Neuroendocrine response to a psychosocial stress test is not related to schizotypy but cortisol elevation predicts inflexibility of semantic memory retrieval

An altered stress response can contribute to the transition from preclinical psychotic symptoms to the clinical manifestation of schizophrenia and other psychotic disorders. The present study was aimed at testing the hypotheses that (i) the autonomic and neuroendocrine responses under psychosocial stress are dysregulated in individuals with high psychosis proneness (schizotypy); (ii) the magnitude of post-stress autonomic activation and cortisol release predicts alterations in semantic memory retrieval. The study was performed in 73 healthy individuals of both sexes with either high or low schizotypal traits preselected out of 609 individuals using the Schizotypal Personality Questionnaire. A psychosocial stress procedure based on public speech was used as a stress model. We found that individuals with high schizotypy engaged in less adaptive emotional stress-coping strategies than low schizotypy individuals. Yet, the neuroendocrine, immune, and sympathetic activation in response to the stress test was not different between the groups. Irrespective of the exposure to the stressor, individuals with high schizotypy were less fluent when retrieving associations from semantic memory. In addition, we demonstrated that acute psychosocial stress reduced the flexibility of semantic memory retrieval. The post-stress mental inflexibility was reliably predicted by the concomitant elevation of cortisol concentrations in saliva. The present study thus brings novel evidence indicating that the acute psychosocial challenge impairs retrieval flexibility in the semantic domain, which may be due to neuroendocrine activation.

P11.18.A Localizing value of EEG recordings in patients with glioblastoma

Background

Glioblastoma is associated with a high risk of epileptic seizures ranging from 40% to 60%. Before the advent of modern imaging techniques, electroencephalography (EEG) was a critical component in evaluating patients with space-occupying lesions. In this retrospective single-center study, we aimed (1) to characterize a cohort of patients with glioblastoma with regards to EEG monitoring, seizure frequency and the frequency of prescribed anti-seizure medications (ASM) and (2) to assess the value of EEG as a localizing technique in patients with glioblastoma.

Material and Methods

We reviewed the charts of 179 patients with glioblastomas between January 1st, 2020 and January 1st, 2022, treated at the Medical University of Vienna. The diagnosis was based on MRI and/or confirmed by biopsy according to the 2016 World Health Organization Classification of Tumors of the Central Nervous System. Patients who received an in-house EEG as part of their diagnostic work-up were included if an MRI/CT scan was available (within an average time of +/-60 days). For localization, focal slowing (theta/delta activity) and/or epileptiform discharges were considered. EEG rating was performed by a board-certified electrophysiologist blinded for the diagnosis and MRI/biopsy findings.

Results

We included 52 patients (29.05% of screened cohort) with at least one EEG and MRI or CT scan performed before or after EEG, following inclusion criteria (median: 2 days; mean: 6 days; range: -29 to 52), in the final analysis. Clinical seizure activity and/or epileptiform discharges on EEG were detected in 46 patients (88.46%), and 48 patients (92.31%) were on ASM.

An IDH-wildtype glioblastoma was diagnosed in 45 patients (86.54%), 4 had an IDH-mutant glioblastoma (7.69%), and in 3 patients, IDH-status was unknown (5.77%). In 22 patients (42.31%), biopsy revealed a positive MGMT promoter methylation status, while 28 were unmethylated (53.84%), and two patients had an unknown MGMT promoter methylation status (3.85%). Intermittent and/or continuous focal slow-wave activity was registered in 45 patients (86.54%). In comparison, epileptiform discharges could only be found in 13 patients (25%). When compared to MRI/CT scans, the hemispheric tumor localization could be determined in 42 cases (80.77%). Moreover, the affected brain lobe was accurately predicted in 35 patients (67.31%). Three patients had diffuse EEG changes (5.77%), and EEG was unremarkable in 7 patients (13.46%).

Conclusion

Overall, our presented data indicate that the hemispheric localization of glioblastoma can be reliably predicted by EEG recordings, while a precise (brain lobe-specific) localization was only possible in around two-thirds of cases.

Absence of a significant interaction of two common NOS1 and 5-HTT polymorphisms on sensorimotor gating in humans

The neurotransmitter serotonin has been critically implicated in the pathogenesis of several mental disorders. The serotonin transporter (5-HTT) is a key regulator of serotonergic neurotransmission and its genetic variability is associated with increased risk of psychopathology. One well known polymorphic locus in the 5-HTT gene affecting its expression is a tandem repeat in the promoter region (5-HTTLPR). It has been reported that 5-HTT is functionally coupled with the neuronal nitric oxide synthase (NOS1 or nNOS), an enzyme catalyzing the production of nitric oxide (NO). We have previously demonstrated that a tandem repeat polymorphism in the promoter of NOS1 exon 1f (Ex1f-VNTR) is associated with sensorimotor gating, a marker of inhibitory processing and a well established endophenotype of several neuropsychiatric disorders. Here we investigated the combined genetic effects of NOS1 Ex1f-VNTR and 5-HTTLPR on sensorimotor gating, measured by prepulse inhibition (PPI) of the acoustic startle reflex, in 164 healthy adults. We found no evidence for the interaction between NOS1 Ex1f-VNTR and 5-HTTLPR on PPI. PPI was associated with NOS1 Ex1f-VNTR, but not 5-HTTLPR. Our data suggest that while NOS1 plays a role in sensorimotor gating, the nitrergic pathway of gating regulation does not involve the action of 5-HTT.

Nonstenotic Carotid Plaques in Ischemic Stroke: Analysis of the STRATIS Registry

BACKGROUND AND PURPOSE

Few studies assess nonstenotic carotid plaques on CTA, and the causative role of these plaques in stroke is not entirely clear. We used CTA to determine the prevalence of nonstenotic carotid plaques (<50%), plaque features, and their association with ipsilateral strokes in patients with cardioembolic and cryptogenic strokes.

MATERIALS AND METHODS

Data were from the Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke (STRATIS) registry, a prospective, nonrandomized registry of patients undergoing thrombectomy with the Solitaire device. The prevalence of nonstenotic carotid plaques ipsilateral and contralateral to the stroke was compared in patients with cryptogenic and cardioembolic strokes. Plaque features were further compared within both subgroups between patients with and without ipsilateral stroke. Adjusted associations among nonstenotic carotid plaque, plaque characteristics, and ipsilateral stroke in both subgroups were determined with logistic regression.

RESULTS

Of the 946 patients in the data base, 226 patients with cardioembolic stroke (median age, 72 years) and 141 patients with cryptogenic stroke (median age, 69 years) were included in the analysis. The prevalence of nonstenotic carotid plaque in the cardioembolic and cryptogenic subgroups was 33/226 (14.6%) and 32/141 (22.7%), respectively. Bilateral nonstenotic carotid plaques were seen in 10/226 (4.4%) patients with cardioembolic and 13/141 (9.2%) with cryptogenic strokes. Nonstenotic carotid plaques were significantly associated with ipsilateral strokes in the cardioembolic stroke (adjusted OR = 1.91; 95% CI, 1.15-3.18) and the cryptogenic stroke (adjusted OR = 1.69; 95% CI, 1.05-2.73) groups. Plaque irregularity, hypodensity, and per-millimeter increase in plaque thickness were significantly associated with ipsilateral stroke in the cryptogenic subgroup.

CONCLUSIONS

Nonstenotic carotid plaques were significantly associated with ipsilateral stroke in cardioembolic and cryptogenic stroke groups, and there was an association of plaque irregularity and hypodense plaque with ipsilateral stroke in the cryptogenic group, suggesting these plaques could be a potential cause of stroke in these patient subgroups.

Importance of PET/CT examination in patients with malignant uveal melanoma

INTRODUCTION

Diagnostic and therapeutic management of the patient with malignant uveal melanoma (MMU) is subject to ongoing efforts to innovate. PET/CT (Positron Emission Tomography / Computed Tomography) examination is important in both diagnosis and metastases.

MATERIAL AND METHODS

Evaluation of the importance of PET/CT examination in the group of patients diagnosed with MMU in the period 12.1.2016 to 6.12.2018. All patients with a diagnosis of secondary retinal detachment, suspected uveal melanoma, underwent standard examinations to detect possible metastases (liver ultrasound, chest X-ray). Patients for whom a stereotactic radiosurgery solution was planned due to the stage of the disease this examination was to exclude metastasis in the liver or lungs. PET/CT examination is part of the protocol within the exclusion criteria for treatment with stereotactic radiosurgery in one day session surgery.

RESULTS

In the group of 84 patients, 47 women (56 %) and 37 men (44 %) were aged between 26 and 90 years. Their average age was 61.4 years. The median group was 64 years, modus 65 years. Of 84 patients, 79 (94 % of cases) had a diagnosis of C69.3 (choroidal melanoma) and 5 patients (6 % of cases) had a diagnosis of C69.4 (ciliary body melanoma). Subsequent PET/CT examination in many patients did not reveal hypermetabolic manifestations that could involve various pathological processes, in others the radiopharmaceutical was captured in the primary tumor area of the uveal tract. Hypermetabolism in eye globe was only found in melanomas with a volume of more than 0.5 cm3. PET/CT examinations were 85, with one patient undergoing examination twice. However, in 25 patients (26 examinations), the radiopharmaceutical was taken up in places that subsequently required closer attention. The initial aim of the examination was to locate possible metastases of MMU. In the others, 3 incidents have been reported: increased metabolism in the lung and liver, thyroid and mediastinal lymph nodes. Of the 85 examinations, 26 (30.6 %) resulted in a hypermetabolic manifestation of accumulation, which was not located in the eye tract, resp. right in the eye. Two malignancies (prostatic carcinoma and rectosigmal carcinoma) have occurred in two patients. Very important was the discovery of MMU metastasis in the liver, which confirmed the important role of PET/CT examination in the management of MMU patients. The metastasis was discovered after repeated PET/CT examination.

CONCLUSION

PET/CT examination is a technically demanding examination and is one of the possibilities of imaging intraocular melanoma in tumors with volume more than 0.5 cm3. It is important in determining the grading and staging of the disease before radiosurgical treatment and also in detecting possible metastases after MMU treatment in cases where ultrasound or MRI examinations do not give a definite result. However, our study confirmed the significance of this examination for randomly detected 2 duplex malignancies (2.4%) and 3 incidentalomas (3.6%) in patients whose ophthalmologist diagnosed uveal melanoma and sent patients for full-body PET/CT examination.

Cryo-FIB preparation of whole cells and tissue for cryo-TEM: use of high-pressure frozen specimens in tubes and planchets

The desire to study macromolecular complexes within their cellular context requires the ability to produce thin samples suitable for cryo‐TEM (cryo‐transmission electron microscope) investigations. In this paper, we discuss two similar approaches, which were developed independently in Utrecht (the Netherlands) and Albany (USA). The methods are particularly suitable for both tissue samples and cell suspensions prepared by a high‐pressure freezer (HPF). The workflows are explained with particular attention to potential pitfalls, while underlying principles are highlighted (‘why to do so’). Although both workflows function with a high success rate, full execution requires considerable experience and remains demanding. In addition, throughput is low. We hope to encourage other research groups worldwide to take on the challenge of improving the HPF– cryo‐FIB‐SEM – cryo‐TEM workflow. We discuss a number of suggestions to this end.

Lay Description

Life is ultimately dictated by the interaction of molecules in our bodies. Highly complex equipment is being used and further developed to study these interactions. The present paper describes methods to prepare small, very thin lamellae (area of 5×5 µm², thickness 50–300 nm) of a cell to be studied in a cryo‐transmission electron microscope (cryo‐TEM). Special care must be taken to preserve the natural state of molecules in their natural environment. In the case of cryo‐TEM, the samples must be frozen and kept frozen to be compatible with the vacuum conditions in the microscope. The frozen condition imposes technical challenges which are addressed. Two approaches to obtain the thin lamellae are described. Both make use of a focused ion beam (FIB) microscope. The FIB allows removal of material with nanometre precision by focusing a beam of ionised atoms (gallium ions) onto the sample. Careful control of the FIB allows cutting out of the required thin lamellae. In both strategies, the thin lamellae remain attached to the original sample, and the ensemble of sample with section and sample holder is transported from the FIB microscope to the TEM while being kept frozen.

The Risk of Stroke and TIA in Nonstenotic Carotid Plaques: A Systematic Review and Meta-Analysis

BACKGROUND

Severe carotid stenosis carries a high risk of stroke. However, the risk of stroke with nonstenotic carotid plaques (<50%) is increasingly recognized.

PURPOSE

We aimed to summarize the risk of TIA or stroke in patients with nonstenotic carotid plaques.

DATA SOURCES

We performed a comprehensive systematic review and meta-analysis in patients with acute ischemic stroke in whom carotid imaging was performed using MEDLINE and the Cochrane Database, including studies published up to December 2019.

STUDY SELECTION

Included studies had >10 patients with <50% carotid plaques on any imaging technique and reported the incidence or recurrence of ischemic stroke/TIA. High-risk plaque features and the risk of progression to stenosis >50% were extracted if reported.

DATA SYNTHESIS

We identified 31 studies reporting on the risk of ipsilateral stroke/TIA in patients with nonstenotic carotid plaques. Twenty-five studies (n = 13,428 participants) reported on first-ever stroke/TIA and 6 studies (n = 122 participants) reported on the recurrence of stroke/TIA.

DATA ANALYSIS

The incidence of first-ever ipsilateral stroke/TIA was 0.5/100 person-years. The risk of recurrent stroke/TIA was 2.6/100 person-years and increased to 4.9/100 person-years if intraplaque hemorrhage was present. The risk of progression to severe stenosis (>50%) was 2.9/100 person-years (8 studies, n = 448 participants).

LIMITATIONS

Included studies showed heterogeneity in reporting stroke etiology, the extent of stroke work-up, imaging modalities, and classification systems used for characterizing carotid stenosis.

CONCLUSIONS

The risk of recurrent stroke/TIA in nonstenotic carotid plaques is not negligible, especially in the presence of high-risk plaque features. Further research is needed to better define the significance of nonstenotic carotid plaques for stroke etiology.

Focused ion beam milling of vitreous water: prospects for an alternative to cryo-ultramicrotomy of frozen-hydrated biological samples

The feasibility of using a focused ion beam (FIB) for the purpose of thinning vitreously frozen biological specimens for transmission electron microscopy (TEM) was explored. A concern was whether heat transfer beyond the direct ion interaction layer might devitrify the ice. To test this possibility, we milled vitreously frozen water on a standard TEM grid with a 30-keV Ga(+) beam, and cryo-transferred the grid to a TEM for examination. Following FIB milling of the vitreous ice from a thickness of approximately 1200 nm to 200-150 nm, changes characteristic of heat-induced devitrification were not observed by TEM, in either images or diffraction patterns. Although numerous technical challenges remain, it is anticipated that 'cryo-FIB thinning' of bulk frozen-hydratred material will be capable of producing specimens for TEM cryo-tomography with much greater efficiency than cryo-ultramicrotomy, and without the specimen distortions and handling difficulties of the latter.

Ultrastructural, tomographic and confocal imaging of the chondrocyte primary cilium in situ

Hyaline cartilage chondrocytes express one primary cilium per cell, but its function remains unknown. We examined the ultrastructure of chick embryo sternal chondrocyte cilia and their interaction with extracellular matrix molecules by transmission electron microscopy (TEM) and, for the first time, double-tilt electron tomography. Ciliary bending was also examined by confocal immunohistochemistry. Tomography and TEM showed the ciliary axoneme to interdigitate amongst collagen fibres and condensed proteoglycans. TEM also revealed the presence of electron-opaque particles in the proximal axoneme which may represent intraciliary-transport (ICT) particles. We observed a wide range of ciliary bending patterns. Some conformed to a heavy elastica model associated with shear stress. Others were acutely deformed, suggesting ciliary deflection by collagen fibres and proteoglycans with which the cilia make contact. We conclude that mechanical forces transmitted through these matrix macromolecules bend the primary cilium, identifying it as a potential mechanosensor involved in skeletal patterning and growth.

Effect of head-down bed rest on the neuroendocrine response to orthostatic stress in physically fit men

The role of neuroendocrine responsiveness in the development of orthostatic intolerance after bed rest was studied in physically fit subjects. Head-down bed-rest (HDBR, -6 degrees, 4 days) was performed in 15 men after 6 weeks of aerobic training. The standing test was performed before, after training and on day 4 of the HDBR. Orthostatic intolerance was observed in one subject before and after training. The blood pressure response after training was enhanced (mean BP increments 18+/-2 vs. 13+/- 2 mm Hg, p<0.05, means +/- S.E.M.), although noradrenaline response was diminished (1.38+/-0.18 vs. 2.76+/-0.25 mol.l(-1), p<0.01). Orthostatic intolerance after HDBR was observed in 10 subjects, the BP response was blunted, and noradrenaline as well as plasma renin activity (PRA) responses were augmented (NA 3.10+/-0.33 mol.l(-1), p<0.001; PRA 2.98+/-1.12 vs. 0.85+/-0.15 ng.ml(-1), p<0.05). Plasma noradrenaline, adrenaline and aldosterone responses in orthostatic intolerant subjects were similar to the tolerant group. We conclude that six weeks of training attenuated the sympathetic response to standing and had no effect on the orthostatic tolerance. In orthostatic intolerance the BP response induced by subsequent HDBR was absent despite an enhanced sympathetic response.

Synthesis and antifungal properties of compounds which target the alpha-aminoadipate pathway

Fungi synthesize lysine via the alpha-aminoadipate pathway, which is not found in plants or animals. This pathway has been proposed as a target for antifungal agents, but until now no reports have appeared to test this proposal. Hampering studies on the susceptibility of filamentous fungi such as those of the clinically important genus Aspergillus is the fact that growth quantitation is notoriously difficult. We have used the recently-reported XTT-based method of biomass quantitation to measure the susceptibility of Aspergillus nidulans strain A28 to growth suppression by novel compounds designed to target early steps in the alpha-aminoadipate lysine biosynthesis pathway, specifically those steps involving (R)-homocitrate and (2R,3S)-homoisocitrate. Three compounds show moderate inhibition of fungal growth, which can be partially restored by the presence of lysine in the growth medium.

Electron tomography of frozen-hydrated isolated triad junctions

Cryoelectron microscopy and tomography have been applied for the first time to isolated, frozen-hydrated skeletal muscle triad junctions (triads) and terminal cisternae (TC) vesicles derived from sarcoplasmic reticulum. Isolated triads were selected on the basis of their appearance as two spherical TC vesicles attached to opposite sides of a flattened vesicle derived from a transverse tubule (TT). Foot structures (ryanodine receptors) were resolved within the gap between the TC vesicles and TT vesicles, and some residual ordering of the receptors into arrays was apparent. Organized dense layers, apparently containing the calcium-binding protein calsequestrin, were found in the lumen of TC vesicles underlying the foot structures. The lamellar regions did not directly contact the sarcoplasmic reticulum membrane, thereby creating an approximately 5-nm-thick zone that potentially constitutes a subcompartment for achieving locally elevated [Ca(2+) ] in the immediate vicinity of the Ca(2+)-conducting ryanodine receptors. The lumen of the TT vesicles contained globular mass densities of unknown origin, some of which form cross-bridges that may be responsible for the flattened appearance of the transverse tubules when viewed in cross-section. The spatial relationships among the TT membrane, ryanodine receptors, and calsequestrin-containing assemblage are revealed under conditions that do not use dehydration, heavy-metal staining, or chemical fixation, thus exemplifying the potential of cryoelectron microscopy and tomography to reveal structural detail of complex subcellular structures.

Responses of sympathoadrenal and renin angiotensin systems to stress stimuli in humans during real and simulated microgravity

Changes of plasma hormone levels were investigated in human subjects after exposure to physical exercise (WL) and insulin induced hypoglycemia (ITT) during space flight or after head down bed rest (HDBR). Exaggerated responses of plasma epinephrine (EPI), norepinephrine (NE) and aldosterone (ALD) were observed after WL during space flight as compared to preflight response. Hypoglycemia during space flight induced attenuated responses of EPI, NE and augmented response of ALD. Exposure to WL during HDBR was followed by significantly exaggerated responses of plasma EPI, NE, ALD, PRA and cortisol. In HDBR the responses of plasma EPI, NE and cortisol were reduced and PRA response was exaggerated during ITT. These data indicate that hormonal responses to ITT and WL are similar at real and simulated microgravity.

Effect of simulated microgravity on endocrine response to insulin-induced hypoglycemia in physically fit men

Adaptation to microgravity is associated with alteration in some endocrine functions. In the present longitudinal study, the counterregulatory hormonal response to insulin-induced hypoglycemia (ITT, 0.1 IU/kg short acting insulin i. v.) was evaluated under simulated microgravity conditions in 15 physically fit subjects. ITT was performed at the beginning of the investigation, and again after completion of 6 weeks of endurance training and after a subsequent period of 4 days of head-down bed rest at a backward tilt of 6 degrees from the horizontal. Endurance training showed a significant increase in maximal aerobic capacity in previously well-trained subjects (increase by 12 %), as well as on attenuation of counterregulatory response of epinephrine to hypoglycemia. After 4 days of bed rest, basal concentrations of plasma norepinephrine was diminished (p < 0.002) and plasma renin activity was enhanced (p < 0.02). After bed rest, decreased responses of the two catecholamines (norepinephrine, p < 0.001; epinephrine, p < 0.001), growth hormone (p < 0.001), and cortisol (p < 0.05) were observed. Response of plasma renin activity after bed rest was increased (p < 0.01). This longitudinal study indicated that 4 days of bed rest in endurance-trained subjects induced increased response of PRA to hypoglycemia and attenuation of other counterregulatory neuroendocrine responses.

Topology of the mitochondrial inner membrane: dynamics and bioenergetic implications

Electron tomography indicates that the mitochondrial inner membrane is not normally comprised of baffle-like folds as depicted in textbooks. In actuality, this membrane is pleomorphic, with narrow tubular regions connecting the internal compartments (cristae) to each other and to the membrane periphery. The membrane topologies observed in condensed (matrix contracted) and orthodox (matrix expanded) mitochondria cannot be interconverted by passive folding and unfolding. Instead, transitions between these morphological states likely involve membrane fusion and fission. Formation of tubular junctions in the inner membrane appears to be energetically favored, because they form spontaneously in yeast mitochondria following large-amplitude swelling and recontraction. However, aberrant, unattached, vesicular cristae are also observed in these mitochondria, suggesting that formation of cristae junctions depends on factors (such as the distribution of key proteins and/or lipids) that are disrupted during extreme swelling. Computer modeling studies using the "Virtual Cell" program suggest that the shape of the inner membrane can influence mitochondrial function. Simulations indicate that narrow cristae junctions restrict diffusion between intracristal and external compartments, causing depletion of ADP and decreased ATP output inside the cristae.

High-resolution CryoFESEM of individual cell adhesion molecules (CAMs) in the glycocalyx of human platelets: detection of P-selectin (CD62P), GPI-IX complex (CD42A/CD42B alpha,B beta), and integrin GPIIbIIIa (CD41/CD61) by immunogold labeling and stereo imaging

The aim of this study was to develop a model for the detection of individual cell adhesion molecules (CAMs) in the glycocalyx of spread human platelets using high-resolution cryo-field emission scanning electron microscopy (cryoFESEM). Three surface glycoprotein CAMs, P-selectin (CD62P), GPIba in the GPI-IX complex (CD42a/CD42b alpha,b beta), and the integrin GPIIbIIIa (CD41/CD61) in the human platelet were selected on the basis of their unique topographic shape. Spread human platelets were indirectly immunolabeled with 10-nm colloidal gold and then cryoimmobilized. After sublimation of water from the cryoimmobilized sample, partially freeze-dried platelets were coated unidirectionally with Pt, stabilized with carbon, and examined in an in-lens cryoFESEM using high-resolution backscattered electron imaging. CAMs were detected by indirect immunogold labeling and the length of each type of CAM was determined using analysis of differences in parallax as measured in the software program Sterecon. Our results demonstrate the efficacy of using high-resolution cryoFESEM to recognize and detect individual CAMs in the glycocalyx. Further advances in production of metal coatings with finer granularity, together with improvements in imaging (tilting and angle of stereo images), may provide better definition of the topography associated with glycosylation and formation of multimeric CAM complexes. (J Histochem Cytochem 49:809-819, 2001)

The emergence of electron tomography as an important tool for investigating cellular ultrastructure

Electron tomography has emerged as the leading method for the study of three-dimensional (3D) ultrastructure in the 5-20-nm resolution range. It is ideally suited for studying cell organelles, subcellular assemblies and, in some cases, whole cells. Tomography occupies a place in 3D biological electron microscopy between the work now being done at near-atomic resolution on isolated macromolecules or 2D protein arrays and traditional serial-section reconstructions of whole cells and tissue specimens. Tomography complements serial-section reconstruction by providing higher resolution in the depth dimension, whereas serial-section reconstruction is better able to trace continuity over long distances throughout the depth of a cell. The two techniques can be combined with good results for favorable specimens. Tomography also complements 3D macromolecular studies by offering sufficient resolution to locate the macromolecular complexes in their cellular context. The technology has matured to the point at which application of electron tomography to specimens in plastic sections is routine, and new developments to overcome limitations due to beam exposure and specimen geometry promise to further improve its capabilities. In this review we give a brief description of the methodology and a summary of the new insights gained in a few representative applications.(J Histochem Cytochem 49:553-563, 2001)

Insulin, catecholamines, glucose and antioxidant enzymes in oxidative damage during different loads in healthy humans

Exercise, insulin-induced hypoglycemia and oral glucose loads (50 g and 100 g) were used to compare the production of malondialdehyde and the activity of antioxidant enzymes in healthy subjects. Twenty male volunteers participated in the study. Exercise consisted of three consecutive work loads on a bicycle ergometer of graded intensity (1.5, 2.0, and 2.5 W/kg, 6 min each). Hypoglycemia was induced by insulin (Actrapid MC Novo, 0.1 IU/kg, i.v.). Oral administration of 50 g and 100 g of glucose was given to elevate plasma glucose. The activity of superoxide dismutase (SOD) was determined in red blood cells, whereas glutathione peroxidase (GSH-Px) activity was measured in whole blood. The concentration of malondialdehyde (MDA) was determined by HPLC, catecholamines were assessed radioenzymatically and glucose was measured by the glucose-oxidase method. Exercise increased MDA concentrations, GSH-Px and SOD activities as well as plasma noradrenaline and adrenaline levels. Insulin hypoglycemia increased plasma adrenaline levels, but the concentrations of MDA and the activities of GSH-Px and SOD were decreased. Hyperglycemia increased plasma MDA concentrations, but the activities of GSH-Px and SOD were significantly higher after a larger dose of glucose only. Plasma catecholamines were unchanged. These results indicate that the transient increase of plasma catecholamine and insulin concentrations did not induce oxidative damage, while glucose already in the low dose was an important triggering factor for oxidative stress.

Topical delivery of 13-cis-retinoic acid by inhalation up-regulates expression of rodent lung but not liver retinoic acid receptors

Chemopreventive retinoids may be more effective if delivered to the lung epithelium by inhalation. 13-cis-Retinoic acid (13-cis-RA) was comparable to all-trans-retinoic acid (RA) in inducing transglutaminase II (TGase II) in cultured human cells. Inhaled 13-cis-RA had a significant stimulatory activity on TGase II in rat lung (P < 0.001) but not in liver tissue (P < 0.544). Furthermore, inhaled 13-cis-RA at daily deposited doses of 1.9 mg/kg/day up-regulated the expression of lung retinoic acid receptors (RARs) alpha, beta, and gamma at day 1 (RARalpha by 3.4-fold, RARbeta by 7.2-fold, and RARgamma by 9.7-fold) and at day 17 (RARalpha by 4.2-fold, RARbeta by 10.0-fold, and RARgamma by 12.9-fold). At a lower aerosol concentration, daily deposited doses of 0.6 mg/kg/day were also effective at 28 days. Lung RARalpha was induced by 4.7-fold, RARbeta by 8.0-fold, and RARgamma by 8.1-fold. Adjustment of dose by exposure duration was also effective; thus, inhalation of an aerosol concentration of 62.2 microg/liter, for durations from 5 to 240 min daily for 14 days, induced all RARs from 30.6- to 74-fold at the shortest exposure time. None of the animals exposed to 13-cis-RA aerosols showed RAR induction in livers. By contrast, a diet containing pharmacological RA (30 microg/g of diet) failed to induce RARs in SENCAR mouse lung, although it induced liver RARs (RARalpha, 21.8-fold; RARbeta, 13.5-fold; RARgamma, 12.5-fold); it also failed to induce lung TGase II. A striking increase of RARalpha expression was evident in the nuclei of hepatocytes. Pharmacological dietary RA stimulated RARalpha, RARbeta, and RARgamma as early as day 1 by 2-, 4-, and 2.1-fold, respectively, without effect on lung RARs. Therefore, 13-cis-RA delivered to lung tissue of rats is a potent stimulant of lung but not liver RARs. Conversely, dietary RA stimulates liver but not lung RARs. These data support the concept that epithelial delivery of chemopreventive retinoids to lung tissue is a more efficacious way to attain up-regulation of TGase II and the retinoid receptors and possibly to achieve chemoprevention.

Defects in TGF-beta signaling overcome senescence of mouse keratinocytes expressing v-Ha-ras

Previous studies have shown that TGFbeta1 expression is upregulated in mouse keratinocytes infected with a v-rasHa retrovirus, although the functional significance of this has not been clear. Here we show that v-rasHa retrovirus transduced primary mouse keratinocytes undergo hyperproliferation followed by a TGFbeta1 dependent G1 growth arrest and senescence. The growth arrest is accompanied by a 15-fold increase in total TGFbeta1 secreted and a fourfold increase in secreted active TGFbeta1. When cultured in the presence of a neutralizing antibody to TGFbeta1, the senescence response is suppressed. Levels of the TGFbeta1 target p15ink4b increase during senescence as does association of this kinase inhibitor with cyclinD/cdk4 complexes. However, p16ink4a, p53 and p19ARF expression also increase during senescence. Genetic analysis shows that TGFbeta1 null and dominant negative TbetaBRII expressing v-rasHa keratinocytes resist the G1 growth arrest and do not senescence. This resistance is associated with low expression of p15ink4b and p16ink4a, constitutive Rb phosphorylation and high levels of cdk4 and cdk2 kinase activity. In contrast, inactivation of TGFbetabeta1 secretion or response does not block the induction of p53 and p19ARF, but the level of p21waf1, a p53 target gene, is reduced in cyclin D/cdk4 and cyclin E/cdk2 complexes. Thus, although multiple senescence pathways are activated in response to a ras oncogene, inactivation of TGFbeta1 secretion or response is sufficient to block the senescence program. Since v-rasHa transduced TGFbeta1-/- keratinocytes form squamous cell carcinomas following skin grafting, these results suggest that in mouse keratinocytes, defects in TGFbeta1 signaling accelerate malignant progression by overcoming oncogene induced replicative senescence.

Health risk assessment for inhalation exposure to arsenic

Health risk assessment was used as the formal process to estimate the likelihood and magnitude of the health effects occurring in humans as a result of environmental and occupational exposure to polluting agents. This study was focused at estimating the human health risk of the general and working population living in the region polluted by arsenic for more than 40 years, from combustion of coal with high arsenic content in the power plant. The exposure to arsenic from inhalation was under investigation. A study period of 40 years (1973-1993) was chosen. The study period was defined taking into account, besides the availability of data, the temporal patterns of the technological processes and the trends over time of environmental concentrations. The results from the arsenic risk assessment study were used for the evaluation of the health risk for different population groups in the polluted areas and for different professions of workers exposed to As in a power plant. The results are applicable for the evaluation of risk in real conditions, for health surveillance and for remedial changes and a potential suggestion on technological improvement.

Cubic membrane structure in amoeba (Chaos carolinensis) mitochondria determined by electron microscopic tomography

Cubic membranes occur in a variety of membrane-bound organelles in many cell types. By transmission electron microscopy (TEM) these membrane systems appear to consist of highly curved periodic surfaces that fit mathematical models analogous to those used to describe lipidic cubic phases. For the first time, a naturally occurring cubic membrane system has been reconstructed in three dimensions by electron microscopic tomography, and its periodicity directly characterized. Double-tilt tomographic reconstruction of mitochondria in the amoeba, Chaos carolinensis, confirms that their cristae (inner membrane infoldings) have the cubic structure suggested by modeling studies based on thin-section TEM images. Analysis of the membrane surfaces in the reconstruction reveals the connectivity of the internal compartments within the mitochondria. In the cubic regions, the matrix is highly condensed and confined to a continuous, small space between adjacent cristal membranes. The cristae form large, undulating cisternae that communicate with the peripheral (inner membrane) compartment through narrow tubular segments as seen in other types of mitochondria. The cubic periodicity of these mitochondrial membranes provides an ideal specimen for measuring geometrical distortions in biological electron tomography. It may also prove to be a useful model system for studies of the correlation of cristae-matrix organization with mitochondrial activity.

Malondialdehyde, lipofuscin and activity of antioxidant enzymes during physical exercise in patients with essential hypertension

DESIGN

To clarify the role of oxidative damage in essential hypertension, levels of lipid peroxidation products (malondialdehyde and lipofuscin) and activity of antioxidant enzymes (superoxide dismutase and glutathione peroxidase) were examined during a short period of physical exercise.

PATIENTS AND METHODS

We studied 11 male patients with mild to moderate essential hypertension in World Health Organization classes I or II and 10 healthy male controls. Physical exercise was performed on a bicycle ergometer at graded intensities of 1.0, 1.5 and 2.0 W/kg body weight Plasma concentrations of lipofuscin, malondialdehyde, epinephrine, norepinephrine, insulin, free fatty acids and glucose were determined. Superoxide dismutase activity was analysed in erythrocytes and glutathione peroxidase activity in whole blood.

RESULTS

Concentrations of lipofuscin and malondialdehyde were significantly elevated in hypertensive patients. Superoxide dismutase activity was not different between groups, while glutathione peroxidase activity was significantly decreased in hypertensive subjects. During exercise, the concentration of malondialdehyde and antioxidant enzyme activities increased significantly in both groups. No differences were found in absolute increases between the normotensive and hypertensive subjects. The levels of glucose, insulin and free fatty acids were similar in both groups. Basal concentrations of catecholamines and also the exercise-induced increases were lower in hypertensive patients.

CONCLUSIONS

Our results indicate increased oxidative damage in patients with essential hypertension, which might be caused by a decrease in the activity of glutathione peroxidase. The ability of superoxide dismutase and glutathione peroxidase to respond to increased production of reactive oxygen species during a short period of physical exercise was not impaired in hypertensive subjects.

Three-dimensional transmission electron microscopy and its application to mitosis research

Transmission electron microscopy produces images that are projections of the original object, with the consequence that features from different depths of the specimen overlap and give a confusing image. This problem is overcome by reconstructing the object in 3D from a series of 2D views using either serial thin section reconstruction or electron tomography. In the serial section approach, the series of 2D views is generated from images of successive serial sections cut thin enough to be effectively 2D slices of the specimen. For electron tomography the series of 2D views is generated by tilting a single, usually thicker, section in the electron beam. Resolution in the depth dimension is limited to twice the section thickness for serial section reconstruction and is determined by the number of tilt views collected (i.e., by the fineness of the angular interval between successive tilt views) for electron tomography. Both methods produce distorted 3D reconstructions because of missing material and alignment difficulties in the case of serial sections and the limited angular tilt range in the case of electron tomography. However, techniques have evolved for minimizing and circumventing these distortions and, as long as the user is aware of the limitations, misinterpretations can be avoided. Since electron tomography provides better resolution (generally 5-20 nm), it is the method of choice for determining detailed structural interactions such as the depth of kinetochore MT penetration into the kinetochore outer plate. On the other hand, serial section reconstruction is more effective for projects that require tracking through a complete object in the specimen, such as counting the number of kinetochore MTs on each kinetochore. If the project requires finding a relatively small object in a large specimen (e.g., finding centrioles in an oocyte), then it is sometimes advantageous to cut thicker plastic sections and analyze them via stereo viewing. The mitotic spindle, however, is generally too complex to be analyzed via stereo viewing. Currently, collapse of plastic sections in the electron beam limits the utility of serial section electron tomography. Once a 3D reconstruction is completed it must be analyzed with the 2D medium of the screen on a computer monitor. The easiest approach is usually to walk through the 3D reconstruction volume slice by slice. However, in order to appreciate 3D interactions, and to communicate the results to others, it is generally necessary to segment key components from the rest of the volume and use modeling and rendering techniques. Rendered surface views can easily be color coded and provided with a number of depth cues to simulate the surface viewing encountered in everyday life. In some instances, it is useful to look through a smaller portion of the reconstruction volume with "X-ray vision." This can accomplished by using volume rendering to create a series of semitransparent views from different tilt angles.

Electron microscopic tomography of rat-liver mitochondria and their interaction with the endoplasmic reticulum

Electron microscopic tomography can provide a complete three-dimensional range of information about subcellular structures. Applied to mitochondria, it has shown that the conventional textbook model of this organelle is incorrect. The infoldings of the inner membrane (called cristae) are connected by narrow tubular regions to each other and to the outside, suggesting that internal diffusion of ions, metabolites and proteins may be restricted. Tomographic reconstruction of mitochondria in situ indicates these organelles may occur in clusters with stacks of endoplasmic reticulum, forming extended structures that may be involved in [Ca++] regulation.

Low-dose automated electron tomography: a recent implementation

Low-dose automated tomography has been implemented on a 400-kV JEOL intermediate voltage electron microscope. Instrumentation and procedures for automatic tomographic series data collection are described. Difficulties encountered and ways to overcome them are discussed. A low-dose tomographic projection series of a triad junction of frog sartorius muscle was semiautomatically collected and a 3-D reconstruction of this organelle was made.

Creating a healthy work environment in the midst of organizational change and transition

In the midst of organizational change and transition, the need for a healthy work environment is greater than ever. Leaders may be in a position of leading staff on a journey they would rather not be on. Although there may not be a choice of destination, there are many decisions to be made along the way that will impact the health and quality of the journey. Creation of a healthy work environment does not occur overnight. It requires acknowledgment of the reality of the present environment, clear behavioral expectations and standards, systems, and structures to ensure the organizational changes are enduring and a means to assess continually the health of the work environment. Leaders have an opportunity and a responsibility to structure organizations in such a way that dignity, integrity, honesty, and compassion are preserved.

Mineralization of collagen may occur on fibril surfaces: evidence from conventional and high-voltage electron microscopy and three-dimensional imaging

The interaction between collagen and mineral crystals in the normally calcifying leg tendons from the domestic turkey, Meleagris gallopavo, has been investigated at an ultrastructural level with conventional and high-voltage electron microscopy, computed tomography, and three-dimensional image reconstruction methods. Specimens treated by either aqueous or anhydrous techniques and resin-embedded were appropriately sectioned and regions of early tendon mineralization were photographed. On the basis of individual photomicrographs, stereoscopic pairs of images, and tomographic three-dimensional image reconstructions, platelet-shaped crystals may be demonstrated for the first time in association with the surface of collagen fibrils. Mineral is also observed in closely parallel arrays within collagen hole and overlap zones. The mineral deposition at these spatially distinct locations in the tendon provides insight into possible means by which calcification is mediated by collagen as a fundamental event in skeletal and dental formation among vertebrates.

Sterecon--three-dimensional reconstructions from stereoscopic contouring

Sterecon is a system for making 3-D reconstructions or measurements by tracing from stereopair images. The stereopair images may come directly from a microscope, such as a transmission or scanning electron microscope. Alternatively, the images may be created from a stack of thin slices, such as a confocal light microscopy depth series, an electron tomographic volume, or a set of serial histological slices. When the structure to be studied is thick or complex, a serial stack of stereoscopic images can be used. Objects are traced within the images, and their coordinates are entered into a line or contour database. The contour database can be used for 3-D structure measurement, and the contours can be displayed as a reconstruction. Sterecon has interfaces from other software which can generate the input images and to other software for further display and analysis.

Double-tilt electron tomography

Fidelity of tomographic reconstructions is improved and reconstruction artifacts are reduced, without increasing the number of projections, by combining tilt series taken around two orthogonal axes. Test reconstructions were made from high-voltage EM of rat liver mitochondria in a 0.6 micron thick plastic section. A number of schemes for selecting tilt angles for the projections are compared. A new method for aligning fiducial markers is described. It uses an iterative algorithm to determine the shift, scale, in-plane rotation and tilt angle for each tilt image, enforcing agreement of the expected locations of the fiducial markers in 3D space. These 3D locations are used to find the orientation between two tilt series and to merge both sets of projections.

The internal compartmentation of rat-liver mitochondria: tomographic study using the high-voltage transmission electron microscope

The three-dimensional organization of the internal compartments of conventionally fixed and embedded rat-liver mitochondria has been determined by tomographic reconstruction from tilt-series images collected on the Albany high-voltage electron microscope. The results indicate that the inner membranes of these organelles are predominantly tubular in the orthodox (expanded matrix) conformation, as previously suggested by scanning electron microscopy. In the condensed (contracted matrix) conformation, the intracristal space opens up into large irregularly shaped compartments which are connected to each other and to the external (intermembrane) space by tubes with approximately the same diameter (20 nm) as those observed in the orthodox state. These results raise several questions, in particular about the nature of the structural transitions that occur in the cristae during matrix expansion and contraction, and about the influence of inner-membrane shape on the diffusion of ions and metabolites between the intracristal and intermembrane compartments.

Three-dimensional reconstruction of Coxiella burnetii-infected L929 cells by high-voltage electron microscopy

Previous examination of thin sections of L929 cells heavily infected with the Q fever Priscilla isolate by conventional transmission electron microscopy indicated that the rickettsiae resided within multiple vacuoles. The present study using high-voltage electron microscopy and three-dimensional reconstruction revealed that, in heavily infected cells, the rickettsiae, in fact, reside in one multilobed vacuole. As a result of asymmetric cell division, the multilobed vacuole containing the rickettsiae apparently segregates into one daughter cell, while the companion daughter cell emerges parasite free. This likely explains the appearance of naive uninfected cells in long-term-infected (i.e., ca. 2 years) cell populations that had not been supplemented with uninfected L929 host cells.

Cytoarchitecture of size-excluding compartments in living cells

By fluorescence ratio imaging of large and small inert tracer particles in living cells, we have previously shown that particles 24 nm in radius are excluded from otherwise uncharacterized compartments in the distal and perinuclear cytoplasm (Luby-Phelps, K. and Taylor, D.L., 1988. Cell Motil. Cytoskel. 10, 28–37). In this study we examined the cytoarchitecture of these compartments. Whole-mount TEM showed that distal size-excluding compartments were devoid of membrane-bounded organelles and were filled with a dense cytomatrix consisting of numerous, long bundles of thin filaments interconnected by a more random meshwork of short thin filaments. The mean diameter of void spaces in the cytomatrix of distal excluding compartments was 31 nm, compared to 53 nm in adjacent non-excluding domains. The height of the distal excluding compartments was generally &lt; or = 50% of the height in the adjacent non-excluding compartment. An electron-dense structure having the same projected outline as the perinuclear size-excluding compartment was visible by whole-mount TEM, but the cells were too thick and osmiophilic in this region to resolve any detail. Immunofluorescence localization of cytoskeletal proteins in distal excluding compartments indicated the presence of filament bundles containing F-actin nonmuscle filamin (ABP280) and alpha-actinin. F-actin and ABP280, but not alpha-actinin, were found also in between these filament bundles. Microtubules and vimentin generally were rare or absent from distal excluding domains. Staining of living cells with DMB-ceramide revealed that the perinuclear size-excluding compartment consisted of a compact, juxtanuclear domain coinciding with the trans-Golgi, surrounded by a more diffuse domain coinciding with a perinuclear concentration of endoplasmic reticulum. Intense immunofluorescence staining for vimentin was also observed in the perinuclear size-excluding compartment. We propose that the most likely mechanism for exclusion from distal compartments is molecular sieving by a meshwork of actin filament bundles interconnected by an F-actin/ABP280 gel network, while exclusion from the perinuclear compartment may be due to close apposition of cisternae in the trans-Golgi and a network or basket of vimentin filaments in the centrosomal region of the cell.

[Differentiation of the ruminal epithelium of cattle during intrauterine development]

The prenatal development of the bovine ruminal epithelium was studied with light- and electronmicroscopical techniques. During the period of the nonstratified epithelium a pseudostratified epithelium is found in the dorso-cranial part, whereas the other areas possess a one-layered epithelium, which is, like the pseudostratified epithelium, transformed to a multilayered epithelium from the 7th week onwards. From the 9th week the period of the stratified epithelium starts with the formation of the stratum profundum and stratum superficiale. First signs of keratinization are seen in the superficial cells from 2.3 months onwards. With 4 months fetal cornified cells can be identified, with 5.5 months a single-layered stratum basale is seen on the differentiating papillar connective tissue, and the superficial cells are transformed to balloon-cells. In suprapapillar areas, a stratum spinosum is formed at the prenatal age of 7.5 months. During epitheliogenesis a horizontal and vertical differentiation of the cells can be observed. The first one includes the differentiation of undifferentiated, embryonal cells to the basal cells of the stratum profundum, the latter the development of the basal cells to spinous cells and then to fetal cornified and balloon-cells. The ultrastructural changes during the process of keratinization were especially considered.

Changes in Müller cell plasma membrane specializations during subretinal scar formation in the rabbit

The aim of this study was to identify changes in Müller cell plasma membrane specializations during experimentally induced subretinal gliosis in rabbits. When rabbits are dosed with sodium iodate, large expanses of retinal pigment epithelium and photoreceptors are destroyed. They are replaced by a subretinal scar consisting mainly of the ascending processes of Müller cells. These processes transform from the slender, highly polarized structures seen in normal animals into irregular processes that form a glia limitans along the basement membrane of the pigment epithelium, left bare following its degeneration. As the scar processes extend through the subretinal space and contract this basement membrane, they undergo dramatic changes in shape that are especially apparent in three-dimensional computer reconstructions of serial thick sections examined by high-voltage electron microscopy. Other changes involve the intercellular junctions and apical microvilli normally associated with the external limiting membrane. These structures become scattered over the surfaces of the ascending processes and are eventually lost. Loss of microvilli is associated with disappearance of immunostaining for a specific glycoconjugate normally associated with the microvillar plasma membrane. The observations document profound changes in Müller cell structural and functional polarity during subretinal scar formation.

Localization of interferon-induced lupus inclusions demonstrated by computer image reconstruction of monensin-treated Daudi cells

A structural analysis of cells that contained the interferon-alpha-induced lupus inclusions (LI) was performed using a high-voltage electron microscope to determine the exact cellular location of LI and their association with normal cell organelles. LI were induced in the human B lymphoblastoid cell line, Daudi, by culturing with the pure recombinant human leukocyte interferon, IFLrA. Just prior to harvesting, a portion of the cells was treated with monensin to selectively swell the Golgi apparatus, and thereby simplify their identification using the electron microscope. Organellar associations between LI and the outer nuclear envelope and Golgi apparatus were identified in stereopairs of 1-micron sections prepared from both cells that were not treated with monensin and those that were treated with monensin. Serial 0.25-micron sections of the monensin-treated cells were prepared, and seven arbitrarily chosen cells were examined. Each of these cells contained a single LI, and it formed throughout an endoplasmic-reticulum region that made contact with both the outer nuclear envelope and the Golgi vesicles. Reconstruction of a cell by computer from the digitized negatives of serial sections clearly illustrated these relationships. This study reports the first determination of the association between LI and the Golgi apparatus. It also identifies the presence of only one LI in every cell, and the routine association of the LI with both the outer nuclear envelope and the Golgi apparatus. The unique cell location of LI formation suggests their functioning in membrane biogenesis, the trafficking of proteins to the plasma membrane or to cytoplasmic vesicles, or the processing of proteins for secretion.

The use of confocal microscopy and STERECON reconstructions in the analysis of sea urchin embryonic cell division

A laser scanning confocal microscope has been used to investigate the development of the sea urchin embryo. The samples were fixed in Carnoy's solution at various developmental stages, stained for DNA with the Feulgen reaction, and optically sectioned with a BioRad MRC-500 confocal microscope. Computer-generated stereographic projection images and a three-dimensional contour tracing and reconstruction system were employed to investigate the cleavage pattern during the 6th cleavage division. Cell division is found to be asynchronous during the 6th cleavage, with macromere derivatives completing division first, followed by mesomeres, and finally by the outer quartet of micromeres (which begins division only after macromeres and mesomeres have completed their respective divisions). Sixth cleavage produces an embryo comprising 60 cells. Asynchronous division was also observed within individual tiers of blastomeres. Variations in the orientations of cell division axes within individual tiers of cells were also observed. The utility of computer-graphics reconstruction techniques for both quantitative and qualitative developmental analysis are discussed.

Confocal microscopy and three-dimensional reconstruction of electrophysiologically identified neurons in thick brain slices

Three-dimensional morphology and electrophysiology were correlated from individual neurons in a thick brain slice preparation. The hippocampal formation from immature and adult rats was cut transverse to the longitudinal axis into 500 microns-thick slices which were maintained under physiologic conditions. Individual neurons were impaled and physiologically characterized using microelectrodes. Recordings were made from the soma and in some cases from a dendrite. The impaled neurons were filled through the microelectrode with the fluorescent dye lucifer yellow and imaged by confocal scanning laser microscopy using an analog preprocessor. As many as 180 optical sections were recorded as a function of depth through the slices. Images are presented as a series of optical sections, stereo pairs, or three-dimensional reconstructions. Both stereo contouring and volume rendering methods were employed, and the reconstructions were viewed from any arbitrary perspective. Dendritic and axonal fields were separated from each other and displayed separately or as different pseudocolors. The three-dimensional reconstructions provided perspectives that were difficult or impossible to appreciate by viewing the optical sections or conventionally formed stereo pairs.

Organelle rearrangement and cell volume changes during squeezing invasion of peritoneal elastic lamina by targeted murine breast carcinoma cells

Murine breast cancer cell lines were developed to selectively invade the peritoneum while they proliferated in ascites form in the abdominal cavity. In a dominant form of invasion, tumor cells showed special affinity for elastin fibers and squeezed through narrow gaps in the elastic fiber meshwork of the stroma. Even in fixed tissue, such cells could be recognized as being in the process of invasive migration because of their dumbbell shape. This appearance was similar to that of diapedetic blood cells traversing bone marrow sinus endothelium. Three-dimensional STERECON graphics reconstruction from serial thick sections of 44 such cells was carried out. The reconstructions showed that, in mid-penetration, the cells spread extensively over the exterior surface of the elastic fiber meshwork. The cell surface contact of these forward projections was mainly with the elastic fiber outer coat of microfibrils, but small areas of the cell surface also fused directly to inner-core elastin. The morphological rearrangement of the cytoskeleton was minimal in both types of attachment areas. The location of these forward facing attachments is consistent with mechanisms for pulling the invasive cell through the gap. Lamellopodia formation and clustering of cytoplasmic organelles occurred more commonly at the forward-facing part of the cell. Morphometry of the reconstructions showed that a contraction of the whole cell occurred during the squeezing/migration process suggestive of an additional pushing process. However, our invasive cell lines showed marked differences in the degree of cell shrinkage. The process of adhesion and squeezing of tumor cells through elastin meshworks in vivo is clearly a complex phenomenon. Changes in cell surface activity appear to play a significant role in establishing the necessary 'foothold' component of invasion and, possibly, in the generation of tractive force as well.

The relative merits of direct morphometry of reconstructions of whole cells, and statistical morphometry by stereology of random sections of cells

Stereology, or the derivation of quantitative, three-dimensional (3-D) data about cells by statistical analysis of the structures of random sections, is widely used in cytology and pathology. However, there are situations where this approach is inadequate, and only an analysis of a homogeneous population of whole cells will give the required results. This involved 3-D reconstruction from physical or optical sections, or tomography or photogrammetry of whole-cell mounts. Use of stereo views of individual sections or projections adds considerably to the information available for both contouring and reconstruction. Recent image-processing advances in clinical radiography have shown, for the first time, that rapid, high-resolution digitization and contrast enhancement enable nearly all structural details to be routinely extracted from the micrographs and adequately portrayed. Three-D whole-cell reconstructions provide the digital data for many kinds of morphometric measurements on both whole cells and their individual organelles and membranes. Rapid fixation or freezing allows improved quantitative structure/function correlations of organelles with disturbances in cell metabolism or gene expression.

Targeting of peritoneum by the small numbers of isogeneic and allogeneic ascites carcinoma cells that infiltrate or attach to peritoneum during ascites growth

In the course of development of an in vivo invasion model, sublines of a series of allogenic and isogeneic carcinoma cell lines have been selected that show enhanced invasion of the peritoneum. It was found that, during the proliferation of tumor cell lines in ascitic form in the abdominal cavity, small numbers of cells infiltrated or firmly adhered to the peritoneum in at least 8/12 of the tumor-host combinations tried. After thorough washing of the peritoneum it was disaggregated by an enzyme mixture, and the resulting mixture of normal and tumor cells was inoculated intraperitoneally. Peritoneal isolations were made serially for 3 to 12 times. In 6 of 8 cases where the isolation produced a stable ascites, the cells showed enhanced peritoneal invasion compared with the parent cell line. The invasion of some of the cell lines was tested in another invasion model consisting of cultured mouse buccal mucosa (9/10 cell lines invaded the explant). In 3/3 cell lines showing enhanced peritoneum invasion in vivo, there was no enhanced invasion of the buccal mucosa. The enhanced peritoneum invasion appears to be tissue specific rather than a general increase in invasion potential. Pairs of high- and low-invasive cell lines were obtained that should be useful for screening for invasion modulating agents using the mouse ascites/peritoneum in vivo model. It is suggested that the method might be generalized to produce various tumor cell lines that target for the normal tissues that are adjacent to proliferating solid or circulating tumors.

High-voltage electron microscopy and three-dimensional graphic study of R and T cells in head and neck carcinomas

Individual head and neck carcinomas show extreme regional cellular differentiation. Some cells are rich in keratin filaments (T cells) and some have little keratin and a high density of free ribosomes (R or RT cells). We attempted to isolate these two cell types in order to test their relative invasiveness in an in vitro model. The high frequency of mitosis of hyperkeratinized cells showed that there was no constraint on the motility of cell division. High-voltage electron microscopy of serial thick sections and three-dimensional graphic reconstruction demonstrated that keratin cytoskeleton filaments were cross-linked into short, thick bundles. However, the keratin cytoskeleton was absent from some portions of the cytoplasm. In normal differentiated keratinized cells, a more uniform spanning of the whole cell by thin keratin intermediate-filament bundles was evident. The cytoplasm may be more mobile in the keratinized tumor cells. Even heavily keratinized T cells, like the less keratinized cell types, may have invasive motility.

Three-dimensional reconstruction of cells from serial sections and whole-cell mounts using multilevel contouring of stereo micrographs

A comprehensive computer-graphics-based system (STERECON) is described for tracing and digitizing contours from individual or stereopair electron micrographs. The contours are drawn in parallel planes within the micrographs. Provision is also made for tracing and digitizing in full three-dimensional (3-D) coordinates in any direction along linear structures such as cytoskeletal elements. The stereopair micrographs are viewed in combination with the contours being traced on a graphics terminal monitor. This is done either by projecting original electron micrograph (EM) negatives onto a screen and optically combining these images with contour lines being drawn on the monitor, or by first digitizing the images and displaying them directly on the monitor along with the contour lines. Prior image digitization allows computer enhancement of the structures to be contoured. Correction and alignment routines are included to deal with variable section thickness, section distortion and mass loss, variations in photography in the electron microscope, and terminal screen curvature when combining projected images with contour lines on the monitor. The STERECON system organizes and displays the digitized data from successive sections as a 3-D reconstruction. Reconstructions can be viewed in any orientation as contour stacks with hidden lines removed; as wire-frame models; or as shaded, solid models with variable lighting, transparency, and reflectivity. Volumes and surface areas of the reconstructed objects can be determined. Particular attention was paid to making the system convenient for the biological user. Users are given a choice of three different stereo-viewing methods.

Immediate ascites conversion of mammary tumors induced in NYLR/Nya mice by 7,12-dimethylbenz-[a] anthracene and urethane feeding and by forced breeding

Intragastric feeding of dimethylbenz-[a]anthracene in corn oil together with urethane in the drinking water and forced breeding were successful in rapidly inducing (2-4 months) mammary tumors (adenoacanthomas) in inbred NYLR/Nya mice, which have a low incidence of spontaneous breast tumors and of other tumors. The tumors could be quickly and permanently transformed to an ascites form by intraperitoneal inoculation of enzyme-dissociated cells and subsequent serial passage of free cells. Only 10 (3 in some cases) serial passages were required, thus conveniently providing multiple isogeneic carcinoma cell lines in this strain of mice. Some tumor cell lines proliferated strongly in the abdominal cavity even on the first passage.

In vitro modulation of differentiation by calcium in organ cultures of human and murine epithelial tissue

The differentiation of epithelial tissue in organ cultures of murine buccal mucosa, various human oral mucosa, and human newborn foreskin was found to be dependent on the calcium concentration of the culture media. In low calcium medium (less than or equal to 0.07 mM) epithelial differentiation was inhibited. The original stratifying layers separate and can be removed, producing a destratified explant. Histologically such an explant consists of a dorsal epithelial layer of basal keratinocytes resting on an intact basal lamina with subjacent stroma. At 0.01 mM calcium, the epithelial layer was one to two cells thick whereas at 0.07 mM it could be three or more layers in thickness with the most superficial cells being spread over the underlying cells. In addition to differentiation, keratinocyte migration over the sides of the explant (epiboly) and epithelial proliferation as determined by [3H]thymidine autoradiography were reduced by culture in low calcium medium. Redifferentiation occurs upon return to normal calcium levels (1.8 mM); addition of hydrocortisone to low calcium media was found to facilitate this redifferentiation.