Microprocessor based waveform analysis of the fetal electrocardiogram during labor

An increase in T wave amplitude of the fetal ECG (FECG) has experimentally been correlated to elevated catecholamine levels and myocardial glycogenolysis. The FECG changes have also been described during human delivery. The present aim was to investigate whether these ECG changes could be reproduced in an easily handled real time microprocessor system, and to correlate them to biochemical and clinical data. During 40 deliveries the FECG signal was transferred to a microcomputer system for real time averaging of the FECG. There was a high capacity of the system to reproduce the ST waveform changes though the averaging procedure reduced the QRS magnitude by 10%. With a normal umbilical artery pH (greater than or equal to 7.25) the highest T/QRS ratios recorded during each delivery was 0.26 +/- 0.19 (mean +/- S.D.). With lowered pH (less than 7.25) the T/QRS increased to 0.33 +/- 0.10 (P less than 0.02). A similar difference between the two groups was seen when the T/QRS ratios from the last hour before birth were compared; 0.13 +/- 0.08 and 0.18 +/- 0.05, respectively (P less than 0.01). Changes in the ST waveform with T/QRS greater than or equal to 0.30, ST segment alterations, or negative T waves appeared during 40% of the deliveries, however, 30% were short standing changes (less than 30 min). Intermediate CTG changes during at least 30 min occurred in 41% and the pattern was classified as abnormal in 18%. Using the scalp electrode as signal source, the ECG analysis could add further information to the routine CTG recording on the fetal condition during delivery.

Characterization of exposure to molds and actinomycetes in agricultural dusts by scanning electron microscopy, fluorescence microscopy and the culture method

Air samples from 79 farms with 10(5) to 10(11) microorganisms/m3 were analyzed by scanning electron microscopy (SEM), fluorescence microscopy (FM), and the culture method. The total exposure to microorganisms (particularly actinomycetes) was underestimated when assessed as colony-forming units (cfu). The average cfu count was one-sixth of the total count according to SEM or FM, and the individual variability was great. This occurrence was partly explained by the aggregation of spores. Single spores accounted for 2-65% of all spores in 35 samples. There was an average of three spores/particle, and 93 (range 67-100)% of the spores were single or in aggregates of respirable size. Aggregation was more pronounced for actinomycetes and at high spore counts. Actinomycetes and bacteria could not be distinguished by FM. Bacteria (other than actinomycetes) were not detected by SEM, yet the total count of microorganisms was similar for FM and SEM. Most particles were spores from actinomycetes and fungi of the genera Aspergillus or Penicillium.

Binding of human extracellular-superoxide dismutase C to cultured cell lines and to blood cells

The high heparin-affinity subtype C of the secretory enzyme extracellular-superoxide dismutase (EC-SOD) was found to bind to cultured mammalian cells, forming an equilibrium between the cells and the medium. To anchorage-dependent cell lines, binding apparently occurred both to the glycocalyx of the cell surfaces and to the sub- and intercellular matrix produced by the cells. Heparan sulfate proteoglycan appeared to be the principal binding substance. The binding capacities of anchorage-dependent cultures were very high, and at maximal binding the amount of EC-SOD C activity associated with the exterior of the cells was several-fold higher than the endogenous intracellular SOD activity. Half-maximal binding occurred at about 8 micrograms/ml EC-SOD C. At low, nonsaturating, physiologic EC-SOD C concentrations, the enzyme concentration in the glycocalyx of cells may be several thousand times higher than in the medium. All 14 investigated anchorage-dependent cell lines, including endothelial cells, bound EC-SOD C avidly. The 10 suspension-growing cell lines were all weaker binders. Blood monomorphonuclear leukocytes and platelets bound little EC-SOD C, whereas no significant binding to neutrophil leukocytes, to erythrocytes and to E. coli could be demonstrated. The findings are compatible with the notion that EC-SOD C in the vasculature forms an equilibrium between plasma and heparan sulfate in the glycocalyx of the endothelium. Furthermore, tissue EC-SOD is probably distributed between heparan sulfate on the surface of most cell types in the organs and in the interstitial matrix. The binding pattern suggests that EC-SOD C has the potential to protect most normal cells in the body and the interstitial matrix, without protecting microorganisms lacking affinity, and without interfering with superoxide radicals produced at the surface of activated neutrophil leukocytes.

Complement activation and anaphylatoxin (C3a and C5a) formation in preeclampsia and by amniotic fluid

The aim of this study was to determine whether the biologically active complement peptides C3a and C5a are formed in pregnancy and whether amniotic fluid can activate complement. C3a and C5a are formed when complement is activated. They increase smooth-muscle contraction, vascular permeability, and histamine release from mast cells and basophils. Thirty pregnant women were studied, 16 with uncomplicated and 14 with preeclamptic pregnancies. The plasma C3a and C5a concentrations before delivery were significantly higher in the preeclamptic than in the normal group. The concentrations returned to normal within 1 week. Plasma, serum, and amniotic fluid from 12 pregnant women (eight uncomplicated and four preeclamptic pregnancies) were drawn in connection with delivery. Amniotic fluid was incubated in fresh autologous serum at 37C for 15 minutes. A dose-dependent formation of C3a and C5a was registered with increasing amounts of amniotic fluid.

Interaction between benzylpenicillin and thiopental in the central nervous system of the male rat

The effect of benzylpenicillin (BPC) pretreatment on the kinetics and brain sensitivity for thiopental was studied in male rats using a previously developed electroencephalgrafic (EEG) threshold method. Thiopental was infused intravenously with constant infusion rate. The rats were killed by decapitation immediately after the first burst suppression of 1 sec. or more (the silent second) which was observed in the EEG-record during the infusion. Thiopental concentration in serum and in different brain regions was determined by a high pressure liquid chromatografic method. After pretreatment with 0.9 g/kg of BPC the dose of thiopental needed to induce the silent second was significantly reduced (-20 per cent) when compared with saline treated controls. The serum concentration was also reduced (-30 per cent) after this BPC pretreatment but the concentrations in the different brain regions were the same in both groups. After pretreatment with 1.2 g/kg of BPC almost all animals had convulsions, the dose needed to obtain the silent second was very much reduced and there were reduced concentrations of thiopental in the different brain regions. After both doses of BPC high negative correlations were found between BPC concentrations in brain tissue and thiopental concentrations in hippocampus and brainstem indicating an interaction between the drugs. The most probable site of this interaction is the organic acid transport system out of the CNS which could be used by both substances. Lipid solubility is not the only factor involved in the distribution of thiopental in the rat brain.

Binding of human extracellular superoxide dismutase C to sulphated glycosaminoglycans

The secretory enzyme extracellular superoxide dismutase (EC-SOD) occurs in at least three forms, which differ with regard to heparin affinity: A lacks affinity, B has intermediate affinity, and C has relatively strong affinity. The affinity of EC-SOD C for various sulphated glycosaminoglycans (GAGs) was assessed (a) by determining the concentration of NaCl required to release the enzyme from GAG-substituted Sepharose 4B and (b) by determining the relative potencies of the GAGs to release EC-SOD C from heparan sulphate-Sepharose 4B. Both methods indicated the same order of affinity. Heparin bound EC-SOD C about 10 times as avidly as the studied heparan sulphate preparation, which in turn was 10 and 150 times as efficient as dermatan sulphate and chondroitin sulphate respectively. Chondroitin sulphate showed weak interaction with EC-SOD C at physiological ionic strength. Heparin subfractions with high or low affinity for antithrombin III were equally efficient. The binding of EC-SOD C to heparin-Sepharose was essentially independent of pH in the range 6.5-9; below pH 6.5 the affinity increased, and beyond pH 9.5 there was a precipitous fall in affinity. The inhibitory effect of NaCl on the binding of EC-SOD C to GAGs indicates that the interaction is of electrostatic nature. EC-SOD C carries a negative net charge at neutral pH, and it is suggested that the binding occurs between the negative charges of the GAG sulphate groups and a structure in the C-terminal end of the enzyme that has a cluster of positive charges. These results are compatible with the notion that heparan sulphate proteoglycans on cell surfaces or in the intercellular matrix may serve to bind EC-SOD C in tissues.

Heparin-, dextran sulfate- and protamine-induced release of extracellular-superoxide dismutase to plasma in pigs

Intravenous heparin has previously been shown to release the high-heparin-affinity fraction C of extracellular-superoxide dismutase (EC-SOD, EC 1.15.1.1) to plasma in man and other mammals. This paper reports on further studies of the phenomena in the pig. A dose-response curve of the effect of heparin revealed that 1000 IU/kg body weight is needed for maximal release of EC-SOD C. This dose is an order of magnitude larger than that needed for the maximal release to plasma of factors such as lipoprotein lipase, hepatic lipase, and diamine oxidase, which are distributed between plasma and endothelium similarly to EC-SOD C. Thus EC-SOD C appears to have an unusually high affinity for endothelial cell-surface sulfated glycosaminoglycans relative to the affinity for heparin. There was no significant difference in releasing potency between unfractionated heparin and heparin subfractions with high or low affinity for antithrombin III. The heparin structure conferring high-affinity binding to antithrombin III is thus not specifically involved in binding to EC-SOD C. The non-biosynthetic compound dextran sulfate 5000 was an order of magnitude more efficient than heparin. Protamine displayed dual effects. Given alone in high dose it released EC-SOD to plasma, probably due to binding to endothelial cell-surface sulfated glycosaminoglycans displacing fraction C of the enzyme. When given after heparin, in a dose just below that expected to neutralize the heparin, protamine reversed the heparin-induced EC-SOD release.

Extracellular superoxide dismutase in the vascular system of mammals

Plasma extracellular superoxide dismutase (EC-SOD) from the pig, cat, rabbit, guinea pig and mouse was found to be heterogeneous with regard to heparin affinity and could be separated into three fractions: A without affinity, B with weak affinity and C with relatively high affinity. Rat plasma EC-SOD was deviant and contained only A and B fractions. There were very large interspecies differences in total plasma EC-SOD activity and in division of the activity between the different fractions. Intravenous injection of heparin resulted in the pig, dog, cat, rabbit, guinea pig and mouse in a prompt increase in the plasma SOD activity. The increase was due to release of EC-SOD C to plasma, most probably from endothelial cell surfaces. In the rat, heparin induced no increase in plasma SOD activity, apparently because of the absence of EC-SOD C in this species. The relative heparin-induced increase in plasma EC-SOD C varied between 2 and 11 in the different species and was distinctly correlated with the heparin affinity of EC-SOD C in the particular species. Apparently the EC-SOD C, present in the vasculature, forms an equilibrium between plasma and endothelium, whereas EC-SOD A and B primarily exist in plasma. The wide diversity of EC-SOD in the vascular system of mammals with regard to total amount, division into fractions and distribution between plasma and endothelium indicates that the pathogenic potential of superoxide radicals in the extracellular space might vary much between species.

Plasma clearance of human extracellular-superoxide dismutase C in rabbits

Extracellular-superoxide dismutase (EC-SOD) is heterogenous in the vasculature with regard to heparin affinity and can be separated into three fractions: A, without affinity; B, with weak affinity; and C, with relatively strong heparin affinity. The plasma clearance of intravenously injected 125I-labeled and unlabeled human EC-SOD C was studied in rabbits. About 90% of injected 125I-EC-SOD C was eliminated from the blood within 5-10 min. Injection of heparin after 10 or 20 min led to an immediate release of all sequestered 125I-EC-SOD C back to the blood plasma. Later injections of heparin led to diminished release, although release could still be demonstrated after 72 h. A half-time of approximately 10 h could be calculated for heparin-releasable 125I-EC-SOD C. Unlabeled EC-SOD C, determined as enzymic activity and with ELISA, was likewise sequestered and released to the same degree as 125I-labeled EC-SOD C by heparin as tested at 20 min and 5 h. The immediacy of the heparin-induced release indicates that the sequestered enzyme had been bound to endothelial cell surfaces. The length of the half-time suggests that the putative cell surface binding has a physiological function and is not primarily a step in enzyme degradation. The distribution of sequestered 125I-labeled EC-SOD C to different organs was determined at times between 10 min and 24 h. Of the organs, the liver contained the most 125I-EC-SOD C, followed by kidney, spleen, heart, and lung. At all investigated times, the content in the analyzed organs was nearly as large as the amount that could be promptly released to plasma by intravenous heparin. This indicates that almost all 125I-EC-SOD C in the organs was present on endothelial cell surfaces and was not bound by other tissue cell surfaces, or was present within the cells.

Postasphyxial cerebral survival in newborn sheep after treatment with oxygen free radical scavengers and a calcium antagonist

Acute, severe intrapartum asphyxia was mimicked by tying the umbilical cord in the exteriorized fetal sheep. After a standard time period cardiopulmonary resuscitation was instituted. In the treatment group (n = 14) the lambs were given a composition of scavengers of oxygen-derived free radicals and a calcium channel blocker. The control group of lambs (n = 12) was given placebo. The trial was blind and randomized. Hemodynamic and neurophysiological variables were measured from 30 min before asphyxia to 2 h postresuscitation. Mean arterial blood pressure, sagittal sinus venous pressure, heart rate, and cardiac output did not differ between the two groups although dramatic changes took place during asphyxia and resuscitation. Cerebral blood flow measured by 133-Xe washout method increased in both groups immediately after resuscitation. The treated animals retained an augmented cerebral blood flow during the 2 h postresuscitation while the control animals lost the increase of cerebral blood flow. The treated lambs recovered their somatosensory evoked potentials partially or completely in eight of 14 cases while the same figures for the control lambs were one of 12 cases. Immediately after resuscitation the cerebral reactions recovered to some extent in both groups but during the following 2 h the cerebral cortical function deteriorated in the control group but improved in the treated lambs. It is concluded that part of the brain damage in connection with acute, severe asphyxia may be inflicted by oxygen-derived free radicals released during the reoxygenation phase after resuscitation and that oxygen-derived free radical scavengers and calcium channel blockers may find a place in cardiopulmonary resuscitation.

Heparin-induced release of extracellular superoxide dismutase to human blood plasma

Extracellular superoxide dismutase (SOD) has previously been shown to be the major SOD isoenzyme in extracellular fluids. Upon chromatography on heparin-Sepharose it was separated into three fractions: A, without affinity; B, with intermediate affinity; and C, with relatively strong heparin affinity. Intravenous injection of heparin leads to a prompt increase in plasma extracellular-superoxide-dismutase (EC-SOD) activity. Heparin induces no release of EC-SOD from blood cells, nor does it activate EC-SOD in plasma, indicating that the source of the released enzyme is the endothelial-cell surfaces. No distinct saturation could be demonstrated in a dose-response curve up to 200 i.u. of heparin per kg body weight, showing that the releasing potency of heparin is lower for EC-SOD than for previously investigated heparin-released factors. Chromatography of human plasma on heparin-Sepharose shows nearly equal amounts of EC-SOD fractions A, B and C. Heparin induces specifically the release of fraction C. The findings point to the existence of an equilibrium of EC-SOD fraction C between the plasma phase and endothelial-cell surfaces. The major part of EC-SOD in the vasculature seems to be located on endothelial-cell surfaces.

Low Apgar score as a risk factor for respiratory disturbances in the newborn infant

The value of the Apgar score as a risk factor for all neonatal respiratory disturbances (RD) was evaluated in a prospective study of an unselected population. All liveborn infants (n = 4656) of mothers living in Gothenburg were screened over one year for signs of respiratory disease. This unselected population could be obtained since virtually all infants in Gothenburg are born in two maternity hospitals, with similar treatment principles, the same equipment standard and neonatal care. A low one minute Apgar score (less than 7) was found to be a powerful risk factor for RD in full term newborns and infants of 33-36 weeks gestation provided that the delivery had been vaginal. In these infants a low Apgar score at five minutes further increased the risk of RD. In immature infants less than 32 weeks and after cesarean section in all gestational ages a low Apgar score did not mean any additional risk of RD. The respiratory component in the Apgar score was not more predictive of RD than any of the others. In most infants with RD, irrespective of Apgar score, there was a few hours interval free from respiratory signs after birth. It has been well shown in other studies that Apgar score is not a reliable index of intrauterine or birth asphyxia. Nevertheless the one-minute score is a powerful predictor of neonatal respiratory difficulties. One explanation might be that Apgar score is correlated with sympathoadrenal activity at birth.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidemiological analysis of the increased risk of disturbed neonatal respiratory adaptation after caesarean section

In a prospective, unselected study of all 4,659 infants born in Göteborg, Sweden, risk factors for all kinds of neonatal respiratory disturbances (RD) after Caesarean section (CS) were analyzed. After CS, a significantly increased incidence rate of RD was found compared to vaginal delivery (24.6% vs. 5.5%). The increased overall risk affected full term infants only but IRDS was more common after CS in preterm infants. Rupture of membranes or uterine contractions prior to CS significantly reduced the incidence rate of RD in full term infants. Acute maternal complications did not affect the incidence. The elevated RD rate could partly be related to an increased incidence of low Apgar score after CS, and to absence of labour and rupture of membranes before the CS. But full term infants with Apgar score of 7 or more, delivered surgically after rupture of membranes and start of contractions, still had almost three times higher incidence of RD.

Interval from rupture of the membranes to delivery and neonatal respiratory adaptation

The influence of the time interval from rupture of the membranes to delivery on neonatal respiratory adaptation was analysed in a prospective study of all infants born in Göteborg, Sweden in one year. The correlation between the incidence of respiratory disorders and the rupture-delivery interval was analysed in all preterm infants (less than or equal to 36 weeks, n = 240) and in all term infants born by caesarean section (n = 452). A uniform pattern was found for all preterm infants, irrespective of mode of delivery, and for the term infants born by caesarean section. The curve was 'U-shaped' with higher incidence of respiratory diseases in infants born immediately after rupture of the membranes than in those born 3-36 h after membrane rupture. The incidence increased again in infants born greater than 36 h after membrane rupture. The same pattern was found for all kinds of respiratory diseases including idiopathic respiratory distress syndrome. Therefore, there seems to be no advantage in postponing delivery greater than 36 h after rupture of the membranes.

Fetal heart rate pattern and risk for respiratory disturbance in full-term newborns

Etiologic and pathogenetic factors responsible for respiratory disturbances in full-term infants are still unclear. The authors' intention was to analyze to what extent fetal stress, expressed in terms of abnormal fetal heart rate pattern, was reflected in neonatal respiratory disturbance. The study was performed prospectively over one year and included 157 term infants. Contrary to general belief, there was a significantly lower incidence of respiratory disturbances after ominous fetal heart rate pattern, ie, basal bradycardia, late or severe variable decelerations, and reduced variability than after a normal fetal heart rate pattern. It is suggested that these results may be due to a favorable effect on the fetal lung of systemic or local factors, produced in response to intrauterine stress.

Fetal cerebral, cardiovascular and metabolic reactions to intermittent occlusion of ovine maternal placental blood flow

In 10 mature, acutely exteriorized fetal sheep cardiovascular, cerebral and metabolic reactions were followed during intermittent occlusions of maternal placenta blood flow. The response was analysed from blood pressure, heart rate, myocardial contractility, combined cardiac output, ST waveform analysis of the fetal ECG, and from the evoked EEG response. The metabolic response was judged from blood gases, pH, lactate and circulating catecholamines. Basal values were within the range seen in the 'chronic' fetal lamb preparation. During moderate asphyxia, achieved by 10 1 min occlusions separated by 2 min periods of free maternal aorta blood flow, cardiovascular performance was increased with a substantial catecholamine surge but minor effects on cerebral and metabolic functions. During the marked asphyxia, achieved by five 2 min occlusions, marked metabolic changes occurred together with abolition of cerebral function. Forty-five minutes after asphyxia, 9/10 of the fetuses had regained cerebral, metabolic and cardiovascular functions.

Maternal treatment with a cardioselective beta-blocking agent--consequences for the ovine fetus during intermittent asphyxia

To evaluate the effect of chronic beta 1-adrenoceptor blockade on physiological adaptation to asphyxia a study was done on exteriorized sheep fetuses of 127-142 days gestational age. Eleven pregnant ewes were infused with metoprolol for 5 days prior to experiment. Another 10 ewes were infused with saline and served as controls. Asphyxia was induced by intermittent complete obstruction of maternal placental blood flow. Fetal electro-cardiogram, heart rate, cardiac output, myocardial contractility and cerebral blood flow were measured together with blood pH, lactate and hypoxanthine. Neurophysiological responses were evaluated by changes in somatosensory evoked electroencephalogram. The beta 1-blocked fetuses showed less responsiveness in myocardial contractility and heart rate during reoxygenation. This curtailed reaction resulted in accelerated lactic acidosis, increased break-down of intracellular energy rich substances and impaired cerebral function. Nine of the ten controls survived the experiment and 8 of them regained their somatosensory evoked EEG potentials, whereas 7 of the 11 beta-blocked fetuses survived and only 3 regained original somatosensory evoked EEG potentials. It is concluded that beta 1-adrenoceptor blockade impairs the adaptive responses to asphyxia in the ovine fetus and decreases its ability to survive severe asphyxia.

Atypical hemangioendothelioma of venous origin. A clinicopathologic, angiographic, immunohistochemical, and ultrastructural study of two endothelial tumors within the concept of histiocytoid hemangioma

Two patients, a 62-year-old man and a 50-year-old woman, both with deep-seated atypical endothelial tumors within the wide concept of histiocytoid hemangioma, are reported. In case 1, the tumor involved the brachial vein, and, in case 2, a medium-sized vein of the anterior neck. In both cases the involved vein was occluded. Angiography in case 1 suggested a tumor that was enclosed by the same fibrous sheath, the conjunctiva vasorum, that enclosed the occluded vein and its concomitant artery. Both tumors were solid, without conspicuous vascular differentiation by light microscopy. Such differentiation, however, was evident from the electron-microscopic examination, which showed tumor cells with endothelial features forming primitive vascular structures. Positive lectin histochemistry (Ulex Europeus I) and positive immunohistochemistry for factor-VIII-related antigen, actin, and vimentin also gave strong support for the endothelial differentiation of the tumor cells. Immunohistochemical studies of markers for histiocytic (alpha 1-antitrypsin, ferritin, lysozyme), epithelial (cytokeratin, epithelial membrane antigen), and neuroectodermal (S-100 protein) and skeletal muscle (myoglobin) differentiation were negative. At follow-up, after 7 years and 2 years, respectively, there were no signs of local recurrence or metastasis.

ST waveform changes of the fetal electrocardiogram during labour--a clinical study

Waveform changes in the fetal electrocardiogram (ECG) are under reassessment as a means of fetal surveillance. The purpose of the study was to identify ST waveform changes from the fetal scalp lead during labour and to compare any change with conventional signs of fetal distress. Two scalp electrodes provided a sufficiently stable signal from which ST waveform changes could be identified and measured as the T/QRS ratio. No infant was clinically hypoxic. Only 26% of the 46 patients studied had a continuously normal CTG whereas 67% had no ST waveform abnormalities. A relation was found between the two variables as the mean T/QRS ratio increased from 0.20 (SD 0.11) during epochs of normal CTG to 0.27 (SD 0.17) with CTG changes. A linear correlation (r = 0.58, P less than 0.01) was found between the T/QRS ratio before birth and the cord plasma lactate values.

Does glucose administration affect the cerebral response to fetal asphyxia?

This study was designed to test whether the fetal brain has an increased resistance towards asphyxia at high levels of blood-glucose, compared with low levels. 35 fetal sheep were exteriorized and investigated under general anesthesia. Cerebral blood flow (CBF) was estimated with the 133Xenon-washout method. Cerebral uptake of oxygen, glucose, and lactate was measured. Somatosensory evoked potentials (SEP) were recorded. The fetuses were subjected to controlled asphyxia by ventilating the ewes with gas mixtures low in oxygen. The blood sugar levels of the fetuses were varied over a four-fold range. During normal oxygenation of the fetus variations in the blood glucose concentration induced considerable changes in the cerebral glucose uptake, whereas CBF and oxygen uptake were unaffected. During asphyxia, hyperglycemia was associated with rapid development of acidosis and reduction in cerebral oxygen consumption together with deterioration of the neurophysiological characteristics of the brain. Far from being beneficial during asphyxia, fetal hyperglycemia appeared to reduce the tolerance of the fetal brain towards asphyxia. This report together with other evidence provides support for the view that extra glucose might be disadvantageous for the asphyxiated fetus.

The humoral antibody response to Shigella dysenteriae type 1 infection, as determined by ELISA

An enzyme-linked immunosorbent assay (ELISA) for determining the class-specific humoral antibody response to the lipopolysaccharide antigen from Shigella dysenteriae serotype 1 bacteria has been tested. Two or more serum samples from each of 60 persons infected with this organism during a dysentery outbreak in a boarding school for young men near Haiphong, Viet Nam, and single serum samples from 39 healthy Vietnamese and from 20 healthy Swedes were included in the study. Comparison of the titres in the sera from the patients and the Vietnamese controls showed that the patients had significantly elevated IgA titres in sera collected 10, 30 and 45 days after onset of infection, and significantly elevated IgG titres in sera collected 30, 45 and 180 days after the onset. The titres in the patients' sera, compared with those in the Swedish controls, were significantly elevated for IgA and IgM as well as IgG in the samples collected after 10, 30, 45 and 180 days. The use of rabbit antisera, specific for enteropathogenic bacteria, and absorption experiments with human sera indicated that the S. dysenteriae type 1 lipopolysaccharide antigen is specific with respect to the O-antigenic polysaccharide chain.