A shorter system delay for haemorrhagic stroke than ischaemic stroke among patients who use emergency medical service

OBJECTIVES

We compare various aspects in the early chain of care among patients with haemorrhagic stroke and ischaemic stroke.

MATERIALS & METHODS

The Emergency Medical Services (EMS) and nine emergency hospitals, each with a stroke unit, were included. All patients hospitalised with a first and a final diagnosis of stroke between 15 December 2010 and 15 April 2011 were included. The primary endpoint was the system delay (from call to the EMS until diagnosis). Secondary endpoints were: (i) use of the EMS, (ii) delay from symptom onset until call to the EMS; (iii) priority at the dispatch centre; (iv) priority by the EMS; and (v) suspicion of stroke by the EMS nurse and physician on admission to hospital.

RESULTS

Of 1336 patients, 172 (13%) had a haemorrhagic stroke. The delay from call to the EMS until diagnosis was significantly shorter in haemorrhagic stroke. The patient's decision time was significantly shorter in haemorrhagic stroke. The priority level at the dispatch centre did not differ between the two groups, whereas the EMS nurse gave a significantly higher priority to patients with haemorrhage. There was no significant difference between groups with regard to the suspicion of stroke either by the EMS nurse or by the physician on admission to hospital.

CONCLUSIONS

Patients with a haemorrhagic stroke differed from other stroke patients with a more frequent and rapid activation of EMS.

QTc prolongation prior to angiography predicts poor outcome and associates significantly with lower left ventricular ejection fractions and higher left ventricular end-diastolic pressures

Background

QT prolongation on the surface ECG is associated with sudden cardiac death. The cause of QT prolongation in ischaemic heart disease (IHD) patients remains unknown, but may be due to a complex interplay between genetic factors and impaired systolic and/or diastolic function through as yet unexplained mechanisms. It was hypothesised that QT prolongation before elective coronary angiography is associated with an increased mortality at six months.

Methods

Complete records of 321 patients who underwent coronary angiography were examined for QT interval corrected for heart rate (QTc), left ventricular ejection fraction (LVEF), left ventricular end-diastolic pressure (LVEDP) and known ischaemic heart disease risk factors. Patients were designated long QTc (LQTc) when they had prolonged QTc intervals or normal QTc (NQTc) when the QTc interval was normal. Patients with atrial fibrillation, bundle branch blocks, no ECG in the 24 hours before angiography, or a creatinine level > 200 μmol/l were excluded. Survival was determined telephonically at six months.

Results

Twenty-eight per cent of the total population had LQTc. During follow up, 15 patients (4.7%) died suddenly, 73% of whom had a LQTc. LQTc was significantly associated with mortality (LQTc 12% vs NQTc 1.7%; p < 0.01), and with lower but normal LVEF (LQTc 52.9 ± 15.4% vs NQTc 61.6 ± 13.6%; p < 0.01), higher LVEDP at LVEF > 45% (LQTc 19.2 ± 9.0 mmHg vs NQTc 15.95 ± 7.5 mmHg; p < 0.05), hypercholesterolaemia and a negative family history of IHD.

Conclusion

In patients with sinus rhythm and normal QRS width, QTc prolongation before coronary angiography predicted increased mortality at six months. QTc also associated strongly with left ventricular systolic and diastolic dysfunction, hypercholesterolaemia and a negative family history of IHD.

Implementation of osteoporosis guidelines: a survey of five large fracture liaison services in the Netherlands

SUMMARY

Implementation of case findings according to guidelines for osteoporosis in fracture patients presenting at a Fracture Liaison Service (FLS) was evaluated. Despite one guideline, all FLSs differed in the performance of patient selection and prevalence of clinical risk factors (CRFs) indicating the need for more concrete and standardised guidelines.

INTRODUCTION

The aim of the study was to evaluate the implementation of case findings according to guidelines for osteoporosis in fracture patients presenting at FLSs in the Netherlands.

METHODS

Five FLSs were contacted to participate in this prospective study. Patients older than 50 years with a recent clinical fracture who were able and were willing to participate in fracture risk evaluation were included. Performance was evaluated by criteria for patient recruitment, patient characteristics, nurse time, evaluated clinical risk factors (CRFs), bone mineral density (BMD) and laboratory testing and results of CRFs and BMD are presented. Differences between FLSs were analysed for performance (by chi-square and Student's t test) and for prevalence of CRFs (by relative risks (RR)).

RESULTS

All FLSs had a dedicated nurse spending 0.9 to 1.7 h per patient. During 39 to 58 months follow-up, 7,199 patients were evaluated (15 to 47 patients/centre/month; mean age, 67 years; 77% women). Major differences were found between FLSs in the performance of patient recruitment, evaluation of CRFs, BMD and laboratory testing, varying between 0% and 100%. The prevalence of CRFs and osteoporosis varied significantly between FLSs (RR between 1.7 and 37.0, depending on the risk factor).

CONCLUSION

All five participating FLSs with a dedicated fracture nurse differed in the performance of patient selection, CRFs and in the prevalence of CRFs, indicating the need for more concrete and standardised guidelines to organise evaluation of patients at the time of fracture in daily practice.

Elevating the uterus (uteropexy) of five mares by laparoscopically imbricating the mesometrium

REASONS FOR PERFORMING STUDY

There is a need for study of a method for restoring a ventrally positioned uterus to a horizontal position involving fertility of mares with delayed uterine clearance.

HYPOTHESIS

A ventrally-angled uterus can be elevated to a horizontal position using a laparoscopic technique.

OBJECTIVE

To develop a laparoscopic technique of imbricating the mesometria to elevate the uterus to a horizontal position.

METHODS

The right and left mesometria of 5 pluriparous mares, all barren for 1-8 years (mean 3.8 years), with a pendulous, ventrally-angled uterus were shortened laparoscopically, by imbrication, with the mares standing, to raise the uterine body and horns to a horizontal position. Sutures were placed through the dorsal aspect of the uterine body and uterine horn and the adjacent region of the mesometrium using a simple continuous suture pattern.

RESULTS

The uterus of all 5 mares was elevated successfully to a horizontal position. Three of the mares became pregnant the same year, without other treatment, after the procedure.

CONCLUSIONS

A pendulous, ventrally-angled uterus can be returned to a normal, horizontal position by imbricating the mesometria, using a laparoscopic technique.

POTENTIAL RELEVANCE

Elevating a ventrally-angled uterus to a horizontal position may improve egress of uterine debris, thereby improving fertility.

Risk of subsequent fracture and mortality within 5 years after a non-vertebral fracture

SUMMARY

The absolute 5-year risk of subsequent non-vertebral fractures (NVFs) in 1,921 patients presenting with a NVF was 17.6% and of mortality was 32.3%. These risks were highest within the first year, indicating the need to study which reversible factors can be targeted to immediately minimise subsequent fracture risk and mortality.

INTRODUCTION

NVFs are the most frequent clinical fractures in patients presenting at the emergency unit because of a clinical fracture. The aim of the study was to determine the 5-year absolute risk (AR) of subsequent NVF and mortality in patients at the time they present with a NVF.

METHODS

Between 1999 and 2001, 1,921 consecutive patients 50+ years from a level 1 trauma centre were included. All NVFs were confirmed on radiograph reports, and mortality was checked in the national obituary database. Available potential risk factors for a subsequent NVF and mortality (age, sex and baseline fracture location: major-hip, pelvis, multiple ribs, proximal tibia/humerus and distal femur; minor-all others) were expressed as hazard ratios (HR) with 95% confidence intervals (CI) using multivariable Cox regression analysis.

RESULTS

The AR for a subsequent NVF was 17.6% and was related to age (HR per decade, 1.44; 95%CI, 1.29-1.60). The AR for mortality was 32.3% and was related to age (HR per decade, 2.59; 95%CI, 2.37-2.84), male sex (HR, 1.74; 95%CI, 1.44-2.10), major fracture at baseline (HR, 5.56; 95%CI, 3.48-8.88; not constant over time) and subsequent fracture (HR, 1.65; 95%CI, 1.33-2.05). The highest risks were found within the first year (NVFs, 6.4%; mortality, 12.2%) and were related to age and, in addition, to baseline fracture location for mortality.

CONCLUSIONS

Within 5 years after an initial NVF, nearly one in five patients sustained a subsequent NVF and one in three died. One third of subsequent NVFs and mortality occurred within 1 year, indicating the need to study which reversible factors can be targeted to immediately prevent subsequent fractures and mortality.

Ovarian function and morphology in the mare after multiple follicular punctures

REASONS FOR PERFORMING STUDY

In the mare, ultrasound-guided transvaginal oocyte recovery and transfer might offer a way to circumvent the demanding procedures of in vitro embryo production. Before clinical application, the possible consequences for subsequent fertility have to be considered.

OBJECTIVES

To examine ovarian function and morphology in mares after repeated follicular punctures.

METHODS

A total of 14-26 follicular puncture sessions were conducted on each of 4 Norwegian pony mares over a period of 8 years. The ovaries of these mares were recovered by bilateral ovariectomy or at post mortem and subjected to macroscopic inspection and histology. For comparison, ovaries were collected from 7 nonaspirated control mares and processed for histology.

RESULTS

In all experimental mares, ovarian function, defined as the ability regularly to ovulate preovulatory follicles and develop corpora lutea, remained normal during their last breeding season. Gross examination and histology showed that normal follicular and corpus luteum development was accompanied by the formation of condensed reparative fibrosis and normal local haemosiderosis of the ovarian stroma in all experimental mares. In one mare, an ovary contained several foci of chronic apostematous oophoritis, while a cystic structure lined with a single layer of epithelial-like cells and surrounded by a cartilaginous capsule was present in the other ovary.

CONCLUSIONS AND POTENTIAL RELEVANCE

Repeated follicular aspirations do not hamper future folliculogenesis, ovulation and corpus luteum formation. However, ovarian puncture induces reparative fibrosis in the ovarian stroma and involves a risk of inducing abscess formation within the ovarian tissue which may impair fertility.

Lameness and effusion of the tarsocrural joints after arthroscopy of osteochondritis dissecans in horses

The presence and degree of tarsocrural joint effusion and lameness, and the result of a hindlimb flexion test were scored subjectively in 79 horses before, and six weeks to 20 months after, arthroscopic surgery to remove osteochondritis dissecans fragments. The scores of all three variables improved significantly after surgery. The score reductions for the right and left hindlimbs, respectively, were 82 per cent and 95 per cent for lameness, 48 per cent and 41 per cent for joint effusion, and 89 per cent and 84 per cent for reaction to flexion (P < or = 0.01). The oldest horses reacted more favourably to the operation, as measured by the reaction to the flexion test, but age was not significantly related to changes in lameness or joint effusion. There was no significant correlation between the time of follow-up examination and the effect of surgery on lameness and reaction to flexion, but an increased time to follow-up was associated with decreased joint effusion.

FAME 3: A novel form of progressive myoclonus and epilepsy

BACKGROUND

Familial adult myoclonic epilepsy (FAME) is associated with myoclonus, tremor, and rare seizures, and is a nonprogressive disorder linked to the FAME 1 locus. A similar disorder has been linked to the FAME 2 locus.

METHODS

Seventeen patients from two families with myoclonus and epilepsy were evaluated clinically and underwent EEG, EMG, jerk-locked averaging, and MRI scanning. Three had responses to magnetic stimulation assessed. Linkage was assessed for microsatellite markers across the FAME 1 and 2 loci.

RESULTS

The median age at onset was 20 years, with many patients having frequent seizures, cognitive impairment, and cerebellar dysfunction. Electrophysiologic features of cortical myoclonus were typically present, but photosensitivity was uncommon. MRI frequently demonstrated cerebellar atrophy. Pathology of a single case showed Purkinje cell loss, dentate atrophy, and neuronal loss and gliosis in the olives and pallidum. Analysis of genotypes for markers at the FAME 1 and FAME 2 loci excluded these as the region containing the same locus in one family, but only the FAME 2 locus was excluded in the other family.

CONCLUSIONS

This form of familial adult myoclonic epilepsy does not show linkage to either of the known familial adult myoclonic epilepsy loci, and is characterized in some members by frequent seizures, cerebellar ataxia, dementia, and progression of the disease. This may represent a new form of progressive myoclonus and epilepsy, which we have termed familial adult myoclonic epilepsy type 3.

An investigation of the ability of the glutaraldehyde test to distinguish between acute and chronic inflammatory disease in horses

The Glutaraldehyde test (GT), a rapid and inexpensive test, has been utilized empirically for many years in bovine practice for diagnosing inflammatory diseases. GT is used primarily to demonstrate increased serum concentrations of fibrinogen and globulin. Glutaraldehyde binds with free amino groups in fibrinogen and immunoglobulin to create a clot in a first degree chemical reaction. The clotting time of the GT estimates the content of proteins produced in response to inflammation. The applicability of GT for diagnosing inflammation in the horse has never been investigated. The objective of this study was to determine the ability of GT to distinguish between acute and chronic inflammatory disease in horses. Thirty-seven horses with suspected inflammatory diseases were evaluated using the GT, history, complete clinical examination and routine blood analysis. GT-times, laboratory results and clinical outcome were compared statistically. Horses that were determined to be acutely affected (based on history, clinical examination and routine blood analysis) tended to have a negative GT (75%). Results of the GT did not correlate with blood fibrinogen concentration. Positive GT also predicted a fatal outcome in 69% of the clinical cases. The results of this trial indicate that GT can be a useful screening test to distinguish between acute and chronic inflammatory disease in horses.

Genotype-phenotype correlation in the long-QT syndrome: gene-specific triggers for life-threatening arrhythmias

BACKGROUND

The congenital long-QT syndrome (LQTS) is caused by mutations on several genes, all of which encode cardiac ion channels. The progressive understanding of the electrophysiological consequences of these mutations opens unforeseen possibilities for genotype-phenotype correlation studies. Preliminary observations suggested that the conditions ("triggers") associated with cardiac events may in large part be gene specific.

METHODS AND RESULTS

We identified 670 LQTS patients of known genotype (LQT1, n=371; LQT2, n=234; LQT3, n=65) who had symptoms (syncope, cardiac arrest, sudden death) and examined whether 3 specific triggers (exercise, emotion, and sleep/rest without arousal) differed according to genotype. LQT1 patients experienced the majority of their events (62%) during exercise, and only 3% occurred during rest/sleep. These percentages were almost reversed among LQT2 and LQT3 patients, who were less likely to have events during exercise (13%) and more likely to have events during rest/sleep (29% and 39%). Lethal and nonlethal events followed the same pattern. Corrected QT interval did not differ among LQT1, LQT2, and LQT3 patients (498, 497, and 506 ms, respectively). The percent of patients who were free of recurrence with ss-blocker therapy was higher and the death rate was lower among LQT1 patients (81% and 4%, respectively) than among LQT2 (59% and 4%, respectively) and LQT3 (50% and 17%, respectively) patients.

CONCLUSIONS

Life-threatening arrhythmias in LQTS patients tend to occur under specific circumstances in a gene-specific manner. These data allow new insights into the mechanisms that relate the electrophysiological consequences of mutations on specific genes to clinical manifestations and offer the possibility of complementing traditional therapy with gene-specific approaches.

Stereotypies: prevalence and association with compulsive and impulsive symptoms in college students

BACKGROUND

Although stereotypic behaviors have been well described in patients with mental retardation, there has been relatively little work on the prevalence and nature of these phenomena in intellectually normal subjects. Stereotypies may conceivably be related to obsessive-compulsive disorder, to perfectionism, or to impulse dyscontrol.

METHODS

This study attempted to assess the prevalence of stereotypic behaviors in a college population and to determine their relationship to compulsive and impulsive symptoms and traits by means of self-rated questionnaires. Questionnaires assessed stereotypies as well as obsessive-compulsive symptoms, perfectionism, and impulsive-aggressive traits.

RESULTS

Stereotypic behaviors were common in this population, and they were time-consuming or problematic in a subgroup of subjects. The total number of stereotypic behaviors was significantly associated with increased scores of obsessive-compulsive symptoms, of perfectionism, and of impulsive-aggressive traits. Other measures of the severity of stereotypic behavior were also associated with obsessive-compulsive symptoms and perfectionism.

CONCLUSIONS

Although the nature of stereotypic behaviors is not well understood, these phenomena can be clinically important in intellectually normal subjects. Stereotypic behaviors deserve further attention from researchers and clinicians.

Stereospecific pharmacokinetics of free and protein-bound ketoprofen in serum and synovial fluid of horses after intravenous and intramuscular administration

OBJECTIVE

To determine intravascular and intrasynovial pharmacokinetics of the R and S enantiomers of ketoprofen after i.v. and i.m. administration to horses.

ANIMALS

6 healthy adult mares.

PROCEDURE

Horses were weighed and ketoprofen (2.2 mg/kg of body weight) was administered i.v. Blood and synovial fluid samples were obtained and analyzed for concentrations of the R and S enantiomers by means of a modified reverse-phase stereospecific high-pressure liquid chromatographic method. Three weeks later, the procedure was repeated, except that ketoprofen was given IM. Protein binding of ketoprofen enantiomers was determined by means of ultrafiltration. Nonlinear least squares methods were used to calculate pharmacokinetic parameters.

RESULTS

Data obtained after i.v. administration best fit an open, two-compartment model. Mean +/- SD S-to-R serum concentration ratios after i.v. and i.m. administration were 1.36 +/- 0.214 and 1.34 +/- 0.245, respectively. Intrasynovial concentrations of the R and S enantiomers of ketoprofen could be measured for only the first 3 hours after i.v. administration; concentrations were less than the limit of quantification by 4 hours after i.v. administration and at all times after i.m. administration. Extent of protein binding of the R enantiomer was not significantly different from extent of protein binding of the S enantiomer; extent of protein binding did not appear to be concentration dependent. Mean free S-to-free R serum concentration ratios, adjusted for protein binding, after i.v. and i.m. administration were 1.58 and 1.56, respectively.

CONCLUSIONS

The R and S enantiomers of ketoprofen are rapidly absorbed and eliminated, have low volumes of distribution, and are highly protein bound.

Identification of a new missense mutation in MyBP-C associated with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is a primary cardiac disease, characterised by idiopathic myocardial hypertrophy, and is caused by defects in sarcomeric protein encoding genes. One of these genes is cardiac myosin binding protein C (MyBP-C), in which a number of splice site and duplication mutations causing HCM have been described. During mutation screening of a South African HCM population by PCR-SSCP, a missense mutation, Arg654His, was detected in one proband. Although the mutation was present in his three adult children, only the proband himself was markedly affected. This is the first report of a disease associated missense mutation in MyBP-C which does not affect the myosin or titin binding domains.

Diminished neurogenic but not pharmacological erections in the 2- to 3-month experimentally diabetic F-344 rat

The rapid spread of locally restricted neural and hormonal signals among the vast array of largely inexcitable corporal smooth muscle cells is an absolute prerequisite to normal erectile function. And yet the mechanism(s) responsible for this phenomenon is not well understood. As a first step toward a more integrative understanding of erectile physiology and/or dysfunction, an 8- to 12-wk period of experimental diabetes was induced in 2-mo-old male Fischer 344 rats by either intraperitoneal streptozotocin (STZ) injection (35 mg/kg; n = 22) or subtotal pancreatectomy (n = 11). Fourteen age-matched control animals received injection of vehicle only while nine others served as sham-operated control animals. Eight STZ-diabetic animals received insulin replacement. Erectile function was assessed by evaluation of penile reflexes and monitoring of intracavernous pressure responses to both electrical stimulation of the cavernous nerve and intracorporal papaverine or nitroglycerin injection. Intracavernous pressure responses to neurostimulation were significantly attenuated in both STZ-diabetic and subtotal pancreatectomy animals compared with age-matched control animals (P < 0.05). Penile reflexes were also significantly diminished (P < 0.05). Regression analysis revealed that diabetes-related decreases in neurostimulated intracavernous pressure responses were strongly correlated with diminished synaptophysin immunoreactivity in the corpora (P < 0.001; r = 0.88). However, there were no detectable diabetes-related differences in pharmacological erections induced by intracavernous papaverine or nitroglycerin injection. Northern analysis revealed a marked diabetes-related increase in the amount of connexin 43 mRNA measured in frozen corporal tissue. Insulin replacement partially restored (attenuated the loss of) synaptophysin immunoreactivity and maintained neurostimulated intracavernous pressure responses to control levels while having no effect on penile reflexes. These observations may have important implications to the understanding of erectile physiology as well as the etiology of diabetes-related erectile dysfunction.

The influence of the angiotensin I converting enzyme genotype in familial hypertrophic cardiomyopathy varies with the disease gene mutation

Familial hypertrophic cardiomyopathy is an autosomal dominant genetically heterogeneous disease characterized by a partial penetrance and variable expressivity. Previous studies showed that the extent of hypertrophy is influenced by the angiotensin I converting enzyme insertion/deletion (I/D) polymorphism. Recently, molecular genetic analysis revealed the existence of healthy carriers and that as many as a quarter of genetically affected individuals do not express the disease. This data prompted us to re-investigate the role of the angiotensin I converting enzyme polymorphism on hypertrophy by assessing both clinically affected individuals and healthy carriers. For this, several families with mutations in the cardiac myosin binding protein C or the beta-myosin heavy chain genes were analysed. The mean maximal intraventricular septum thickness was compared as a function of angiotensin I converting enzyme genotypes in all genetically affected individuals (n = 114), and in subsets of subjects carrying either a splice acceptor site mutation in the cardiac myosin binding protein C gene (n = 33), or various missense mutations in the cardiac beta-myosin heavy chain gene (n = 81) or finally, mutation in the Arg403 codon of the beta-myosin heavy chain gene (n = 54). Significant association between the D allele and hypertrophy was observed only in the case of Arg403 codon mutations (mean septum thickness for subjects with the DD genotype: 19.3 +/- 2.7 mm: with the ID genotype: 13.4 +/- 1.3 mm and with the II genotype: 11.0 +/- 0.9 mm; P < 0.02). These results were confirmed by the chi 2 test showing an over-representation of DD genotype in patients carrying an Arg403 codon mutation associated with septal hypertrophy (P < 0.05). Our data confirms that the angiotensin I converting enzyme genotypes can influence the phenotypic expression of hypertrophy and shows that this influence depends on the mutation, raising the concept of multiple genetic modifiers in familial hypertrophic cardiomyopathy.

X-linked dilated cardiomyopathy. Molecular genetic evidence of linkage to the Duchenne muscular dystrophy (dystrophin) gene at the Xp21 locus

BACKGROUND

X-linked cardiomyopathy (XLCM) is a rapidly progressive primary myocardial disorder presenting in teenage males as congestive heart failure. Manifesting female carriers have later onset (fifth decade) and slower progression. The purpose of this study was to localize the XLCM gene locus in two families using molecular genetic techniques.

METHODS AND RESULTS

Linkage analysis using 60 X-chromosome-specific DNA markers was performed in a previously reported large XLCM pedigree and a smaller new pedigree. Two-point and multipoint linkage was calculated using the LINKAGE computer program package. Deletion analysis included multiplex polymerase chain reaction (PCR). Dystrophin protein was evaluated by Western blotting with N-terminal and C-terminal dystrophin antibody. Linkage of XLCM to the centromeric portion of the dystrophin or Duchenne muscular dystrophy (DMD) locus at Xp21 was demonstrated with combined maximum logarithm of the scores of +4.33, theta = 0 with probe XJ1.1 (DXS206) using two-point linkage and +4.81 at XJ1.1 with multipoint linkage analysis. LOD scores calculated using other proximal DMD genomic and cDNA probes and polymerase chain reaction polymorphisms supported linkage. No deletions were observed. Abnormalities of cardiac dystrophin were shown by Western blotting with N-terminal dystrophin antibody, whereas skeletal muscle dystrophin was normal, suggesting primary involvement of the DMD gene with preferential involvement of cardiac muscle.

CONCLUSIONS

XLCM is due to an abnormality within the centromeric half of the dystrophin genomic region in heart. This abnormality could be due to 1) a point mutation in the 5' region of the DMD coding sequence preferentially affecting cardiac function, 2) a cardiac-specific promoter mutation that alters expression in this tissue, 3) splicing abnormalities, resulting in an abnormal cardiac protein, or 4) deletion mutations undetectable by Southern and multiplex polymerase chain reaction analysis.

Limulus striated muscle provides an unusual model for muscle contraction

Although nearly two decades have passed since de Villafranca (1961) described A-band shortening, controversy persists. Here we will review the data which has been amassed since de Villafranca 's description. We will conclude that A-bands and thick filaments shorten during sarcomere shortening in Limulus striated muscle. Further we will suggest that two machines operate in this muscle: a tension generating sliding filament system and a tension generating thick filament shortening system. Also we will suggest a mechanism of force generation of the filament shortening system and provide evidence for a cycling bridge mechanism for this muscle.

Dynamic laser light scattering of papain-treated thick filaments from limulus striated muscle in suspension

Using quasielastic light scattering we have previously shown an increase in high frequency internal motion of isolated thick filament upon activation. This we have attributed to cross-bridge motion. Here we show that after cleavage of the S1 moiety of myosin from isolated filaments with papain, calcium ions no longer activate the isolated filaments to produce high-frequency motions.

Change in fixed-charge in the thick filament lattice of Limulus striated muscle with sarcomere shortening

A highly significant increase in fixed-charge occurs in the A-bands of Limulus striated muscle following activation and sarcomere shortening. This is in striking contrast to vertebrate striated muscle. Treatment with either papain or alkaline phosphatase reduces this fixed-charge. The increase in charge may serve as a motive force in thick filament shortening.

Quasi-elastic light scattering of suspensions of Limulus thick myofilaments in relaxed (long) activated and rerelaxed (short) states

Photoelectron count autocorrelation function of light scattered by Limulus thick myofilament suspensions was measured as a function of scattering angle in the relaxed, activated and rerelaxed states. By using the cumulants method of data analysis, the average linewidth over large ranges of KL (up to 120), has been calculated with K and L being, respectively, the magnitude of the momentum transfer vector and the length of the myofilament. We have observed a dramatic increase in the average linewidth denoting the presence of additional high frequency components for the myofilament suspension on the activated state. By confirming our results on the size of the myofilaments from electron micrographs, we are able to attribute the high frequency (kHz) components to the "correlated" cross-bridge motions, representing, to our knowledge, the first direct experimental evidence of such movements in isolated thick myofilament suspensions.

Glial cells in the earthworm ventral nerve cord make an A-type nexus

Nexuses have been demonstrated between glial cell processes in the earthworm ventral nerve cord. The nexuses have been demonstrated by freeze-cleavage to be A-type neuxuses, thus demonstrating for the first time the type of nexus present in the Annelida. If the nexal cleavage pattern has physiological significance then the results suggest that physiologically the nexuses of the earthworm may be similar to those of vertebrates.

Nexus of frog ventricle

Here were demonstrate in Rana pipiens ventricle a nexus with very unusual morphology. This tissue has been reported previously to lack nexuses. The nexus appears in thin sections of ventricle, fixed in aldehyde and OsO4 or permanganate as a series of punctate membrane appositions regularly alternating with regions of membrane separation. The junctional width at membrane appositions, as determined by microdensitometry and optical measurements, is 15-17 nm, and the width of the electron-translucent region between the junctional membranes is 1.8 nm. These values correspond closely to similar measurements of the more typical nexues in frog liver. Along the nexus the mean distance between punctate appositions is 74.5 nm. Freeze-cleave replicas of the nexuses between myocardial cells show particles 10.4 nm in diameter arranged in arrays of up to nine linked circles or partial circles on the PF-face and similar arrays of pits of shallow grooves on the EF-face. The mean diameter of the circles on both membrane fracture faces is 76.7 nm comparsion of the thin-sectioned and freeze-cleaved nexuses demonstrates an excellent correspondence between the spacing of membrane appositions along the junction and the diameters of the freeze-cleaved circles of particles and pits or grooves.

The resistance of the septum of the median giant axon of the earthworm

It is generally thought that nexuses constitute low-resistance pathways between cell interiors in epithelial, neural, muscular, and even connective tissues. However, there are no reliable estimates of the specific resistance of a nexus. The reason for this is that in most cases the surfaces of nexuses between cells are geometrically complex and therefore it has been very hard to accurately estimate nexal areas. However, the septa of the median giant axon have a relatively simple shape. Moreover, in this preparation, it is possible to make a measuring current flow parallel to the axon axis so that from the voltage difference appearing between intracellular electrodes during current flow, the specific septal membrane resistance could be calculated. The average specific nexal resistance obtained was 5.9 omega cm(2) if one assumes that 100 percent of the septum is nexus. The steady state I-V curve for the septum is linear (+/- 10 mV). Placement of electrodes was validated by septa even though the septa were found to be permeable to fluorescein and TEA. Exposure of the axon to hypertonic saline impedes the movement of fluorescein across the septa. By analogy with other tissues it is concluded that hypertonic solutions disrupt nexuses.A mathematical model was derived which predicts the steady- state transmembrane potential vs. distance from a point source of intracellular current. When the specific nexal membrane resistance is 5.9 omega cm(2), the prediction closely approximates the fall of transmembrane potential vs. distance in an ordinary infinite cable. This is commensurate with the electrophysiological behavior of this multicellular "axon."