Colocalization of the cyclin B homologue p56 and beta-tubulin during the cell cycle in a unicellular eucaryote dinoflagellate

We provide evidence for an unusual behavior of the cyclin B homologue, p56, in the dinoflagellate Crypthecodinium cohnii. p56, of which we previously demonstrated the presence in this original eukaryotic protist, is present all along the cell cycle progression, and is exclusively cytoplasmic as revealed after immunofluorescence labeling with anti-p56 Ab and counterstaining with Dapi. It was never found in the nucleus as is the case in higher eukaryotic cells. During mitosis, p56 was essentially associated with the mitotic apparatus: centrosomes and mitotic spindle, as shown after double immunofluorescence labeling with anti p56 and anti beta-tubulin Ab. Using high pressure freeze fixation, we clearly detected in transmission electron microscopy (TEM) the localization of p56 cyclin B homologue and beta-tubulin: single immunogold labeling demonstrated that p56 is localized along the whole cell cortex, along the cleavage furrow of anaphase to cytokinesis cells and into cytoplasmic channels passing throughout the mitotic nucleus where is located the mitotic spindle. Double immunogold labeling realized with anti-p56 and anti-beta-tubulin antibodies confirm that p56 antigens colocalize with beta-tubulin in many sites. The significance of the exclusively cytoplasmic localization of the cyclin B homologue is discussed.

Spectrin St Claude, a splicing mutation of the human alpha-spectrin gene associated with severe poikilocytic anemia

An alpha-spectrin variant with increased susceptibility to tryptic digestion, alpha(II/47), was previously observed in a child with severe, recessively inherited, poikilocytic anemia. The molecular basis of this variant, spectrin St Claude, has now been identified as a splicing mutation of the alpha-spectrin gene due to a T --> G mutation in the 3' acceptor splice site of exon 20. This polypyrimidine tract mutation creates a new acceptor splice site, AT --> AG, and leads to the production of two novel mRNAs. One mRNA contains a 12 intronic nucleotide insertion upstream of exon 20. This insertion introduces a termination codon into the reading frame and is predicted to encode a truncated protein (108 kD) that lacks the nucleation site and thus cannot be assembled in the membrane. In the other mRNA, there is in-frame skipping of exon 20, predicting a truncated (277 kD) alpha-spectrin chain. The homozygous propositus has only truncated 277 kD alpha-spectrin chains in his erythrocyte membranes. His heterozygous parents are clinically and biochemically normal. This allele was identified in 3% of asymptomatic individuals from Benin, Africa.

In situ localization of two fibrillar collagens in two compact connective tissues by immunoelectron microscopy after cryotechnical processing

Two fibrillar collagens, the worm cuticular collagen and the vertebrate Type I fish scale collagen, both organized in a compact tissue, were localized by immunogold electron microscopy in resin sections after freeze-fixation and freeze-substitution. Identification of these two fibrillar collagens failed with the use of postembedding labelling after conventional electron microscopic processing. Positive labeling of the Type I collagen was observed in sections of fish scales freeze-fixed by either slam-freezing or high-pressure freezing, freeze-substituted in acetone with or without osmium tetroxide, and embedded in LR White. The worm cuticular collagen was detected in sections of cuticle that were freeze-fixed, freeze-substituted (necessarily with osmium tetroxide added to acetone), and embedded in either LR White or Epon. It was also detected in specimens pre-fixed by aldehydes before freeze-fixation. The Type I fish scale collagen appears to be more sensitive than the fibrillar cuticular collagen of worms to the procedures employed for postembedding immunoelectron microscopy. Our results have shown that freeze-fixation and freeze-substitution preserved the antigenicity of the fibrillar collagens organized in a compact three-dimensional network, whereas immunolabeling failed after conventional electron microscopic procedures. These cryostabilization techniques appear to be of value to improve the immunolocalization of collagens.

[Cardiac sudden death in adults]

Sudden death is becoming a matter for concern as this type of accident represents an increasing proportion of deaths from cardio-vascular causes. A campaign is being launched aimed at promoting early diagnosis and appropriate action at the time of the event itself. At the same time it is necessary to get to know the target population better, especially with regard to the specific anatomical conditions which are the cause of death. For the last seven years we have been carrying out a descriptive pathological research study. The first stage took form of a three year retrospective study (1989-1991) involving 365 subjects victims of sudden death. The second part was a prospective study carried out in 1994. Heart disease emerged as the principal cause of death, something which is already well known. More interesting was the discovery that 72.3% of the subjects were completely asymptomatic despite the fact that in 85% of cases they had bi-truncal or tri-truncal lesions. The same findings emerged from the study of a subgroup of persons who had died suddenly as a result of acute stress. The data obtained are extremely homogeneous. When compared to the findings obtained from a control group of the same age who had died as the result of violence, the difference between the two populations is highly significant. Finally we should like to draw attention to the lack of epidemiological data on sudden death available in France at the present time, and this despite the fact that it is undoubtedly a public health priority. There is a need to promote both education and action in relation to this somewhat disturbing subject.

Stressful events as a trigger of sudden death: a study of 43 medico-legal autopsy cases

The reports relating emotional stress to sudden death are largely anecdotal. In addition to experimental and electrophysiological studies, an opportunity for a better understanding of possible stress-related sudden death (SSD) may be provided by medicolegal autopsies. The goal of our autopsy study was to analyze cardiovascular pathologic findings in cases of SSD and if possible identify mechanisms by which the stressful event (SE) could be the cause. Forty three cases were studied (29 males and 14 females). In all cases, the SE and the death were witnessed. The age range was 22 to 90 years in males (mean, 52) and 30 to 92 years in females (mean, 64). Death occurred in all cases without premonitory symptoms. In 20 cases, death occurred during the SE and in the other 23 cases occurred within 2 h of the event. SE included fear, 15 cases; altercation, 21 cases; sexual activity, 3 cases; police questioning or arrest, 4 cases. According to police reports, in 40 cases (90%), the victims had no previous clinical history of cardiovascular disease. At autopsy, the heart weight in males ranged from 255 to 1000 g with a mean of 517 g and in females the range was 250-700 g with a mean of 417 g. In only 3 cases, gross and microscopic examination of the heart was normal. In 2 of the remaining 40 cases the subjects died of subarachnoid hemorrhage. In 38 cases, a cardiac cause of death was found as follows: coronary heart disease, 27 cases; cardiomyopathy, 6 cases; aortic valvular stenosis, 2 cases and right ventricular dysplasia, 3 cases. A coronary artery thrombosis was found in 8 cases of sudden coronary death. Post myocardial infarction fibrosis was present in 25 cases (92%) of sudden coronary death. In conclusion, it appears from our autopsy study that SSD occurs primarily in those individuals with severe heart disease, especially coronary heart disease.

Direct visualization of a vast cortical calcium compartment in Paramecium by secondary ion mass spectrometry (SIMS) microscopy: possible involvement in exocytosis

The plasma membrane of ciliates is underlaid by a vast continuous array of membrane vesicles known as cortical alveoli. Previous work had shown that a purified fraction of these vesicles actively pumps calcium, suggesting that alveoli may constitute a calcium-storage compartment. Here we provide direct confirmation of this hypothesis using in situ visualization of total cell calcium on sections of cryofixed and cryosubstituted cells analyzed by SIMS (secondary ion mass spectrometry) microscopy a method never previously applied to protists. A narrow, continuous, Ca-emitting zone located all along the cell periphery was observed on sections including the cortex. In contrast, Na and K were evenly distributed throughout the cell. Various controls confirmed that emission was from the alveoli, in particular, the emitting zone was still seen in mutants totally lacking trichocysts, the large exocytotic organelles docked at the cell surface, indicating that they make no major direct contribution to the emission. Calcium concentration within alveoli was quantified for the first time in SIMS microscopy using an external reference and was found to be in the range of 3 to 5 mM, a value similar to that for sarcoplasmic reticulum. After massive induction of trichocyst discharge, this concentration was found to decrease by about 50%, suggesting that the alveoli are the main source of the calcium involved in exocytosis.

Triterpenoid saponins from the root of Sideroxylon foetidissimum

Two novel triterpenoid saponins named sideroxyloside B and sideroxyloside C were isolated from the root of Sideroxylon foetidissimum. On the basis of spectroscopic and chemical methods, their structures were established as 3-O-beta-D-glucopyranosyl-28-O([beta-D-apiofuranosyl-(1-->3)-beta- D- xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->4)] [beta-D-apiofuranosyl(1-->3)]-alpha-L-rhamnopyranosyl-(1-->2)-alph a-L- arabinopyranosyl) protobassic acid and 28-O([beta-D-xylopyranosyl-(1-->4)- alpha-L-rhamnopyranosyl-(1-->4)] [beta-D-apiofuranosyl-(1-->3)]-alpha-L- rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl) protobassic acid, respectively.

Detection of the 4977 base pair mitochondrial DNA deletion in paraffin-embedded heart tissue using the polymerase chain reaction--a new method to probe sudden cardiac death molecular mechanisms?

Detection of mitochondrial DNA deletions is performed in fresh or frozen material. At our institute, however, heart samples from subjects referred for autopsy are systematically processed for histologic examination (that is, paraffin-embedded). We were interested to know if mtDNA deletions can be detected in such material. Our data indicate that: 1) the most frequently observed deletion--the 4977 base pair deletion--can easily be detected in paraffin-embedded heart tissue; 2) this assay is sufficiently sensitive, since very low levels of the deletion can be found in normal heart tissue from young adults; and 3) buffered formalin appears to be the fixative of choice. Recent literature shows that repeated episodes of ischemia result in the accumulation of mtDNA deletions in myocardial cells. Because ischemic heart disease is a major cause of sudden cardiac death, a sensitive method for the detection of mtDNA damage in myocardial cells will be an important tool to facilitate understanding of unexpected cardiac arrest mechanisms.

[Sudden coronary death outside of hospital; an comparative autopsy study of subjects with and without previous cardiovascular diseases]

Autopsy studies of the heart of 221 subjects who suffered pre-hospital coronary sudden death were performed at the Paris Medico-Legal Institute over a period of 3 years to compare the lesions observed in subjects without known cardiovascular disease (Group A: n = 160; 72.4%) with those of subjects with known cardiovascular disease (Group B: n = 61). The proportion of men was greater in Group B (77%) that in Group A (62.5%). The average age of sudden death was the same in both groups: 65 years for men and 77 years for women. Sudden death usually occurred in the home (83%) at rest and, in one third of the cases, during sleep. Sudden death occurred in a context of severe coronary artery disease in both groups: significant triple vessel stenosis (> 75%) in 60% of subjects in both groups but thrombosis was found in only 13% of cases in Group A and 15% of cases in Group B. The mean weight of the heart was significantly greater than normal in both groups and in both sexes. In addition, the mean weight of the heart of subjects in Group B was significantly greater than that of subjects in Group A (p < 0.05). This autopsy study showed that prehospital coronary sudden death was the first sign of coronary disease in 70% of cases. Irrespective of whether the subject had known cardiovascular disease or not, sudden death occurred under similar circumstances and, in both cases, in the context of severe coronary artery disease.

Sudden out-of-hospital coronary death in patients with no previous cardiac history. An analysis of 221 patients studied at autopsy

Many epidemiological, clinical, and autopsy studies have demonstrated that the risk of sudden coronary death (SCD) is linked to the severity of coronary atherosclerotic lesions and to their thrombotic potential. However it remains unknown why some individuals manifest no clinical evidence of coronary disease until the onset of sudden death. The aim of this autopsy study has been to analyze the sociodemographic, clinical, and pathological features in case of sudden out-of-hospital coronary death where the death was the first manifestation of coronary disease. The results have been compared with those obtained from victims of SCD with known cardiac history. A total of 377 autopsies of sudden out-of-hospital cardiovascular deaths were performed at the Forensic Institute of Paris between 1989 and 1991. A total of 221 were SCD. A total of 160 of these subjects (72.4%) had no cardiac history (group A). The other 61 victims of SCD had cardiac antecedents (group B). Men account for 63% and 77% of the SCD in groups A and B respectively and are 12 years younger than women at the onset of SCD in both groups (65/77 years). Our study showed that in both groups SCD occurs in 83% of cases at home (and at rest) and in 30% of these cases while sleeping. Autopsy showed that SCD be it with or without antecedent occurs on a background of severe coronary disease with multivessels stenoses but coronary thrombosis was rarely observed (15%). SCD occurred in the context of underlying cardiomegaly.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolated myocardial fibrosis as a cause of sudden cardiac death and its possible relation to myocarditis

In performing medicolegal autopsies on sudden deaths, there occur a number of cases in which no cause of death can be found. In particular, no evidence of macroscopic cardiac abnormalities can be observed. However, extensive histological screening may reveal isolated areas of myocardial fibrosis. The five cases presented discuss the etiology of this fibrosis and its possible relation to myocarditis. The cases involve white women between the ages of 19 and 25 with no previous medical history. The weight of the heart in all five cases was normal. Macroscopic evidence of fibrosis was visible in four out of five cases. No other macroscopic abnormalities were observed. Histologically, there was evidence of scarring or interstitial fibrosis in all five cases. In four of the cases, additional screening permitted the observation of dispersed inflammatory foci consisting of lymphocytes, plasmocytes and macrophages. Two of the cases demonstrated eosinophil and neutrophil aggregates in the center of necrotic foci. No evidence of vascular inflammatory phenomena was observed in any of the five cases. According to the Dallas criteria, three of the five cases fulfill the requirements for myocarditis and one of the five cases for borderline myocarditis. The Dallas criteria, however, do not take into consideration the possible association between inflammation and myocardial fibrosis since many of the reported series of myocarditis have been from hospital autopsies or endomyocardial biopsies and have not taken into account sudden death from fibrotic sequelae of myocarditis.(ABSTRACT TRUNCATED AT 250 WORDS)

["Medicolegal" bone fluorosis. Apropos of 2 cases of possible criminal poisoning]

We report two cases of skeletal fluorosis in two men, 55 and 69 year-old. The physical findings and the roentgenograms were typical and chemical analysis confirmed the diagnosis. Surprisingly, fluoride concentrations in blood and urine were increased at the beginning of the hospitalizations and lower during the hospitalizations. The origin of fluor intake remained unknown, leading to consider a possible criminal poisoning. Then, we discuss the attitude of physician in a case a possible criminal poisoning: denunce the crime to the police or not, as regards french law.

[Efficacy of antihypertensive treatment in the French population. A multicenter survey]

In order to assess the efficacy of antihypertensive treatment in the population, a study was undertaken in 5 French cities during the commercial fairs of Grenoble, Marseilles, Nice, Toulouse and Lille. The blood pressure was measured according to the WHO recommendations in volunteers. The study included a total of 7107 subjects of both sexes, with 4064 subjects in the 35-64 year age group. The therapeutic efficacy was evaluated in the 791 hypertensive patients who knew their antihypertensive therapy. Taking < 160/95 mmHg as the criterion of efficacy, 52 to 73% of the hypertensive patients were well controlled. However, if the therapeutic objective of normalisation of the blood pressure (BP < 140/90 mmHg) is taken as the criterion of efficacy, only 23 to 29% of the hypertensive patients were controlled whilst their BP remained significantly higher than that of normotensive controls of the same age. The difference in efficacy of antihypertensive therapy between the cities may be explained by the heterogenicity of the populations whereas the treatment did not differ significantly. After adjustment analysis with respect to sex showed that women were better controlled than men whatever the criterion chosen. The group controlled at BP < 160/95 mmHg only differed from the group < 140/90 with respect to the average BP value which was higher before treatment and decreased less with treatment; though this did not achieve statistical significance. In matters of public health, if the ideal blood pressure is taken as < 140/90 mmHg, this study shows that the objective is only attained in one out of four patients in the population studied.

[Structure of arterial intima in children and adolescents. A pathological study of 101 cases]

This was a macroscopic and histological study of the arteries of 101 unselected subjects from 0 to 20 years of age without cardiovascular pathology, autopsied to determine the cause of death at the medico-legal Institute of Paris. Stary's classification was used as a reference. Multiple Biopsies were taken from throughout the arterial system: initial aorta, carotid artery and its bifurcation, descending supra and infra renal aorta, iliac artery and left anterior descending artery. In this population, we found arterial lesions in 63% of subjects in the 15 to 20 year age range and this confirms previously reported data, especially by Stary. The lesions were identical irrespective of the site of biopsy and predominated at the bifurcations. No difference was observed with regards to sex and the lesions progressed after puberty.

Advantages of fast-freeze fixation followed by freeze-substitution for the preservation of cell integrity

The use of fast-freeze fixation (FFF) followed by freeze-substitution (FS) has supplied new data in a variety of domains due to the rapidity of this fixation compared to the slow process of the conventional chemical fixation. FFF completely arrests all the cell's biological reactions, and physically immobilizes most molecules within a few milliseconds. This review deals with the main results we obtained concerning the preservation of organelles particularly sensitive to osmotic shock, the maintenance in situ of soluble or depolymerizable cell components, the visualization of brief transient events, and the opening up of new prospects in the field of immunocytochemical labeling.

Cryo-electron microscopy of vitrified specimens: an approach to the study of bulk specimens

We are using and developing cryo-electron microscopy of vitrified specimens. Our main interests concern the structure of muscle and muscular components. Micrographs which generally contain periodic features are analyzed by numerical image processing methods. To detect artifacts induced by the electron microscopy techniques, we correlate our results to those obtained by X-ray diffraction. In this paper, we describe our approach to the study of bulk specimens. Vitrification of such specimens is assessed by cryo-X-ray diffraction. Microscopy is done on cryo-substituted specimens.

Time-resolved cryo-electron microscopy of vitrified muscular components

Biological objects may be arrested in defined stages of their activity by fast freezing and may then be structurally examined. If the time between the start of activity and freezing is controlled, structural rearrangements due to biological function can be determined. Cryo-electron microscopy shows great potential for the study of such time-dependent phenomena. This study examines the actin polymerization process using cryo-electron microscopy of vitrified specimens. Actin filaments are shown to undergo a structural change during polymerization. In the early stages of the polymerization process (t less than 2 min), filaments exhibit a pronounced structural variation and frequently show a central low-density area. In the later stages of the polymerization, F-actin-ADP filaments have a more uniform appearance and rarely display a central low-density area. These findings, analysed on the basis of a previously proposed polymerization model, suggest that polymerization intermediates (F-actin-ATP and more probably F-actin-ADP-Pi) and filaments at steady state (F-actin-ADP) have different structures. To investigate the physiological relevance of these results at the cellular level, the potential of cryo-substitution in preserving the structure of muscular fibre was assessed. Optical diffraction patterns of relaxed and contracted frog cutaneous muscle are similar to the corresponding X-ray diffraction patterns. The resolution of the images extends to about 7 nm. These results show that dynamic study of muscle contraction is possible using cryo-substitution.