Novel Automated Suturing Technology for Minimally Invasive Mitral Chord Implantation: A Preclinical Evaluation Study

OBJECTIVE

This study evaluated the ergonomics and time requirements of using a novel automated suturing and titanium fastener deployment technology for chordal replacement in human heart specimens in open and minimally invasive cardiac surgery (MICS) simulators.

METHODS

Five cardiac surgeons used novel, manually powered expanded polytetrafluoroethylene (ePTFE) suturing devices to automate suture placement between mitral leaflets and papillary muscles in explanted cadaver hearts, along with customized titanium fastener delivery devices to secure suture and trim suture tails. This mitral chordal replacement test was conducted using surgical models simulating open and MICS mitral repair access. The study was approved by the institutional ethical board.

RESULTS

After a brief introduction to this technique using plastic models, study surgeons performed 48 chordal replacements in human mitral valves, placing 18 in an open model and 30 in a right minithoracotomy model. The time range to complete a single chordal replacement was between 55 s and 8 min, with an overall mean duration of 3.6 ± 1.5 min. No difference in duration of implantation was recorded for the MICS and open sternotomy simulators used. Good control of suture delivery was reported in 95.8% (n = 46) of leaflet aspect of the sutures and in 100% (N = 48) of papillary muscle sutures.

CONCLUSIONS

Automated mitral chordal ePTFE suturing simulated through open and MICS access demonstrated quality handling and accurate placement of sutures in human heart specimens. A clinical trial using this technology is currently ongoing. This innovation may present an important advance facilitating enhanced minimally invasive mitral valve repair.

Effect of conventional and rapid-deployment aortic valve replacement on the distance from the aortic annulus to coronary arteries

OBJECTIVES

This study aimed to compare the effect of surgical aortic valve replacement (SAVR) on coronary height in patients undergoing SAVR with rapid-deployment or SAVR with several standard sutured bioprostheses. This study may identify patients at higher risk of coronary obstruction during valve-in-valve procedures.

METHODS

We analysed 112 patients [mean age 71 (9 SD) years] who underwent SAVR with either a rapid-deployment aortic bioprosthesis (EDWARDS INTUITY Elite Valve) or other standard sutured biological valves. The coronary heights were assessed by computed tomography scan with the Philips 3D HeartNavigator system.

RESULTS

Two groups of patients were analysed: 51 (45.5%) patients implanted with an RD-AVR, which is a supra-annular valve that requires 3 anchoring sutures without the use of pledgets, and 61 (54.5%) patients implanted with a conventional supra-annular sutured bioprosthesis. The mean right and left coronary artery-to-annulus (RCAA and LCAA) heights at baseline were 16.9 (4.6 SD) and 14.2 (4.0 SD) mm in the standard sutured group and 16.3 (3.5 SD) and 12.8 (2.9 SD) mm in the RD-AVR group, respectively; a significantly shorter distance was observed for the left coronary artery in the rapid-deployment group (P = 0.420 for RCAA height and P = 0.044 for LCAA). Postoperatively, the mean RCAA and LCAA heights were significantly decreased in both groups compared to baseline. A mean of 11.5 (4.8 SD) mm for the RCAA and 7.9 (4.3 SD) mm for the LCAA in the standard sutured group as well as 14.4 (3.9 SD) mm for the RCAA and 9.0 (3.1 SD) mm for the LCAA in the RD-AVR group were observed (P < 0.001 for RCAA and LCAA in both the sutured and rapid-deployment groups). Despite the significant difference in the mean distance from the left coronary artery to annulus between the groups at baseline, the postoperative mean distance of the LCAA to the sewing ring was still higher in the RD-AVR group.

CONCLUSIONS

A significantly shorter coronary artery-to-aortic annulus distance for both the right and left main coronary arteries was observed after AVR with different conventional sutured supra-annular bioprostheses compared to AVR with rapid-deployment valves. These findings might be relevant for bioprosthesis selection, especially for young patients.

Maximum Ankle Plantarflexion and Dorsiflexion Allow for Optimal Arthroscopic Access to the Talar Dome: An Anatomic 3-Dimensional Radiography Study

PURPOSE

(1) to improve the comprehension of the topographical position of the talar dome beneath the inferior articular surface of the tibia and, (2) to illustrate the changes of possible access to the articular surface of the talar dome during arthroscopic treatment of talar osteochondral defects in an anatomical model.

METHODS

Twenty matched pairs (n = 40) of anatomical ankle specimen were used. All specimens were mounted in a standardized fashion, 3-dimensional radiography was performed in 4 defined positions (maximum dorsiflexion, neutral position, noninvasive distraction, and maximum plantarflexion). All radiographs were analyzed and statistically compared.

RESULTS

Anterior accessibility was highest in maximum plantarflexion (medial: 49.20 ± 9.86%, lateral: 48.19 ± 8.85%), followed by non-invasive distraction (medial: 33.60 ± 7.96%, lateral: 31.98 ± 8.30%). Neutral position (medial: 19.34 ± 6.90%, lateral: 17.54 ± 6.63%) and dorsiflexion (medial: 15.36 ± 5.03%, lateral: 13.88 ± 4.33%) were not able to significantly increase accessibility. Posterior accessibility was greatest in maximum dorsiflexion (medial: 56.69 ± 9.65%, lateral: 46.82 ± 8.36%), followed by neutral position of the ankle joint (medial: 40.95 ± 8.28%, lateral: 31.06 ± 6.92%). Noninvasive distraction (medial: 31.41 ± 8.18%, lateral: 22.99 ± 7.63%) was still significantly better than plantarflexion (medial: 14.54 ± 5.10%, lateral: 13.89 ± 3.14%) and slightly increased accessibility to the talar dome. Medially, a central area of 5.89 ± 9.76% was accessible by maximum plantarflexion and maximum dorsiflexion from anterior and posterior, respectively, laterally a central blind spot of 4.99 ± 8.61% was detected.

CONCLUSIONS

From an anatomical point of view, maximum joint positions of the ankle (i.e., plantarflexion and dorsiflexion) allow for better access to the talar dome in anterior and posterior ankle arthroscopy. Noninvasive distraction may increase accessibility in anterior approaches, but has no benefit from posterior.

CLINICAL RELEVANCE

This study provides insight into the morphology of the ankle joint in a standardized laboratory setup and illustrates the influence of different surgically relevant ankle joint positions. The presented data allow for better preoperative planning for the arthroscopic treatment of talar osteochondral defects.

Mitral Butterfly: Preclinical Experience of a Novel Chordal Repair Device Using an Artificial Papillary Muscle

Transcatheter mitral repair is based on the principle of artificial monochordal repair. In this paper, the authors show an alternative, based on the realization of an artificial papillary muscle concept that avoids multiple chordal replacements and fixation in the myocardium. Unlike the interposition of artificial chordae between the free edge of the leaflet and the myocardium, the so-called Mitral Butterfly device collects a multitude of chordae in a matrix connected to a swing arm, stabilizing prolapsing forces with a broad atrial support. Device testing in chronic animal models and in silico substantiated the underlying device concept and performance after 90 days.

Off-pump tricuspid valve repair by automated sutured tricuspid annular plication via transatrial cannulation: preclinical ex vivo and in vivo results

OBJECTIVES

Surgical repair is considered the gold standard treatment for severe symptomatic tricuspid valve (TV) regurgitation. However, patients undergoing isolated surgical tricuspid repair face a high perioperative mortality while long-term data on interventional treatment options are currently missing. We investigated a novel, minimally invasive approach for transatrial off-pump beating-heart tricuspid annular plication based on the surgical Hetzer repair.

METHODS

TV annular plication for the creation of a double-orifice valve using novel devices for automated annular suturing was performed in 10 human heart specimens in an ex vivo perfusion model under endoscopic guidance. Additionally, the technique was tested in an in vivo porcine model using the transatrial access under echocardiographic and fluoroscopic guidance.

RESULTS

Endoscopically guided conduction of the procedure was successful in all 10 human heart specimens in the ex vivo perfusion model with 1 observed suture pull-through of 60 sutures placed (1.7%). TV measurements yielded significant reductions of the TV septal-lateral diameter (50.9 ± 7.3 vs 42.6 ± 7.9 mm; P = 0.015) and the TV area (1208 ± 399 vs 193 ± 122 mm2; P < 0.0001). TV plication without direct vision using device-embedded intracardiac echocardiography, epicardial echocardiography and fluoroscopy was feasible in both acute animals with no observed device-related adverse events.

CONCLUSIONS

Successful plication was completed in 10 ex vivo human hearts, additionally proof-of-concept was conducted in 2 animals. We herein present encouraging early preclinical results of a novel minimally invasive technique for TV repair, which warrants further investigation.

Vascular coverage of the anterior knee region - an anatomical study

Descriptions of vessel angiosomes or perforasomes throughout the human body are quite frequent, and led to the development of flaps nowadays commonly used to surgically cover skin and soft tissue defects. In these procedures, the surgeon requires a profound anatomical knowledge of the respective blood vessels and the extent of the perfused area to define the size of the graft. In the region of the knee joint, descriptions of flaps based on the superior lateral genicular artery and descending genicular artery are quite frequent. In contrast, information regarding other popliteal branches is scarce or non‐existent. The aim of this study was to provide a concise and complete overview on the extent and variability of the perforator angiosomes of the femoral and popliteal arteries in the anterior knee region. Twenty lower extremities were dissected, the respective perforators identified and perfused with dye. All resulting angiosomes were marked and documented. A total of 84 angiosomes were identified in all specimens, with an average of 4.2 (3–6) angiosomes per specimen. The average size of the angiosomes was 97.04 ± 72.30 cm² (8.61–360.41 cm²), their source vessels had an average diameter of 1.42 ± 0.54 mm (0.60–3.25 mm). The complex and highly variable distribution of perforator angiosomes of the anterior knee region and especially of its less frequently investigated distal part was demonstrated. Based on these results, the planning of existing perforator flaps in this region and the development of flaps including the inferior medial or inferior lateral genicular arteries may be facilitated.

The Twist of the Achilles Tendon - Associations of Torsions in the Lower Extremity

Achilles tendinopathy and rupture of the Achilles tendon (AT) are frequent pathologies. Even though they may be associated with the twisted morphology of the AT, quantitative data on the extent of the twist of the entire AT are not available. The aim of this study was to investigate the torsion of the AT based on its individual parts and to evaluate a possible correlation with the torsion of the long bones of the lower extremity. Forty embalmed lower extremities were included in this study. The lateral deviation of the AT and its torsional angle as well as the angles of the individual parts in trans-section were measured. Thereafter, the torsions of femur and tibia were evaluated. Measuring the lateral deviation of the fibers resulted in an average torsion of the AT of 34.59° (SD 16.8°). The angles of the different parts of the AT in trans-section resulted in a median AT torsion of 15.73°, showing various patterns of rotations of the individual muscles. A statistically significant correlation between the torsions of the lower extremity and the AT (P =0.0242, r = 0.40) as well as a correlation between the femoral torsion and the AT torsion (P = 0.0127, r = 0.44) were found. This study adds to the morphological understanding of the torsion of the AT and its correlation with the torsions of the long bones of the lower extremity. Especially, the torsion of the femur seems to be connected to the torsion of the tendon. Clin. Anat. 31:1085-1091, 2018. © 2018 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

RNA editing of Filamin A pre-mRNA regulates vascular contraction and diastolic blood pressure

Epitranscriptomic events such as adenosine-to-inosine (A-to-I) RNA editing by ADAR can recode mRNAs to translate novel proteins. Editing of the mRNA that encodes actin crosslinking protein Filamin A (FLNA) mediates a Q-to-R transition in the interactive C-terminal region. While FLNA editing is conserved among vertebrates, its physiological function remains unclear. Here, we show that cardiovascular tissues in humans and mice show massive editing and that FLNA RNA is the most prominent substrate. Patient-derived RNA-Seq data demonstrate a significant drop in FLNA editing associated with cardiovascular diseases. Using mice with only impaired FLNA editing, we observed increased vascular contraction and diastolic hypertension accompanied by increased myosin light chain phosphorylation, arterial remodeling, and left ventricular wall thickening, which eventually causes cardiac remodeling and reduced systolic output. These results demonstrate a causal relationship between RNA editing and the development of cardiovascular disease indicating that a single epitranscriptomic RNA modification can maintain cardiovascular health.

Pledget-Armed Sutures Affect the Haemodynamic Performance of Biologic Aortic Valve Substitutes: A Preliminary Experimental and Computational Study

Surgical aortic valve replacement is the most common procedure of choice for the treatment of severe aortic stenosis. Bioprosthetic valves are traditionally sewed-in the aortic root by means of pledget-armed sutures during open-heart surgery. Recently, novel bioprostheses which include a stent-based anchoring system have been introduced to allow rapid implantation, therefore reducing the duration and invasiveness of the intervention. Different effects on the hemodynamics were clinically reported associated with the two technologies. The aim of this study was therefore to investigate whether the differences in hemodynamic performances are an effect of different anchoring systems. Two commercially available bio-prosthetic aortic valves, one sewed-in with pledget-armed sutures and one rapid-deployment, were thus tested in this study by means of a combined approach of experimental and computational tools. In vitro experiments were performed to evaluate the overall hydrodynamic performance under identical standard conditions; computational fluid dynamics analyses were set-up to explore local flow variations due to different design of the anchoring system. The results showed how the performance of cardiac valve substitutes is negatively affected by the presence of pledget-armed sutures. These are causing flow disturbances, which in turn increase the mean pressure gradient and decrease the effective orifice area. The combined approach of experiments and numerical simulations can be effectively used to quantify the detailed relationship between local fluid-dynamics and overall performances associated with different valve technologies.

Conventional versus rapid-deployment aortic valve replacement: a single-centre comparison between the Edwards Magna valve and its rapid-deployment successor

OBJECTIVES

Sutureless and rapid-deployment valves were recently introduced into clinical practice. The Edwards INTUITY valve system is a combination of the Edwards Magna pericardial valve and a subvalvular stent-frame to enable rapid deployment. We performed a parallel cohort study for comparison of the two valve types.

METHODS

All patients receiving either an Edwards Magna Ease valve or an Edwards INTUITY valve system due to aortic stenosis from May 2010 until July 2014 were included. Patients undergoing bypass surgery, an additional valve procedure, atrial ablation surgery or replacement of the ascending aorta were excluded. Preoperative characteristics, operative specifications, survival, valve-related adverse events and transvalvulvar gradients were compared.

RESULTS

One hundred sixteen patients underwent rapid-deployment aortic valve replacement [mean age 75 years (SD: 8); 62% female] and 132 patients underwent conventional aortic valve replacement [70 years (SD: 9); 31% female; P < 0.001]. Conventional valve patients were taller and heavier. The mean EuroSCORE II was 3.1% (SD: 2.7) and 4.4% (SD: 6.0) for rapid-deployment and conventional valve patients, respectively (P = 0.085). The mean implanted valve size was higher in the conventional group [23.2 mm (SD: 2.0) vs 22.5 mm (SD: 2.2); P = 0.007], but postoperative transvalvular mean gradients were comparable [15 mmHg (SD: 6) vs 14 mmHg (SD: 5); P = 0.457]. A subgroup analysis of the most common valve sizes (21 and 23 mm; implanted in 63% of patients) revealed significantly reduced mean postoperative transvalvular gradients in the rapid-deployment group [14 mmHg (SD: 4) vs 16 mmHg (SD: 5); P = 0.025]. A significantly higher percentage received minimally invasive procedures in the rapid-deployment group (59 vs 39%; P < 0.001). The 1- and 3-year survival rate was 96 and 90% in the rapid-deployment group and 95 and 89% in the conventional group (P = 0.521), respectively. Valve-related pacemaker implantations were more common in the rapid-deployment group (9 vs 2%; P = 0.014) and postoperative stroke was more common in the conventional group (1.6 vs 0% per patient year; P = 0.044).

CONCLUSIONS

We conclude that this rapid-deployment valve probably facilitates minimally invasive surgery. Furthermore, a subgroup analysis showed reduced transvalvular gradients in smaller valve sizes compared with the conventionally implanted valve of the same type. The favourable haemodynamic profile and the potentially different spectrum of valve-related adverse events should be addressed in further clinical trials.

Primary cardiac tumors on the verge of oblivion: a European experience over 15 years

Background

Primary tumors of the heart represent an exceedingly rare entity in cardiac surgery and literature regarding management and outcome is rare. The aim of this study was to translate 15 years of experience in both multimodal diagnosis and surgical treatment of one of the largest collective of patients in literature into a detailed analysis of patient prognosis, mean survival and best treatment approach.

Methods and results

All patients who underwent open-heart surgery at the Hospital of the Medical University of Vienna for primary cardiac tumor excision between 1999 and 2014 were analyzed retrospectively. Mean follow-up was 76.8 months. Descriptive statistical measurements were applied.

113 patients were identified, 71 (62.8%) female and 42 (37.2%) male patients with a mean age of 57.9 ± 16.8 years. 90.3% (n = 102) masses were benign, 9.7% (n = 11) were malignant. Complete resection was possible for 99% and for 18.2% of benign and malignant masses, respectively. 2.9% of benign tumors and 45.5% of malignant tumors relapsed. The 30-day mortality was 1.8% (n = 2). Mean survival was 187.2 ± 2.7 months and 26.2 ± 9.8 months for benign and malignant pathologies, respectively. Sarcoma patients who underwent adjuvant combination-chemotherapy or adjuvant mono-chemotherapy and radiation had a statistically significant survival advantage of 41.5 months.

Conclusion

Primary cardiac tumors remain challenging in the clinical setting. A multimodality treatment approach especially for sarcoma patients prolongs mean survival and should be regarded as the standard of care.

Left ventricular thrombus in a patient with cutaneous T-cell lymphoma, hypereosinophilia and Mycoplasma pneumoniae infection - a challenging diagnosis: a case report

Differential diagnoses of cardiac masses include primary benign and malignant neoplasms, secondary neoplasms, and non-neoplastic masses, such as thrombi. Owing to different therapeutic approaches and the way these affect the prognosis, the early and correct diagnostic determination of the etiology of a cardiac mass is of utmost importance and essential for the appropriate management of patients.

We report a case of a 52-year-old woman with a left ventricular mass in the setting of a recent Mycoplasma pneumoniae infection and a medical history of cutaneous T-cell lymphoma and hypereosinophilia. Imaging findings were consistent with both an infiltrative process of the lymphoma and a cardiac thrombus. An estimated very high risk for embolization led to the indication for open-heart surgery for the removal of the cardiac mass. Histopathological examination confirmed the presence of a thrombus; there were no signs of malignancy. The patient was discharged 11 days after surgery in good general condition and is now in outpatient care for follow-up and further management.

This case highlights possible challenges in the diagnostic assessment of cardiac masses and their management in a patient with several underlying diseases and a complex medical history.

A rare case of obstructive right atrial lipoma

Benign cardiac tumours are rare and cardiac lipomas account only for a small fraction among those. Most of these tumours differ in terms of clinical manifestation, diagnosis, morphology and size, and are therefore not diagnosed easily unless they become symptomatic. We report the case of a 71-year-old Caucasian woman with recurrent episodes of shortness of breath presenting with an acute exacerbation of dyspnoea and hypertensive crisis. Diagnosis of a right atrial lipoma with a coexisting patent foramen ovale was established on echocardiography and computed tomography, and the patient was evaluated for elective surgery. Comprising the entire free wall of the right atrium, the tumour was removed during open heart surgery on cardiopulmonary bypass. The right atrium and the orifices of both the superior and inferior vena cava were reconstructed with bovine pericardium. No evidence of tumour relapse was observed during successive follow-up visits.

Pacemaker lead malpositioning led to subsequent ischemic strokes despite antiplatelet and anticoagulation therapy

Pacemaker lead malpositioning may lead to severe clinical adverse events. Rarely, cases of inadvertent placement of a lead into the left ventricle are reported in the literature. We herein report a case of pacemaker lead malpositioning into the left ventricle via a persistent foramen ovale in a male caucasian patient. After this procedural adverse event, the patient suffered from two ischemic strokes despite antiplatelet and anticoagulation therapy.

Pacemaker lead malposition in the left atrial roof is masked by normal pacing thresholds

Pacemaker lead malpositioning with subsequent cardiac tamponade is a rare, but serious adverse event. We herein report a case of pacemaker lead malpositioning in a 76-year old female caucasian patient. The lead was malpositioned into the roof of the left atrium after perforation of the superior vena cava, resulting in cardiac tamponade. After fast surgical revision and an uneventful post-operative period, the patient was discharged in excellent condition.

A rare case of primary cardiac B cell lymphoma

Primary cardiac lymphomas represent an extremely rare entity of extranodal lymphomas and should be distinguished from secondary cardiac involvement of disseminated lymphomas belonging to the non-Hodgkin’s classification of blood cancers. Only 90 cases have been reported in literature. Presentation of cardiac lymphomas on imaging studies may not be unambiguous since they potentially mimic other cardiac neoplasms including myxomas, angiosarcoma or rhadomyomas and therefore require multimodality cardiac imaging, endomyocardial biopsy, excisional intraoperative biopsy and pericardial fluid cytological evaluation to establish final diagnosis.

Herein we report the case of a 70 y/o immunocompetent Caucasian female with a rapidly progressing superior vena cava syndrome secondary to a large primary cardiac diffuse large B cell lymphoma (NHL lymphoma) almost completely obstructing the right atrium, right ventricle and affecting both mitral and tricuspid valve. The patient had no clinical evidence of disseminated disease and was successfully treated with extensive debulking during open-heart surgery on cardiopulmonary bypass and 6 cycles of rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone chemotherapy (R-CHOP).

Giant lateral left ventricular wall aneurysm sparing the submitral apparatus

Left ventricular aneurysms are a frequent and serious complication following acute transmural myocardial infarction and are most commonly located at the ventricular apex. The majority of these patients presents with severe mitral insufficiency, congestive heart failure, systemic embolism and sudden cardiac death. Giant aneurysms occurring in a submitral position between anterior and posterior papillary muscles on the lateral ventricular wall constitute a minor entity and those leaving the mitral apparatus intact are extremely rare.

Herein, we report the case of a 57 y/o Caucasian male patient with a past medical history of coronary artery disease and myocardial infarction with a giant left ventricular aneurysm measuring 15x10x8 cm in diameter. Despite the size of the aneurysm and its close topographical relation to the posterior mitral annulus the mitral apparatus was intact with a competent valve and normal left atrial size. He underwent successful surgical ventricular restoration.

Repeat measurements of glycated haemoglobin A(1c) and N-terminal pro-B-type natriuretic peptide: divergent behaviour in diabetes mellitus

BACKGROUND

Patients with diabetes mellitus have a substantially increased risk of developing cardiovascular disease. However, the absolute risk greatly varies not only among patients, but the risk profile for an individual patient may also change over time. We investigated the prognostic role of repetitive measurements of Glycated haemoglobin A(1c) (HbA(1c) ) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) in patients with longstanding diabetes.

MATERIALS AND METHODS

For this prospective, observational study data from 544 consecutive patients were collected between 2005 and 2008. HbA(1c) and NT-proBNP were measured at baseline and after 1 year. The median observation period was 40 months. Endpoints were all-cause mortality, cardiac, cardiovascular and all-cause hospitalizations.

RESULTS

N-terminal pro-B-type natriuretic peptide concentrations significantly increased from 230 ± 385 to 280 ± 449 pg mL(-1) (P < 0·001); during the same time, HbA(1c) significantly decreased from 7·6 ± 1·5 to 7·3 ± 1·2 (P < 0·001). NT-proBNP was the best baseline predictor in a Cox regression model consisting of NT-proBNP, HbA(1c) , age, gender and duration of diabetes for all endpoints (P < 0·001). NT-proBNP at follow-up was the best predictor for the remaining period (P < 0·001, all endpoints). HbA(1c) at baseline and follow-up was predictive for all-cause hospitalizations (P = 0·005 both). In a third model that investigated the plasticity of both markers, changes in HbA(1c) concentration had no predictive value, but a change of NT-proBNP concentration was highly predictive (P = 0·025 all-cause mortality, P < 0·001 all other endpoints).

CONCLUSIONS

N-terminal pro-B-type natriuretic peptide and HbA(1c) concentrations significantly diverged over a 1-year period. NT-proBNP was the most potent predictor of outcome at baseline and follow-up, and changes in NT-proBNP concentrations were linked to an altered risk profile, unlike changes in HbA(1c) levels.

Scaling-index method as an image processing tool in scanning-probe microscopy

The scaling-index method (SIM) is a novel tool for image processing in scanning-probe microscopy. Originating from the theory of complex systems, the SIM can be used in order to extract structural information from arbitrary data sets. This method can readily be applied to the analysis of digital atomic-force microscopy (AFM) images. Especially for biomedical diagnostics, where genetic material is investigated by various microscopic methods, a reliable image segmentation based on the SIM algorithm is helpful. As a first application, AFM-images of GTG-banded human metaphase chromosomes (with G bands obtained by Trypsin using Giemsa) are compared with micrographs from conventional light microscopy by means of a scaling-index analysis. While the grey-level distributions of the optical and the AFM-images are largely different from each other, the scaling-index images are remarkably similar. Using this method, a fingerprint of an image can be produced which helps in the classification and interpretation of the measured data.

Microstructural and Magnetic Studies on Hydrothermally Prepared Hematite

Hematite particles of various shapes and sizes have been prepared hydrothermally at different pH values ranging from 3 to 10 from ferric chloride solution at 180&deg;C. Particle size decreases with an increase in the pH of precipitation as observed from Transmission Electron Micrographs (TEM). A comparison of TEM and mean crystallite diameter (MCD) from XRD data reveals that the particles prepared are polycrystalline in nature. The polycrystallinity decreases with an increase in the pH of precipitation, and at pH 10 almost single crystalline nature of particles is obtained. Polycrystalline monodispersed pseudocubic particles obtained at pH 3 exhibit very high coercive force and remanent magnetization which decreases with an increase in pH, whereas Morin transition temperature, Tm, shows an opposite trend. Magnetic a.c. susceptibility increases with an increase in pH up to pH 7 and then decreases. A probable mechanism for the formation of polycrystalline particles has been suggested in order to explain the above trends in magnetic behavior.

Characterization of resistance to essential oils in a strain of Pseudomonas aeruginosa (VR-6)

VR-6, a strain of Pseudomonas aeruginosa, harboured a plasmid and was not inhibited by 20 microliters ml-1 of essential oils (eucalyptus, lemongrass, palmarosa, and peppermint). On treatment with acridine orange, a clone VR-6-AO-1 was obtained which was susceptible to 16.6 microliters ml-1 of eucalyptus or palmarosa oil. The plasmid DNA content of this clone was similar to the parent strain.

Hb Potomac (101 Glu replaced by Asp): speculations on placental oxygen transport in carriers of high-affinity hemoglobins

Blood from a woman with unexplained erythrocytosis had increased oxygen affinity, but no abnormality could be detected by electrophoresis or chromatography of her hemolysate. Separation of the tryptic peptides of her beta chains disclosed two half-sized peaks in the regions of beta T-11. The faster of these was abnormal, with the structure beta 101 Glu replaced by Asp. The new hemoglobin was called "Potomac." Three of the proband's four surviving siblings and both of her children were carriers. Differences in the ratio of carrier: normal children born to male of female carriers of 23 other high-affinity hemoglobins were not significant. The high proportion of carriers in this kindred was probably due to chance alone, and not because high maternal oxygen affinity interfered with oxygen transport to fetuses with normal hemoglobin.