Association of somatic comorbidity and treatment adherence in patients with psychotic disorder

BACKGROUND

Increased risk for somatic comorbidity in individuals with schizophrenia has been well established. In addition, psychiatric patients with somatic illnesses are more likely to have more psychiatric readmissions. Increased burden of treatment related to chronic somatic comorbidities may be associated with lower adherence to psychiatric medication.

METHODS

Cross-sectional study of 275 patients with schizophrenia spectrum disorder. A general practitioner performed a complete physical health checkup for all participants, including a complete medical examination and laboratory tests. Patients' adherence, attitudes, insight, and side-effects were evaluated using the Attitudes toward Neuroleptic Treatment Scale. Overall symptomatology was measured using the Brief Psychiatric Rating Scale. Regression analysis was used to investigate interactions and associations among health beliefs, disease burden, and treatment adherence. Separate regression models were utilized to account for the complexity of health behavior and treatment adherence pathways.

RESULTS

Patients' somatic comorbidity and health behavior were not associated with adherence or attitudes toward antipsychotic treatment. High dose of antipsychotics and obesity were related to the need for medical interventions, while a healthy diet reduced the risk. Higher BPRS score and older age were associated with having somatic symptoms. Somatic comorbidities had no negative effects on treatment adherence or attitudes.

CONCLUSION

This study focuses on exploring possible associations between health beliefs and treatment adherence pathways in patients with psychotic disorders. Contrary to our hypotheses, we found no evidence to support our health belief and diseases burden models and their associations.

Rare coding variants in ten genes confer substantial risk for schizophrenia

Rare coding variation has historically provided the most direct connections between gene function and disease pathogenesis. By meta-analysing the whole exomes of 24,248 schizophrenia cases and 97,322 controls, we implicate ultra-rare coding variants (URVs) in 10 genes as conferring substantial risk for schizophrenia (odds ratios of 3-50, P < 2.14 × 10-6) and 32 genes at a false discovery rate of <5%. These genes have the greatest expression in central nervous system neurons and have diverse molecular functions that include the formation, structure and function of the synapse. The associations of the NMDA (N-methyl-D-aspartate) receptor subunit GRIN2A and AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptor subunit GRIA3 provide support for dysfunction of the glutamatergic system as a mechanistic hypothesis in the pathogenesis of schizophrenia. We observe an overlap of rare variant risk among schizophrenia, autism spectrum disorders1, epilepsy and severe neurodevelopmental disorders2, although different mutation types are implicated in some shared genes. Most genes described here, however, are not implicated in neurodevelopment. We demonstrate that genes prioritized from common variant analyses of schizophrenia are enriched in rare variant risk3, suggesting that common and rare genetic risk factors converge at least partially on the same underlying pathogenic biological processes. Even after excluding significantly associated genes, schizophrenia cases still carry a substantial excess of URVs, which indicates that more risk genes await discovery using this approach.

Daily functioning and symptom factors contributing to attitudes toward antipsychotic treatment and treatment adherence in outpatients with schizophrenia spectrum disorders

BACKGROUND

Poor adherence and negative attitudes to treatment are common clinical problems when treating psychotic disorders. This study investigated how schizophrenia core symptoms and daily functioning affect treatment adherence and attitudes toward antipsychotic medication and to compare patients using clozapine or other antipsychotics.

METHOD

A cross-sectional study with data from 275 patients diagnosed with schizophrenia spectrum disorder. Patients adherence, attitudes, insight and side-effects were evaluated using the Attitudes toward Neuroleptic Treatment scale. Overall symptomology was measured using the Brief Psychiatric Rating Scale (BPRS), the Health of the Nation Outcome Scale (HoNOS). The functioning was assessed using activities of daily living scale, instrumental activities of daily living scale and social functioning of daily living scale.

RESULTS

Self-reported treatment adherence was high. Of the patients, 83% reported using at least 75% of the prescribed medication. Having more symptoms was related with more negative attitude towards treatment. There was a modest association with functioning and treatment adherence and attitude toward antipsychotic treatment. Attitudes affected on adherence in non-clozapine but not in clozapine groups.

CONCLUSION

Early detection of non-adherence is difficult. Systematic evaluation of attitudes toward the treatment could be one way to assess this problem, along with optimized medication, prompt evaluation of side effects and flexible use of psychosocial treatments.

Physical health examination in outpatients with schizophrenia: the cost effectiveness of laboratory screening tests

BACKGROUND

Guidelines on laboratory screening in schizophrenia recommend annual monitoring of fasting lipids and glucose. The utility and the cost effectiveness of more extensive laboratory screening have not been studied.

METHODS

The Living Conditions and the Physical Health of Outpatients with Schizophrenia Study provided a comprehensive health examination, including a laboratory test panel for 275 participants. We calculated the prevalence of the results outside the reference range for each laboratory test, and estimated the cost effectiveness to find an aberrant test result using the number needed to screen to find one abnormal result (NNSAR) and the direct cost spent to find one abnormal result (DCSAR, NNSAR x direct cost per test) formulas. In addition, we studied whether patients who were obese or used clozapine had more often abnormal results.

RESULTS

A half of the sample had 25-hydroxyvitamin D below, and almost one-fourth cholesterol, triglycerides or glucose above the reference range. One-fifth had sodium below and gamma glutamyltransferase above the reference range. NNSAR was highest for potassium (137) and lowest for 25-hydroxyvitamin D (2). DCSAR was below 5€ for glucose, all lipids and sodium, and below 10€ for creatinine and gamma glutamyltransferase. Potassium (130€), pH-adjusted ionized calcium (33 €) and thyroid stimulating hormone (33€) had highest DCSARs. Several abnormal results were more common in obese and clozapine using patients.

CONCLUSIONS

An annual laboratory screening panel for an outpatient with schizophrenia should include fasting glucose, lipids, sodium, creatinine, a liver function test and complete blood count, and preferably 25-hydroxyvitamin D.

Multiple physical healthcare needs among outpatients with schizophrenia: findings from a health examination study

BACKGROUND

Despite the abundant literature on physical comorbidity, the full range of the concurrent somatic healthcare needs among individuals with schizophrenia has rarely been studied.

AIMS

This observational study aimed to assess the distressing somatic symptoms and needs for physical health interventions in outpatients with schizophrenia, and factors predicting those needs.

METHODS

A structured, comprehensive health examination was carried out, including a visit to a nurse and a general practitioner on 275 outpatients with schizophrenia. The required interventions were classified by type of disease. Logistic regression was used to assess the influence of sociodemographic factors, lifestyle, functional limitations, factors related to psychiatric disorder, and healthcare use on the need for interventions.

RESULTS

In total, 44.9% of the patients (mean age 44.9 years) reported somatic symptoms affecting daily life; 87.6% needed specific interventions for a disease or condition, most commonly for cardiovascular, dermatological, dental, ophthalmological, and gastrointestinal conditions, and for altered glucose homeostasis. Smoking and obesity predicted significantly a need of any intervention, but the predictors varied in each disease category. Strikingly, use of general practitioner services during the previous year did not reduce the need for interventions.

CONCLUSIONS

Health examinations for outpatients with schizophrenia revealed numerous physical healthcare needs. The health examinations for patients with schizophrenia should contain a medical history taking and a physical examination, in addition to basic measurements and laboratory tests. Prevention and treatment of obesity and smoking should be given priority in order to diminish somatic comorbidities in schizophrenia.

Dyspepsia and constipation in patients with schizophrenia spectrum disorders

Constipation and dyspepsia are disturbing gastrointestinal symptoms that are often ignored in research on physical comorbidities of schizophrenia. The aim was to assess dyspepsia and constipation in a sample of outpatients with schizophrenia spectrum psychoses. A general practitioner performed a thorough physical health check for 275 outpatients and diagnosed constipation and dyspepsia. This study assessed the possible contribution of several sociodemographic, lifestyle, and clinical variables to constipation and dyspepsia using logistic regression analysis. This study also assessed whether these symptoms were associated with abnormal laboratory findings. The prevalence of constipation was 31.3%, and of dyspepsia 23.6%. Paracetamol (OR =3.07, 95% CI =1.34-7.02) and clozapine use (OR =5.48, 95% CI =2.75-10.90), older age (OR =1.04, 95% CI =1.01-1.06), and living in sheltered housing (OR =2.49, 95% CI =1.16-5.33) were risk factors for constipation. For dyspepsia the risk factors were female sex (OR =2.10, 95% CI =1.15-3.83), non-steroidal anti-inflammatory drugs (OR =2.47, 95% CI =1.13-5.39), and diabetes medication (OR =2.42, 95% CI =1.12-5.25). Patients with dyspepsia had lower haemoglobin and haematocrit and higher glucose values than those without dyspepsia. Patients with constipation had lower thrombocyte values than patients without constipation. However, these findings were explained by factors pre-disposing to constipation and dyspepsia. Clozapine use markedly increases the risk of constipation and may lead to life-threatening complications. In addition, analgesics and diabetes medication were related to gastrointestinal symptoms. These medications and their association to gastrointestinal symptoms should be kept in mind when treating patients with schizophrenia.

Diabetes and Schizophrenia

People with schizophrenia have 2- to 5-fold higher risk of type 2 diabetes than the general population. The traditional risk factors for type 2 diabetes, especially obesity, poor diet, and sedentary lifestyle, are common in people with schizophrenia already early in the course of illness. People with schizophrenia also often have low socioeconomic status and income, which affects their possibilities to make healthy lifestyle choices. Antipsychotic medications increase the risk of type 2 diabetes both directly by affecting insulin sensitivity and indirectly by causing weight gain. Lifestyle modification interventions for prevention of diabetes should be an integral part of treatment of patients with schizophrenia. In the treatment of type 2 diabetes in patients with schizophrenia, communication and collaboration between medical care and psychiatric treatment providers are essential.

Clozapine use and sedentary lifestyle as determinants of metabolic syndrome in outpatients with schizophrenia

BACKGROUND

Schizophrenia patients are in danger of developing metabolic syndrome (MetS) and its outcomes type 2 diabetes and cardiovascular disease. Antipsychotic treatment and adverse lifestyle increase the burden of metabolic problems in schizophrenia, but little is known about the role of patients' current psychiatric problems and living arrangements in MetS.

AIMS

This study aims to evaluate correlations between MetS, severity of psychiatric symptoms, living arrangements, health behaviour and antipsychotic medication in outpatients with schizophrenia spectrum disorders.

METHODS

A general practitioner and psychiatric nurses performed a comprehensive health examination for all consenting patients with schizophrenia spectrum disorders treated in a psychosis outpatient clinic. Examination comprised of an interview, a questionnaire, measurements, laboratory tests and a general clinical examination. Diagnosis of MetS was made according to International Diabetes Federation (IDF) definition. Correlations were calculated and logistic regression analysis performed with SAS.

RESULTS

276 patients (men n = 152, mean age ± standard deviation = 44.9 ± 12.6 years) participated in the study; 58.7% (n = 162) of them had MetS according to the IDF definition. Clozapine use doubled the risk of MetS (OR = 2.04, 95% CI 1.09-3.82, P = 0.03), whereas self-reported regular physical activity decreased the risk significantly (OR = 0.32, 95% CI 0.18-0.57, P < 0.001). We found no correlations between MetS and living arrangements or current severity of psychiatric symptoms.

CONCLUSIONS

MetS was alarmingly common in our sample. Even moderate physical activity was associated with decreased risk of MetS. Promotion of a physically active lifestyle should be one of the targets in treatment of schizophrenia, especially in patients using clozapine.

Effects of adrenomedullin on hypertrophic responses induced by angiotensin II, endothelin-1 and phenylephrine

We examined whether adrenomedullin (AM), a vasoactive peptide with significant expression and binding sites in the heart, modulates the hypertrophic response in cultured neonatal rat ventricular myocytes. Myocyte hypertrophy was induced by treating the cells with angiotensin II (Ang II), endothelin-1 (ET-1) or alpha-adrenergic agonist, L-phenylephrine (PHE). All treatments resulted in a hypertrophic response as reflected by increased protein synthesis and expression of atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) genes. AM treatment resulted in a complete inhibition of the Ang II-induced increase in ANP and BNP gene expression and secretion. In contrast, no inhibitory effect was seen in either ET-1-induced natriuretic peptide gene expression or PHE-induced ANP and BNP gene expression and secretion. AM had only a modest effect on basal levels of natriuretic peptide secretion and gene expression. When AM mRNA levels in isolated neonatal rat myocytes treated for 48 h with Ang II, ET-1 or PHE were measured, only Ang II induced a consistent increase in AM gene expression. These results indicate that AM is not invariably associated with attenuation of the hypertrophic response but its effect is dependent on the stimulus activating myocyte hypertrophy. AM may form an important autocrine/paracrine growth-inhibitory loop in Ang II-induced myocyte hypertrophy.

Effects of src kinase and TGFbeta1 on the differentiation and morphogenesis of MDCK cells grown in three-dimensional collagen and Matrigel environments

This study attempted to analyse in detail the effect of src kinase on the growth and differentiation of MDCK cells in different extracellular matrix (ECM) environments. A method was developed to label the membrane proteins in situ and the distribution of cytoskeletal and junctional proteins was visualized in three-dimensional cell complexes, using optical sections generated by confocal microscopy. Independently of the ECM, non-transformed MDCK cells formed differentiated cell cysts with one or a few lumina, with the apical side facing the lumen; ZO-1 was expressed at the tight junctions close to the apical side and beta-catenin, E-cadherin and fodrin along the entire lateral walls. The phenotype of src kinase activated MDCK cells was strongly dependent on the ECM and varied from an irregular cluster in collagen I, to tubular structures in laminin or proteoglycans, and finally to a polarized cell cyst in Matrigel. In collagen I, E-cadherin and beta-catenin were seen partially along the lateral walls and partially in the cytoplasm of src-transformed MDCK cells; fodrin was released into the cytoplasm and ZO-1 was not visualized. When the src-transformed cells were cultivated in Matrigel, their junctional proteins were recruited to the cell membranes and ZO-1 reappeared at the apical face. Thus, the components of Matrigel could overcome the deleterious effect of src on the polarity of MDCK cells. TGFbeta1, together with its receptors and other soluble factors in Matrigel, were responsible for the induction of differentiation. The results show that tyrosine phosphorylation sensitizes the epithelial MDCK cells to ECM and TGFbeta1.

Type XIII collagen: a novel cell adhesion component present in a range of cell-matrix adhesions and in the intercalated discs between cardiac muscle cells

Recent analysis of type XIII collagen surprisingly showed that it is anchored to the plasma membranes of cultured cells via a transmembrane segment near its amino terminus. Here we demonstrate that type XIII collagen is concentrated in cultured skin fibroblasts and several other human mesenchymal cell lines in the focal adhesions at the ends of actin stress fibers, co-localizing with the known focal adhesion components talin and vinculin. This co-occurrence was also observed in rapidly forming adhesive structures of spreading and moving fibroblasts and in disrupting focal adhesions following microinjection of the Rho-inhibitor C3 transferase into the cells, suggesting that type XIII collagen is an integral focal adhesion component. Moreover, it appears to have an adhesion-related function since cell-surface expression of type XIII collagen in cells with weak basic adhesiveness resulted in improved cell adhesion on selected culture substrata. In tissues type XIII collagen was found in a range of integrin-mediated adherens junctions including the myotendinous junctions and costameres of skeletal muscle as well as many cell-basement membrane interfaces. Some cell-cell adhesions were found to contain type XIII collagen, most notably the intercalated discs in the heart. Taken together, the results strongly suggest that type XIII collagen has a cell adhesion-associated function in a wide array of cell-matrix junctions.

Role of vinculin in the maintenance of cell-cell contacts in kidney epithelial MDBK cells

Microinjection of fluorophore-tagged cytoskeletal proteins has been a useful tool in studies of formation of focal adhesions (FA). We used this method to study the maintenance of adherens junctions (AJ) and tight junctions (TJ) of epithelial Madin-Darby bovine kidney cells. We chose alpha-actinin and vinculin as markers, because they are present both at adherens junctions and focal adhesions and their binding partners have been well characterized. Isolated FITC-labelled chicken alpha-actinin and vinculin were injected into confluent cells where they were rapidly incorporated both in FAs and AJs. The FAs remained unchanged, whereas cell-cell contacts began to fade within an hour after injection and the cells were joined to polykaryons having 5 to 13 nuclei. Short fragments of cell membranes containing injected proteins, actin, beta-catenin, cadherin, claudin, occludin and ZO-1 were visible inside the polykaryons indicating that both AJs and TJs were disintegrated as a single complex. Microinjected FITC-labelled vinculin head domain was also incorporated to both AJs and FAs, but instead of fusions it rapidly induced the detachment of the cells from the substratum probably due to high affinity of vinculin head to talin. Vinculin tail domain had no apparent effect on the cell morphology. Since small GTPases are involved in the building up of AJs, we injected active and inactive forms of cdc42 and rac proteins together with vinculin to see their effect. Active forms reduced the formation of polykaryons presumably by strengthening AJs, whereas inactive forms had no apparent effect. We suggest that excess alpha-actinin and vinculin uncouple the cell-cell adhesion junctions from the intracellular cytoskeleton which leads to fragmentation of junctional complexes and subsequent cell fusion. The results show that cell-cell adhesion sites are more dynamic and more sensitive than FAs to an imbalance in the amount of free alpha-actinin and intact vinculin.

Helicobacter pylori induces formation of stress fibers and membrane ruffles in AGS cells by rac activation

Helicobacter pylori induces signaling cascades leading to changes in cytoskeleton and an inflammatory response. Information on the morphological changes and cytoskeletal rearrangements induced by attachment of the bacterium is contradictory and signal transduction pathways are not well known. Since rho family of small GTPases is known to mediate cytoskeletal response to various extracellular stimuli, and is also involved in several other important signal transduction pathways, we have investigated the role of rac and cdc42 in H. pylori-induced cytoskeletal changes in cultured carcinoma AGS cells. AGS cells grown with serum expressed actin filaments in the form of short stress fibers and thin network at the edges, which were depolymerized by removal of serum. In serum-starved cells both type I and type II strains of H. pylori induced formation of actin filaments and lamellipodia-like structures. Microinjection of active rac induced similar changes, but injection of inactive rac prevented the effects of H. pylori, while active or inactive cdc42 did not have any significant effect. Cytoskeletal effects of H. pylori were inhibited by actinomycin D, but not completely by cycloheximide. These results indicate that rac activation is involved in signal transduction cascade leading to cytoskeletal reorganization induced by H. pylori and that gene activation and synthesis of new proteins is necessary in this process.

A neutralizing antibody against human DNA polymerase epsilon inhibits cellular but not SV40 DNA replication

The contribution of human DNA polymerase epsilon to nuclear DNA replication was studied. Antibody K18 that specifically inhibits DNA polymerase activity of human DNA polymerase epsilon in vitro significantly inhibits DNA synthesis both when microinjected into nuclei of exponentially growing human fibroblasts and in isolated HeLa cell nuclei. The capability of this neutralizing antibody to inhibit DNA synthesis in cells is comparable to that of monoclonal antibody SJK-132-20 against DNA polymerase alpha. Contrary to the antibody against DNA polymerase alpha, antibody K18 against DNA polymerase epsilon did not inhibit SV40 DNA replication in vitro. These results indicate that DNA polymerase epsilon plays a role in replicative DNA synthesis in proliferating human cells like DNA polymerase alpha, and that this role for DNA polymerase epsilon cannot be modeled by SV40 DNA replication.

Translocation of MARCKS and reorganization of the cytoskeleton by PMA correlates with the ion selectivity, the confluence, and transformation state of kidney epithelial cell lines

The role of protein kinase C (PKC) in the regulation of the cytoskeleton of epithelial cells with tightly sealed contacts, poor contacts, and without contacts were investigated by incubating them with a protein kinase C activator phorbol myristoyl acetate (PMA). The morphology and organization of the membrane skeleton and stress fibers as well as the localization of an actin-bundling PKC substrate MARCKS in confluent MDCK cells originating from the distal tubulus of dog kidney, LLC-PK1 cells originating from the proximal tubulus of pig kidney, src-transformed MDCK cells, epidermoid carcinoma A431 cells, and MDCK cells grown in low calcium medium (LC medium) in low density were visualized with phase contrast and immunofluorescence microscopy. Four different responses to the PMA-treatment in actin-based structures of cultured epithelial cells were observed: 1) disintegration of the membrane skeleton in confluent MDCK cells; 2) depolymerization of the stress fibers in confluent MDCK and LLC-PK1 cells; 3) formation of the membrane skeleton in A431 cells, and 4) formation of the stress fibers and membrane skeleton in LC-MDCK cells. Thus, it seems that in fully confluent tightly sealed epithelium, activation of PKC has a deleterious effect on actin-based structures, whereas in cells without contacts or loose contacts, activation of PKC by PMA results in improvement of actin-based cytoskeletal structures. The main difference between the two kidney cell lines used is their selectivity to ion transport: the monolayer of LLC-PK1 cells is anion selective and MDCK cells cation selective. We propose a model where alterations in the ionic milieu within the MDCK cells by means of cation channels affect the disintegration of the membrane skeleton. The distribution of MARCKS followed the distribution of fodrin in both cell lines upon PMA-treatment, suggesting that phosphorylation of MARCKS by PKC may contribute in the regulation of the integrity of the membrane skeleton.

Effect of PMA on the integrity of the membrane skeleton and morphology of epithelial MDCK cells is dependent on the activity of amiloride-sensitive ion transporters and membrane potential

The signaling pathways from an activation of protein kinase C (PKC) by phorbol myristate acetate (PMA) to the rearrangement of actin-based cytoskeleton and membrane skeleton of epithelial MDCK cells were studied by visualizing the cytoskeletal organization with immunofluorescence microscopy and by measuring intracellular pH, sodium ion concentration and membrane potential with the aid of fluorescent intracellular indicators. Upon PMA treatment the MDCK cells lost their cubic shape and acquired a spindle-like morphology. The stress fibers were depolymerized, and fodrin, the main component of the membrane skeleton, was released from the lateral walls to the cytosol. These changes were accompanied by depolarization of the cells, decrease in the intracellular pH and sodium ion concentration. In order to test the mutual correlation between the PMA-induced alterations we treated the cells with PMA in the presence of channel inhibitors or ionophores and in defined media. The effects of PMA on the membrane skeleton and morphology could be reversed in media lacking Na+ or K+ ions or by hyperpolarizing agents, dimethylamiloride and valinomycin, suggesting that the effects of PMA on the cytoskeleton were dependent on the ion gradients and membrane potential across the cell membrane. Moreover, the morphological changes and instabilization of the membrane skeleton of MDCK cells took place spontaneously without PMA in depolarizing conditions, in potassium gluconate buffer. We suggest that the membrane potential across the cell membrane of MDCK cells together with the activity of amiloride-sensitive cation transporters transmits signals in the protein kinase C (PKC) pathway leading from activation of PKC to fibroblast-like morphology and cytoplasmic localization of membrane skeleton components, features characteristic for cancer cells.

Regulation of the disassembly/assembly of the membrane skeleton in Madin-Darby canine kidney cells

The effects of pH, temperature, block of energy production, calcium/calmodulin, protein phosphorylation, and cytoskeleton-disrupting agents (cytochalasin D, nocodazole) on the integrity of the membrane skeleton were studied in polarized MDCK cells. The intracellular distributions of alpha-fodrin, actin, and ankyrin were monitored by immunofluorescence microscopy. The membrane skeleton, once assembled, seemed to be quite stable; the only factors releasing alpha-fodrin from the lateral walls were the acidification of the cytoplasm and the depletion of extracellular calcium ions. Upon cellular acidification, some actin was also released from its normal location along the lateral walls and was seen in colocalization with alpha-fodrin in the cytoplasm, whereas ankyrin remained associated with the lateral walls. No accumulation of plasma membrane lipids was observed in the cytoplasm of acidified cells, as visualized by TMA-DPH. These results suggest that the linkages between the fodrin-actin complex and its membrane association sites are broken upon acidification. The pH-induced change in alpha-fodrin localization was reversible upon restoring the normal pH. Reassembly of the membrane skeleton, however, required temperatures above +20 degrees C, normal energy production, proper cell-cell contacts, and polymerized actin. Release of alpha-fodrin from the lateral walls to the cytoplasm was also observed upon depletion of extracellular calcium ions. This change was accompanied by the disruption of cell-cell contacts, supporting the role of proper cell-cell contacts in the maintenance of the membrane skeleton polarity. These results suggest that local alterations of the cytoplasmic pH and calcium ion concentration may be important in regulating the integrity of the membrane skeleton.

The polarity of the membrane skeleton in retinal pigment epithelial cells of developing chicken embryos and in primary culture

We studied the morphogenesis and the membrane skeleton in the retinal pigment epithelium during chicken embryogenesis and in culture, by using immunofluorescence and electron microscopy. During embryogenesis two distinct membrane skeletal structures were formed, an apical and a basolateral one. The former was seen in the apical surface already in the 10-day-old embryos. It was comprised of ankyrin and alpha-fodrin and showed a codistribution with Na+,K(+)-ATPase and an as yet uncharacterized cadherin-like molecule. The basolateral membrane skeleton was seen in the lateral walls already in the 10-day-old embryos, and later, between the 13th and 17th embryonic days, it also appeared at the basal membrane, coincidentally with the formation of the basal infoldings. It consisted of ankyrin and alpha-fodrin, but did not codistribute with any of the integral membrane proteins studied (Na+,K(+)-ATPase and cadherins). In culture, the retinal pigment epithelial cells retained their polarized morphology. Compared with the situation in vivo, however, there was a distinct translocation of the membrane skeletal components fodrin and ankyrin from the apical surface to the lateral walls, accompanied by a similar redistribution of Na+,K(+)-ATPase and the cadherin-like molecule. The results suggest that (1) there is, in the retinal pigment epithelium, an apical Na+,K(+)-ATPase-membrane skeleton structure stabilized by contacts between the retinal pigment epithelium and the neural retina, possibly mediated by a cadherin-like molecule, and that (2) there is another fodrin/ankyrin-based membrane skeleton in the basolateral walls that is important for the maintenance of the extensive folding of these surface areas.

Induction of cell fusion in cultured fibroblasts and epithelial cells by microinjection of EGTA, GTP gamma S and antifodrin antibodies

CaCl2, EGTA, GTP gamma S and anti-alpha-fodrin antibodies were injected into fibroblast-like IMR-33 cells and Madin-Darby bovine kidney (MDBK) epithelial cells cultured both in the presence and absence of cycloheximide and fetal calf serum. EGTA, GTP gamma S antifodrin antibody induced fusion of MDBK cells within one hour after injection. The cells formed polykaryons with up to 15 nuclei, reaching an average fusion index of 20%. IMR-33 cells fused at a slower kinetics and only upon injection of GTP gamma S or antifodrin antibodies. No fusions were seen in serum-deprived, quiescent cells. On the other hand, cycloheximide treatment did not prevent the fusions. The results show that cells can be induced to fuse by using agents that interfere with the regulation of the G-proteins, intracellular calcium level or membrane skeleton. We suggest that the putative fusogens are resident proteins of the plasma membrane which become exposed upon destabilization of the membrane skeleton.

Intracellular sites involved in the biogenesis of bile canaliculi in hepatic cells

Studies in hepatoma cells and hepatocytes have revealed that the biogenesis of bile canalicular membrane involves microvilli-lined vesicles (MLV), which are formed in well differentiated cells. The vesicles grow as a function of time and are presumably vectorially transported to cell surface contact sites of attached cells. We demonstrate that a fluorescent head group-labeled lipid analog, N-(lissamine rhodamine B sulfonyl)phosphatidylethanolamine (N-Rh-PE), after its exogenous insertion into the plasma membrane of HepG2 cells at 4 degrees C, accumulates in these microvilli-lined vesicles at 37 degrees C. This shows that the MLV are a target for plasma membrane-derived lipids. Furthermore, also the Golgi apparatus is involved in the formation of the vesicles. After initial accumulation of the fluorescent sphingolipid precursor, 6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]hexanoic acid (C6-NBD)-ceramide in the Golgi apparatus at 37 degrees C, prolonged incubation at 37 degrees C results in the appearance of NBD fluorescence in the microvilli-lined vesicles. The transport route for the Golgi-derived material to the developing bile canalicular vesicle is not an indirect pathway, i.e. involving transcytosis via the basolateral plasma membrane. This could be demonstrated by including bovine serum albumin (BSA) in the incubation media, a lipid scavenger that will remove any C6-NBD-lipids exposed at the basolateral membrane. At these conditions, lipid trafficking between the Golgi complex and MLV still occurred. We further demonstrate that the targeting from the Golgi apparatus to the bile canaliculus is also operational in isolated human hepatocytes. The latter results suggests that the Golgi complex is involved in both the formation of bile canaliculi and in bile secretion in fully differentiated cells.

The effects of PMA and TFP and alterations in intracellular pH and calcium concentration on the membrane associations of phospholipid-binding proteins fodrin, protein kinase C and annexin II in cultured MDCK cells

Annexin II, alpha-fodrin and protein kinase C (PKC) are associated with the cytoplasmic surface of the plasma membranes. When assayed with liposomes, they show affinity for acidic phospholipids and bind calcium ions. They also respond to or participate in cell signal transduction by altered membrane binding properties. In the present work we have studied the properties of these proteins in epithelial MDCK cells in response to elevated intracellular calcium ion concentration, lowered pH, treatment with tumor promoter phorbol myristoyl acetate (PMA) and calmodulin inhibitor trifluoperazine (TFP). In untreated polarized MDCK cells annexin II was seen both along the lateral walls and membranes of intracellular vesicles, fodrin was located along the lateral walls, whereas PKC was seen in the cytoplasm. There was no observable translocation of these proteins upon elevation of the intracellular calcium concentration using a calcium ionophore A23187. On the other hand, treatment with TFP led to a release of annexin II from the plasma membranes which was accompanied by a transient peak in the intracellular calcium. Treatment with PMA led to a loss of the cubic form of the cells, a slight elevation in the intracellular calcium concentration and a drop in the intracellular pH. Simultaneously fodrin was released from the lateral walls, but still remained insoluble in Triton X-100, PKC became associated with the intracellular membranes and fibers, whereas annexin II remained along the lateral walls. These changes could be prevented by clamping the intracellular pH neutral during PMA treatment. On the other hand, lowering of intracellular pH below 6.5 with the nigericin treatment led to a similar translocation of fodrin and PKC as PMA. This suggests that the protein redistribution is caused by cytoplasmic acidification and is due to an increased hydrophobicity and enhanced protonation of lipids and proteins. In contrast, no changes were seen in the annexin II distribution in response to altered pH. Hence, its release by TFP is presumably due to changes in the cationic properties of the inner phase of the plasma membrane. Thus, proteins which show similar binding properties with liposomes show different characteristics in their association with the intracellular membranes.

Bile canaliculus formation in cultured HEPG2 cells

BACKGROUND

The plasma membrane of hepatocytes can be divided in sinusoidal, lateral and apical membrane, each with functionally and structurally distinct features. The apical domain consists of the bile canalicular structures. The morphogenesis and the polarization of hepatocytes is still poorly known.

EXPERIMENTAL DESIGN

We used HepG2 cells, a hepatoma cell line to study the formation of the bile canaliculi in the apical part of the cells. The cells were synchronized by using nocodazole. The formation of the bile canaliculi was monitored by using immunofluorescence microscopy, confocal laser scanning microscopy, and immunoelectron microscopy. Antibodies to alpha-fodrin and villin were used. Actin was visualized with rhodamine phalloidin.

RESULTS

Confocal laser scanning microscopy showed accumulations of actin, villin and fodrin at the cell membranes 8 to 12 hours after the release of the nocodazole block. These sites probably represent areas destined to develop into bile canaliculi. Later, immature bile canaliculi were discerned that were located asymmetrically between adjacent cells. Transmission electron microscopy of serial sections showed that they were always connected with the surface of the cell. Mature bile canaliculi appeared between adjacent cells 48 hours after the release of the nocodazole block. They were round, vesicle-like structures lined with microvilli and sealed by tight junctions and desmosomes. They were usually seen between two juxtaposed cells, and often several cells contributed to their formation. Typically, mature bile canaliculi were delineated by a subplasmalemmal filamentous meshwork of fodrin and actin, resembling a terminal web of enterocytes. Actin and villin were also found in microvillar cores.

CONCLUSIONS

The results show that (i) bile canaliculi are formed de novo between two or more juxtaposed cells; (ii) canalicular-formation is accompanied by a distinct accumulation of the membrane skeletal and microvillar proteins fodrin, actin and villin at the apical surfaces of the cells, suggesting that they play an important role in bile canaliculus morphogenesis, and that (iii) apical membrane differentiation in the cells contributing to the formation of a single canaliculus is an asymmetric process.

A comparative study of 1H NMR lineshape fitting analyses and biochemical lipid analyses of the lipoprotein fractions VLDL, LDL and HDL, and total human blood plasma

The purpose of this work was two-fold. In the first instance, 1H NMR spectra of the ultracentrifuged lipoprotein fractions (VLDL, LDL and HDL) from six volunteers with different clinical conditions were measured. The methylene regions of the experimental spectra were modelled in the frequency domain using non-linear lineshape fitting analyses. In this way the resolvable Lorentzian component structures of the methylene regions of these lipoprotein fraction spectra could be determined. Second, the lipoprotein fraction analyses were used to construct simplified component structures, which interpreted the lipoprotein fraction spectra well, and were feasible to use in the total plasma spectra analyses. The considerable overlap problem of the resonances was properly handled in this way. The NMR-based relative amounts of the lipoproteins (relative integrated intensities of the lipoprotein model signals) obtained were compared to the biochemically resolved relative molar percentages of the lipoprotein fractions and also of the lipid contents between the lipoprotein complexes. It was noticed that nearly all correlations were extremely good. Thus, it is suggested that the developed methodology could be used as a fast method to predict the relative amounts of the lipoproteins and also possibly the relative lipid contents between the major lipoprotein categories directly from the proton NMR spectrum of a total blood plasma sample. Furthermore, if internal or external reference for the integrated intensities of the proton NMR resonances were used, it should also be possible to obtain the absolute amounts of these quantities.

Recycling pathways of glucosylceramide in BHK cells: distinct involvement of early and late endosomes

Recycling pathways of the sphingolipid glucosylceramide were studied by employing a fluorescent analog of glucosylceramide, 6(-)[N-(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]hexanoylglucosyl sphingosine (C6-NBD-glucosylceramide). Direct recycling of the glycolipid from early endosomes to the plasma membrane occurs, as could be shown after treating the cells with the microtubule-disrupting agent nocodazole, which causes inhibition of the glycolipid's trafficking from peripheral early endosomes to centrally located late endosomes. When the microtubuli are intact, at least part of the glucosylceramide is transported from early to late endosomes together with ricin. Interestingly, also N-(lissamine rhodamine B sulfonyl)phosphatidylethanolamine (N-Rh-PE), a membrane marker of the fluid-phase endocytic pathway, is transported to this endosomal compartment. However, in contrast to both ricin and N-Rh-PE, the glucosylceramide can escape from this organelle and recycle to the plasma membrane. Monensin and brefeldin A have little effect on this recycling pathway, which would exclude extensive involvement of early Golgi compartments in recycling. Hence, the small fraction of the glycolipid that colocalizes with transferrin (Tf) in the Golgi area might directly recycle via the trans-Golgi network. When the intracellular pH was lowered to 5.5, recycling was drastically reduced, in accordance with the impeding effect of low intracellular pH on vesicular transport during endocytosis and in the biosynthetic pathway. Our results thus demonstrate the existence of at least two recycling pathways for glucosylceramide and indicate the relevance of early endosomes in recycling of both proteins and lipids.

Different organizational states of fodrin in cultured MDCK cells are induced by treatment with low pH, calmodulin antagonist TFP, and tumor promoter PMA

We have investigated the molecular mechanisms underlying dynamic organization of the fodrin network by treating the epithelial MDCK cells with various agents affecting intracellular pH, intracellular calcium ion concentration, intracellular calmodulin, and protein kinase C (PKC) activity. Elevation of intracellular calcium level by A23187 or treatment with trifluoperazine (TFP), a calmodulin inhibitor, did not have any drastic effect on the fodrin distribution as judged by immunofluorescence microscopy. A long-term incubation with phorbol-12-myristate-13-acetate (PMA), a protein kinase C activator, in contrast, released fodrin from the lateral walls of the MDCK cells, leading to a diffuse cytoplasmic distribution. TFP, along with PMA, accelerated destabilization of the fodrin skeleton. Treatment with TFP alone rapidly released the cells from the substratum, which, however, could be prevented by PMA. We have previously shown that lowering of intracellular pH (< 6.5) leads to a removal of fodrin from its basolateral residence (Eskelinen et al., 1992) and that this translocation is reversed upon returning normal pH. We now show that the rebuilding of the membrane skeleton can be prevented if TFP is added to the acidified cells. Moreover, in TFP-treated acidified cells, fodrin shows a clusterlike organization similar to that observed in resting lymphocytes. We also noticed that interconversions between these different organizational states of fodrin are independent of the intracellular calcium concentration. Thus manipulation of the intracellular pH and treatment with TFP and PMA reveals different organizational states of the fodrin skeleton. This suggests that fodrin may participate in PMA-, TFP- and pH-sensitive signal transduction pathways.

Proton nuclear magnetic resonance lineshape studies on human blood plasma lipids from newborn infants, healthy adults, and adults with tumors

The usefulness of proton NMR spectroscopy of human blood plasma for cancer research has been extensively studied in recent years. Two main starting points have been offered by Fossel et al. (N. Engl. J. Med. 315, 1369 (1986)) and Mountford et al. (FEBS Lett. 203, 164 (1986)). In this work the experimental proton NMR spectra of blood plasma were analyzed with the aid of the multivariate lineshape fitting method. An appropriate model structure, in terms of the various lipoprotein (VLDL, LDL, and HDL) signals, for the methylene region was used. Neonates, healthy adults, and adults with nonmalignant and malignant tumors were studied. The linewidth of the methylene region was found to be linearly dependent on the relative concentrations of the lipoproteins. The correlation coefficient was -0.89 (P less than 0.001) for VLDL and 0.88 (P less than 0.001) for HDL. A correlation between VLDL concentration and age, 0.76 (P less than 0.001), was also established. VLDL was modeled using two components. The half-linewidth of the lower field component was slightly elevated for the adults with large metastases. This might be in association with the fucose-containing proteolipid complex detected earlier in cancer cells or in sera of cancer patients. Some signals of this complex may fall in the same region of the spectra. The spectra for the neonates were indicated to be totally different from the adults. This and other related questions were explained by means of the model parameters and the relative concentrations of the lipoproteins VLDL, LDL, and HDL. The presented technique can be used as a rapid research tool for figuring out the relative concentrations of the lipoproteins in blood plasma and explaining the reasons behind the changes in the spectra.

Low intracellular pH induces redistribution of fodrin and instabilization of lateral walls in MDCK cells

We have studied the effect of intracellular pH on the establishment and maintenance of the cellular polarity in MDCK cells by utilizing nigericin which causes lowering of the cytoplasmic pH. At pH below 6.5, MDCK cells lost their polarized morphology and became roundish, with an increased apical area and shortened and unstable lateral walls. The lateral wall marker proteins uvomorulin and Na,K-ATPase remained segregated to the lateral walls in the acidified cells, as shown by immunofluorescence microscopy. Fodrin, on the other hand, was released from its normal basolateral residence and was found in the cytoplasm. Actin, which normally co-localizes with fodrin along the basolateral walls, showed a dotty distribution in the cytoplasm of acidified cells, while stress fibers remained intact. Microtubular network appeared flattened, but the Golgi complex retained its apical position. The pH change-induced alterations were readily reversible, as the normal basal-apical polarity (columnar shape, distinct apical and lateral domains with apposing and stiff lateral membranes) was reformed within 10 minutes after restoring the normal pH gradient across the cell membrane. This coincided with the translocation of fodrin from the cytoplasm to the lateral walls. The results show that lowering of intracellular pH leads to temporary segregation of fodrin from the other components of the membrane skeleton assembly, and that association of fodrin with the lateral walls seems to be a prerequisite for their close apposition and for the maintenance of normal basal-axial polarity.

Coated endosomal vesicles: sorting and recycling compartment for transferrin in BHK cells

We have investigated receptor-mediated endocytosis of transferrin (Tf) in baby hamster kidney (BHK) cells, using fluorescence and electron microscopy, and by carrying out colocalization experiments with clathrin antibodies and a fluorescently tagged glycolipid. Early during internalization, Tf was found in small vesicles (100-150 nm in diameter) located at the cell periphery. The ligand remained associated with such vesicles when the latter concentrated towards the cell center, before ending up in the juxtanuclear area. Throughout this vesicular trafficking pathway, clathrin colocalized with Tf. We conclude that Tf is processed intracellularly via small coated endosomal vesicles (CEV) and is not delivered into large tubular endosomes (CURL; compartment for uncoupling receptors and ligands), typical for ligand trafficking to lysosomes. By determining the kinetics of Tf internalization and by comparing the flow of Tf to that of a fluorescent glycolipid, it can also be concluded that CEVs display sorting and recycling properties, implying that small vesicles can be shed from or fuse with CEVs. Acidic pH does not prevent the formation of CEVs, but their intracellular movement, towards the cell center, is impeded.

A lineshape fitting model for 1H NMR spectra of human blood plasma

A lineshape fitting model was constructed for classifying the overlapping information in the 1H NMR spectrum of human blood plasma. A reliable assignment of the overlapping fatty acid (-CH2-)n and -CH3 resonances of the various lipoproteins (VLDL, very low density lipoprotein; LDL, low density lipoprotein; HDL high density lipoprotein) is introduced, and for the first time detailed characteristics (chemical shifts, half linewidths, and relative intensities) of the individual lipoprotein components were obtained directly from the whole plasma spectrum. This was achieved by combining the constructed lineshape fitting model and the proper 400 MHz proton NMR measurements from blood plasma of a healthy donor, from fractions of the different lipoproteins, and from plasma samples in which the lipoprotein fractions were separately added. The results suggest fair promise of future applications of the rapid and easy NMR analysis of lipoprotein distribution in various research and clinical situations.

Salvage of glucosylceramide by recycling after internalization along the pathway of receptor-mediated endocytosis

To examine the (intra)cellular fate of a glycolipid, normally residing at the cell surface, a fluorescent analog of glucosylceramide, 6-[N-(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]hexanoylglucosylsp hingosine (C6-NBD-glucosylceramide), was inserted into the plasma membrane of baby hamster kidney cells at low temperature. Upon warming the cells to 37 degrees C, part of the glycolipid analog was internalized. A comparison with receptor-mediated uptake of transferrin revealed that after 2 min of warming, both C6-NBD-glucosylceramide and the transferrin-transferrin receptor complex are localized in the same intracellular compartment (early endosomes). We conclude that C6-NBD-glucosylceramide is internalized along the pathway of receptor-mediated endocytosis. When, after internalization of part of the membrane-inserted glycolipid analog, the residual pool of plasma membrane C6-NBD-lipid was removed by "back exchange" with a lipid acceptor, C6-NBD-glucosylceramide molecules can be shown to return intact to the plasma membrane. This demonstrates that glycolipids, analogous to a variety of protein receptors, are able to recycle to the plasma membrane after internalization.

1H NMR studies on human plasma lipids from newborn infants, healthy adults, and adults with tumors

The 1H NMR spectra of the lipid region of human plasma from healthy adults, neonates, and patients with malignant and nonmalignant tumors have been recorded on a JNM-GX400 FT spectrometer operating at 399.6 MHz for protons. The chemical shifts of methylene and methyl groups of plasma lipids were measured with respect to the higher field component of the methyl proton resonance of the lactate molecule. The results show that there are changes in the chemical shifts of the methylene proton resonances among the plasma from healthy adults, adults with tumors, and neonates. The shifts observed in the case of cancer patients and neonates are in the direction opposite to the shift measured from the plasma of healthy adults. Thus, the observed changes cannot be explained by the activity in the cell proliferation of tissues which is high in the cases of both healthy neonates and patients with malignant tumors, but they most probably reflect the different lipoprotein compositions of neonates, healthy adults, and adults with tumors.

Location and identification of colloidal gold particles on the cell surface with a scanning electron microscope and energy dispersive analyzer

The use of colloidal gold particles for locating cell surface components by scanning electron microscopy (SEM) has been restricted due to difficulties in the identification of these gold particles under SEM. It is shown here how the gold particles bound to cell surfaces can be located and identified under SEM using the secondary electron imaging (SEI) mode with an energy dispersive X-ray microanalyzer (EDS). This enables reliable identification of gold particles and good quality micrographs of the cells to be achieved at the same time. The distribution of receptors for two lectins, concanavalin A (ConA) and wheat germ agglutinin (WGA), on the surface of cultured Raji cells and human erythrocytes is presented as an example. Raji cells and erythrocytes were fixed with glutaraldehyde, post-fixed with a glutaraldehyde-tannic acid mixture and then incubated with ConA- or WGA-coated gold particles. After dehydration and critical point drying, the specimen filters were mounted on copper stubs and coated with carbon. The cells were examined on a JEOL TEMSCAN 100CX II electron microscope. The gold particles could be identified with the EDS analyzer, which was able to detect the Au spectrum when the electron beam was focused on single gold particles using a magnification of 100,000 or more. High-resolution photographs of the same cells were obtained up to the same magnification of 100,000.

The kinetics of drug-membrane interactions in human erythrocytes from neonates

The kinetics of drug-membrane interactions of erythrocytes from neonates were compared with those from adults by monitoring the time course of the shape transformations and vesicle release caused by drugs, using a light microscope--video recording technique. Both crenation caused by lysophosphatidylcholine (LPC) and cupping caused by chlorpromazine (CPZ) took place more slowly in the neonatal cells than in the cells from adults. The equilibrium concentrations of LPC and CPZ in erythrocytes did not differ significantly between the neonates and adults, however. The slower responses of the neonatal erythrocytes can be explained by the presence of negatively charged phosphatidylethanolamine and phosphatidylserine in the outer layer of the erythrocyte membrane, which may reduce the rate of incorporation of amphipathic LPC and attract cationic CPZ to remain in the outer membrane layer, lowering the rate of inward bending of the membrane normally caused by CPZ.

The kinetics of drug-membrane interactions in human erythrocytes

The time course of the shape transformations and vesicle release in human erythrocytes caused by lysophosphatidylcholine and chlorpromazine was monitored using a light microscope-video recording technique. The time required for the erythrocytes to reach a stage I echinocytic shape decreased from 4.0 to 2.0 s, when the concentration of the lysophosphatidylcholine solution injected was increased from 1 to 25 microM. The time required to reach stage II decreased from 8.3 to 3.5 s and that required for vesicle release and the formation of stage IV spherocytes decreased from 78.0 to 11.6 s. Correspondingly, the time needed for the formation of stage I stomatocytes decreased from 2.3 to 1.0 s and that for stage II stomatocytes from 3.1 to 2.0 s, when the ambient chlorpromazine concentration was increased from 50 to 200 microM. The kinetics of the shape transformations of the erythrocytes were dependent on the ambient drug concentration. The rate of shape transformations could be predicted from a formula derived for the kinetics of the incorporation of the detergent into the cell membrane, providing that the affinity coefficient and mass transfer coefficient for drugs changed as a function of the free drug concentration. The results give a time scale for the drug-membrane interactions, i.e., the formation of stages I and II for drug-lipid bilayer interactions and the release of vesicles for drug-cytoskeleton interactions.

Microscopic estimation of bacteria and cells in urine. II. A clinical study on the application of the theoretical considerations to clinical practice

An improved technique for diagnosing acute urinary tract infections (UTI) by means of microscopic estimation of bacteria, leucocytes, erythrocytes and epithelial cells in urine was tested clinically in a total of 1,807 samples obtained from hospital departments. Marked bacteriuria (greater than or equal to 10(5) bacteria per ml of urine) was found microscopically in 13.1% of the urines. Of these 1.9% were falsely positive. Altogether 3.5% of the samples were falsely negative. When the sample collection was controlled carefully and detailed information on possible collection errors was given regularly, sensitivity and specificity indices of the microscopic technique were 85.3 and 98.1, respectively. Microscopic finding of cocci, e.g. Enterococci and Str. agalactiae, was more difficult than that of rods. Alongside bacteriuria, finding of leucocytes (greater than 5 leucocytes per microscopic field) was of great importance for UTI diagnostics, and it strengthened further the microscopic diagnosis, while erythrocytes and epithelial cells were of very poor significance for UTI diagnosis. The results show that the microscopic technique described here is a reliable and suitable method for UTI diagnostics in routine clinical laboratories which examine daily large numbers of samples, most of them negative.

Effect of lysophosphatidylcholine on salt permeability through the erythrocyte membrane under haemolytic conditions

Human erythrocytes were incubated in haemolytic salt or sucrose media and the amount of potassium and haemoglobin released were monitored. In hypotonic NaCl and KCl solutions potassium release and haemolysis increased with time showing that the cell membrane had been injured and became permeable to intra- and extracellular cations which, due to intracellular haemoglobin, causes water influx and continuous haemolysis. Both potassium release and haemolysis remained, however, at their 2-minute level in the presence of LPC. Thus, LPC could reseal the membrane and prevent continuous salt fluxes. It protected erythrocytes from hypotonic haemolysis and the protection was more efficient in NaCl than in sucrose media. This suggests that the increase in the critical volume of erythrocytes caused by LPC occurs both in electrolyte and sucrose media, and the additional protection observed in electrolyte media is due to the resealing of the injured cell membrane by LPC. The repairing mechanism was mediated via the membrane lipids or integral proteins, since the time-course of haemolysis of erythrocytes swollen in NaCl media at the spectrin-denaturing temperature of 49.5 degrees C was similar to that at room temperature with and without LPC. LPC did not protect erythrocytes from colloid osmotic haemolysis caused by ammonia influx in an isotonic NH4Cl medium, but protected the cells from colloid osmotic haemolysis caused by sodium influx through nystatin-channels in NaCl media without any area or volume increase. Hence, LPC could not prevent ammonia influx through the lipid bilayer, but suppressed sodium influx through nystatin-channels presumably via LPC interference with cholesterol.

Microscopic observation and video recording of cellular response to sudden changes in environment

A method to record responses of single cells to rapid changes in their environment is described. A rectangular glass microcapillary is filled with the cell suspension under investigation and placed under a light microscope. With the aid of a micromanipulator a smaller microcapillary with a narrowed tip, which was still over 10 times wider than the cell diameter, is driven into the larger, cell containing, microcapillary. The environment of the cells is changed by injecting a new medium via the smaller capillary and the cell responses are recorded using a video recording system. The usefulness of the system has been examined by studying the time course of the osmotic swelling of erythrocytes after water injection and the shape transformations caused by lysophosphatidylcholine.

Cation permeability and mechanical properties of the erythrocyte membrane under the influence of lysophosphatidylcholine (LPC) in isotonic and hypotonic media

The osmotic behaviour of erythrocytes under the influence of lysophosphatidylcholine (LPC) was investigated at temperatures of +4 degrees C and 20 degrees C by allowing them either to swell rapidly in hypotonic media in the presence of LPC or to swell gradually at first and then interact with LPC. Prelytic potassium release, the degree of hemolysis and the cell volume under various osmotic conditions were measured, together with the 'returning volumes', i.e. the volumes in an isotonic solution to which the cells returned from that in the hypotonic solution. LPC had a hemolyzing effect on erythrocytes in an isotonic medium and in slightly hypotonic media under all the osmotic conditions investigated, and the degree of hemolysis increased with increasing concentrations of LPC or decreasing temperatures, being greater during gradual than during rapid swelling. LPC also produced a prelytic leakage of potassium connected with the decrease in cell volume in an isotonic medium and in 'returning volumes' in all the media and under all the osmotic conditions investigated. The semipermeability of the membrane was preserved in all these cases, however, for osmotic swelling of the erythrocytes was observed, although to a lesser extent than without LPC. During rapid swelling both the curves for the prelytic potassium leakage and the degree of hemolysis were shifted towards more dilute solutions. Since the critical hemolytic volume was not increased, the shift in potassium leakage and hemolysis caused by LPC may be due to increased rigidity in the cell membrane. The curves for both potassium leakage and hemolysis shifted towards more concentrated solutions during gradual swelling, perhaps due to increased membrane fragmentation.

Normal and homogeneous red blood cell populations over a wide range of hyper-iso-hypotonic media. III. Corrected volumes in Coulter Counter measurements

The volumes of human erythrocytes after rapid and gradual swelling in hypotonic NaCl media were measured using a Coulter Counter ZB at temperatures of +4 degrees C and +20 degrees C together with potassium leakage, the degree of hemolysis and the 'returning volume', i.e., the volume in an isotonic solution to which the cells will return from that in a hypotonic solution. The methodological and systematic errors in the volume measurements were corrected by taking into account the shape dependence of the Coulter Counter and the change in cell population during hemolysis, whereafter the measured cell volume values and the comparison between them become more reliable. The curves for cell volume as an inverse function of osmotic pressure appeared to be non-linear. The slopes were small at first but showed a rapid increase as the cells approached their maximal volume. The critical hemolytic volume was approx. 8% higher at +20 degrees C after both rapid and gradual swelling than at +4 degrees C and approx. 4% higher after a gradual swelling as compared with a rapid swelling both at +4 degrees C and +20 degrees C. A decrease in temperature resulted in an increase in the critical osmotic pressure both in rapid and gradual hemolysis, but did not greatly affect the amount of prelytic K+ leakage. The critical osmotic pressure was smaller in gradual hemolysis than in rapid hemolysis and the prelytic K+ leakage was doubled at both +4 degrees C and +20 degrees C. The shifts in osmotic fragility as a function of temperature may be due to differences in the visco-elastic properties of the cell membrane, but the shifts in osmotic fragility as a function of swelling rate may be connected with differences in potassium leakage and membrane stretch.

The hypotonic hemolysis and the protective action of lysophosphatidylcholine

Lysophosphatidylcholine (LPC) protected against hypotonic hemolysis during rapid swelling of erythrocytes in spherocytic concentrations without any increase in the maximal cell volume. The total prelytic potassium release was increased, but the prelytic potassium release per cell was the same or decreased in the presence of LPC. The comparison of measured and calculated cell volume increase suggested that the prelytic potassium release must have been connected with a considerable sodium influx suggesting serious damage of the cell membrane already during swelling in the absence of LPC. Gradual swelling shifted hemolysis to more dilute solutions and LPC did not further increase the shift. We suggest that LPC protects the erythrocytes against hypotonic hemolysis during rapid swelling via a prevention of the initial membrane damage through altering the interaction between lipid bilayer and membrane cytoskeleton in the same way as occurs during incubation in a medium with low ionic strength.

Ferene-S as the chromogen for serum iron determinations

Ferene-S was tested as the iron chromogen and the results were compared with the chromogen Ferrozine. With Ferene-S the volume of serum could be halved. We also tried to adapt Ferene-S in total iron binding capacity determinations but failed. From the interfering substances in serum iron determination the effects of bilirubin, copper and zinc were tested. Bilirubin was not observed to have any effect on iron values with Ferene-S or Ferrozine as chromogens. Copper ions had a distinct additive effect with both chromogens, but it could be eliminated by the addition of thiourea to the solutions. Zinc had no effect.

Effects of glutaraldehyde and critical point drying on the shape and size of erythrocytes in isotonic and hypotonic media

Scanning electron microscopy (SEM) was applied to studies on osmotically swollen erythrocytes fixed by a method using increasing concentrations of glutaraldehyde (GA), OsO4 as a post fixative, and critical point drying (CPD). This fixation method prevented the osmotic effect of GA itself and preserved the cellular equilibrium shape intact in various media, i.e. discocytes in an isotonic medium and ellipsoids or spheres and ghosts in a hypotonic medium. The discocytes were reduced less in diameter and area than the ellipsoids and spheres during CPD, but the degree of volume shrinkage was of the same magnitude (approx. 73%) regardless of the cell shape. The shrinkage of the discocytes was advanced until the dry volume (approx. 29 microm3) was reached, while the shrinkage of the osmotically swollen cells ceased earlier. A miniaturization process coupled with solvent evaporation is suggested as an explanation for this. The osmotic swelling of erythrocytes was studied quantitatively with the aid of SEM micrographs. The increase in volume was about 60%, which is in agreement with the values obtained by light microscopy for unfixed and GA-fixed cells in the present work and with those reported in the literature.