Limitations of Apical Sparing Pattern in Cardiac Amyloidosis: A Multicenter Echocardiographic Study

BACKGROUND

Although impaired left ventricular (LV) global longitudinal strain (GLS) with apical sparing is a feature of cardiac amyloidosis (CA), its diagnostic accuracy has varied across studies. We aimed to determine the ability of apical sparing ratio (ASR) and most common echocardiographic parameters to differentiate patients with confirmed CA from those with clinical and/or echocardiographic suspicion of CA, but with this diagnosis ruled out.

METHODS

We identified 544 patients with confirmed CA and 200 controls as defined above (CTRL Patients). Measurements from transthoracic echocardiograms (TTE) were performed using artificial intelligence software (Us2.AI, Singapore) and audited by an experienced echocardiographer. Receiver-operating characteristic curve analysis was used to evaluate the diagnostic performance and optimal cutoffs for the differentiation of CA patients from CTRL Patients. Additionally, a group of 174 healthy subjects (Healthy CTRL) was included to provide insight on how Patients and Healthy controls differed echocardiographically.

RESULTS

LV GLS was more impaired (-13.9 ± 4.6% vs -15.9 ± 2.7%, p < 0.0005) and ASR was higher (2.4 ± 1.2 vs 1.7 ± 0.9, p < 0.0005) in the CA group vs. CTRL Patients. Relative wall thickness and ASR were the most accurate parameters for differentiating CA from CTRL Patients (AUC: 0.77 and 0.74, respectively). However, even with the optimal cutoff of 1.67, ASR was only 72% sensitive and 66% specific for CA, indicating presence of apical sparing in 32% of CTRL Patients and even in 6% Healthy CTRLs.

CONCLUSIONS

Apical sparing did not prove to be a CA-specific biomarker for accurate identification of CA, when compared to clinically similar controls with no CA.

Value of 3D echocardiography in the diagnosis of arrhythmogenic right ventricular cardiomyopathy

Aims

The 2010 Task Force Criteria (TFC) require that both right ventricular (RV) regional wall-motion abnormalities (WMA) and specific RV size cut-offs be met in order to fulfil one of the major criterion for arrhythmogenic right ventricular cardiomyopathy (ARVC) diagnosis. Currently, 2D echocardiography (2DE) and cardiovascular magnetic resonance imaging (cMRI) are used to determine if these criteria are met. Little is known about the diagnostic value of 3D echocardiography (3DE) in ARVC. The aim of this study was to determine whether a combination of 2DE-3DE is non-inferior to the currently used 2DE-cMRI combination in the diagnosis of patients with ARVC.

Methods and results

Thirty-nine individuals (47±15 years) with suspected ARVC underwent evaluation of the RV with cMRI, 2DE, and 3DE. 3DE and cMRI were independently used to obtain RV volumes, ejection fraction (EF) and determine the presence of segmental RV WMA. Studies were blindly classified as meeting criteria for ARVC in accordance with the 2010 TFC. Kappa statistics were used to test the concordance between 2DE–cMRI and 2DE–3DE approaches. Using the 2DE–cMRI approach, 3/39 were not affected, 5/39 possible, 8/39 borderline, and 23/39 definite ARVC. The proposed 2DE–3DE approach yielded 5/39 not affected, 7/39 possible, 8/39 borderline, and 19/39 definite diagnoses. The two approaches were highly concordant (k = 0.71; 95% confidence interval: 0.44–0.84). Although 3DE underestimated RV volumes in comparison with cMRI, interfering, in some instances with the fulfilment of a major criterion, it was able to identify more RV WMA (28/39) than 2DE (11/39), with a detection-rate comparable to cMRI (33/39) highlighting a unique advantage.

Conclusion

The combination of 2DE–3DE for ARVC diagnosis is comparable to the conventional 2DE–cMRI approach. 3DE should be performed in all suspected ARVC patients to aide in the detection of WMA.

Abnormal longitudinal strain reduction of basal left ventricular segments in patients recovered of COVID-19

Background:

The Severe acute respiratory syndrome coronavirus 2, is the pathogen that causes COVID-19. Cardiovascular (CV) involvement during this infection, has been related to adverse outcomes. Interestingly, some patients may remain symptomatic beyond the first 14 days of disease diagnosis. Although a particular reduction on left ventricular (LV) global longitudinal strain (GLS) in basal segments has been recently described in patients hospitalized with diagnosis of COVID-19, the correlation of these findings with the persistence of symptoms has not been determined.

Objectives:

The objective of this study is to describe echocardiographic findings in patients recovered from COVID-19 and to determine its association with persistent dyspnea.

Methods:

Seventy-six patients were analyzed. Forty-six were asymptomatic (group N°1) and 30 referred persistent dyspnea at the time of examination (group N°2), and a cohort of 25 healthy individuals was included as a control group. Total LV GLS, average basal LV GLS, and average mid-apical LV GLS were assessed. Basal-mid-apical index (BMAI) was calculated. A difference in BMAI bigger than 15% between both groups was stablished as cutoff point.

Results:

Nonsignificative differences on standard echocardiographic measurements were found between the analyzed groups. When compared to the control group, there was nonsignificative reduction on basal LV GLS values in patients with persistent dyspnea. However, BMAI values were bigger than 15% in 70% of patients from group N°2 but in none of the patients from the control group ( = 0.0002).

Conclusions:

This new index allowed to identify an abnormal relation in LV GLS values between basal and medium-apical segments among patients recovered from COVID-19 and persistent dyspnea.

Low-dose radiation therapy for hand osteoarthritis: shaking hands again?

BACKGROUND

Hand osteoarthritis (HOA) is one of the most common causes of pain and functional disability in western countries and there is still no definitive cure. Low-dose radiation therapy (LDRT) has anti-inflammatory properties that have shown to be effective in the symptomatic relief of various degenerative musculoskeletal disorders. We designed a clinical protocol using LDRT for symptomatic HOA and present results and tolerance in the first 100 patients included.

MATERIALS AND METHODS

Between April 2015 and March 2021, 100 patients with a median age of 60 were treated. Fifty-seven patients suffering from proximal/distal interphalangeal joint pain, 40 patients with thumb arthritis, 2 patients with radiocarpal joint affection and 1 patient with metacarpophalangeal joint pain were enrolled. LDRT comprised of 6 fractions of 0.5-1 Gy on every other day up to a total dose of 3-6 Gy. Clinical response was evaluated according to the visual analog scale (VAS) for pain level and the von Pannewitz score (VPS) for joint functionality. Any patients not achieving subjective adequate pain relief after 8 weeks of treatment were offered a second identical LDRT course.

RESULTS

With a median follow-up of 10.5 months (range 7.55-12.45), 94% reported an improvement in the pain, with a significant reduction in the VAS level after 3, 6 and 12 months (p < 0.001). Sixty-three patients needed a second course of treatment at a median time interval of 12 weeks (range 9-14). The mean VAS score before treatment was 8 (range 3-10). After treatment, it was 5 (range 1-10). After 3, 6 and 12 months, the mean VAS scores were 4 (range 0-9), 3 (range 0-9) and 3.5 (range 0-9), respectively. Seventy patients reported functionality improvements after LDRT according to the von Pannewitz score. No acute or late complications were observed.

CONCLUSION

LDRT appears to be safe and useful for HOA and is associated with good rates of pain relief and functionality improvements. However, further studies are necessary to confirm these promising results.

Aortic and Mitral Disease due to an Unusual Etiology

Relapsing polychondritis (RP) is a rare multisystem disease characterized by inflammation in cartilaginous structures and other connective tissues throughout the body, affecting the ears, nose, eyes, joints, respiratory tract, heart, and blood vessels. Cardiovascular involvement is the second most common cause of mortality after laryngotracheal involvement.[1] Here, we report a successful surgical case of RP in which the patient underwent aortic and mitral valve replacement and concomitant coronary artery bypass grafting.

A versatile Johansson-type tender x-ray emission spectrometer

We present a high energy resolution x-ray spectrometer for the tender x-ray regime (1.6-5.0 keV) that was designed and operated at Stanford Synchrotron Radiation Lightsource. The instrument is developed on a Rowland geometry (500 mm of radius) using cylindrically bent Johansson analyzers and a position sensitive detector. By placing the sample inside the Rowland circle, the spectrometer operates in an energy-dispersive mode with a subnatural line-width energy resolution (∼0.32 eV at 2400 eV), even when an extended incident x-ray beam is used across a wide range of diffraction angles (∼30° to 65°). The spectrometer is enclosed in a vacuum chamber, and a sample chamber with independent ambient conditions is introduced to enable a versatile and fast-access sample environment (e.g., solid/gas/liquid samples, in situ cells, and radioactive materials). The design, capabilities, and performance are presented and discussed.

Machine learning based automated dynamic quantification of left heart chamber volumes

AIMS

Studies have demonstrated the ability of a new automated algorithm for volumetric analysis of 3D echocardiographic (3DE) datasets to provide accurate and reproducible measurements of left ventricular and left atrial (LV, LA) volumes at end-systole and end-diastole. Recently, this methodology was expanded using a machine learning (ML) approach to automatically measure chamber volumes throughout the cardiac cycle, resulting in LV and LA volume-time curves. We aimed to validate ejection and filling parameters obtained from these curves by comparing them to independent well-validated reference techniques.

METHODS AND RESULTS

We studied 20 patients referred for cardiac magnetic resonance (CMR) examinations, who underwent 3DE imaging the same day. Volume-time curves were obtained for both LV and LA chambers using the ML algorithm (Philips HeartModel), and independently conventional 3DE volumetric analysis (TomTec), and CMR images (slice-by-slice, frame-by-frame manual tracing). Automatically derived LV and LA volumes and ejection/filling parameters were compared against both reference techniques. Minor manual correction of the automatically detected LV and LA borders was needed in 4/20 and 5/20 cases, respectively. Time required to generate volume-time curves was 35 ± 17 s using ML algorithm, 3.6 ± 0.9 min using conventional 3DE analysis, and 96 ± 14 min using CMR. Volume-time curves obtained by all three techniques were similar in shape and magnitude. In both comparisons, ejection/filling parameters showed no significant inter-technique differences. Bland-Altman analysis confirmed small biases, despite wide limits of agreement.

CONCLUSION

The automated ML algorithm can quickly measure dynamic LV and LA volumes and accurately analyse ejection/filling parameters. Incorporation of this algorithm into the clinical workflow may increase the utilization of 3DE imaging.

A first look into the influence of triathlon wetsuit on resting blood pressure and heart rate variability

The purpose of this study was to investigate the effects of wearing a wetsuit on resting cardiovascular measures (blood pressure (BP), heart rate variability (HRV)). The influence of position (upright, prone) and wetsuit size were also explored. Participants (n=12 males, 33.3±12.1 years) had BP and HRV measured during six resting conditions: standing or prone while not wearing a wetsuit (NWS), wearing the smallest (SWS), or largest (LWS) wetsuit (based upon manufacturer guidelines). Heart rate was recorded continuously over 5-mins; BP was measured three times per condition. HRV was represented by the ratio of low (LF) and high (HF) frequency (LF/HF ratio); mean arterial pressure (MAP) was calculated. Each dependent variable was analyzed using a 2 (position) x 3 (wetsuit) repeated measures ANOVA (α=0.05). Neither HRV parameter was influenced by position x wetsuit condition interaction (p>0.05) and MAP was not influenced by position (p=0.717). MAP and LF/HF ratio were both influenced by wetsuit condition (p<0.05) with higher during SWS than NWS (p=0.026) while LF/HF ratio was lower during SWS compared to NWS (p=0.032). LF/HF ratio was influenced by position being greater during standing vs. prone (p=0.001). It was concluded that during resting while on land (i.e., not submerged in water), wearing a small, tight-fitting wetsuit subtlety altered cardiovascular parameters for healthy, normotensive subjects.

Inoculation of lactic acid bacteria on meat surfaces as a means of decontamination in semitropical conditions

Reduction of microbial populations on carcasses has been achieved and reported by some authors by spraying solutions of organic acids, mainly lactic acid, on the meat surface. However, in practice, lactic acid is very expensive. Production of lactic acid in situ by a controlled lactic fermentation seemed to be a feasible answer. The objective of the present study was to explore the viability of this concept at semitropical conditions, i.e. temperatures around 25°C. In a first experiment, seven starters were tested for their ability to produce lactic acid and reducing the growth rate of pseudomonads, taking these microorganisms as indicators of contamination by spoilage microorganisms. The lactic acid bacteria strains were isolated from native Mexican maize-based beverages, and inoculated on the meat surface. Addition of sucrose and wrapping the samples in PVC film in order to induce a microaerophilic environment encouraged the over-growth of L. bulgaricus and P. pentosaceous over pseudomonads. A second experiment was designed to test a mixture of these two strains and a commercial starter with respect to lactic acid production, overgrowth of lactic acid bacteria over pseudomonads, decolouration and oxidation of the meat samples. It was concluded that a commercial starter (L. plantarum + M. kristinae-varians) resulted in a reduction of pseudomonas growth rate, without notably affecting meat colour and degree of oxidation.

Structural and functional properties of Escherichia coli-derived nucleoplasmin. A comparative study of recombinant and natural proteins

Fourier transform infrared spectroscopy, circular dichroism and prediction techniques have been used to investigate the conformational properties of nucleoplasmin isolated from oocytes and eggs of Xenopus. laevis and overexpressed in Escherichia coli. A simple and fast method allows purification of recombinant nucleoplasmin free of truncated and/or aggregated forms, and therefore provides a suitable sample to carry out the structural and functional comparison between these proteins. The secondary structure of the three proteins estimated from both spectroscopic techniques was very similar, and was found to be 31--33% loops, 27--34% beta structure, 22--26% turns and 9-14% alpha helix. Prediction studies, in good agreement with experimental data, also suggest that beta structure is the major regular conformation, and that loops and turns are the most abundant conformational features within the secondary structure of nucleoplasmin. Furthermore, the spectroscopic characterization of a truncated version of the protein, lacking 80 residues at the C-terminus, and the prediction data indicate that the secondary structure elements of the protein are segregated into two regions. The N-terminal fragment (comprising residues 1--120) which holds all the putative beta strands, and the solvent-exposed C-terminal region, that is suggested to be enriched in turn and loop structures. The phosphate/protein monomer molar ratios, obtained from chemical analysis and mass spectrometry, are 0, 3 and 7--10 for recombinant, oocyte and egg nucleoplasmin, respectively. Phosphorylation does not significantly affect the secondary structure of the protein, but clearly modulates its ability to decondense sperm nuclei and to remove basic proteins from DNA.

Evaluation of an immunocapture-agglutination test (Brucellacapt) for serodiagnosis of human brucellosis

We evaluated the validity and the usefulness of a new test for the diagnosis of human brucellosis based on an immunocapture-agglutination technique. A total of 315 sera from 82 patients with a diagnosis of brucellosis, 157 sera from patients in whom brucellosis was suspected but not confirmed, and 412 sera from people living in rural areas with endemic brucellosis were studied. The seroagglutination test (SAT), Coombs anti-Brucella test, and Brucellacapt test were evaluated. All the initial sera from the 82 patients proved to be positive in Brucellacapt and Coombs tests, while only 75 (91.4%) were positive in the SAT. If a >/=1/160 diagnostic threshold titer was defined for the Brucellacapt test, Coombs test, and SAT, the sensitivities were 95.1, 91.5, and 65.8%, respectively. Taking the same diagnostic threshold titer for the 157 sera from the unconfirmed but suspected patients, the specificities of the Brucellacapt, Coombs, and SAT were 81.5, 96.2, and 100%, respectively; for the 412 control sera, the specificities were 99.0, 99.8, and 100%. The diagnostic efficiency (area below the receiver operating characteristic curve) of Brucellacapt was 0.987852 (95% confidence interval [CI], 0.95109 to 0.99286), very similar to the diagnostic efficiency of the Coombs test (0.97611; 95% CI, 0.94781 to 0.99146) and higher than that of SAT (0.91013; 95% CI, 0.86649 to 0.94317). The results of the Brucellacapt test were compared with those of the Coombs test (correlation coefficient, 0.956; P = 0.000) and SAT (correlation coefficient, 0.866; P = 0.000). The study shows very good correlation between the Brucellacapt and Coombs tests, with a high concordance between titers obtained in the two tests. Nevertheless, lower correlation and concordance were found between the Brucellacapt and Coombs tests when the results for titers of >/=1/160 were compared (0.692; P = 0.000). In acute brucellosis, the Brucellacapt and Coombs tests render positive titers of >/=1/160. When the titers are lower, they increase significantly in the following 30 days, despite the evolution of SAT titers. In contrast, Brucellacapt and Coombs titers are always high (>/=1/640) in brucellosis with long evolution, whether SAT titers are higher or lower than 1/160.

Mushroom body defect, a gene involved in the control of neuroblast proliferation in Drosophila, encodes a coiled-coil protein

Neurogenesis relies on the establishment of the proper number and precisely controlled proliferation of neuroblasts, the neuronal precursor cells. A role for the mushroom body defect (mud) gene in both of these aspects of neuroblast behavior, as well as possible roles in other aspects of fruit fly biology, is implied by phenotypes associated with mud mutations. We have localized mud by determining the sequence change in one point mutant, identifying a predicted ORF affected by the mutation, and showing that an appropriate segment of the genome rescues mud mutant phenotypes. An analysis of mud cDNAs and a survey of mud transcripts by Northern blotting indicate that the gene is subject to differential splicing and is expressed primarily during embryogenesis but also, at lower levels, during subsequent developmental stages in a sexually dimorphic manner. The gene is predicted to encode a polypeptide without obvious homologs but with two prominent structural features, a long coiled coil that constitutes the central core of the protein and a carboxyl-terminal transmembrane domain.

Evaluation of six serological tests in diagnosis and postoperative control of pulmonary hydatid disease patients

Latex agglutination (LA), passive hemagglutination (PHA), immunoelectrophoresis (IEP) and specific IgE, IgM, IgG enzyme-linked immunosorbent assay (ELISA) tests for diagnosis and postoperative follow-up of 79 patients with surgically confirmed pulmonary hydatidosis were evaluated. Specific IgG ELISA was the most sensitive test (83.5%) and the least sensitive tests were specific IgE ELISA (44.3%) and IEP (50.6%). The specificity obtained for all the serologic test was above 97% in all cases. The greatest number of false positives in all tests (except IEP) occurred in patients with Taenia saginata and Taenia solium cysticerci infestations and in patients with lymphoma and leukemia. Specific IgG ELISA demonstrated the highest negative predictive value (93.8%). No statistically significant differences (p > 0.050) were found in the sensitivity of the tests when patients with only one cyst and patients with various cysts were compared. Considering only the patients without relapse, the percentage of seropositive patients increased in all tests at 1 and 3 months after surgery. After that time the percentage of seropositive patients decreased. At 48 months after surgery all patients without relapse became negative in IEP, specific IgE ELISA, and specific IgM ELISA. The antibody titers in all seropositive patients increased during the 3 months after surgery. From these 3 months onward, antibody levels decreased in all serologic tests studied in the group of patients without relapse. The patients who had relapses during the first year after surgery presented persistently elevated antibody titers in all postoperative sera. The antibody titers of the patients who relapsed between the third and fourth years after surgery decreased progressively the third month after surgery, and increased in the serum obtained at the moment of relapse diagnosis. Our results show that persistence of elevated antibody titers in patients with pulmonary hydatidosis in the year after surgery or titer increase after a progressive decrease are indicative of relapse or reinfection.

The haplolethal region at the 16F gene cluster of Drosophila melanogaster: structure and function

Extensive aneuploid analyses had shown the existence of a few haplolethal (HL) regions and one triplolethal region in the genome of Drosophila melanogaster. Since then, only two haplolethals, 22F1-2 and 16F, have been directly linked to identified genes, dpp and wupA, respectively. However, with the possible exception of dpp, the actual bases for this dosage sensitivity remain unknown. We have generated and characterized dominant-lethal mutations and chromosomal rearrangements in 16F and studied them in relation to the genes in the region. This region extends along 100 kb and includes at least 14 genes. The normal HL function depends on the integrity of a critical 4-kb window of mostly noncoding sequences within the wupA transcription unit that encodes the muscle protein troponin I (TNI). All dominant lethals are breakpoints within that window, which prevent the functional expression of TNI and other adjacent genes in the proximal direction. However, independent mutations in these genes result in recessive lethal phenotypes only. We propose that the HL at 16F represents a long-range cis regulatory region that acts upon a number of functionally related genes whose combined haploidy would yield the dominant-lethal effect.

Topology of sarcoplasmic reticulum Ca2+-ATPase: an infrared study of thermal denaturation and limited proteolysis

Sarcoplasmic reticulum Ca2+-ATPase structure and organization in the membrane has been studied by infrared spectroscopy by decomposition of the amide I band. Besides the component bands assignable to secondary structure elements such as alpha-helix, beta-sheet, etc...., two unusual bands, one at 1,645 cm(-1) in H2O buffer and the other at 1,625 cm(-1) in D2O buffer are present. By perturbing the protein using temperature and limited proteolysis, the band at 1,645 cm(-1) is tentatively assigned to alpha-helical segments located in the cytoplasmic domain and coupled to beta-sheet structure, whereas the band at 1,625 cm(-1) arises probably from monomer-monomer contacts in the native oligomeric protein. The secondary structure obtained is 33% alpha-helical segments in the transmembrane plus stalk domain; 20% alpha-helix and 22% beta-sheet in the cytoplasmic domain plus 19% turns and 6% unordered structure. Thermal unfolding of Ca2+-ATPase is a complex process that cannot be described as a two-state denaturation. The results obtained are compatible with the idea that the protein is an oligomer at room temperature. The loss of the 1,625 cm(-1) band upon heating would be consistent with a disruption of the oligomers in a process that later gives rise to aggregates (appearance of the 1,618 cm(-1) band). This picture would also be compatible with early results suggesting that processes governing Ca2+ accumulation and ATPase activity are uncoupled at temperatures above 37 degrees C, so that while ATPase activity proceeds at high rates, Ca2+ accumulation is inhibited.

[Occult gallbladder disease or microlithiasis in patients with acute pancreatitis: a frequent clinical event]

BACKGROUND

Patients with acute pancreatitis (AP) and a normal gallbladder by standard echographic evaluation may have "occult" gallbladder disease or microlithiasis with recurrent episodes of AP.

AIM

To conduct a prospective evaluation of patients with the diagnosis of non-biliary AP in order to detect "occult" gallbladder disease and to compare its clinical presentation with that of biliary AP.

PATIENTS AND METHODS

Patients admitted with the diagnosis of AP to a clinical hospital were included in the study. According to an abdominal ultrasound study, patients were classified as having or not cholelithiasis. A duodenal biliary drainage was performed in 15 patients with AP and without gallbladder stones.

RESULTS

Patients without cholelithiasis had recurrent AP more often than patients with biliary AP (53 and 3.3% respectively). Excessive alcohol ingestion did not rule out the possibility of biliary etiology. In 6 patients, the analysis of duodenal bile showed cholesterol crystals, and cholecystectomy confirmed the existence of gallbladder disease in 5. All of them remained asymptomatic during a follow-up period of four years. One patient refused surgery, with subsequent development of gallstones and recurrent episodes of AP. In other 4 patients, gallbladder disease was confirmed by percutaneous gallbladder puncture or during cholecystectomy. No recurrence of AP were observed during the follow-up

CONCLUSIONS

Microlithiasis or "occult" gallbladder disease accounts for at least 67% of the original "non-biliary" AP. Duodenal bile analysis is a useful and necessary technique for the evaluation of patients with "non-biliary" acute pancreatitis. Careful clinical and echographic follow-up of this subgroup of patients with AP is mandatory.

Inferior vena cava catheterization in the neonate by the percutaneous femoral vein method

Placement of percutaneous femoral venous catheters in neonates is rarely performed for long-term central venous access. We studied 44 neonates (gestational age, 32.4 +/- 48 weeks, postnatal age, 18 +/- 32 days) with lack of other venous access sites. The femoral vein was entered with a 19-gauge introducer needle with placement of a 2F silastic catheter localized at the inferior vena cava-right atrial junction. Catheter-related sepsis, bacteremia, or thrombophlebitis did not occur in any patients. Our findings suggest that percutaneous femoral-vena cava catheters can be safely used when other nonfemoral sites are unavailable.

The Turbidity of Cell Nuclei in Suspension: A Complex Case of Light Scattering

The turbidity of a suspension of cell nuclei isolated from animal tissue homogenates is a complex case of non-Rayleigh scattering. As a first approximation to this system, we have characterized a number of factors that may contribute to the observed turbidity: cation-dependent chromatin condensation, thermal denaturation of chromatin, nuclear shrinking, and changes in the optical properties of the membrane bilayer. Small differences in cation concentration, particularly in the case of divalent cations, lead to large changes in chromatin supramolecular organization, thus to large turbidity effects; thermally-induced changes in turbidity have a similar origin, although they are less pronounced. Under certain circumstances, either salts or heat may induce condensation of chromatin, the latter being connected to the inner side of the nuclear envelope, nuclear shrinking ensues, and this in turn modifies the suspension turbidity. Finally, changes in the physical properties of the lipid bilayers or of the phospholipids in the nuclear envelopes may also have significant effects, though smaller than chromatin changes, in the overall turbidity of the nuclear suspension.

Functional recovery of troponin I in a Drosophila heldup mutant after a second site mutation

To identify proteins that interact in vivo with muscle components we have used a genetic approach based on the isolation of suppressors of mutant alleles of known muscle components. We have applied this system to the case of troponin I (TnI) in Drosophila and its mutant allele heldup2 (hdp2). This mutation causes an alanine to valine substitution at position 116 after a single nucleotide change in a constitutive exon. Among the isolated suppressors, one of them results from a second site mutation at the TnI gene itself. Muscles endowed with TnI mutated at both sites support nearly normal myofibrillar structure, perform notably well in wing beating and flight tests, and isolated muscle fibers produce active force. We show that the structural and functional recovery in this suppressor does not result from a change in the stoichiometric ratio of TnI isoforms. The second site suppression is due to a leucine to phenylalanine change within a heptameric leucine string motif adjacent to the actin binding domain of TnI. These data evidence a structural and functional role for the heptameric leucine string that is most noticeable, if not specific, in the indirect flight muscle.

An assessment of the biochemical applications of the non-ionic surfactant Hecameg

A number of properties and effects of the novel non-ionic detergent Hecameg (6-O-(N-heptylcarbamoyl)-methyl-alpha-D-glucopyranoside) have been examined in view of its possible biochemical applications. In particular, its critical micellar concentration has been measured, and its effects on pure lipid membranes, soluble and membrane-bound enzymes have been recorded. Hecameg has some advantageous and some less advantageous properties; its relatively high critical micellar concentration (16.5 mM), almost insensitive to pH or ionic strength changes, makes it suitable for reconstitution procedures in which detergent must be removed by dialysis. It is also an effective lipid-solubilizing agent, producing leakage of vesicle contents at detergent concentrations well below the solubilizing range. Among the drawbacks, the presence of an amide group in the molecule may interfere with the protein amide group in spectroscopic measurements. It also appears to be less gentle than other nonionic surfactants towards certain enzyme activities.

Abnormal muscle development in the heldup3 mutant of Drosophila melanogaster is caused by a splicing defect affecting selected troponin I isoforms

The troponin I (TnI) gene of Drosophila melanogaster encodes a family of 10 isoforms resulting from the differential splicing of 13 exons. Four of these exons (6a1, 6a2, 6b1, and 6b2) are mutually exclusive and very similar in sequence. TnI isoforms show qualitative specificity whereby each muscle expresses a selected repertoire of them. In addition, TnI isoforms show quantitative specificity whereby each muscle expresses characteristic amounts of each isoform. In the mutant heldup3, the development of the thoracic muscles DLM, DVM, and TDT is aborted. The mutation consists of a one-nucleotide displacement of the 3' AG splice site at the intron preceding exon 6b1, resulting in the failure to produce all exon 6b1-containing TnI isoforms. These molecular changes in a constituent of the thin filaments cause the selective failure to develop the DLM, DVM, and TDT muscles while having no visible effect on other muscles wherein exon 6b1 expression is minor.

[Characteristics of severe esophagitis in patients with collagen diseases]

Connective tissue disease may alter esophageal function generating symptoms due to gastroesophageal reflux and motor disturbances. Fifteen patients with connective tissue diseases and severe esophagitis defined by the presence of esophageal stenosis or ulcerations were studied. Diagnosis was made with radiologic, endoscopic and manometric studies. Dysphagia was present in 11 and gastroesophageal reflux in all. All patients has an hypotensive and shorter lower esophageal sphincter. Better therapeutic results were obtained with surgical treatment.

Electrical activity of the lateral rectus muscle and abducens nerve during unconditioned eye retraction induced by corneal stimulation in the cat

Horizontal eye movements, the electromyogram of the lateral rectus muscle and the evoked electroneurogram of the VIth nerve were recorded in the alert cat during air puff stimulation of the cornea. A burst of activity was observed in the lateral rectus muscle following air puff stimulation of the ipsilateral or contralateral eye. This activity produced rotational eye movement. The VIth nerve produced two volleys of activity that were interpreted as the R1 and R2 parts of the reflex. It can be concluded that the lateral rectus muscle participates in the ocular retraction following trigeminal stimulation. It is further suggested that motoneurons in the main abducens nucleus participate in the corneal reflex, permitting several final pathways for conditioned and unconditioned nictitating membrane extension.

Solubilization of sarcoplasmic reticulum membranes by sodium dodecylsulphate. A Fourier-transform infrared spectroscopic study

In order to improve our understanding of membrane protein solubilization by sodium dodecylsulphate, sarcoplasmic reticulum vesicles have been treated with this surfactant at different detergent: protein mole ratios. Effects on Ca2(+)-ATPase activity, membrane protein solubilization, and protein conformation have been independently monitored, and correlations among the various parameters have been observed. The thermal denaturation of sarcoplasmic reticulum proteins in the presence of sodium dodecylsulphate has also been characterized spectroscopically.