A refined approach for evaluating small datasets via binary classification using machine learning

Classical statistical analysis of data can be complemented or replaced with data analysis based on machine learning. However, in certain disciplines, such as education research, studies are frequently limited to small datasets, which raises several questions regarding biases and coincidentally positive results. In this study, we present a refined approach for evaluating the performance of a binary classification based on machine learning for small datasets. The approach includes a non-parametric permutation test as a method to quantify the probability of the results generalising to new data. Furthermore, we found that a repeated nested cross-validation is almost free of biases and yields reliable results that are only slightly dependent on chance. Considering the advantages of several evaluation metrics, we suggest a combination of more than one metric to train and evaluate machine learning classifiers. In the specific case that both classes are equally important, the Matthews correlation coefficient exhibits the lowest bias and chance for coincidentally good results. The results indicate that it is essential to avoid several biases when analysing small datasets using machine learning.

The seven troubles with norm-compliant robots

Many researchers from robotics, machine ethics, and adjacent fields seem to assume that norms represent good behavior that social robots should learn to benefit their users and society. We would like to complicate this view and present seven key troubles with norm-compliant robots: (1) norm biases, (2) paternalism (3) tyrannies of the majority, (4) pluralistic ignorance, (5) paths of least resistance, (6) outdated norms, and (7) technologically-induced norm change. Because discussions of why norm-compliant robots can be problematic are noticeably absent from the robot and machine ethics literature, this paper fills an important research gap. We argue that it is critical for researchers to take these issues into account if they wish to make norm-compliant robots.

Investigating the conservatism-disgust paradox in reactions to the COVID-19 pandemic: A reexamination of the interrelations among political ideology, disgust sensitivity, and pandemic response

Research has documented robust associations between greater disgust sensitivity and (1) concerns about disease, and (2) political conservatism. However, the COVID-19 disease pandemic raised challenging questions about these associations. In particular, why have conservatives—despite their greater disgust sensitivity—exhibited less concern about the pandemic? Here, we investigate this “conservatism-disgust paradox” and address several outstanding theoretical questions regarding the interrelations among disgust sensitivity, ideology, and pandemic response. In four studies (N = 1,764), we identify several methodological and conceptual factors—in particular, an overreliance on self-report measures—that may have inflated the apparent associations among these constructs. Using non-self-report measures, we find evidence that disgust sensitivity may be a less potent predictor of disease avoidance than is typically assumed, and that ideological differences in disgust sensitivity may be amplified by self-report measures. These findings suggest that the true pattern of interrelations among these factors may be less “paradoxical” than is typically believed.

Corona and value change. The role of social media and emotional contagion

People share their emotions on social media and evidence suggests that in times of crisis people are especially motivated to post emotional content. The current Coronavirus pandemic is such a crisis. The online sharing of emotional content during the Coronavirus crisis may contribute to societal value change. Emotion sharing via social media could lead to emotional contagion which in turn could facilitate an emotional climate in a society. In turn, the emotional climate of a society can influence society's value structure. The emotions that spread in the current Coronavirus crisis are predominantly negative, which could result in a negative emotional climate. Based on the dynamic relations of values to each other and the way that emotions relate to values, a negative emotional climate can contribute to societal value change towards values related to security preservation and threat avoidance. As a consequence, a negative emotional climate and the shift in values could lead to a change in political attitudes that has implications for rights, freedom, privacy and moral progress. Considering the impact of social media in terms of emotional contagion and a longer-lasting value change is an important perspective in thinking about the ethical long-term impact of social media technology.

Propagation of Spin-Wave Packets in Individual Nanosized Yttrium Iron Garnet Magnonic Conduits

Modern-day CMOS-based computation technology is reaching its fundamental limitations. The emerging field of magnonics, which utilizes spin waves for data transport and processing, proposes a promising path to overcome these limitations. Different devices have been demonstrated recently on the macro- and microscale, but the feasibility of the magnonics approach essentially relies on the scalability of the structure feature size down to the extent of a few 10 nm, which are typical sizes for the established CMOS technology. Here, we present a study of propagating spin-wave packets in individual yttrium iron garnet (YIG) conduits with lateral dimensions down to 50 nm. Space and time-resolved microfocused Brillouin-light-scattering (BLS) spectroscopy is used to characterize the YIG nanostructures and measure the spin-wave decay length and group velocity directly. The revealed magnon transport at the scale comparable to the scale of CMOS proves the general feasibility of magnon-based data processing.

Neoadjuvante Daylight Photodynamische Therapie bei Spinozellulärem Karzinom an der Kopfhaut zum Debulking des Nachexzisionsareals

Das spinozelluläre Karzinom ist der zweithäufigste diagnostizierte Hauttumor in Deutschland und die Inzidenz nicht melanozytärer Hauttumoren ist weltweit steigend. Solange eine ambulante Behandlung möglich ist, wird dies sowohl vom Patienten häufig gewünscht und ist weiterhin ökonomisch sinnvoll. Im Rahmen der Therapie der aktinischen Keratosen gewinnt die Tageslicht-PDT (DL-PDT) zunehmend Bedeutung gegenüber der klassischen PDT.

Dieser Fall beschreibt die neoadjuvante DL-PDT als Therapiemöglichkeit zur Demarkation eines gesicherten, aber klinisch nicht abgrenzbaren spinozellulären Tumors mit nachfolgender R0-Resektion. Die DL-PDT ersetzt hierbei nicht die mikrografisch kontrollierte chirurgische Exzision mit histologisch tumorfreien Rändern, ergänzt diese jedoch, um eine kleinere Exzision vornehmen zu können.

Wired Emotions: Ethical Issues of Affective Brain-Computer Interfaces

Ethical issues concerning brain-computer interfaces (BCIs) have already received a considerable amount of attention. However, one particular form of BCI has not received the attention that it deserves: Affective BCIs that allow for the detection and stimulation of affective states. This paper brings the ethical issues of affective BCIs in sharper focus. The paper briefly reviews recent applications of affective BCIs and considers ethical issues that arise from these applications. Ethical issues that affective BCIs share with other neurotechnologies are presented and ethical concerns that are specific to affective BCIs are identified and discussed.

[Histological, biochemical and spectroscopic changes of articular cartilage in osteoarthritis: is there a chance for spectroscopic evaluation?]

BACKGROUND

Non-destructive techniques for the detection and classification of pathological changes of cartilage in the early stages of osteoarthritis are required for arthroscopic and open surgery of joints. Biochemical and histological changes in cartilage with different degrees of destruction were analysed and correlated to changes in the spectroscopic characteristics of cartilage.

PATIENTS, MATERIAL AND METHODS

24 patients (n = 25 knees) with severely destructed knee joints received total knee replacement. The cartilage of the resected joints was classified according to the ICRS system. Defined cartilage specimens were investigated spectroscopically employing NIRS (near-infrared spectroscopy). In the following the cartilage specimens were harvested to determine the content of proteoglycan (GAG) and hydroxyproline (HP) as an essential part of collagen. Histological evaluation of the Mankin score and Otte score was performed using haematoxylin/eosin and safranin-O staining. Spearman's rank correlation coefficient was used to characterise links between the parameters investigated.

RESULTS

We found significant correlations between spectroscopic, histological and biochemical characteristics. NIRS corresponded to the content of GAG (ρ = 0.58) and HP (ρ = 0.59), as well as to the Mankin (ρ = 0.55) and Otte (ρ = 0.5) scores. Furthermore, the ICRS classification correlated with histological evaluation (Mankin score ρ = 0.725 and Otte score ρ = 0.736), as to be expected.

CONCLUSION

Characteristic cartilage changes in different degrees of osteoarthritis can be detected and evaluated by the spectroscopic method NIRS as a non-destructive technique. However, the quality of this technical evaluation cannot compete with biochemical and histological analysis.

Molecular-sized fluorescent nanodiamonds

Doping of carbon nanoparticles with impurity atoms is central to their application. However, doping has proven elusive for very small carbon nanoparticles because of their limited availability and a lack of fundamental understanding of impurity stability in such nanostructures. Here, we show that isolated diamond nanoparticles as small as 1.6 nm, comprising only ∼400 carbon atoms, are capable of housing stable photoluminescent colour centres, namely the silicon vacancy (SiV). Surprisingly, fluorescence from SiVs is stable over time, and few or only single colour centres are found per nanocrystal. We also observe size-dependent SiV emission supported by quantum-chemical simulation of SiV energy levels in small nanodiamonds. Our work opens the way to investigating the physics and chemistry of molecular-sized cubic carbon clusters and promises the application of ultrasmall non-perturbative fluorescent nanoparticles as markers in microscopy and sensing.

Highly sensitive detection of physiological spins in a microfluidic device

Sensing and imaging paramagnetic species under physiological conditions is a key technology in chemical and biochemical analytics, cell biology, and medical sciences. At submicrometer length scales, nitrogen-vacancy (NV) centers in diamond offer atom-sized probes for magnetic fields. We show that spin relaxation of an ensemble NV sensor allows sensing of adsorbed and freely diffusing manganese(II) ions and adsorbed ferritin. Sensitivities approach 175 Mn ions and 10 ferritin proteins per diffraction limited spot under ambient conditions.

High sensitivity magnetic imaging using an array of spins in diamond

We present a solid state magnetic field imaging technique using a two-dimensional array of spins in diamond. The magnetic sensing spin array is made of nitrogen vacancy (NV) centers created at shallow depths. Their optical response is used for measuring external magnetic fields in close proximity. Optically detected magnetic resonance is read out from a 60 x 60 microm(2) field of view in a multiplexed manner using a charge coupled device camera. We experimentally demonstrate full two-dimensional vector imaging of the magnetic field produced by a pair of current carrying microwires. The presented wide-field NV magnetometer offers, in addition to its high magnetic sensitivity and vector reconstruction, an unprecedented spatiotemporal resolution and functionality at room temperature.

Glycolipid trafficking in Drosophila undergoes pathway switching in response to aberrant cholesterol levels

In lipid storage diseases, the intracellular trafficking of sphingolipids is altered by conditions of aberrant cholesterol accumulation. Drosophila has been used recently to model lipid storage diseases, but the effects of sterol accumulation on sphingolipid trafficking are not known in the fly, and the trafficking of sphingolipids in general has not been studied in this model organism. Here, we examined the uptake and intracellular distribution of a fluorescent glycolipid analog, BODIPY-lactosyl-ceramide, in Drosophila neurons. The uptake mechanism and intracellular trafficking route of this simple glycolipid are largely conserved. Our principle finding is that cholesterol steers trafficking of the glycolipid between Golgi, lysosome, and recycling compartments. Our analyses support the idea that cholesterol storage in Drosophila triggers a switch in glycolipid trafficking from the biosynthetic to the degradative endolysosomal pathway, whereas cholesterol depletion eliminates recycling of the glycolipid. Unexpectedly, we observe a novel phenomenon we term "hijacking," whereby lactosyl-ceramide diverts the trafficking pathway of an endocytic cargo, dextran, completely away from its lysosomal target. This work establishes that glycolipid trafficking in Drosophila undergoes changes similar to those seen in mammalian cells under conditions of cholesterol storage and therefore validates Drosophila as a suitable model organism in which to study lipid storage diseases.

A fluorescent glycolipid-binding peptide probe traces cholesterol dependent microdomain-derived trafficking pathways

BACKGROUND

The uptake and intracellular trafficking of sphingolipids, which self-associate into plasma membrane microdomains, is associated with many pathological conditions, including viral and toxin infection, lipid storage disease, and neurodegenerative disease. However, the means available to label the trafficking pathways of sphingolipids in live cells are extremely limited. In order to address this problem, we have developed an exogenous, non-toxic probe consisting of a 25-amino acid sphingolipid binding domain, the SBD, derived from the amyloid peptide Abeta, and conjugated by a neutral linker with an organic fluorophore. The current work presents the characterization of the sphingolipid binding and live cell trafficking of this novel probe, the SBD peptide. SBD was the name given to a motif originally recognized by Fantini et al in a number of glycolipid-associated proteins, and was proposed to interact with sphingolipids in membrane microdomains.

METHODOLOGY/PRINCIPAL FINDINGS

In accordance with Fantini's model, optimal SBD binding to membranes depends on the presence of sphingolipids and cholesterol. In synthetic membrane binding assays, SBD interacts preferentially with raft-like lipid mixtures containing sphingomyelin, cholesterol, and complex gangliosides in a pH-dependent manner, but is less glycolipid-specific than Cholera toxin B (CtxB). Using quantitative time-course colocalization in live cells, we show that the uptake and intracellular trafficking route of SBD is unlike that of either the non-raft marker Transferrin or the raft markers CtxB and Flotillin2-GFP. However, SBD traverses an endolysosomal route that partially intersects with raft-associated pathways, with a major portion being diverted at a late time point to rab11-positive recycling endosomes. Trafficking of SBD to acidified compartments is strongly disrupted by cholesterol perturbations, consistent with the regulation of sphingolipid trafficking by cholesterol.

CONCLUSIONS/SIGNIFICANCE

The current work presents the characterization and trafficking behavior of a novel sphingolipid-binding fluorescent probe, the SBD peptide. We show that SBD binding to membranes is dependent on the presence of cholesterol, sphingomyelin, and complex glycolipids. In addition, SBD targeting through the endolysosomal pathway in neurons is highly sensitive to cholesterol perturbations, making it a potentially useful tool for the analysis of sphingolipid trafficking in disease models that involve changes in cholesterol metabolism and storage.

A fluorescent sphingolipid binding domain peptide probe interacts with sphingolipids and cholesterol-dependent raft domains

We have designed a tagged probe [sphingolipid binding domain (SBD)] to facilitate the tracking of intracellular movements of sphingolipids in living neuronal cells. SBD is a small peptide consisting of the SBD of the amyloid precursor protein. It can be conjugated to a fluorophore of choice and exogenously applied to cells, thus allowing for in vivo imaging. Here, we present evidence to describe the characteristics of the SBD association with the plasma membrane. Our experiments demonstrate that SBD binds to isolated raft fractions from human neuroblastomas and insect neuronal cells. In protein-lipid overlay experiments, SBD interacts with a subset of glycosphingolipids and sphingomyelin, consistent with its raft association in neurons. We also provide evidence that SBD is taken up by neuronal cells in a cholesterol- and sphingolipid-dependent manner via detergent-resistant microdomains. Furthermore, using fluorescence correlation spectroscopy to assay the mobility of SBD in live cells, we show that SBD's behavior at the plasma membrane is similar to that of the previously described raft marker cholera toxin B, displaying both a fast and a slow component. Our data suggest that fluorescently tagged SBD can be used to investigate the dynamic nature of glycosphingolipid-rich detergent-resistant microdomains that are cholesterol-dependent.

Cell tracking velocimetry as a tool for defining saturation binding of magnetically conjugated antibodies

BACKGROUND

Continuous flow immunomagnetic separation is an attractive alternative to current batch mode immunomagnetic separation methods because it is capable of high sorting speeds at mild cell conditions, and grants the operator better control of separation process. The control of the separation is dependent on knowledge of the amount of magnetic label attached to the cell (magnetic labeling intensity), however. Determination of the magnetic labeling is accomplished by measuring cell magnetophoretic mobility using a newly developed technique of Cell Tracking Velocimetry (CTV).

METHODS

Flow cytometry was used to define the antibody binding characteristics of a fluorescently tagged primary antibody. Subsequently, CTV was used to measure antibody-binding characteristics of a magnetically tagged secondary antibody.

RESULTS

The results of this study show that CTV is capable of providing valuable information concerning the cell labeling by magnetically tagged antibodies. It was demonstrated that the magnetically conjugated antibody binding curve exhibits the same exponential increase to saturation characteristics as that seen with the fluorescently tagged antibody. Further, it was shown that the intensity of the secondary magnetic labeling is directly proportional to the intensity of the primary fluorescent label.

CONCLUSIONS

CTV is an accurate tool for evaluation of magnetically conjugated antibodies. The ability to determine the intensity of magnetic labeling is necessary for the development of continuous flow immunomagnetic separations based on cell magnetophoresis.

Single-cell gel/comet assay applied to the analysis of UV radiation-induced DNA damage in Rhodomonas sp. (Cryptophyta)

The single-cell gel/comet assay is an electrophoretic technique used to detect single-strand breaks in DNA. Damage is assessed examining individual cells under an epifluorescent microscope. UV-induced DNA damage consists mostly of the formation of pyrimidine dimers; therefore, most of the damage cannot be detected using a standard comet assay. The enzyme T4 endonuclease V breaks DNA strands at sites of pyrimidine dimers. The main objective of this work is to evaluate the comet assay to detect UV-induced damage in DNA after an initial treatment of cells with T4 endonuclease V. This work was conducted on Rhodomonas sp. (Cryptophyta), a marine unicellular flagellate. Cells of Rhodomonas sp. were exposed to 12 h visible + ultraviolet-A + ultraviolet-B (VIS + UVA + UVB) and VIS (control), with and without T4 endonuclease V. Cells exposed to VIS + UVA + UVB showed approximately 200% more damage than control if these were treated with T4 endonuclease V. Rhodomonas sp. were exposed to 3, 6, 9 and 12 h of VIS, VIS + UVA and VIS + UVA + UVB. Damage induced by VIS + UVA + UVB as detected by the comet assay increased along with exposure time. However, damage caused by VIS and VIS + UVA remained relatively constant at all times. Results of this study indicate that the comet assay is more sensitive to UV radiation damage when used in conjunction with T4 endonuclease V. This modification of the comet assay can be used as an alternative technique to detect DNA damage in single cells caused by UV radiation.

Transient expression of human telomerase extends the life span of normal human fibroblasts

We utilized the Cre/lox recombination system to transiently express the catalytic subunit of telomerase (hTERT) in normal diploid foreskin fibroblasts (BJ cells). A retroviral construct containing an hTERT cDNA, flanked by loxP-sites was introduced into near senescent BJ cells (population doubling 85). At population doubling (PD) 92, which exceeds the typical life span of these cells, we excised the gene via Cre-mediated recombination. All clones lost telomerase activity and showed telomere shortening over an additional 50 PDs. Interestingly, the average telomere length in these cells became shorter than in untreated BJ cells at senescence. This may be due to hTERT preferentially elongating the shortest telomeres, leading to greater length uniformity. In summary, transient telomerase expression and only a very small average telomere elongation by hTERT resulted in a 50% increase in life span of human fibroblasts. This suggests a potentially safe use of hTERT in tissue engineering.

Three-dimensional reconstructions of normal and aneurysmatic left ventricles in vivo using transesophageal echocardiography

OBJECTIVE

To perform three-dimensional surface reconstructions to provide spatial delineations of a normal and an aneurysmatic left ventricle, using transesophageal echocardiography.

DESIGN

Prospective study.

SETTING

University hospital.

PARTICIPANTS

Eight patients in cardiogenic shock admitted to the intensive care unit and two patients undergoing surgery with general anesthesia.

INTERVENTIONS

Using a multiplane transesophageal echocardiography probe, nine echocardiographic cross-sectional images of the heart at approximately 20 degrees angular increments were obtained from midesophageal level in each patient for three-dimensional surface reconstructions. Multiple determinations of cardiac output using the thermodilution principle were also made in each patient to verify the accuracy of three-dimensional data sets.

MEASUREMENTS AND MAIN RESULTS

End-diastolic and end-systolic volumes were determined from three-dimensional data sets using the disc-summation method. Stroke volume was derived as the difference between end-diastolic and end-systolic volumes. Stroke volume was also calculated from thermodilution cardiac output measurements and heart rate. Correlation and limits of agreement between stroke volumes derived by the two methods were determined. Three-dimensional wire-frame models of a normal and an aneurysmatic left ventricle at end-systole were constructed from the nine echocardiographic cross-sectional images. Correlation coefficient between stroke volume derived from three-dimensional data sets using the disc-summation method and that measured by the thermodilution method was 0.91 (p < 0.001). Wire-frame models reveal a normal symmetric cavity and an aneurysmal cavity in sharp relief.

CONCLUSIONS

Three-dimensional surface reconstruction can be performed from multiple cross-sectional images obtained using an unmodified commercially available multiplane transesophageal echocardiography probe, to reveal the left ventricular cavity in sharp relief. High correlation between stroke volume calculated from three-dimensional data sets and that measured by the thermodilution method attests to the accuracy of the three-dimensional data sets.

Gene transfer into hepatocytes and human liver tissue by baculovirus vectors

Gene therapy of liver diseases requires the development of efficient vectors for gene transfer in vivo. Retroviral and adenoviral vectors have been shown to deliver genes efficiently into hepatocytes in vitro and in vivo. However, these vectors do not allow for exclusive infection of the liver which would be highly advantageous for in vivo gene therapy strategies. We have recently demonstrated that genetically modified baculoviruses (Autographa californica nuclear polyhedrosis virus) efficiently deliver genes into cultured cells and have a strong preference for hepatocytes of different origin. Baculoviral gene transduction efficiency into human hepatocytes was determined to approach 100% and expression levels are high, provided that gene expression is controlled by mammalian promoters. In this report, we present further properties of baculoviruses regarding their use for hepatocyte gene transfer. Baculovirus-mediated gene expression declines rapidly in the hepatocellular carcinoma cell line Huh7 and more slowly in primary cultures of mouse hepatocytes. Direct application of baculoviruses for gene delivery to the liver in vivo is hampered by serum components, presumably by complement. However, we demonstrate here that baculoviral gene transfer is feasible in ex vivo perfused human liver tissue. This result suggests the development of a strategy using baculoviral vectors for liver-directed gene therapy.

Left ventricular volume calculations using a multiplanar transoesophageal echoprobe; in vitro validation and comparison with biplane angiography

BACKGROUND

Biplane angiographic and transthoracic echocardiographic volume calculations have shown to be sufficiently reliable in symmetric hearts; however, they are unreliable in the presence of aneurysmatic distortions. Multiplane transoesophageal echocardiography offers unobstructed cross-sectional views of the heart from one stable transducer position with the potential of imaging irregular cavity forms more accurately. It was the purpose of this in vitro study to compare the precision of multiplanar transoesophageal echocardiography to that of biplane angiography in determining left ventricular volumes, especially in aneurysmatic models.

METHODS

Seven silicon rubber models of the left ventricle from post-mortem specimens (four with aneurysms) were filled with 30 different volumes (range 153-256 ml, 197 +/- 30 ml). Echocardiographic cross-sections (20 degree rotational steps) were obtained from different transducer positions, utilizing a multiplanar probe with a central rotational axis. Volumes were calculated using the disc-summation method. For comparison the same volumes were determined by standard biplane angiography. The minimum number of echo cross-section necessary to optimize precision was analysed by calculating volumes for each increasing equidistant rotational step.

RESULTS

Linear correlation between measured volume using a multiplanar transoesophageal echoprobe and true volume was high (r = 0.97) and significantly better than for biplane angiography (r = 0.88; P < 0.001). Measurement bias and imprecision were also significantly lower with multiplanar echocardiography than with biplane angiography (3.9 +/- 7.1% vs 11.1 +/- 15.4%, and 2.0 +/- 3.7% vs 5.9 +/- 8.3%; P < 0.001). Precision of biplane angiographic volume measurements was significantly influenced by the presence of aneurysmatic distortions. Multiplanar echo volumes, however, were not influenced by left ventricular geometry and transducer positions. Nine echo cross-sections provided optimal precision.

CONCLUSIONS

Three-dimensional echocardiographic volume calculations using a multiplanar transoesophageal echoprobe and the disc-summation method provide precise measurements unaffected by left ventricular geometry and transducer position in an in vitro setting. Standard biplane angiography is significantly less precise.

[Gender, work load and list profile in general practice. Experiences from a patient listing project]

A list patient project was carried out in four Norwegian municipalities in 1993. Female general practitioners from one of the involved communities soon showed frustration about the their experience that the new system had increased their work load. Although the new system was intended primarily to serve the needs of the population, the problems experienced by the female doctors were taken as warnings about future problems for the servants of the system. We therefore wanted to study relationships between experienced work load, list profiles and procedures for establishment of the patient lists among male and female doctors in Trondheim and Tromsø, the two largest project municipalities. Our data confirm the impression of increased work load and dissatisfaction with the list profiles. We find that female doctors have shorter lists and a higher proportion of female patients, and are less accessible. We discuss elements which might influence these problems in the future, especially as regards list profiles, the establishment of lists, and priorities related to people's free choice of doctor.

Patients with sexually transmitted disease: a well-defined HIV risk group in general practice?

Since patients with sexually transmitted disease (STD) form the most apparent risk group for HIV infection in general practice, differences in sexual behaviour in patients with and without STD were studied. Patients fulfilling at least one of four clinical criteria for suspicion of STD were offered four microbiological tests and a serological HIV test and were asked to complete a questionnaire concerning possible HIV exposure. Control patients were selected from a sample of ordinary consulting patients in general practice, without clinical suspicion of STD. The answers to the questionnaires given by six male and 52 female patients with a positive microbiological test for STD were compared with answers given by control patients matched for sex, age, education and geographical region. Females with STD had multiple male partners more often than controls. STD patients were more uncertain whether they had had sex with a HIV-positive person, and they reported more previous gonorrhea than the control patients. The proportion of patients who reported practicing oral sex was the same in both groups, while data for anal sex were insufficient. There were no significant differences in the use of condoms with a new partner, although there was a higher proportion of never-users of condoms among the STD patients. Identifying STD patients on clinical grounds is difficult in general practice. Clinical criteria have limited sensitivity because of asymptomatic infections, and the specificity is low. Patients with microbiologically confirmed STD should receive HIV-related attention, but attention to STD patients alone is not enough. Many people without STD have sexual behaviour which may exposure them to the HIV virus. The only means to a selective approach is increased attention to an appropriate sexual medical history.

[Effect of 1 week's administration of prednisone on gastric acid secretion and liberation of gastrin in healthy humans]

In a double-blind, randomized study we examined the effects of an oral administration of prednisone (60 mg/day for 6 days) or placebo on gastric acid output basally (BAO), in response to peptone meals 1%, 2%, 4% and 8%, 500 ml each) and to pentagastrin 6 micrograms/kg s.c. to determine maximal acid output, MAO) and on plasma gastrin levels in 14 healthy volunteers. Gastric acid output was measured by intragastric titration (pH 5.5). For gastrin determination we used a specific radioimmunoassay. Experiments were performed one day (day 0) before giving the drugs and one day (day 7) and one month (day 30) after finishing the treatment. Both groups were comparable in their gastric acid responses on day 0. Six days treatment with prednisone did not significantly alter BAO, MAO and the gastric acid response to peptone and pentagastrin. Also, one month after finishing the treatment there were no significant differences in gastric acid output. Both groups had similar plasma gastrin levels on each day. Prednisone did not significantly alter plasma gastrin levels. We conclude that a six-day treatment with prednisone does not alter BAO, MAO and gastric secretory responses to peptone nor release of gastrin in healthy human volunteers.