KaiC-like proteins contribute to stress resistance and biofilm formation in environmental Pseudomonas species

KaiC is the central cog of the circadian clock in Cyanobacteria. Close homologues of this protein are widespread among nonphotosynthetic bacteria, but the function, interaction network, and mechanism of action of these proteins are still largely unknown. Here, we focus on KaiC homologues found in environmental Pseudomonas species. Using bioinformatics, we describe the distribution of this protein family in the genus and reveal a conserved interaction network comprising a histidine kinase and response regulator. We characterize experimentally the only KaiC homologue present in Pseudomonas putida KT2440 and Pseudomonas protegens CHA0. Through phenotypic assays and transcriptomics, we show that KaiC is involved in osmotic and oxidative stress resistance in P. putida and in biofilm production in both species. KaiC homologues are found in different phosphorylation states and physically interact with a cognate histidine kinase and response regulator. In contrast with cyanobacterial counterparts, the expression and phosphorylation of KaiC homologues do not correlate with light variations under 12:12 light: dark cycles in either Pseudomonas species, and KaiC itself is not required to support a light-driven behaviour in P. putida. Overall, this suggests that KaiC homologues in Pseudomonas species are involved in environmental stress resistance but not in responses to diurnal rhythms.

The DEAD-box RNA helicase RhlE2 is a global regulator of Pseudomonas aeruginosa lifestyle and pathogenesis

RNA helicases perform essential housekeeping and regulatory functions in all domains of life by binding and unwinding RNA molecules. The bacterial RhlE-like DEAD-box RNA helicases are among the least well studied of these enzymes. They are widespread especially among Proteobacteria, whose genomes often encode multiple homologs. The significance of the expansion and diversification of RhlE-like proteins for bacterial fitness has not yet been established. Here, we study the two RhlE homologs present in the opportunistic pathogen Pseudomonas aeruginosa. We show that, in the course of evolution, RhlE1 and RhlE2 have diverged in their biological functions, molecular partners and RNA-dependent enzymatic activities. Whereas RhlE1 is mainly needed for growth in the cold, RhlE2 also acts as global post-transcriptional regulator, affecting the level of hundreds of cellular transcripts indispensable for both environmental adaptation and virulence. The global impact of RhlE2 is mediated by its unique C-terminal extension, which supports the RNA unwinding activity of the N-terminal domain as well as an RNA-dependent interaction with the RNase E endonuclease and the cellular RNA degradation machinery. Overall, our work reveals how the functional and molecular divergence between two homologous RNA helicases can contribute to bacterial fitness and pathogenesis.

Auxiliary domains of the HrpB bacterial DExH-box helicase shape its RNA preferences

RNA helicases are fundamental players in RNA metabolism: they remodel RNA secondary structures and arrange ribonucleoprotein complexes. While DExH-box RNA helicases function in ribosome biogenesis and splicing in eukaryotes, information is scarce about bacterial homologs. HrpB is the only bacterial DExH-box protein whose structure is solved. Besides the catalytic core, HrpB possesses three accessory domains, conserved in all DExH-box helicases, plus a unique C-terminal extension (CTE). The function of these auxiliary domains remains unknown. Here, we characterize genetically and biochemically Pseudomonas aeruginosa HrpB homolog. We reveal that the auxiliary domains shape HrpB RNA preferences, affecting RNA species recognition and catalytic activity. We show that, among several types of RNAs, the single-stranded poly(A) and the highly structured MS2 RNA strongly stimulate HrpB ATPase activity. In addition, deleting the CTE affects only stimulation by structured RNAs like MS2 and rRNAs, while deletion of accessory domains results in gain of poly(U)-dependent activity. Finally, using hydrogen-deuterium exchange, we dissect the molecular details of HrpB interaction with poly(A) and MS2 RNAs. The catalytic core interacts with both RNAs, triggering a conformational change that reorients HrpB. Regions within the accessory domains and CTE are, instead, specifically responsive to MS2. Altogether, we demonstrate that in bacteria, like in eukaryotes, DExH-box helicase auxiliary domains are indispensable for RNA handling.

Viral chimeras decrypt the role of enterovirus capsid proteins in viral tropism, acid sensitivity and optimal growth temperature

Despite their genetic similarities, enteric and respiratory enteroviruses (EVs) have highly heterogeneous biophysical properties and cause a vast diversity of human pathologies. In vitro differences include acid sensitivity, optimal growth temperature and tissue tropism, which reflect a preferential in vivo replication in the respiratory or gastrointestinal tract and are thus key determinants of EV virulence. To investigate the underlying cause of these differences, we generated chimeras at the capsid-level between EV-D68 (a respiratory EV) and EV-D94 (an enteric EV). Although some chimeras were nonfunctional, EV-D94 with both the capsid and 2A protease or the capsid only of EV-D68 were both viable. Using this latter construct, we performed several functional assays, which indicated that capsid proteins determine acid sensitivity and tropism in cell lines and in respiratory, intestinal and neural tissues. Additionally, capsid genes were shown to also participate in determining the optimal growth temperature, since EV-D94 temperature adaptation relied on single mutations in VP1, while constructs with EV-D68 capsid could not adapt to higher temperatures. Finally, we demonstrate that EV-D68 maintains residual binding-capacity after acid-treatment despite a loss of infectivity. In contrast, non-structural rather than capsid proteins modulate the innate immune response in tissues. These unique biophysical insights expose another layer in the phenotypic diversity of one of world's most prevalent pathogens and could aid target selection for vaccine or antiviral development.

A new real-time RT-PCR targeting VP4-VP2 to detect and quantify enterovirus D68 in respiratory samples

Causing an international outbreak of respiratory disease, Enterovirus D68 quickly entered the closed circle of emerging viral pathogens of public health significance. As rapid and accurate detection of EV-D68 is essential for an efficient clinical management, we designed and validated a new highly efficient one-step quantitative rRT-PCR specific to EV-D68 VP4-VP2 region. With 100% specificity and 95.6% sensitivity to all EV-D68 strains, this new assay can be reliably used to detect and quantify EV-D68 in respiratory samples and represents an interesting additional tool for diagnosis as it targets an original region of the genome.

Training high--living low: changes of aerobic performance and muscle structure with training at simulated altitude

This study was undertaken to test the hypothesis that endurance training in hypoxia is superior to training of the same intensity in normoxia. To avoid adaptation to hypoxia, the subjects lived under normoxic conditions when not training. A secondary objective of this study was to compare the effect of high- vs. moderate-intensity training on aerobic performance variables. Thirty-three men without prior endurance training underwent a cycle ergometer training of 6 weeks, 5 d/week, 30 minutes/d. The subjects were assigned to 4 groups, N-high, N-low, H-high and H-low based on the training criteria normoxia (N; corresponding to a training altitude of 600 m), vs. hypoxia (H; training altitude 3850 m) and intensity (high; corresponding to 80% and low: corresponding to 67% of VO2max). VO2max measured in normoxia increased between 8.5 to 11.1%, independent of training altitude or intensity. VO2max measured in hypoxia increased between 2.9 and 7.2%. Hypoxia training resulted in significantly larger increases than normoxia training. Maximal power that subjects could maintain over a thirty-minute period (measured in normoxia or hypoxia) increased from 12.3 - 26.8% independent of training altitude. However, subjects training at high intensity increased performance more than subjects training at a low intensity. Muscle volume of the knee-extensors as measured by magnetic resonance imaging increased significantly in the H-high group only (+ 5.0%). Mitochondrial volume density measured by EM-morphometry in biopsy samples of m. vastus lat. increased significantly in all groups with the highest increase seen in the H-high group (+ 59%). Capillary length density increased significantly in the H-high group only (+ 17.2%). The main finding of this study is that in previously untrained people, training in hypoxia while living at low altitude increases performance in normoxia to the same extent as training in normoxia, but leads to larger increases of aerobic performance variables when measured under hypoxic conditions. Training intensity had no effect on the gain of VO2max. On the level of skeletal muscle tissue, the combination of hypoxia with high training intensity constitutes the most effective stimulus for increasing muscle oxidative capacity.

Molecular adaptations in human skeletal muscle to endurance training under simulated hypoxic conditions

This study was performed to explore changes in gene expression as a consequence of exercise training at two levels of intensity under normoxic and normobaric hypoxic conditions (corresponding to an altitude of 3,850 m). Four groups of human subjects trained five times a week for a total of 6 wk on a bicycle ergometer. Muscle biopsies were taken, and performance tests were carried out before and after the training period. Similar increases in maximal O(2) uptake (8.3-13.1%) and maximal power output (11.4-20.8%) were found in all groups. RT-PCR revealed elevated mRNA concentrations of the alpha-subunit of hypoxia-inducible factor 1 (HIF-1) after both high- (+82.4%) and low (+78.4%)-intensity training under hypoxic conditions. The mRNA of HIF-1alpha(736), a splice variant of HIF-1alpha newly detected in human skeletal muscle, was shown to be changed in a similar pattern as HIF-1alpha. Increased mRNA contents of myoglobin (+72.2%) and vascular endothelial growth factor (+52.4%) were evoked only after high-intensity training in hypoxia. Augmented mRNA levels of oxidative enzymes, phosphofructokinase, and heat shock protein 70 were found after high-intensity training under both hypoxic and normoxic conditions. Our findings suggest that HIF-1 is specifically involved in the regulation of muscle adaptations after hypoxia training. Fine-tuning of the training response is recognized at the molecular level, and with less sensitivity also at the structural level, but not at global functional responses like maximal O(2) uptake or maximal power output.

Expression of the mouse metallothionein-I and -II genes provides a reproductive advantage during maternal dietary zinc deficiency

The function of metallothionein in zinc homeostasis was examined by using mice homozygous for knockout (KO) of the metallothionein-I or -II (MT-I and MT-II) genes. Pregnant MT-I/II KO mice or control mice were fed a zinc-deficient (1 microg/g or 5 microg/g) diet or a zinc-adequate (50 microg/g) diet during specific periods of pregnancy, and the effects on morphogenesis of the embryos were determined at day 14 of pregnancy (day 1 = vaginal plug). In the homozygous MT-I/II KO, as well as in the nontransgenic control mice, severe dietary zinc deficiency (1 microg/g) beginning on day 1 of pregnancy was embryotoxic and teratogenic, and the majority of the embryos in both strains were dead by mid-gestation. However, 53% of the surviving embryos in the MT-I/II KO mice were morphologically abnormal compared to only 32% of the embryos in the control mice. In subsequent experiments, moderate dietary zinc deficiency (5 microg/g beginning on day 1 of pregnancy or 1 microg/g dietary zinc beginning on day 8 of pregnancy) exerted teratogenic, but not embryotoxic effects. Embryos in the MT-I/II KO mice were 260 to 290% as likely to develop abnormally than were embryos in the control mice fed these same diets. These results demonstrate that the expression of the MT-I and -II genes in pregnant females improves reproductive success during maternal dietary zinc deficiency.

Effect of RBC shape and deformability on pulmonary O2 diffusing capacity and resistance to flow in rabbit lungs

Isolated rabbit lungs were perfused with washed and resuspended human red blood cells (RBCs) in the presence of drugs known to change the shape and deformability of RBCs. With sodium salicylate (0.5-2 g/l), which causes echinocytosis and increases RBC deformability, lung diffusing capacity for O2 (DLO2) increased by 21%. When chlorpromazine, which induces stomatocytosis and stiffens RBCs, was given (50 mg/l), DLO2 decreased by 18%. With sodium salicylate, the mean pulmonary artery pressure dropped by 14% from control values, whereas it increased by 18% under chlorpromazine. Comparative experiments with hemoglobin solutions did not reveal any effect of those two drugs either on DLO2 or on pulmonary arterial pressure, which indicates that the effects of sodium salicylate and chlorpromazine were due to changes in RBC shape and deformability. It is concluded that RBC shape and deformability affect pulmonary artery pressure and oxygen diffusing capacity, which may have an influence on oxygen transfer to tissue and hence be of clinical relevance.

Lung diffusing capacity and red blood cell volume

The aim of this study was to test whether a large surface to volume ratio of the red blood cells is advantageous for O2 transfer in lungs. Suspensions of washed large (human) and small (sheep) red blood cells were used to perfuse in random order isolated cat lungs (n = 7). The lungs were kept at 27 degrees C, ventilated with 1.0 l/min and perfused with 110 ml/min. Hemoglobin concentration was 70 g/l. Assuming an inhomogeneous lung with an alveolar dead space compartment, pulmonary diffusing capacity for O2 (DLO2) was 0.53 +/- 0.10 ml.min-1.mmHg-1 (mean +/- SD) when perfusing with sheep red cells and 0.52 +/- 0.13 with human red cells. On the basis of a lung model with a low VA/Q and a high VA/Q compartment the values were 0.86 and 0.93. Thus, DLO2 was not larger with smaller red blood cells, i.e. with higher red cell surface area per blood volume. Possible explanations for this unexpected result are discussed.

Gas transfer in isolated lungs perfused with red cell suspension or hemoglobin solution

Rapid mixing experiments have shown that the reaction between oxygen and hemoglobin is faster in hemoglobin solutions than in red cell suspensions. In this study we tested whether this observation can also be made in the lung. Excised rabbit lungs were perfused either with washed human red cell suspensions or with hemoglobin solutions, each with 50 g hemoglobin/L, and steady-state diffusing capacities (DLO2) for oxygen elimination measured. Mean settings were a temperature of 29.5 degrees C of the inflowing and outflowing perfusate of the lung, a total ventilation of 1.7 L.min-1, and a perfusion rate of 116 ml.min-1. Under those conditions resulted a DLO2 with hemoglobin solution of 0.68 +/- 0.18 ml.min-1.mm Hg-1, and a significantly lower value of 0.50 +/- 0.06 ml.min-1.mm Hg-1 with red cell suspension (P less than 0.01). An extraerythrocytic diffusing resistance, formed by a plasma layer and/or arising from a dynamic diffusion boundary layer, which is also known as unstirred layer, could explain the lower value with red cell suspensions.

Resistance of mammalian red blood cells of different size to hypertonic milieu

1. The resistance of different mammalian red blood cells (RBCs) to hyperosmotic environments was studied. RBCs of six mammalian species were exposed to 10 increasingly hyperosmotic NaCl solutions for 24 hr at 5 degrees C. 2. The osmolality at which the amount of liberated haemoglobin reached a preset level (e.g. 3-4% of the total haemoglobin) showed a linear correlation with negative slope with RBC volume. This indicates that small RBCs are more resistant to hyperosmotic milieu than large ones. 3. A similar relation can be found from literature data when maximal urinary tonicities are plotted as a function of RBC volume, i.e. animals with the ability to produce highly concentrated urine have small RBCs. 4. RBC volume and maximal urinary tonicity in mammals are therefore tightly linked. Future research will have to show whether this correlation is fortuitous or not and whether, as can be speculated, RBC size is directly or indirectly regulated by the kidney.

Effects of altering dead space volume on respiration and air sac gases in geese

Dead space volume (VD) was altered in spontaneously breathing, anesthetized geese from values far above (about 115 ml) to those far below (about 3 ml) the normal VD (approximately 40 ml). Respiratory gases were measured in cranial (CrS) and caudal air sacs (CdS) and in blood. The major findings were as follows: Ventilation increased linearly with VD, by increases in tidal volume (VT) at constant breathing rate (fresp); effective parabronchial ventilation, (VT-VD) X fresp, remained constant and so did arterial blood gases. No changes occurred in CrS gas composition. CdS PCO2 declined with decreasing VD, and the respiratory exchange ratio increased, reaching values above unity at the lowest VD. The gas composition in CrS, and particularly its relation to end-expired gas composition, is in agreement with current models of the gas flow pattern in the avian lung. The PCO2 values in CdS are higher than expected by simple models, e.g. by dead space re-inhalation. Neopulmonic gas exchange and incomplete gas mixing are suggested to contribute significantly to the gas composition of CdS.

Effects of increasing metabolism by 2,4-dinitrophenol on respiration and pulmonary gas exchange in the duck

The effects of pharmacologically elevated metabolism on respiration and parabronchial gas exchange were studied in the anesthetized, spontaneously breathing duck using 2,4-dinitrophenol (DNP), injected in successive single doses of 1.2-2.5 mg per kg body mass. Oxygen uptake, MO2, increased with the cumulative amount of DNP, reaching a sevenfold resting level at the highest DNP level tolerated, 15 mg/kg. Ventilation increased nearly as much as MO2, mainly by an increase in respiratory frequency, fresp. Cardiac output increased somewhat less than MO2, mediated by increases in both cardiac frequency and stroke volume. Arterial blood-gases showed little change; however, mixed venous PO2 dropped significantly, and PCO2 increased significantly, with stimulated metabolism. Pulmonary diffusing capacity, DO2, showed a significant rise with MO2, beyond that expected from a reduction of functional lung heterogeneity. The results show that pharmacological stimulation of metabolism can evoke responses in the respiratory and circulatory systems that are comparable to those observed with exercise. The mechanism by which parabronchial diffusing capacity increases during elevated metabolism remains to be investigated.

Simultaneous O2 and CO diffusing capacity estimates from assumed lognormal VA, Q and DL distributions

O2 and CO pulmonary transfer data obtained in dogs under steady-state conditions in hypoxia by Savoy et al. (Respir. Physiol. 42: 43-59, 1980) have been submitted to reevaluation and have yielded new estimates of the lung diffusing capacity, DL. For the proposed DL computation it has been assumed that functional inhomogeneity can be considered as resulting from lognormal distributions of the VA/Q and VA/DL ratios. The standard deviation, sigma, of the VA/Q distribution is computed from the measured (PA -Pa)CO2, and the same sigma value is assumed to prevail for the VA/DL distributions. This is equivalent to assume constant DL/Q ratios in the entire lung. With the so defined distributions, DL values, called D sigma O2 and D sigma CO, were sought, for which the model calculations yielded O2 partial pressures and CO fluxes equal to those measured. Compared with DL estimates computed with conventional procedures, these results show that D sigma O2 is twice as large as DLO2 computed with ideal alveolar PO2 and that D sigma CO lies between DLCO computed with the mean alveolar PCO and that computed with the ideal alveolar PCO. The D sigma O2/D sigma CO ratio was on the average 1.2, a value which, unlike the ratios obtained with conventional DLO2 and DLCO estimates, is in good agreement with the characteristics of diffusion and of chemical association of O2 and CO with blood.

Airflow in the avian respiratory tract: variations of O2 and CO2 concentrations in the bronchi of the duck

Variations of CO2 and O2 concentrations within a respiratory cycle were recorded at various sites in the bronchial system of anesthetized, spontaneously ventilating ducks, using small metal cannulae introduced into the main bronchus (MB), a medioventral (MV) or mediodorsal (MD) secondary bronchus and connected to a mass spectrometer for continuous gas analysis. The following results were obtained and conclusions drawn. (1) Since during inspiration, CO2 concentration (FCO2) was close to zero all along MB and since FCO2 was nearly constant throughout the respiratory cycle in MV, it must be inferred that on inspiration, no significant amount of air passes directly either from MV to MB or in the opposite direction, there being thus a complete functional valving of the MV orifices. In particular the Hazelhoff loop mechanism (inspiratory reflux of lung gas into the MB) is not operative. (2) During expiration, FCO2 in MV was only slightly higher than that in the trachea, but substantially above FCO2 deep in MB. This suggests that most of the expiratory flow from caudal air sacs is diverted through the paleopulmo and only little exits directly through MB. It is shown that the functional valving of bronchial air flow is advantageous for gas exchange as it reduces air shunts and provides a nearly steady lung ventilation.

Gas tension profile of the lung of the viper, Vipera xanthina palestinae

Oxygen and carbon dioxide concentrations along the lung of five awake, resting Palestine vipers were continuously measured by mass spectrometry. Ventilatory volumes, body wall movements and heart rate were also measured. In the anterior part of the faveolar (respiratory) lung, oxygen and carbon dioxide concentrations returned to within 1% of inspired composition with each inspiration. Between breaths, changes of 0.5-2% in gas concentrations were seen in the faveolar region but practically no changes occurred in the caudal, non-respiratory lung (air sac) where mean oxygen and carbon dioxide concentrations of 16.4% and 2.5% respectively were recorded. The respiratory exchange ratio dropped from near 1.5 in the anterior faveolar region to zero in the transition zone to the air sac. Instantaneous R values declined with breath-holding time in each location along the length of the lung. Gas exchange appears greatest in the posterior faveolar region near the heart and there is evidence of cardiogenic gas mixing in this region. The posterior air sac may either passively respond to air movements in the anterior lung or it may participate in ventilation. During periods of extended breath-holding (10-15 min) pronounced body wall movements were seen but there was no air flow from the mouth and gas exchange continued in the lung with rapidly decreasing R.

Incomplete gas mixing in air sacs of the duck

During normal breathing, the CO2 concentration in caudal air sacs of birds is higher, and the O2 concentration lower, than expected on the basis of the known air flow pattern. We have experimentally tested two hypotheses which could explain this finding: (1) Preferential shunting of re-inspired dead space gas into caudal air sacs; (2) Incomplete mixing of inspired and residential air sac gas. - Different portions of the inspired air in anesthetized ducks were labeled by injecting a small bolus of argon (Ar) into the trachea. The resulting Ar concentration was recorded continuously in the caudal thoracic air sac at the ostium and in deeper regions.-The amount of Ar entering the sac was found to be independent of the volume inspired prior to injection of the label, and hypothesis (1) thus dismissed. However, during inspiration and subsequent expiration the Ar bolus was found to be neither perfectly mixed within the inspired gas nor with the air sac residential gas. More than 10 sec of breath-hold were necessary for air sac gas to approach an equilibrium value. Gas layering (stratification) in caudal air sacs gas is proposed to cause the high CO2 and low O2 levels during steady state breathing, as air sac residential gas equilibrates with a layer of dead space gas that enters the air sac on each breath and contains a higher CO2 and lower O2 concentration than the mixed inspirate.

Comparison of steady state pulmonary diffusing capacity estimates for O2 and CO in dogs

In view of the fact that the inhomogeneity effects on pulmonary diffusing capacity (DL) estimates are quite different for O2 and for CO, simultaneous determinations of steady-state DLCO and DLO2 were attempted and compared. To this end, pulmonary gas exchange was measured in 17 anesthetized and artificially ventilated dogs, in hypoxia with and without carbon monoxide in inspired gas (FIO2 = 0.12, FICO = 0.0009 to 0.0016). The diffusing capacity estimates were computed by two conventional procedures, the first (Dapp) taking into account the mean alveolar partial pressures and the second (DVDA) the ideal alveolar partial pressures. It was found that the presence of COHb in blood, inevitable in the steady-state DLCO procedure, leads to a marked underestimation of DLO2; therefore DLCO values could only be adequately compared to DLO2 values obtained in the absence of CO from inspired gas. These DLO2 were 18.5 and 33.4 mumol . min-1 . Torr-1 . kg-1 for the mean DappO2 and DVDAO2, respectively, whereas the DLCO values obtained after 15 to 25 min CO inspiration were 30.0 and 83.4 mumol . min-1 . Torr-1 . kg-1 for the mean DappCO and the mean DVDACO, respectively. The salient feature is that with both procedures the mean value of DLCO estimate is higher than the corresponding DLO2 estimate. This finding suggests that in anesthetized, artificially ventilated dogs DappO2 and DVDACO estimates obtained by steady-state procedures in hypoxia are largely influenced by inhomogeneity effects and of limited value for assessment of the diffusing properties of the lung. DappCO and DVDAO2 are also affected by inhomogeneities but to a lesser degree.

Pulmonary O2 diffusing capacity estimates from assumed log-normal VA/Q distributions

Steady-state pulmonary gas exchange has been measured in hypoxia in 33 mongrel dogs with the aim of comparing DLO2 estimates obtained with three procedures differing by the models assumed for functional inhomogeneity. In the first procedure the lung was assumed to be homogeneous and the corresponding DLO2 estimate was 15 mumol . min-1. Torr-1 . kg-1. In the second procedure, which is the one commonly used in respiratory physiology, alveolar dead space was considered as the unique form of functional inhomogeneity and the corresponding DLO2 estimate was 31 mumol . min-1. Torr-1 . kg-1. In the third procedure, which has been specially worked out for this study, functional inhomogeneity was represented by a log-normal distribution of the VA/Q ratios and the corresponding DLO2 estimate was 50 mumol . min-1 . Torr-1 . kg-1. The relation between the DLO2 estimates by the second and by the third procedures was found to depend upon the blood pH. This could be explained on the basis of the effects of acidosis on the blood capacitances for O2 and for CO2. Analysis suggests that in hypoxia where normally the O2 capacitance is about half the CO2 one, the third procedure yields DLO2 estimates about twice as large as those obtained by the second one.

[Unrecognized hyperthyroidism in hospital patients. Analysis of clinical symptoms compared to aged euthyroid goiter patients]

During a 14-month period hyperthyroidism has been diagnosed in 39 of 2916 inpatients of a general medical service. Graves' disease was present in only 8 cases. 21 patients had solitary autonomous nodules or multiple autonomous nodules (toxic multinodular goiter). In 10 patients the type of hyperthyroidism could not be established. The referring practitioner suspected hyperthyroidism in all 8 patients with Graves' disease, but in only 5 of the 31 remaining cases. The relative rarity of Graves' disease in inpatients reflects the fact that this form of hyperthyroidism is easily recognized by the practitioner and treated on an out-patient basis. Graves' disease patients and those with autonomous solitary or multiple nodules were of comparable age and had an identical serum free-thyroxin. Thus, neither higher age nor lower thyroxin is responsible for the atypical clinical presentation of autonomous nodules. A comparison with age- and sex-matched carriers of euthyroid goiters identified weight loss, resting pulse rate over 90 and auricular fibrillation as reliable clinical features. A thyroid function test is therefore indicated in every patient with a goiter and one of the three above clinical findings.

[Importance of thyroid diseases in internal medical hospital]

Retrospective analysis of 2627 and prospective analysis of 289 inpatients (mean age: 57 years) of the Department of Internal Medicine, University of Berne, disclosed euthyroid goiter in 33.9%. 65% of the patients had urinary iodine excretion below 100 microgram per gram creatinine. Thus, iodination of salt (raised to 10 mg potassium iodide per kg in 1962) is still inadequate. 1.4% of the inpatients had hyperthyroidism. Hypothyroidism was diagnosed in 0.5% of the inpatients, which is about three times less than in comparable prospective English studies. The finding raises the possibility that cases of hypothyroidism have been frequently missed. Antibodies against thyroglobulin and/or microsomal antigen were present in 8.5% of 105 goiter patients and 4.0% of 124 patients without goiter. This is a definitely lower incidence than has been reported in comparable English populations and confirms reports from other Alpine endemic goiter areas. Among the 2916 patients of the entire study only 3 cases (0.1%) of clear-cut chronic lymphocytic (Hashimoto) thyroiditis were found.