Whole-genome sequencing-based antimicrobial resistance and shedding dynamics of Escherichia coli isolated from calves before and after antimicrobial group treatments

The fattening of calves is often associated with high antimicrobial use and the selection of antimicrobial resistance (AMR). The objective of this observational longitudinal study was to describe the AMR and strain dynamics, using whole-genome sequencing (WGS), of fecal Escherichia coli in a cohort of 22 calves. All calves received antimicrobial group treatments on Day (D) 1 (oxytetracycline, intramuscularly) and on D4 through D12 (doxycycline, in-feed). Additionally, eight calves received individual parenteral treatments between D7 and D59, including florfenicol, amoxicillin, marbofloxacin, and gamithromycin. Rectal swabs were collected from all calves on D1 (prior to treatment), D2, D9, and D82. The swabs were spread onto Enterobacterales-selective agar, and three E. coli colonies per plate were subjected to WGS. Out of 264 isolates across all calves and sampling times, 80 unique strains were identified, a majority of which harbored genes conferring resistance to tetracyclines, streptomycin, and sulfonamides. The diversity of strains decreased during the in-feed antimicrobial group treatment of the calves. On D82, 90% of isolates were strains that were not isolated at previous sampling times, and the median number per strain of AMR determinants to tetracyclines, florfenicol, β-lactams, quinolones, or macrolides decreased compared to D9. Additionally, clonal dissemination of some strains represented the main transmission route of AMR determinants. In this study, WGS revealed important variations in strain diversity and genotypic AMR of fecal E. coli over time in calves subjected to group antimicrobial treatments.

IMPORTANCE

The continued emergence and spread of antimicrobial resistance (AMR) determinants are serious global concerns. The dynamics of AMR spread and persistence in bacterial and animal host populations are complex and not solely driven by antimicrobial selection pressure. In calf fattening, both antimicrobial use and carriage prevalence of antimicrobial-resistant bacteria are generally recognized as high. This study provides new insights into the short-term, within-farm dynamics and transmission of AMR determinants in Escherichia coli from the dominant fecal flora of calves subjected to antimicrobial group treatments during the rearing period. The diversity of E. coli strains decreased over time, although, in contrast to previous observations in extended-spectrum β-lactamase-producing Enterobacterales, the predominance of a few clones was not observed. The spread of AMR determinants occurred through the dissemination of clonal strains among calves. The median number per strain of AMR determinants conferring resistance to selected antimicrobials decreased toward the end of the rearing period.

Characterization of third-generation cephalosporin-resistant Escherichia coli from slaughter calves and fattening pigs: A pilot study for monitoring antimicrobial resistance by whole genome sequencing in Switzerland

INTRODUCTION

Whole genome sequencing (WGS) was introduced into Swiss antimicrobial resistance monitoring in 2022 as an additional method to phenotypic antimicrobial susceptibility testing by broth microdilution to characterize presumptive third-generation cephalosporin-resistant (3GC-R) Escherichia coli. Caecal samples from Swiss slaughter calves and fattening pigs, as well as beef and pork meat from Swiss retail taken in 2021, were analyzed for the presence of 3GC-R E. coli according to European harmonized protocols. In 2021, 3GC-R E. coli was detected in 23,8 % of slaughter calves, 5,9 % of fattening pigs, and 0 % of meat. Comparative analysis of the antimicrobial resistance results obtained by phenotypic measurement and those obtained by the detection of corresponding underlying molecular mechanisms by WGS showed very high agreement (99 %). Resistance to third-generation cephalosporins (3GCs) was mainly associated with the presence of blaCTX-M-15 in E. coli isolates from calves and blaCTX-M-1 in E. coli isolates from pigs and mutations in the ampC-promoter (g.-42 C>T) in E. coli isolates from both animal species. Moreover, WGS data were used for phylogenetic analysis based on multi locus sequence types (MLST) and core genome MLST(cgMLST) revealing that 3GC-R E. coli isolated from Swiss slaughter calves and fattening pigs were genetically diverse. In this study, it was shown that using WGS alone to monitor antimicrobial resistance could detect trends in known molecular antimicrobial resistance mechanisms while also providing other valuable information about the isolates, such as genetic relatedness. However, only by combining phenotypic susceptibility testing and WGS early detection of previously unknown resistance mechanisms will be possible.

Intra- and Interspecies Spread of a Novel Conjugative Multidrug Resistance IncC Plasmid Coharboring blaOXA-181 and armA in a Cystic Fibrosis Patient

A novel multidrug resistance conjugative 177,859-bp IncC plasmid pJEF1-OXA-181 coharboring the carbapenemase-coding blaOXA181 and the aminoglycoside resistance 16S rRNA methyltransferase-coding armA genes was detected in two unrelated Escherichia coli gut isolates of ST196 and ST648, as well as two ST35 Klebsiella pneumoniae gut and sputum isolates of a cystic fibrosis patient. The armA gene was located within the antimicrobial resistance island ARI-A and the blaOXA181 gene, which was preceded by IS903 and ISEcp1Δ was inserted within the transfer genes region without affecting conjugation ability. Comparative plasmid analysis with other related IncC plasmids showed the presence of blaOXA181, as well as its integration site, are thus far unique for these types of plasmids. This study illustrates the potential of a promiscuous multidrug resistance plasmid to acquire antibiotic resistance genes and to disseminate in the gut of the same host. IMPORTANCE Colocalization of carbapenemases and aminoglycoside resistance 16S rRNA methylases on a multidrug resistance conjugative plasmid poses a serious threat to public health. Here, we describe the novel IncC plasmid pJEF1-OXA-181 cocarrying blaOXA-181 and armA as well as several other antimicrobial resistance genes (ARGs) in different Enterobacterales isolates of the sputum and gut microbiota of a cystic fibrosis patient. IncC plasmids are conjugative, promiscuous elements which can incorporate accessory antimicrobial resistance islands making them key players in ARGs spread. This plasmid was thus far unique among IncC plasmids to contain a blaOXA-181 which was integrated in the transfer gene region without affecting its conjugation ability. This study highlights that new plasmids may be introduced into a hospital through different species hosted in one single patient. It further emphasizes the need of continuous surveillance of multidrug-resistant bacteria in patients at risk to avoid spread of such plasmids in the health care system.

Application of embryo biopsy and sex determination via polymerase chain reaction in a commercial equine embryo transfer program in Argentina

Embryo biopsy for fetal sexing has clinical application, but few reports are available of its use within an active embryo transfer program. We evaluated results on biopsy of 459 embryos over one breeding season. There were no significant differences in pregnancy rate between biopsied and non-biopsied embryos (72% vs 73%) or for biopsied embryos recovered at the centre (73%) compared with those shipped overnight (72%). However, the pregnancy rate decreased significantly in shipped embryos biopsied ≥20h after collection. Overall, 86% of biopsies provided a sex diagnosis. The likelihood of a positive genomic (g) DNA result was significantly higher for biopsies from large blastocysts (96%) than from smaller embryos (70-85%). In total, 38% of biopsies were positive for Y chromosome DNA (Y-DNA) and were diagnosed as male. Subsequently, 95% of Y-DNA-positive embryos were confirmed as male and 78% of Y-DNA-negative embryos were confirmed as female. The accuracy of prediction of female (Y-DNA negative) was significantly higher when the biopsy sample was probed for Y-DNA only compared with probing for both gDNA and Y-DNA. We estimate that by transferring only Y-DNA-negative embryos, 3% of potential female pregnancies may have been lost, and production of male pregnancies was reduced by 72%.

Training to reduce postural sway and increase functional reach in the elderly

Poor balance is one of the most common risk factors for falling, a common cause of work-related injury and death. To evaluate the effects of a 10-week intervention program on balance in older adults, 12 participants aged 61-77 years (age = 70.4 +/- 5.4 years; mean +/- SD) completed an exercise program (60 min, 2 days.week-1 for 10 weeks) performed while laying/sitting on large air-filled exercise balls (Thera-Band). Several postural sway composite scores (determined while standing with feet apart and semitandem, eyes open and closed) improved (p < or = 0.05) including medial-lateral amplitude and speed of sway (reduced by approximately 9%), and instantaneous speed (reduced by approximately 13%). Reductions in XY area approached (p = 0.06) statistical significance and anterior-posterior amplitude and speed of sway did not change. Functional reach also improved (20.3%). These results suggest that challenging the physiological systems involved in balance control while on the nonstable support surface of the exercise balls improves both static and dynamic balance in older adults and may reduce the risk for falling.

Molecular coherent scattering data for tissue in photon transport Monte Carlo codes

The suitability of introducing molecular interference effects into coherent scattering phenomenology is considered here in the case of X and gamma photon transport in biological tissues. In order to make its implementation practicable in most of the existing open user Monte Carlo codes, a self-consistent basic set of tabulations for the linear differential scattering coefficient was proposed. The tabulations were critically reviewed by testing their validity over the entire range of the momentum transfer variable from 0 to 10(10) nm(-1). Implementation in three different Monte Carlo codes was performed, and they proved to be reliable.

Photon backscattering tissue characterization by energy dispersive spectroscopy evaluations

Techniques for in vivo tissue characterization based on scattered photons have usually been confined to evaluating coherent and Compton peaks. However, information can also be obtained from the energy analysis of the Compton scattered distribution. This paper looks at the extension of a technique validated by the authors for characterizing tissues composed of low-atomic-number elements. To this end, an EDXRS (energy dispersive x-ray spectrometry) computer simulation procedure was performed and applied to test the validity of a figure of merit able to characterize binary compounds. This figure of merit is based on the photon fluence values in a restricted energy interval of the measured distribution of incoherently scattered photons. After careful experimental tests with 59.54 keV incident photons at scattering angles down to 60degrees, the simulation procedure was applied to quasi-monochromatic and polychromatic high-radiance sources. The results show that the characterization by the figure of merit, which operates satisfactorily with monochromatic sources, is unsatisfactory in the latter cases, which seem to favour a different parameter for compound characterization.

Mixtures of Ascorbyl-stearate and Vitamin D3: A Monolayer Study at the Gas/Water Interface

Vitamin C and vitamin D3 perform different and important activities in living systems. Vitamin D3 forms stable monomolecular films at the gas/water interface and, at higher concentrations, produces large aggregates in water solutions. Because of their amphiphilic structure, vitamin C alkyl esters form monolayers, micelles, vesicles, or microemulsions in water, depending on composition, concentration, solvent, and temperature. In this work the monolayer of 6-O-ascorbyl-stearate and vitamin D3 was studied to investigate the behavior of the two compounds and their mixtures at the gas/water interface at different temperatures, at different pH, and in the presence of Ca2+ in the subphase. The results show that stable Langmuir films are formed in all molar ratios, with repulsive interactions between the two components, and that the presence of calcium ions modifies the properties of the monolayer.

Kienböck's disease. II. Risk factors, diagnosis, and ergonomic interventions

The term CTD has been used to refer to those musculoskeletal impairments that appear to be work-related and tend to be chronic. Upper extremity CTD are categorized in three major groups: tendon disorders, neurovascular disorders, and nerve. Kienböck's disease, on the other hand, has been documented in the workplace and has a similar etiology, but due to current anatomic classifications cannot be considered a CTD. With this in mind, the present article reviews risk factors, diagnosis, and treatment, with the purpose of providing physicians, engineers, and designers with information to reduce the risk of workers developing this potentially debilitating disease. Furthermore, additional support will be accumulated and combined with Part I of this article with the intent of introducing into the literature a new category of upper extremity CTD: Bone Disorders.

Kienböck's disease. I. Anatomy and Etiology

Cumulative trauma disorders (CTD) pose a major industrial problem in terms of increased medical costs, lost productivity and degraded worker health and safety. From an anatomical view, CTD's are classified into three major categories: tendon disorders, neurovascular disorders and nerve disorders. Up until recently these categories seemed to cover CTD of the upper extremity, however, Kienböck's disease, a typically less common disease and one that does not fit into the established CTD categories, has been observed to exhibit CTD characteristics and does appear in the manufacturing environment. The most common types of employment observed to exhibit individuals with this disease are carpentry, jobs involving the use of pneumatic tools (wrench), spot welders, sheet metal work, farmers and factory workers. The present article makes a critical examination of the relevant anatomy and etiologic aspects of this disease.

The effect of wrist and arm postures on peak pinch strength

This paper examines the effect of various arm postures on peak pinch strength. Twenty (20) able-bodied, male subjects volunteered to participate in a set of two experiments. The first experiment examined the effect of shoulder and elbow posture on peak pinch strength. The second experiment examined the effect of forearm posture, wrist posture, and pinch type on peak pinch strength. Results from the first experiment indicated that elbow posture had a significant effect on pinch strength. It was documented that extreme elbow flexion decreased pinch strength by up to 9%. Results from the second experiment indicated that deviated wrist postures, forearm postures, and pinch type significantly decreased pinch strength as much as 33%. Ergonomic guidelines which utilize the above factors as significant modifiers of pinch strength capacity may assist ergonomists to reduce the risk of injury and development of cumulative trauma disorders in the workplace.

Design-oriented functional capacity evaluation: the available motions inventory--a review

The accommodation of a task to the unique abilities of an individual with a disability is becoming increasingly the responsibility of the employer. Functional capacity evaluation (FCE) provides the information necessary for rational design decisions when modifying work stations. The currently used FCE systems have been designed to assess an individual's performance for a range of reasons other than industrial task accommodation. The Available Motions Inventory (AMI) is a system that has been developed specifically to address the design issues raised when accommodating an industrial task to a person with a neuromuscular impairment. This system has a unique scoring system that allows intra-individual ability comparisons that support task allocation decisions. Some general principles of task design are developed for persons with cerebral palsy, but the strength of assessment lies in its application to a specific individual performing a specific task.

Atrioventricular septal defect: quantitative anatomy of the left ventricle

A morphometric study was performed in 18 human hearts with atrioventricular septal defect not associated with other anomalies; 16 hearts had common atrioventricular orifices, and 2 presented separate right and left atrioventricular orifices. A total of eight parameters were analyzed, characterizing ventricular wall thickness, length and circumference of the inflow and outflow tracts, and circumference of the left orifice and aortic orifice. The data were compared with previously published patterns of normality. In addition, the volume of the aortic outflow tract was calculated. The inflow tract was shorter than the outflow tract, and the length of the diaphragmatic wall was equal to the sum of the lengths of the inflow tract and ventricular wall thickness at the level of the apex.

The effect of music amplitude on the reaction to unexpected visual events

The effects of music amplitude on participants' response time to randomly presented, unexpected, visual events were investigated. Ninety participants completed a motor-reaction task without music and with music played at 60, 70, or 80 dBA. Males preferred more intense music than females did, with males selecting a comfort level of 72 dBA and females, 66 dBA. However, participants' reaction time and the total time to respond to a randomly activated red light were independent of gender. All participants responded more quickly when the music was played at 70 dBA (close to their comfort level) than when it played at lower (60 dBA) or higher (80 dBA) amplitudes. It is proposed that people may react more quickly to visual events (e.g., the sudden appearance of a plane on the screen of an air traffic controller, or the unpredictable activation of a car's rear brake lights when driving) with music playing at a volume preset to maintain individual comfort levels against other situational background noise.

Psychophysical frequency and sustained exertion at varying wrist postures for a drilling task

Two laboratory experiments were conducted; first, to utilize the psychophysical approach (method of adjustment) to establish maximum acceptable frequency (MAF) for a sheet metal drilling task and, second, to examine the effect of sustained, static exertion upon objective and subjective measures under similar task conditions. In both experiments, the wrist posture (flexation, ulnar deviation) required by the task was varied. Twelve healthy females served as subjects. Results show that the psychophysically adjusted task frequency was significantly lower when wrist deviation was required, particularly flexion. MAF for one-third (25 degrees) and two-thirds (50 degrees) flexion were 88% and 73%, respectively, of those selected in the neutral posture. Furthermore, these results were supported by trends in grip strength, heart rate, blood pressure, EMG and perceived exertion. Results from the sustained exertion trials revealed that significant increases in physiological parameters occurred during 3-minute sessions and that this trend was exasperated with deviated wrist posture, particularly flexion. Considering results of both experiments, it was concluded that while the neutral wrist posture may be preferred for a drilling operation, task frequency should be reduced for deviated postures when redesign is not feasible and it is further recommended that deviation be limited to one-third maximum flexion (25 degrees) and two-thirds maximum ulnar deviation (30 degrees). It is also suggested that the psychophysical approach may be utilized to establish 'acceptable' parameters for other industrial tasks involving upper extremity stress, particularly in the current absence of more objective biomechanical and/or physiological criteria for reducing the risk of exposure to cumulative trauma disorders.

Differentiation of a human rhabdomyosarcoma cell line after antineoplastic drug treatment

The feasibility of treating solid tumours with differentiation therapy using antineoplastic drugs is currently being investigated, but the emergence of multidrug resistance remains the major limitation to this therapeutic approach. A rhabdomyosarcoma cell line resistant to actinomycin D (RD-DAC) has been used as an in vitro model to investigate, with light and electron microscopy, the degree of differentiation in multidrug-resistant cells. The parental cell line (RD), derived from a human embryonic-type rhabdomyosarcoma, is undifferentiated, with no evidence of specific ultrastructural markers. Examination of resistant cells by transmission electron microscopy revealed myofilaments arranged parallel to the long axis of the cell, which was considered clear evidence of myogenic differentiation. These observations suggest that actinomycin D, the drug of choice in the treatment of rhabdomyosarcoma, induces differentiation in the cell line RD. It is postulated that multidrug resistance can interfere with cellular differentiation.

Maximum acceptable frequencies for females performing a drilling task in different wrist postures

This paper presents a study on the effect of wrist posture; flexion, extension, ulnar deviation, and radial deviation on maximum acceptable frequencies (MAF) for a drilling task using a psychophysical approach. Twelve females were selected from a college population to serve as subjects and an adjustable workstation was used to simulate a drilling task. The results revealed that flexion, extension, and radial deviation all had a significant effect on MAF but, ulnar deviation did not. The postures have been ranked in order of possible risk of contributing to CTD injury, with neutral having the lowest rank (lowest risk) and flexion having the highest rank (greatest risk).

Psychophysically acceptable weights for a combination lifting task using bags with handles

This paper presents a study on a combination lift and lower manual handling task and was designed to simulate the loading of grocery bags into a car trunk. Twelve male subjects performed an externally paced task of lifting grocery bags loaded with weights from 15 cm above the floor and over a wooden sill. There were two different sill heights of 70 cm and 90 cm, and for each of these heights there were two frequencies of 3 and 6 lifts per cycle. The dependent variables were maximum acceptable weight of lift (MAWOL). A unique lifting sequence and a modified version of the psychophysical methodology were used to determine MAWOL. There was a significant difference in the MAWOL across the two sill heights as well as the MAWOL at the two different frequencies. Plastic bags were determined to increase the average load lifted by 27% as compared to paper bags. At normal grocery bag weights, the increased load carrying capacity represents an increase in the safety factor. Not only can the risk of lower back injuries be decreased by using plastic bags with handles but the risk of developing a cumulative trauma disorder could also be decreased.

Expression of epidermal growth factor receptor in chick embryo myocardiocytes: relation with desmin expression during cardiac development

The epidermal growth factor receptor is related with processes of cell replication and differentiation. We used the intermediate filament protein desmin as a marker to study the relation between muscle cell differentiation and modifications in the expression of this receptor during heart development in the chick embryo. Epidermal growth factor receptor was expressed as early as Hamburger and Hamilton's stage 17, when myocardiocytes are still poorly differentiated and desmin-negative. Expression became steadily weaker as the heart matured, and decreased after Hamburger and Hamilton's stage 25, a key stage in heart maturation characterized by a sharp increase in desmin expression. Our findings suggest that in the chick embryo, the expression of epidermal growth factor receptor becomes steadily weaker as myocardiocyte differentiation progresses.

Actin, tropomyosin and alpha-actinin as markers of differentiation in human rhabdomyosarcoma cell lines induced with dimethyl sulfoxide

Most rhabdomyosarcomas are poorly differentiated malignant tumors. Dimethyl sulfoxide has been shown to modulate cell differentiation in cultured human cells. We induced differentiation in human rhabdomyosarcoma cell lines A-673, RD and A-204 with 1.25% dimethyl sulfoxide, and used desmin, the protein most frequently used as a marker of muscle cell differentiation, to trace this process. As alternative markers of the degree of differentiation, we quantified the expression of the proteins actin, tropomyosin and alpha-actinin in these cell lines, and followed the changes in expression of these proteins after induction for 8, 12, 24, 48 and 72 hrs. In the process of differentiation, protein expression in both the cytoplasm and cytoskeleton was significantly increased by treatments lasting 12 hrs. (alpha-actinin) and 24 hrs. (actin). On the basis of our results, alpha-actinin can be considered as an earlier marker of differentiation than actin in human rhabdomyosarcoma cell lines. However, the earliest indication of differentiation was a modification in desmin expression (8 hrs.). Because changes in tropomyosin expression were less marked, we consider this protein as a poor marker of rhabdomyosarcoma cell differentiation.

Training of ambulatory individuals with cerebral palsy

The effect of training on the physical work capacity (PWC) and the physiological response to simulated tasks of seven ambulatory individuals with cerebral palsy (CP) were studied. Energy demand for each work task was determined by percentage of PWC (%PWC). Results indicate that an eight week training program increased the PWC as evaluated by an exercise test on the Schwinn Air-Dyne Ergometer. The performance of the individuals for the simulated tasks measured in %PWC increased significantly, suggesting that individuals with CP could benefit from a training program and would be able to work eight hours before experiencing fatigue.

A treatment for carpal tunnel syndrome: results of a follow-up study

OBJECTIVE

This study was a follow-up evaluation of carpal tunnel syndrome (CTS) subjects based on objective and subjective measures utilizing a conservative treatment method. It was hypothesized that the CTS individuals would maintain their improvements over the course of a 6-mo period after treatments.

DESIGN

The design used was a case control study in which the improvements of the CTS subjects were compared within themselves and with a matched comparison group. The treatments were performed at a private chiropractic clinic, and the objective and subjective measures were independently taken in an industrial engineering laboratory. All CTS subjects were volunteers from a random sample. Forty-three individuals were evaluated at the pretreatment period and in the 6-mo follow-up. Only 22 subjects returned for reevaluation. The treatment duration was not controlled.

RESULTS

The results indicate that CTS subjects had maintained improvements in most of the objective measures and pain and distress ratings over the pretreatment level (p < .05) at 6 mo post-treatment. When compared to a matched comparison group, CTS-treated subjects demonstrated no significant differences (p < .05) in grip strength (for females), pinch strength, forearm pronation and supination forces, assembly task performance and pain and distress scores.

CONCLUSION

The results of statistical analyses indicate that CTS subjects can be treated and achieve a significant recovery to within normal comparative levels of non-CTS subjects in most subjective and objective measures.

Production of a new monoclonal antibody recognizing alpha-actinin: analysis of the changes in subcellular expression in the developing chick heart

A new monoclonal antibody that recognizes alpha-actinin in cardiac muscle cells was used in a quantitative study (fluorescence activated cell sorting and polyacrylamide gel electrophoresis) of the expression of this protein during chick embryo development, to determine the changes in cytoplasmic and cytoskeletal compartments. alpha-Actinin expression was weak in early stages of development (Hamburger and Hamilton stage 18) and increased steadily until Hamburger Hamilton stage 40. In all stages, the protein was more abundant in the cytoplasmic compartment. The monoclonal antibody cross-reacted with alpha-actinin in chicken smooth and striated muscle cells and also showed a faint cross-reaction with human cardiac muscle alpha-actinin.

A treatment for carpal tunnel syndrome: evaluation of objective and subjective measures

This study was designed to assess the efficacy of a proposed new and unique program relative to treatment and troubleshooting for diagnostic causes of carpal tunnel syndrome (CTS). Objective measures of anthropometry, strength, range of motion, muscle activity, and task performance, together with subjective ratings of pain were observed in a group of individuals diagnosed with CTS. These measures were compared to a control population showing no symptoms of CTS prior to undergoing treatment and following completion of the treatment program. Results indicate that individuals with CTS had significantly lower values on some strength, range of motion, and slower task performance than did the control group. Ratings of pain and distress were also significantly higher than the controls, and in the literature the CTS group's values approached levels of chronic pain. Analysis of posttreatment cases revealed statistically significant improvements in several strength measures of up to 25% over pretreatment values. Significant improvement was also shown in several range of motion measures of up to 22%. Finally, a significant reduction of 15% in pain and distress ratings was demonstrated in the posttreatment cases.

Morphometric study of right ventricle in 32 cases of tetralogy of Fallot

The right ventricle was the object of a morphometric study in a total of 32 human hearts with tetralogy of Fallot. Most subjects died in the perinatal period and weighed between 720 and 5,000 g. Nine internal parameters were measured in each right ventricle and substituted into the appropriate stereometric formula to yield volumes for each right ventricular chamber. The data obtained were compared to patterns of normality previously obtained by mathematical analysis. The results can be summarized as follows: 1. The right ventricular wall in the present series was thicker than normal, particularly near the tricuspid valve annulus. 2. Pulmonary valve and pulmonary infundibulum perimeter were below normal. 3. Tricuspid valve perimeter was above normal. 4. Above normal figures were obtained for length and volume of the right ventricular inflow tract. 5. Increased outflow tract length contrasted with below normal figures for outflow tract volume. 6. In a large number of cases (95%) the distance between the crista supraventricularis and the pulmonary sigmoid leaflets was reduced. Characterization of these changes may help to elucidate the embryological origin of tetralogy of Fallot.