant immunotherapy on surgery in non-small-cell lung cancer.

OBJECTIVE: Whether cycle number influences the subsequent pathological or surgical outcomes remained unclear. This study aimed to assess the efficacy and surgical safety of neoadjuvant immunochemotherapy-based treatment in the real-world setting. METHODS: Clinical data of patients who received neoadjuvant immunochemotherapy for non-small-cell lung cancer between 2018 and 2021 were collected. Oncological outcomes such as objective response rate (ORR), major pathological response (MPR), and pathological complete response (pCR), and surgical outcomes including operating time, intraoperative bleeding, postoperative drainage, and hospital stay were analyzed. RESULTS: In total, 176 patients were included, among whom 102 cases were lung squamous carcinoma (LUSQ). After immunochemotherapy, 98 (56%) of patients achieved ORR. Notably, the ORR (63% vs. 46%, p = 0.039) and pCR (45% vs. 27%, p = 0.022) were significantly higher in patients with LUSQ. For patients who received two, three, four, and five or more cycles, the ORRs were 52%, 67%, 53%, and 50% (p = 0.36). In post hoc analysis, cycle numbers showed no significant association with MPR or pCR (p = 0.14 and p = 0.073). Treatment cycles showed no influence on operating time, postoperative drainage, and hospital stay (p = 0.79, 0.37, and 0.22). Notably, the blood loss index of patients who received more than four cycles was higher than those receiving four or fewer cycles (mean blood loss: two or fewer cycles 153.1, three cycles 113.8, four cycles 137.6, and five or more cycles 293.3, respectively). CONCLUSIONS: This study indicated that cycles of neoadjuvant immunochemotherapy had no significant effect on the feasibility and safety of surgery. Although not statistically significant, patients who received five or more cycles of treatment experienced higher intraoperative blood loss.

Artificial intelligence for stepwise diagnosis and monitoring of COVID-19.

BACKGROUND: Main challenges for COVID-19 include the lack of a rapid diagnostic test, a suitable tool to monitor and predict a patient's clinical course and an efficient way for data sharing among multicenters. We thus developed a novel artificial intelligence system based on deep learning (DL) and federated learning (FL) for the diagnosis, monitoring, and prediction of a patient's clinical course. METHODS: CT imaging derived from 6 different multicenter cohorts were used for stepwise diagnostic algorithm to diagnose COVID-19, with or without clinical data. Patients with more than 3 consecutive CT images were trained for the monitoring algorithm. FL has been applied for decentralized refinement of independently built DL models. RESULTS: A total of 1,552,988 CT slices from 4804 patients were used. The model can diagnose COVID-19 based on CT alone with the AUC being 0.98 (95% CI 0.97-0.99), and outperforms the radiologist's assessment. We have also successfully tested the incorporation of the DL diagnostic model with the FL framework. Its auto-segmentation analyses co-related well with those by radiologists and achieved a high Dice's coefficient of 0.77. It can produce a predictive curve of a patient's clinical course if serial CT assessments are available. INTERPRETATION: The system has high consistency in diagnosing COVID-19 based on CT, with or without clinical data. Alternatively, it can be implemented on a FL platform, which would potentially encourage the data sharing in the future. It also can produce an objective predictive curve of a patient's clinical course for visualization. KEY POINTS: • CoviDet could diagnose COVID-19 based on chest CT with high consistency; this outperformed the radiologist's assessment. Its auto-segmentation analyses co-related well with those by radiologists and could potentially monitor and predict a patient's clinical course if serial CT assessments are available. It can be integrated into the federated learning framework. • CoviDet can be used as an adjunct to aid clinicians with the CT diagnosis of COVID-19 and can potentially be used for disease monitoring; federated learning can potentially open opportunities for global collaboration.

Minimally Invasive Carinal Reconstruction Using Bronchial Flap and Omental Flap Reinforcement.

Carinal reconstruction and omental flap harvesting are traditionally performed through open approaches. We report a case in which carinal reconstruction with bronchial flap and omental flap reinforcement was performed using minimally invasive approaches. The omental flap was harvested laparoscopically and wrapped around the anastomosis, which reduced the risk of airway anastomosis complications. Noncircumferential resection and reconstruction used bronchial flap, which made it easier to perform under video-assisted thoracoscopic surgery conditions. Minimally invasive carinal reconstruction with bronchial flap and omental reinforcement after neoadjuvant treatment can be safely performed.

Management of Brachiocephalic Vein Injury During Tubeless Subxiphoid Thoracoscopic Thymectomy.

We have reported the usefulness of the subxiphoid video-assisted thoracoscopic surgery approach in thymectomy. However, such a new method may have unknown complications that rarely occur. The brachiocephalic vein has been considered to be the vessel that is most frequently injured when performing thymectomy because of the skeletal anatomy. We herein report a case of intraoperative injury of brachiocephalic vein using tubeless subxiphoid thoracoscopic thymectomy. No additional complications have been found in the 3 months since the operation. Though subxiphoid video-assisted thoracoscopic surgery thymectomy is a safe and less invasive operation, intraoperative complications are possible, and surgeons should express caution.

Uniportal video-assisted thoracoscopic surgery in the treatment of traumatic diaphragmatic hernia with an aortic arch pseudoaneurysm.

We present an unusual case of a 72-year-old patient with a concurrent aortic arch pseudoaneurysm and right diaphragmatic hernia, who was successfully treated using an aortic endovascular stent and diaphragmatic repair via uniportal video-assisted thoracoscopic surgery.

Genetic evaluation of Atlantic salmon for growth traits incorporating SNP markers.

Genetic evaluations of individual fish were calculated for growth traits in North American Atlantic salmon with and without inclusion of genetic markers. The number of SNP markers was reduced to 6,000 and further to 270 in order to reduce the problem of overparameterization. SNP genotypes were predicted for all ungenotyped animals in the pedigree. Analysis of traits used a model with polygenic effects and SNP markers together. Polygenic effects refer to the additive genetic effects that remain after accounting for SNP genotypes. SNP marker genotypes were included as covariates to evaluate fish for growth traits (weight and length) in different environments (freshwater and seawater) with genders separated. Including regressions on SNP marker genotypes reduced the sum of squares of residuals by 2.7%-12.5% and increased the variability of Mendelian sampling effects (i.e., within-family variation) compared to traditional animal model evaluations. Genetic evaluations may be carried out with a few hundred markers which may be more affordable for genotyping large numbers of fish.

A genome scan for selection signatures comparing farmed Atlantic salmon with two wild populations: Testing colocalization among outlier markers, candidate genes, and quantitative trait loci for production traits.

Comparative genome scans can be used to identify chromosome regions, but not traits, that are putatively under selection. Identification of targeted traits may be more likely in recently domesticated populations under strong artificial selection for increased production. We used a North American Atlantic salmon 6K SNP dataset to locate genome regions of an aquaculture strain (Saint John River) that were highly diverged from that of its putative wild founder population (Tobique River). First, admixed individuals with partial European ancestry were detected using STRUCTURE and removed from the dataset. Outlier loci were then identified as those showing extreme differentiation between the aquaculture population and the founder population. All Arlequin methods identified an overlapping subset of 17 outlier loci, three of which were also identified by BayeScan. Many outlier loci were near candidate genes and some were near published quantitative trait loci (QTLs) for growth, appetite, maturity, or disease resistance. Parallel comparisons using a wild, nonfounder population (Stewiacke River) yielded only one overlapping outlier locus as well as a known maturity QTL. We conclude that genome scans comparing a recently domesticated strain with its wild founder population can facilitate identification of candidate genes for traits known to have been under strong artificial selection.

New tubeless video-assisted thoracoscopic surgery for small pulmonary nodules.

Objectives: Problems associated with intubation, chest drainage and urinary catheterization can have a negative impact on patient's recovery after thoracic surgery. We therefore evaluated the feasibility of a new tubeless (spontaneous ventilation without tracheal intubation, urinary catheterization, and no post-operative chest drain placement) approach to perform video-assisted thoracoscopic surgery (VATS) for small pulmonary nodules (SPN) less than 2cm in diameter. Methods: From 1 January 2012 to 31 December 2014, 34 patients with SPNs were treated using tubeless VATS in our centre. To be eligible for this approach, the patient must have a body mass index (BMI) of less than 25; ASA grade of II or less; no history of prostate or renal disease and no parenchymal air leak at the end of surgery. All operations were performed via an anterior uniportal VATS under spontaneous ventilation without tracheal intubation. Results: All patients [29 male:5 females; average age: 58 ± 19 years old] completed their operation under spontaneous ventilation, without conversion to endotracheal intubation. There was good operative exposure and definite diagnosis was obtained in all patients. The anaesthesia and operating time were 23 ± 3 min and 43 ± 10 min, respectively. No major intra-operative or post-operative complications were seen. Patients recovered from their anaesthesia (fully awake) within a mean time of 18 ± 3 min after surgery, and were eating 42 normally on an average of 5 ± 1 h post-operatively. No patients had pain on deep breathing or coughing (Bruggemann Comfort Score < 2). Within 24 h after surgery, 26 patients were discharged, while the remaining 8 patients were discharged on the second day. None of the patients needed re-invention with chest drainage or urinary catheterization even after discharge. All patients remained well at a median [interquartile range] follow-up time of 3[2-5] weeks. Conclusions: Tubeless VATS approach for SPNs is feasible in carefully selected patients. Intubation, chest drainage, and/or urinary catheterization may not be necessary in all patients.

The external morphology of adult female Egrasilus labracis as shown using hexamethyldisilazane treated, uncoated specimens for scanning electron microscopy.

The description and application of a modified Scanning Electron Microscope preparation technique using hexamethyldisilazane for small parasitic copepods was demonstrated though a high resolution depiction of individuals of Ergasilus labracis sampled from three spined stickleback (Gasterosteus aculeatus) in Bay D'Espoir, Newfoundland during summer 2015 and from archival samples retrieved from Atlantic salmon par (Salmo salar) stored at the Atlantic reference centre, St. Andrews, New Brunswick. The specimens were very well preserved showing high quality detail of important features and verifying those previously described using light microscopy by Hogans. Additionally the technique allowed excellent in situ demonstrations of mouth parts, swimming legs, and unusual and previously undescribed features of the second antenna including prominent striations and pore-like structures found to define the claw. It is thought that this technique will become a quick and efficient tool for describing important taxonomic features of small parasitic copepods like E. labracis or other similar small aquatic organisms. Microsc. Res. Tech. 79:657-663, 2016. © 2016 Wiley Periodicals, Inc.

Non-intubated combined with video-assisted thoracoscopic in carinal reconstruction.

Carinal reconstruction is a difficult technique combined with video-assisted thoracoscopic surgery (VATS). It has a high requirement on the operator's skills in operating thoracoscope and meanwhile requires the close cooperation from anesthesiologists. Tracheal intubation and ventilator-assisted ventilation are key steps to ensure the success of surgery. However, tracheal intubation itself may influence the exposure of surgical field and increase the difficulty of anastomosis. In close cooperation of anesthesiologists, we did not perform tracheal intubation; rather, we carried out non-intubated complete VATS carinal reconstruction in a patient with adenoid cystic carcinoma (ACC) of the lower trachea. The awake complete VATS carinal reconstruction was successfully performed. The anastomosis lasted about 36 hours, and the whole surgical procedure lasted 230 min. The intraoperative blood loss was about 80 mL. The patient recovered well 100 min after surgery. A semi-solid diet began 6 hours following the surgery. This non-intubated anesthesia method makes the surgery easier, especially during the anastomosis of stumps. It is feasible and safe to apply this anesthesia technique in carinal reconstruction.

Video-Assisted Thoracic Surgery Resection and Reconstruction of Carina and Trachea for Malignant or Benign Disease in 12 Patients: Three Centers' Experience in China.

BACKGROUND: Although video-assisted thoracoscopic surgery (VATS) has been widely applied to both peripheral and central lung cancer treatment in many centers, there is great hesitation to adopt it for carinal or tracheal surgical procedures. The aims of this study were to explore the feasibility of VATS in the treatment of benign and malignant diseases involving the carina and trachea and to highlight relevant techniques. METHODS: Patients undergoing VATS carinal or tracheal procedures between May 2012 and July 2015 from three centers in China were included in this study. Their clinical characteristics, operative details, and postoperative course were analyzed. RESULTS: Twelve patients underwent five different types of VATS airway reconstructions with or without lobectomy: including right bronchial resection with partial carinal reconstruction (3 patients), tracheal resection and reconstruction (4 patients), tracheal or right bronchial resection with carinal reconstruction (3 patients), left bronchial resection with carinal reconstruction (1 patient), and right pneumonectomy with carinal reconstruction (1 patient). Complete resection was achieved in all patients. The mean operative time was 224 ± 78 minutes, and the median time of the first anastomosis was 41 minutes (range, 15 to 60 minutes), regardless of whether the reconstruction was a tracheal or carinal. The median estimated blood loss was 100 mL (range 10 to 1000 mL). The mean postoperative hospital stay was 12.5 ± 2.5 days. There was no perioperative mortality or major morbidity. Median duration of follow-up was 12 months (range 5 to 43 months). CONCLUSIONS: VATS resection and reconstruction of the carina or trachea are feasible, and these procedures can be safely performed using the techniques described. We believe, with the accumulation of VATS experience, these procedures could be adopted as routine approaches in tracheal surgery.

The comparison between novel and traditional three-dimensional image system in thoracoscopy: glasses-less vs. glass.

BACKGROUND: Although three-dimensional (3D) thoracoscopic technology has been available for some time, it is not widely utilized in most centers. Dimness, unsatisfied visualization and discomfort associated with wearing 3D glasses might account for such phenomenon. We have recently developed a "Glass-less" 3D system for thoracoscopic surgery to avoid these in issues. METHODS: Surgical residents will be invited to perform a set of commonly used surgical procedures using "Glass-less" 3D and conventional 3D system. The procedure duration will be recorded and analyzed. Besides, they will be asked to finish questionnaires before and after procedure. RESULTS: A total of 25 volunteers were participated in the study. The mean working time of them was 18.3 years. 3D image system was not routinely used by most of them. High maintenance cost was the major reason for the result (8/25). Most of them showed great expectation of 3D system on ideal visualization and comfortability (19/25, 21/25). Majority of participants preferred glass-less 3D system rather than the conventional one referring to image quality (14/25), effect (13/25), accessibility (17/25) and overall performance (16/25). However, most of them felt uncomfortable when using glass-less 3D (17/25). Regarding to operation precision, 10 of them preferred glass-less 3D while 11 considered no difference. No difference was observed in the comparison of procedure duration. CONCLUSIONS: Glass-less 3D image system was a novel technology which offered ideal image, similar operational precision as the conventional 3D system. Although inappropriate utilization might lead to discomfort experience, improvements would be acquired after proper adjustments.

White light, autofluorescence and narrow-band imaging bronchoscopy for diagnosing airway pre-cancerous and early cancer lesions: a systematic review and meta-analysis.

BACKGROUND: We aimed to summarize the diagnostic accuracy of white light bronchoscopy (WLB) and advanced techniques for airway pre-cancerous lesions and early cancer, such as autofluorescence bronchoscopy (AFB), AFB combined with WLB (AFB + WLB) and narrow-band imaging (NBI) bronchoscopy. METHODS: We searched for eligible studies in seven electronic databases from their date of inception to Mar 20, 2015. In eligible studies, detected lesions should be confirmed by histopathology. We extracted and calculated the 2×2 data based on the pathological criteria of lung tumor, including high-grade lesions from moderate dysplasia (MOD) to invasive carcinoma (INV). Random-effect model was used to pool sensitivity, specificity, diagnostic odds ratio (DOR) and the area under the receiver-operating characteristic curve (AUC). RESULTS: In 53 eligible studies (39 WLB, 39 AFB, 17 AFB + WLB, 6 NBI), diagnostic performance for high-grade lesions was analyzed based on twelve studies (10 WLB, 7 AFB, 7 AFB + WLB, 1 NBI), involving with totally 2,880 patients and 8,830 biopsy specimens. The sensitivity, specificity, DOR and AUC of WLB were 51% (95% CI, 34-68%), 86% (95% CI, 73-84%), 6 (95% CI, 3-13) and 77% (95% CI, 73-81%). Those of AFB and AFB + WLB were 93% (95% CI, 77-98%) and 86% (95% CI, 75-97%), 52% (95% CI, 37-67%) and 71% (95% CI, 56-87%), 15 (95% CI, 4-57) and 16 (95% CI, 6-41), and 76% (95% CI, 72-79%) and 82% (95% CI, 78-85%), respectively. NBI presented 100% sensitivity and 43% specificity. CONCLUSIONS: With higher sensitivity, advanced bronchoscopy could be valuable to avoid missed diagnosis. Combining strategy of AFB and WLB may contribute preferable diagnosis rather than their alone use for high-grade lesions. Studies of NBI warrants further investigation for precancerous lesions.

Occurrence of the parasitic copepod Ergasilus labracis on Threespine Sticklebacks from the south coast of Newfoundland.

A study conducted from August to October 2013 surveyed Threespine Sticklebacks Gasterosteus aculeatus (n = 822) for the presence of parasitic copepods in the vicinity of large sea-cage salmonid farms in Bay d'Espoir, Newfoundland. The majority of parasitic copepods surveyed were Ergasilus labracis (n = 4,684). Other parasitic copepods observed on Threespine Sticklebacks during the survey included chalimus-stage Lepeophtheirus spp. (n = 3), adult Argulus alosae (n = 2), and a single Thersitina gasterostei. This represents a new host record for E. labracis. The copepods were present on fish collected in a broad range of temperatures (6.9-17.7°C) and salinities (10.2-30.2 [Practical Salinity Scale]). The parasitic copepods were most commonly found on larger hosts estimated to be age 1 or older. Surprisingly, the highest infestations (approximately 65%) were found on regions of the hosts outside of the gills (behind the pectoral fins and pelvic spines); in some cases, the copepods had inflicted significant damage to the skin of their hosts. Among host fish with evidence of an additional infection, such as microsporidian tumors (xenomas) or hemorrhagic-like symptoms (dark red abdomens and bloody mucus), the prevalence of E. labracis was significantly higher (43.4%) than among healthy fish (28.9%) despite there being no significant difference in size between the two fish health groups. In contrast, intensity (mean number of individual parasites per host) was significantly higher among healthy hosts (23.6) than among unhealthy ones (7.63). Although this parasite has been listed as present in Newfoundland previously, it has a broad host range and has been reported to be pathogenic to farmed salmonids. Therefore, its potential impact on wild and farmed fish populations around Newfoundland should not be underestimated.

The N2 paradox: similar outcomes of pre- and postoperatively identified single-zone N2a positive non-small-cell lung cancer.

OBJECTIVES: Resection of N2a non-small-cell lung cancer (NSCLC) diagnosed preoperatively is controversial but there is support for resection of unexpected N2 disease discovered at surgery. Since the seventh TNM edition, we have intentionally resected clinical N2a disease. To validate this policy, we determined prognostic factors associated with all resected N2 disease. METHODS: From a prospective database of 1131 consecutive patients undergoing elective resection for primary lung cancer over a period of 8 years, we identified 68 patients (35 females (51.4%), mean age 66 years, standard deviation (SD) 9 years) who had pathological N2 disease. All patients had positron emission computed tomography (CT-PET) staging and selective mediastinoscopy. A Cox-regression analysis was performed to identify prognostic factors. RESULTS: At a median follow-up of 38.7 months (standard error 10, 95% confidence interval (CI) 19.0-58.4), the overall median survival was 22.2 months (95% CI 14.6-29.8) with 1-, 2- and 5-year survival rates of 63.3, 46.6 and 13.2%, respectively. Survival after resection of pN2 disease is adversely affected by the need for pneumonectomy, multizone pN2b involvement and by non-compliance with adjuvant chemotherapy. Pathological involvement of the subcarinal zone but no other zone appears to be associated with an adverse prognosis (hazard ratio (HR) 1.87, P = 0.063). Importantly, long-term survival is not different between those patients who have a negative preoperative PET-CT scan and yet are found to have pN2 after resection, and those who are single-zone cN2a positive before resection on PET-CT scan (HR 1.37, P = 0.335). CONCLUSIONS: Our results support a policy of intentionally resecting single-zone N2a NSCLC identified preoperatively as part of a multimodality therapy.

Differences in performance of five types of aortic valve prostheses: haemodynamic assessment by dobutamine stress echocardiography.

BACKGROUND: In patients being considered for aortic valve replacement, there remains controversy over which design or tissue offers the best performance. We aimed to evaluate in a single study the haemodynamic performances of five different widely used aortic valve prostheses: stentless porcine xenograft (Elan), stentless bovine pericardium (Pericarbon Freedom), stented porcine xenograft (Aspire), stented bovine pericardium (More) and mechanical (Ultracor). We also compared them with normal aortic valves and stenosed valves of variable severity. METHODS AND RESULTS: Preoperative echocardiography and dobutamine stress echocardiography at 1 year postoperatively were undertaken in 106 patients (n=18-24 from each group). Stentless bioprostheses, whether porcine or bovine, displayed superior haemodynamics across nearly all echocardiographic parameters: lower gradients, larger effective orifice area, higher dimensionless severity index (DSI) and lower resistance, when compared with stented or mechanical prostheses. Comparing both stented designs, bovine tissue performed the worst at rest, but with stress, there was no difference. The stress performances of the stentless bioprostheses were similar to the mildly stenosed native aortic valve, whereas the performances of the stented and mechanical prostheses resembled that of native valves with mild-to-moderate stenoses. Haemodynamic differences, however, did not translate into differences in left ventricular mass reduction at 1 year. CONCLUSIONS: Stentless bioprostheses displayed haemodynamics superior to stented or mechanical prostheses and had the closest performance to a normal, native aortic valve. Stress DSI data, least reliant on variable annulus/valve sizes and flow rates, provided the best haemodynamic discrimination.

Density, viscosity and electrical conductivity of protic alkanolammonium ionic liquids.

Ionic liquids are molten salts with melting temperatures below the boiling point of water, and their qualification for applications in potential industrial processes does depend on their fundamental physical properties such as density, viscosity and electrical conductivity. This study aims to investigate the structure-property relationship of 15 ILs that are primarily composed of alkanolammonium cations and organic acid anions. The influence of both the nature and number of alkanol substituents on the cation and the nature of the anion on the densities, viscosities and electrical conductivities at ambient and elevated temperatures are discussed. Walden rule plots are used to estimate the ionic nature of these ionic liquids, and comparison with other studies reveals that most of the investigated ionic liquids show Walden rule values similar to many non-protic ionic liquids containing imidazolium, pyrrolidinium, tetraalkylammonium, or tetraalkylphosphonium cations. Comparison of literature data reveals major disagreements in the reported properties for the investigated ionic liquids. A detailed analysis of the reported experimental procedures suggests that inappropriate drying methods can account for some of the discrepancies. Furthermore, an example for the improved presentation of experimental data in scientific literature is presented.

Early impact of aortic wrapping on patients undergoing aortic valve replacement with mild to moderate ascending aorta dilatation.

BACKGROUND: The management of mild to moderate dilatation of the ascending aorta of less than 5 cm is controversial, particularly when concomitant surgical correction of aortic valve is required. We investigate the impact of a simple method of aorta reduction using Dacron graft wrapping during aortic valve replacement on the rest of the aorta. METHODS: We studied 14 patients who had ascending aorta dilatation of 4-5 cm before undergoing aortic wrapping during their aortic valve replacement and compared with their post-operative imaging within a month. RESULTS: The diameters of the ascending aorta wrapped with the Dacron graft were significantly reduced within 4 weeks after surgery from 44.7 +/- 2.6 to 33.6 +/- 3.9 mm (p < 0.001). This was associated with significant reduction in the diameter of rest of ascending aorta: coronary sinuses (from 37.9 +/- 4.9 mm to 33.3 +/- 6.1 mm; p < 0.001), sinotubular junction (from 33.2 +/- 4.7 mm to 30.6 +/- 4.4 mm, p = 0.02), and aortic arch (from 34.7 +/- 4.3 mm to 32.6 +/- 4.1 mm, p = 0.03). CONCLUSIONS: Reduction of ascending aortic dilatation by wrapping with a Dacron graft in this preliminary study is associated with favourable early reversed aortic remodelling. This supports the hypothesis that correction of mild-moderate dilatation of the ascending aorta with Dacron wrapping at the time of aortic valve surgery may prevent the progression of the dilatation, although the long-term study on a larger population is needed to confirm its benefits.

Limitations of conventional approaches to identify myocyte nuclei in histologic sections of the heart.

Accurate nuclear identification is crucial for distinguishing the role of cardiac myocytes in intrinsic and experimentally induced regenerative growth of the myocardium. Conventional histologic analysis of myocyte nuclei relies on the optical sectioning capabilities of confocal microscopy in conjunction with immunofluorescent labeling of cytoplasmic proteins such as troponin T, and dyes that bind to double-strand DNA to identify nuclei. Using heart sections from transgenic mice in which the cardiomyocyte-restricted alpha-cardiac myosin heavy chain promoter targeted the expression of nuclear localized beta-galactosidase reporter in >99% of myocytes, we systematically compared the fidelity of conventional myocyte nuclear identification using confocal microscopy, with and without the aid of a membrane marker. The values obtained with these assays were then compared with those obtained with anti-beta-galactosidase immune reactivity in the same samples. In addition, we also studied the accuracy of anti-GATA4 immunoreactivity for myocyte nuclear identification. Our results demonstrate that, although these strategies are capable of identifying myocyte nuclei, the level of interobserver agreement and margin of error can compromise accurate identification of rare events, such as cardiomyocyte apoptosis and proliferation. Thus these data indicate that morphometric approaches based on segmentation are justified only if the margin of error for measuring the event in question has been predetermined and deemed to be small and uniform. We also illustrate the value of a transgene-based approach to overcome these intrinsic limitations of identifying myocyte nuclei. This latter approach should prove quite useful when measuring rare events.