[Diagnostic assessment of peritoneal fluid cytology in horses with abdominal neoplasia]

OBJECTIVE

To evaluate the diagnostic value of peritoneal fluid (PF) cytology for clinical diagnosis of abdominal neoplasia in horses.

MATERIAL AND METHODS

Ten horses with histopathologically confirmed abdominal neoplasia, in which a PF analysis was performed, were included in this retrospective study. PF was analyzed for total protein concentration and a nucleated cell count was performed. Using cytological criteria of malignancy, the PF samples were evaluated regarding their probability of malignancy.

RESULTS

Cytologic classification of cells according to criteria of malignancy allowed a positive cytologic diagnosis of neoplasia in 5 out of 10 peritoneal fluid samples. Malignant lymphoma was the most commonly diagnosed neoplasia (3/10) and could be identified by cytology in 2/3 cases. In 1/2 horses with plasma cell myeloma neoplastic cells were similarly found. Malignant melanoma (2/10) was diagnosed using cytology in one case (presence of melanin-containing cells). Cytological diagnosis of malignant neoplasia was established in the only horse with gastric squamous cell carcinoma, but the morphology of the identified tumour cells did not allow a specific diagnosis. Thus, a definitive diagnosis was achieved in 4/5 horses with proven abdominal neoplasia. The horses with adenocarcinoma (1/10) and haemangiosarcoma (1/10) had no evidence of neoplasia based on cytological findings. No relationship between total protein concentration or the nucleated cell count with the histolopathological diagnosis of abdominal neoplasia was found. Abnormal mitotic figures were considered of greater diagnostic value than the overall mitotic rate.

CONCLUSION

The implementation of nuclear criteria of malignancy in the cytologic evaluation of PF samples allows the identification of neoplastic cells to an acceptable degree. For this purpose, the knowledge of the highly variable morphological features of mesothelial cells is essential. The absence of malignant cells does not rule out abdominal neoplasia.

CLINICAL RELEVANCE

PF cytology should be considered as a valuable, minimally invasive, simple, and rapid diagnostic technique in horses with suspected abdominal neoplasia.

Diagnostische Aussagekraft der Zytologie von Bauchpunktaten bei abdominalen Tumoren des Pferdes

Gegenstand und Ziel: Retrospektive Analyse zur Aussagekraft der Zytologie von Bauchpunktaten (BP) hinsichtlich der Intra-vitam-Diagnostik abdominaler Neoplasien. Material und Methoden: Vorgestellt werden 10 Pferde mit histopathologisch bestätigter abdominaler Tumormanifestation, bei denen ante mortem eine Abdominozentese mit Punktatuntersuchung stattfand. Im Bauchpunktat (BP) wurden die Gesamteiweißkonzentration und die Zellzahl bestimmt. Die zytologische Beurteilung erfolgte hinsichtlich der Malignitätswahrscheinlichkeit anhand definierter Malignitätskriterien. Ergebnisse: Bei fünf der 10 Pferde konnte anhand der Zytologie des BP eine Neoplasie bestätigt werden. Das maligne Lymphom war der am häufigsten (2/3 BP) diagnostizierte Tumor. Bei 1/2 Pferden mit multiplem Myelom ergab sich ebenfalls ein positiver Befund des BP. Das maligne Melanom (2/10) wurde in einem Fall über das BP diagnostiziert. Der positive Nachweis gelang ferner bei einem Pferd mit Plattenepithelkarzinom des Magens, wobei die Tumorzellmorphologie hier keine spezifische Tumordiagnose ergab, sodass eine solche nur bei 4/5 Neoplasien möglich war. Ein Adenokarzinom und ein Hämangiosarkom konnten nicht erfasst werden. Der Punktatcharakter erlaubte keinen Rückschluss auf die Tumorart. Das Vorliegen abnormer Mitosen hatte einen größeren diagnostischen Wert als die Mitoserate. Schlussfolgerung: Die Anwendung nukleärer Malignitätskriterien ermöglicht eine akzeptable Identifizierung von Tumorzellen bei Kenntnis der morphologischen Variabilität von Mesothelzellen. Das Fehlen maligner Zellen schließt jedoch eine Neoplasie nicht aus. Klinische Relevanz: Die zytologische Untersuchung des BP ist wertvoller Bestandteil des diagnostischen Vorgehens bei Verdacht auf eine abdominale Tumorose.

Small animal bone healing models: standards, tips, and pitfalls results of a consensus meeting

Small animal fracture models have gained increasing interest in fracture healing studies. To achieve standardized and defined study conditions, various variables must be carefully controlled when designing fracture healing experiments in mice or rats. The strain, age and sex of the animals may influence the process of fracture healing. Furthermore, the choice of the fracture fixation technique depends on the questions addressed, whereby intra- and extramedullary implants as well as open and closed surgical approaches may be considered. During the last few years, a variety of different, highly sophisticated implants for fracture fixation in small animals have been developed. Rigid fixation with locking plates or external fixators results in predominantly intramembranous healing in both mice and rats. Locking plates, external fixators, intramedullary screws, the locking nail and the pin-clip device allow different degrees of stability resulting in various amounts of endochondral and intramembranous healing. The use of common pins that do not provide rotational and axial stability during fracture stabilization should be discouraged in the future. Analyses should include at least biomechanical and histological evaluations, even if the focus of the study is directed towards the elucidation of molecular mechanisms of fracture healing using the largely available spectrum of antibodies and gene-targeted animals to study molecular mechanisms of fracture healing. This review discusses distinct requirements for the experimental setups as well as the advantages and pitfalls of the different fixation techniques in rats and mice.

[Learning and optimising minimally invasive techniques by operating on embalmed human corpses]

The expansion of minimally invasive surgery worldwide provokes an intensive interest of all surgical disciplines in gaining possibilities for research, learning and teaching by operating on human corpses. Despite the fact that German anatomical institutes in general have the infrastructure to realise such clinical cooperations, at present they may offer such opportunities only to a restricted degree, since the concentration on student teaching and anatomic research limits the capacity of the staff for a commitment in this field of applied science. To provide a basis for future estimations of the efforts necessary to perform solo surgery on the human cadaver, especially with emphasis on research, quality control and teaching, this article reports on practical experiences with such a project named "ANAtoMIC", identifying minimal conditions which have to be realised.

Anatomic guidelines for the prevention of abdominal wall hematoma induced by trocar placement

A knowledge of the parietal structures of the abdominal wall is necessary to minimize risks of operative procedures like laparoscopy. For means to prevent intraoperative bleeding and the occurrence of abdominal wall hematoma, we studied the course of the inferior epigastric arteries and the ascending branch of the deep circumflex iliac artery in 21 human cadavers. The abdominal wall structures were dissected and the distances of the arteries in relation to anatomic structures such as the umbilicus, pubic symphysis, superior ischial spine and lower edge of the rib-cage were measured. Comparison of the morphometric results obtained with the location of 36 trocar incision sites recommended in the common literature yields the information that about half of these incision sites incur the risk of injuring the arteries.

[Effect of common head gear on horses]

The functions of the most common head-gears for horses are analysed from a biomechanical point of view. With the exception of the stable halter are all of them designed to enlarge the tensile forces transmitted through the reins or the longe, and to concentrate the enlarged forces on sensitive parts of the horse's head: the nose, or the lips, mandible and tongue. Since the direction, duration and size of these tensile forces are the essential factors to modulate signals for controlling the horse, a device has been developed to measure, or at least roughly quantify these forces. The mechanical characteristics of bosal, caveçon, serreta, kappzaum and hackamore are demonstrated and compared with those of the two major types of bits: those with and without levers.

A calculation of the forces acting on the human acetabulum during walking. Based On in vivo force measurements, kinematic analysis and morphometry

Information about the loading of the human acetabulum during walking is necessary for a functional understanding of the morphology of the pelvic girdle and the hip joint as well as for the optimization of endoprosthetic therapy in osteoarthritis. For this purpose, experimental data of the forces acting on the femur in walking taken from the literature [Bergmann et al.: J. Biomech. 1993;26: 969-990] were combined with our own kinematic and morphometric data, to transform the force vectors from the femoral into a pelvic and an acetabular frame. During the walking cycle, the resultant force vector takes a rather constant course relative to the pelvis and its orientation seems to be highly regulated to act within a small range of angles. Only small deviations occur from the angles against the vertical which the resultant peak force forms in the frontal plane (F = 11 degrees, medially orientated) and in the sagittal plane (S = 5 degrees, ventrally orientated). The experimental results form the basis for a model of the incongruous hip joint as an elastic joint, the femoral head being centered between compliant elements.

Maternal selenium status influences the concentration and binding pattern of zinc in human milk

To study the health effects of high dietary maternal selenium intake breast milk, blood and toe-nails were collected from 143 women (20-24 days of lactation) living in Venezuelan states of Yaracuy and Portuguesa. Depending on the regional selenium intake level three regions were defined within the total range of 90-980 microgram per day. The samples were analyzed by means of INAA for the determination of trace elements, including selenium and zinc. The significant inverse correlation between Se and Zn in breast milk found in former studies was confirmed. Investigation of the Zn-binding pattern in milk whey was carried out by an on-line combination HPLC (SEC) for protein separation and ICP-AES for element detection. Six Zn-binding compounds including citrate were detected. A highly significant negative correlation was found between the citrate, which is the main low-molecular Zn-binding compound, and the maternal daily selenium intake. We determined that the decrease in zinc concentration is due to a decrease in the citrate level, which depends on the selenium concentration in breast milk. The selenium concentration in breast milk is, in turn, proportional to the dietary intake. In addition, significant changes in the UV- and Zn-profiles were observed in the milk whey with the highest selenium content, indicating that above a certain maternal intake level substantial changes in the composition of mammary secretory cells occur. This effect can be of interest for estimation of the safe dietary intake level of selenium.

Is elastic energy storage of quantitative relevance for the functional morphology of the human locomotor apparatus?

Elastic storage of energy in the vertebrate locomotor apparatus is supposed to be an important functional factor in cyclic and acyclic movements. In terms of physics, for humans a proof for the occurrence and quantitative relevance of this phenomenon in vivo and under physiological conditions has been missing until now. In addition to the large amount of plausible, but inconclusive information about elasticity in humans and animals, we describe a simple experiment to prove the existence of quantitatively relevant elastic energy storage in the human locomotor apparatus. Ten volunteers (5 female, 5 male) each assumed a relaxed, upright posture on a steel platform. After the release of a support, the volunteers and the platform fell for a defined distance of 33 mm. Loaded with the volunteers, the platform fell significantly (p < 0.001) faster than predicted by the laws of stiff body mechanics (50 vs. 82 ms). For a minimum time of 50 ms, the human locomotor apparatus is able to support an average external power output of more than 400 W by means of an energy transfer of more than 20 J. During the fall, no EMG activities of the ankle flexors could be recorded. We conclude that the acceleration of the platform fall is induced by elastic elements serving as energy sources. Elastic energy storage is of quantitative relevance for the functional morphology and biomechanics of the human locomotor apparatus.

[Is indirect posturography using force plates equivalent to direct posturography by movement analysis? A physical observation]

Piezoelectric force plates are accurate and convenient aids for the monitoring of coordination in erect humans. However, the results obtained with such "indirect" posturographic measurements should not be "over-interpreted". The information on the spatial location of the centre of pressure (CoP) provided by the force plate permits conclusions to be drawn about the regulation of the "sway" of the centre of gravity (CoG) only when other information on the acceleration situation of the body is available. Otherwise the systematic error of the measurement exceeds the amount of the true "sway" even for physiological cyclic movement frequencies of 0.5 Hz or more.

[The lumbar ligamentum flavum. Anatomic characteristics with reference to microdiscotomy]

One important step in lumbar discotomy is the safe penetration and exact partial removal of the Lig. flavum. This is a crucial prerequisite for the selective and gentle removal of prolapsed and sequestrated intervertebral disc tissue. Extensive lancing of the Lig. flavum should be avoided, to minimize intraoperative and postoperative complications, such as injuries to the nerves and the Dura mater, instabilities, bleeding and scarring. As there has up to now been insufficient information on the anatomy of the Lig. flavum especially regarding microdiscotomy, an analysis of the Ligg. flava L2/L3 to L5/S1, guided by this aim, was carried out on 36 corpses kept in formaline (16 f, 20 m; 52-78 y). Preparations showed the lumbar Ligg. flava to be embodied in the Foramina interarcualia in a characteristic configuration. There also proved to be defined insertion areas on the laminae of the vertebral arches, which must be taken into consideration during the operative exposure. The Lig. flavum rises from the cranial vertebral arch from the ventral surface of the lamina (6.8 mm) whilst the insertion area on the caudal lamina covers the dorsal and the ventral surface. The extent at the ventral surface is 2.2 mm in average. Taking the insertion proportions into account we would suggest the Lig. flavum to be divided as follows: Pars interspinalis, which clearly differs from the Lig. interspinale (and from the M. interspinalis), and which houses venous anastomoses in its dorsal, ridge-shaped extension. Pars interlaminaris, which starts at the laminae and constitutes the target area for flavotomy in its lateral section, and Pars capsularis, which merges into the capsular structures of the facets. In all levels examined, there proved to be dorso-ventrally a typical change in the direction of the course of the fibres in the Pars interlaminaris. Whilst the direction of the fibres dorsally is oriented cranio-medially to caudo-laterally at an angle between 15 degrees and 30 degrees to the median line, the ventral fibres of the Lig. flavum are strictly aligned cranio-caudally. The changes in the directions of the fibres are continuous with the fibres being very closely intertwined, without there being any spatium at all. The texture of the Lig. flavum is, therefore, a mirror image of that of the autochthonuous muscular system of the back, even if the overlapping angle area is considerably smaller. The different segment levels show a segment-specific thickness profile. The analysis has provided anatomic information about the Ligg. flava L2/L3 to L5/S1. These data represent important prerequisites for a selective, gentle and safe intraoperative procedure for discotomy.

[Shape transformations of the lumbar spine in relation to passive extension of the lower extremities in the sagittal level]

PROBLEM

The interdependencies between movements of the thighs and the lumbar vertebral shape are of high practical interest. Which are the normals of this phenomenon?

METHOD

In an experiment on 107 volunteers without before known spinal disorders and complaints of back pain (47 f, 60 m, 17 a-30 a), the interdependencies between movements of the thighs in the sagittal and the lumbar back profile were analysed. Hip joint movements were provoked by a lift jack, elevating the feet to the volunteers, which sat on a bicycle chair. The hip joint flexion was measured by a Zebris CMS 50. The sagittal profile of the lower back was sensed by a comb of steel needles with low friction support.

RESULTS

At 30 degrees of hip flexion, 68% of the volunteers demonstrated a kyphotic, 17% a straight and 15% a lordotic lumbar shape. Starting at 90 degrees of hip flexion, "definitively kyphosating movements" of the lumbar motion segments occur. At the end of the motion, 89% of the volunteers had a kyphotic, 3% a straight and 8% a lordotic lumbar configuration. Each 2 degrees of additional hip joint flexion caudo-cranially one more lumbar motion segment is recruited for the definitive kyphosation of the lumbar spine.

CONCLUSIONS

Instead of a "physiological shape of the lumbar spine" its "physiological function" or its "physiological interaction between shape und function" should be in the focus of future discussions. In the sitting, hip joint flexion leads to a coupled motion of the thighs, the pelvic girdle and the lumbar vertebral column with the consequence of a kyphosation of the lumbar back shape.

[Landing after jumps--wrong technique promotes spondylolysis]

The double-S-shape of the vertebral column usually is explained to be an adaptation to the functional requirements of axial shock absorption. We investigated the effects of axial impacts on the coupled motions of the pelvic girdle and the vertebral column. In contrast to the predictions of the bending spring model, in the first few miliseconds after impact induction the vertebral column shows a tendency of lumbal straightening. This effect may be one reason for high stresses in the vertebral arches, promoting spondylolysis and spondylolisthesis. In sports, high axial impact loads, especially provoked by wrong landing techniques after jumps, should be avoided.

Speciation of Se, Fe and Zn in Human Milk Whey: The use of Instrumental Neutron Activation Analysis (INAA) to corroborate element profiles measured with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)

In human milk trace elements normally exist in a form which can easily be absorbed by the newborn infant. For investigations of the bioavailability of trace elements it is necessary to carry out a speciation analysis of the elements of interest. An independent analytical method has been used for the quality control of the shape of the element profiles obtained from the speciation analysis of Se, Fe and Zn in individual samples of human milk whey after chromatographic separation. For the element detection in the untreated milk fractions Instrumental Neutron Activation Analysis (INAA) was chosen as the reference method. Element distribution patterns have been obtained with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) using on-line digestion of the fraction, reduction and hydride formation of Se ("T"-mode). Prior results are compared with those obtained by means of element detection in the untreated fractions ("U"-mode) with ICP-AES. The elution profiles of Se, Fe and Zn in human milk whey obtained by means of ICP-AES detection using the "T"-mode show good agreement with the distribution patterns obtained with INAA. Recoveries of 103% for Fe, 86% for Zn and 87% for Se were obtained. The element distribution patterns of Fe and Zn obtained with ICP-AES speciation using the "T"-mode also show good agreement with those obtained by means of ICP-AES using the "U"-mode.

Parenteral aluminum loading in critical care medicine. Part II: Response to aluminum load from long-term parenteral nutrition

OBJECTIVE

Evaluation of the iatrogenic aluminum load by aluminum-contaminated nutritive infusion solutions in long-term total parenteral nutrition (TPN).

PATIENTS

16 consecutive patients (6 children, 10 adults) who had to undergo total parenteral nutrition for more than one month. Three of them were from a home parenteral nutrition program. The duration of TPN was up to 68 months. The parenteral aluminum load was calculated on the basis of the individual TPN programs. Six patients were exposed to an additional parenteral aluminum load in the course of intensive care. Comparative group: To establish a reference range, the serum aluminum concentrations were determined in 71 unloaded patients who had to undergo minor surgical procedures. ALUMINUM ANALYSIS: Strict adherence to a contamination-free sampling and processing technique. The aluminum determination was performed at the Hahn-Meitner-Institute Berlin by means of graphite-furnace atomic absorption spectrometry (GFAAS).

RESULTS

The TPN-associated daily aluminum load was 3.5 +/- 0.4 micrograms/kg body weight (bw) in children and 2.2 +/- 1.8 micrograms/kg bw in adults. 59 +/- 6% of the intravenous aluminum load in children and 42 +/- 16% in adults was due to the highly contaminated small-volume calcium, inorganic phosphate, trace element and vitamin parenterals. The median serum aluminum concentration under TPN was 10.9 micrograms/l (range: 5.0-26.9 micrograms/l) and was thus 7.3 times higher than in the preoperative control group (median: 1.5 micrograms/l, 95% confidence interval: < 0.6-3.5 micrograms/l). Individual values ranged up to 36.8 micrograms/l.

CONCLUSIONS

The aluminum intake of patients on parenteral nutrition in Germany is thus on occasion considerably above the ASCN/ASPEN recommendations for the limitation of intravenous aluminum loading (ASCN: American Society for Clinical Nutrition; ASPEN: American Society for Parenteral and Enteral Nutrition). The toxicological significance of parenteral aluminum loading is discussed. The results suggest that limits should be established for the Aluminum contamination of infusion solutions.

Parenteral aluminum loading in critical care medicine. Part I: Aluminum content of infusion solutions and solutions for parenteral nutrition

BACKGROUND

For patients with disturbed aluminum (Al) excretion, a high Al intake is not without risk. As main aluminum sources infusion solutions and solutions for parenteral nutrition have been identified. This study will give current survey of aluminum loading of the above-mentioned preparations.

MATERIAL AND METHODS

The aluminum loading of 139 different infusion solutions and solutions for parenteral nutrition was determined. The solutions were from the clinical pharmacy of the Klinikum Steglitz of the Free University Berlin or were bought in a public pharmacy. The aluminum content was determined by means of two different, independent analytical methods: a) graphite furnace atomic absorption spectroscopy (GFAAS) and b) inductively coupled plasma atomic emission spectroscopy (ICP-AES). The agreement of the measured values was good except for five samples, where different values were found. Mistakes due to contamination were excluded on the basis of the results of measuring standard reference materials.

RESULTS

Small-volume additives of TPN (total parenteral nutrition) formulations were highly contaminated with aluminum, e.g. Ca and phosphate solutions (29-12,000 micrograms/l), vitamin C solutions (700-1,200 micrograms/l) and trace element solutions (67-6,200 micrograms/l). Furthermore about 44% of the crystalline amino acid solutions and lipid emulsions had an aluminum content of 25 to 55 micrograms/l. Low aluminum levels were found in carbohydrate solutions, NaCl and KCl solutions and in distilled water (aqua ad injectabilia).

CONCLUSIONS

Many of the solutions for parenteral nutritional support have an aluminum content which exceeds, in part considerably, the suggested threshold concentration of 25 micrograms/l (0.93 mumol/l), recommended by the American Society for Clinical Nutrition (ASCN) and the American Society for Parenteral and Enteral Nutrition (ASPEN). The pharmaceutical industry should be required to check the manufacturing process for avoidable sources of contamination, and threshold values for aluminum loading by intravenously applied pharmaceuticals should be laid down in the German and European pharmacopoeia. In cases where contaminations cannot be eliminated during the manufacturing process after careful checking, the aluminum content of the infusion solution should be declared for the user.

[Temperature range in bipolar high frequency coagulation of the appendiceal stump]

Since laparoscopic appendectomy is performed more frequently disturbances of cecal motility have been found postoperatively in many cases. The etiology of this "syndrome of the fifth day" has not been cleared yet. To assess whether high-frequency bipolar electrocautery could be one of the etiologic factors, measurements of temperature were performed in lamb bowel, cadaver appendices and in vivo during laparoscopic appendicectomy. Next to the appendix stump ligation at the cecum wall the mean maximal temperature was as high as 53.2 degrees C. We believe that high frequency electrocoagulation is one of the etiologic factors of disturbances of the cecal motility especially if safety distances are not followed.

[Determination of minerals and trace elements in selenium tea from the Enschi district, People's Republic of China, and in its infusions using inductively coupled plasma-atomic emission spectrometry, graphite furnace atomic absorption spectrometry and instrumental neutron activation analysis]

The Enschi district in Hubei province, Peoples Republic of China is geochemically one of the two seleniferous regions, producing both selenium (Se) black tea and the Se green tea. Three samples of green tea with different Se contents and one non-Se tea were analysed. The following mineral and trace elements were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES): K, Ca, Mg, Na, P, S, Al, Mn, Fe, Ba, Sr, Co, Ni, Cu, Zn, Mo, and Cr. Except for Mo, Co, and Cr, all other elements in infusions of the samples analysed were also measured, since their concentrations are lying over their detection limits. The Se content in the tea samples and in the infusions were measured with graphite furnace atomic absorption spectrometry (GFAAS). The accuracy of Se determination was tested by measuring untreated tea samples with instrumental neutron activation analysis (INAA). The Se content in the measured samples was 1 to 8.5 micrograms/g. In addition to Se, 17 other elements were measured in the tea samples and 14 others in the infusions. With this data the extractable part of this elements in the infusion were calculated. Up to 10% of the Se was found in a first infusion.

Detection by HPLC-ICP of metallothionein in serum of an epileptic child with valproate-associated hepatotoxicity

A patient who developed valproate-associated hepatotoxicity had significantly lower serum levels of total protein, albumin and selenium than the controls. This study shows that with the beginning of the hepatic coma metallothionein (MT) appeared in the serum mainly in the form of Zn-thionein, which altered the Zn distribution pattern of the serum in a characteristic manner. HPLC-ICP3 was successfully applied to the simultaneous speciation of elements and characterization of MT by the use of one gel permeation column.

Micronuclei induced by 2-chlorobenzylidene malonitrile contain single chromosomes as demonstrated by the combined use of flow cytometry and immunofluorescent staining with anti-kinetochore antibodies

The effects of the tear gas 2-chlorobenzylidene malonitrile (CS) on micronucleus induction and cell cycle kinetics were studied in Chinese hamster and Ehrlich ascites tumour cells using flow cytometric analysis of micronuclei and nuclei in suspension, and indirect immunofluorescent staining of kinetochores in micronuclei. In both cell lines CS induced a concentration-dependent inhibition of the fraction of cells in mitosis as observed by simultaneous flow cytometric measurements of DNA content and side scatter intensities of cell nuclei. Micronucleus frequency increased during the delayed division of cells accumulated by CS in mitosis and reached a plateau when most of these cells have divided. The height of this plateau depended on the CS concentration. Results obtained by flow cytometric analysis of the frequency of CS-induced micronuclei did not agree quantitatively with results obtained by microscopic analysis due to cells showing CS-induced fragmented nuclei. Nearly all CS-induced micronuclei exhibited kinetochores, the majority of which (60-70%) showed one kinetochore per micronucleus implying the presence of a single metaphase chromosome in these micronuclei. DNA distributions of micronuclei measured by flow cytometry showed pronounced peaks corresponding to the DNA distribution of chromosomes measured by flow karyotyping. Even micronuclei containing two of the large chromosomes could be observed as distinct peaks in the distributions. The combined results of flow cytometric analysis of micronucleus distributions and immunofluorescence staining of kinetochores in micronuclei suggest that CS induces micronuclei mainly by damaging the spindle fibres of single chromosomes during mitosis, thus possibly leading to aneuploidy and polyploidy.