Negligible In Vitro Recovery of Macromolecules from Microdialysis Using 100 kDa Probes and Dextran in Perfusion Fluid

Microdialysis is applied in neurointensive care to monitor cerebral glucose metabolism. If recoverable, macromolecules may also serve as biomarkers in brain disease and provide clues to their passage across the blood-brain barrier. Our study aimed to investigate the in vitro recovery of human micro- and macromolecules using microdialysis catheters and perfusion fluids approved for clinical use. In vitro microdialysis of a bulk solution containing physiological or supraphysiological concentrations of glucose, lactate, pyruvate, human IgG, serum albumin, and hemoglobin was performed using two different catheters and perfusion fluids. One had a membrane cut-off of 20 kDa and was used with a standard CNS perfusion fluid, and the other had a membrane cut-off of 100 kDa and was perfused with the same solution supplemented with dextran. The flow rate was 0.3 µl/min. We used both push and push-pull methods. Dialysate samples were collected at 2-h intervals for 6 h and analyzed for relative recovery of each substance. The mean relative recovery of glucose, pyruvate, and lactate was > 90% in all but two sets of experiments. In contrast, the relative recovery of human IgG, serum albumin, and hemoglobin from both bulk solutions was below the lower limit of quantification (LLOQ). Using a push-pull method, recovery of human IgG, serum albumin, and hemoglobin from a bulk solution with supraphysiological concentrations were above LLOQ but with low relative recovery (range 0.9%-1.6%). In summary, exchanging the microdialysis setup from a 20 kDa catheter with a standard perfusion fluid for a 100 kDa catheter with a perfusion solution containing dextran did not affect the relative recovery of glucose and its metabolites. However, it did not result in any useful recovery of the investigated macromolecules at physiological levels, either with or without a push-pull pump system.

Spatial fractionation of phosphorus accumulating biofilm: stratification of polyphosphate accumulation and dissimilatory nitrogen metabolism

The spatial distribution of microorganisms represents a critical issue in understanding biofilm function. The aim of the current work was to develop a method for biofilm fractionation, facilitating the analysis of individual spatial biofilm layers using metagenomic approaches. Phosphorus accumulating biofilm applied in an enhanced biological phosphorus removal wastewater treatment plant, were fractionated, and analyzed. The fractionated biofilm revealed a surprising spatial distribution of bacteria and genes, where potential polyphosphate accumulating organisms account for ∼ 47% of the inner layer microbiome. A spatial distribution of genes involved in dissimilatory nitrogen reduction was observed, indicating that different layers of the biofilm were metabolically active during the anoxic and aerobic zones of the phosphorus removal process. The physical biofilm separation into individual fractions unveiled functional layers of the biofilm, which will be important for future understanding of the phosphorus removal wastewater process.

Microbial ecological processes in MBBR biofilms for biological phosphorus removal from wastewater

Phosphorus is both a major environmental pollutant and a limiting resource. Although enhanced biological phosphorus removal (EBPR) is used worldwide for phosphorus removal, the standard activated sludge-based EBPR process shows limitations with stability and efficiency. Recently, a new EBPR moving bed biofilm reactor (MBBR) process has been developed at HIAS (Hamar, Norway), enabling a phosphorus removal stability above 90% during a whole year cycle. To increase the knowledge of the HIAS (MBBR) process the aim of the current work was to characterize the MBBR microbiota and operational performance weekly for the operational year. Surprisingly, we found a major succession of the microbiota, with a five-fold increase in phosphorus accumulating organisms (PAOs), and major shifts in eukaryote composition, despite a stable phosphorus removal. Temperature was the only factor that significantly affected both phosphorus removal and the microbiota. There was a lower phosphor removal during the winter, coinciding with a higher microbiota alpha diversity, and a lower beta diversity. This differs from what is observed for activated sludge based EBPR. Taken together, the knowledge gained from the current microbiota study supports the efficiency and stability of MBBR-based systems, and that knowledge from activated sludge-based EBPR approaches cannot be translated to MBBR systems.

Glucagon-like peptide 1 receptor activation regulates cocaine actions and dopamine homeostasis in the lateral septum by decreasing arachidonic acid levels

Agonism of the glucagon-like peptide 1 (GLP-1) receptor (GLP-1R) has been effective at treating aspects of addictive behavior for a number of abused substances, including cocaine. However, the molecular mechanisms and brain circuits underlying the therapeutic effects of GLP-1R signaling on cocaine actions remain elusive. Recent evidence has revealed that endogenous signaling at the GLP-1R within the forebrain lateral septum (LS) acts to reduce cocaine-induced locomotion and cocaine conditioned place preference, both considered dopamine (DA)-associated behaviors. DA terminals project from the ventral tegmental area to the LS and express the DA transporter (DAT). Cocaine acts by altering DA bioavailability by targeting the DAT. Therefore, GLP-1R signaling might exert effects on DAT to account for its regulation of cocaine-induced behaviors. We show that the GLP-1R is highly expressed within the LS. GLP-1, in LS slices, significantly enhances DAT surface expression and DAT function. Exenatide (Ex-4), a long-lasting synthetic analog of GLP-1 abolished cocaine-induced elevation of DA. Interestingly, acute administration of Ex-4 reduces septal expression of the retrograde messenger 2-arachidonylglycerol (2-AG), as well as a product of its presynaptic degradation, arachidonic acid (AA). Notably, AA reduces septal DAT function pointing to AA as a novel regulator of central DA homeostasis. We further show that AA oxidation product γ-ketoaldehyde (γ-KA) forms adducts with the DAT and reduces DAT plasma membrane expression and function. These results support a mechanism in which postsynaptic septal GLP-1R activation regulates 2-AG levels to alter presynaptic DA homeostasis and cocaine actions through AA.

Distensibility of the anal canal in patients with idiopathic fecal incontinence: a study with the Functional Lumen Imaging Probe

BACKGROUND

Anatomical structures and their distensibility vary along the length of the anal canal. The anal sphincter muscles have dynamic properties that are not well-reflected by standard manometry. Abnormal distensibility of the anal canal may be of importance in idiopathic fecal incontinence (IFI). The functional lumen imaging probe (FLIP) allows detailed studies of the distensibility and axial variation of sphincters. We aimed at comparing segmental distensibility of the anal canal in patients with IFI and healthy subjects.

METHODS

The FLIP was used for distension of the anal canal in 22 patients with IFI (17 female, age 27-82 years) and 21 healthy volunteers (18 female, age 32-73 years). The distensibility was determined from changes in luminal diameter. Closure of the anal canal during voluntary squeeze was computed as the combined length of closed anal canal and time. Pressure-strain elastic modulus was computed at rest.

KEY RESULTS

In all subjects, the proximal anal canal was the most distensible segment. During distension at rest and during squeeze the middle and distal anal canal became significantly larger in IFI than in healthy (F < 22.4, p < 0.05). The closure of the anal canal during voluntary squeeze did not differ between healthy (75.9 ± 92.9 mm s) and IFI patients (90.4 ± 105 mm s; p = 0.6). Compared with healthy, IFI patients had lower pressure-strain elastic modulus of the middle and distal (q > 4.5, p < 0.05) but not the proximal anal canal (q < 0.7, p > 0.05).

CONCLUSIONS & INFERENCES

Patients with IFI have increased distensibility of the middle and distal parts of the anal canal.

Phage typing of Salmonella Typhimurium - is it still a useful tool for surveillance and outbreak investigation?

Phage typing has for decades been useful as a phenotypical, definitive method for epidemiological characterisation of Salmonella Typhimurium. The system recommended by the World Health Organization (WHO) Collaborative Centre for phage typing of Salmonella has, however, become rather complex, and the present study illustrates the challenges of sufficient standardisation of the interpretation of lysis results to make sure that the same strain is assigned to the same phage type in different laboratories. Even though molecular typing methods will replace phenotypic characterisation methods in the future, it is our opinion that phage typing will remain for some time a useful tool to strengthen global Salmonella surveillance. Therefore, improved standardisation and quality assurance is essential to obtain a robust and harmonized method that allows comparison of results between laboratories.

Phage typing of Salmonella Typhimurium – is it still a useful tool for surveillance and outbreak investigation?

Phage typing has for decades been useful as a phenotypical, definitive method for epidemiological characterisation of Salmonella Typhimurium. The system recommended by the World Health Organization (WHO) Collaborative Centre for phage typing of Salmonella has, however, become rather complex, and the present study illustrates the challenges of sufficient standardisation of the interpretation of lysis results to make sure that the same strain is assigned to the same phage type in different laboratories. Even though molecular typing methods will replace phenotypic characterisation methods in the future, it is our opinion that phage typing will remain for some time a useful tool to strengthen global Salmonella surveillance. Therefore, improved standardisation and quality assurance is essential to obtain a robust and harmonised method that allows comparison of results between laboratories.

Development of a new nomenclature for Salmonella Typhimurium multilocus variable number of tandem repeats analysis (MLVA)

Multilocus variable number of tandem repeats analysis (MLVA) has recently become a widely used highly discriminatory molecular method for typing of the foodborne pathogen Salmonella Typhimurium. This method is based on amplification and fragment size analysis of five repeat loci. To be able to easily compare MLVA results between laboratories there is a need for a simple and definitive nomenclature for MLVA profiles. Based on MLVA results for all human S. Typhimurium isolates in Denmark from the last five years and sequence analysis of a selection of these isolates, we propose a MLVA nomenclature that indicates the actual number of repeat units in each locus. This nomenclature is independent of the equipment used for fragment analysis and, in principle, independent of the primers used. A set of reference strains is developed that can be used for easy normalisation of fragment sizes in each laboratory.

An outbreak of Salmonella Typhimurium infections in Denmark, Norway and Sweden, 2008

In November-December 2008, Norway and Denmark independently identified outbreaks of Salmonella Typhimurium infections characterised in the multiple-locus variable number of tandem repeats analysis (MLVA) by a distinct profile. Outbreak investigations were initiated independently in the two countries. In Denmark, a total of 37 cases were identified, and multiple findings of the outbreak strain in pork and pigs within the same supply chain led to the identification of pork in various forms as the source. In Norway, ten cases were identified, and the outbreak investigation quickly indicated meat bought in Sweden as the probable source and the Swedish authorities were alerted. Investigations in Sweden identified four human cases and two isolates from minced meat with the distinct profile. Subsequent trace-back of the meat showed that it most likely originated from Denmark. Through international alert from Norway on 19 December, it became clear that the Danish and Norwegian outbreak strains were identical and, later on, that the source of the outbreaks in all three countries could be traced back to Danish pork. MLVA was instrumental in linking the outbreaks in the different countries and tracing the source. This outbreak illustrates that good international communication channels, early alerting mechanisms, inter-sectoral collaboration between public health and food safety authorities and harmonised molecular typing tools are important for effective identification and management of cross-border outbreaks. Differences in legal requirements for food safety in neighbouring countries may be a challenge in terms of communication with consumers in areas where cross-border shopping is common.

An outbreak of Salmonella Typhimurium infections in Denmark, Norway and Sweden, 2008

In November-December 2008, Norway and Denmark independently identified outbreaks of Salmonella Typhimurium infections characterised in the multiple-locus variable number of tandem repeats analysis (MLVA) by a distinct profile. Outbreak investigations were initiated independently in the two countries. In Denmark, a total of 37 cases were identified, and multiple findings of the outbreak strain in pork and pigs within the same supply chain led to the identification of pork in various forms as the source. In Norway, ten cases were identified, and the outbreak investigation quickly indicated meat bought in Sweden as the probable source and the Swedish authorities were alerted. Investigations in Sweden identified four human cases and two isolates from minced meat with the distinct profile. Subsequent trace-back of the meat showed that it most likely originated from Denmark. Through international alert from Norway on 19 December, it became clear that the Danish and Norwegian outbreak strains were identical and, later on, that the source of the outbreaks in all three countries could be traced back to Danish pork. MLVA was instrumental in linking the outbreaks in the different countries and tracing the source. This outbreak illustrates that good international communication channels, early alerting mechanisms, inter-sectoral collaboration between public health and food safety authorities and harmonised molecular typing tools are important for effective identification and management of cross-border outbreaks. Differences in legal requirements for food safety in neighbouring countries may be a challenge in terms of communication with consumers in areas where cross-border shopping is common.

Large outbreaks of Salmonella Typhimurium infection in Denmark in 2008

An outbreak of Salmonella Typhimurium phage type U292 has been ongoing in Denmark since 1 April, with 1,054 cases registered until 23 October 2008. Extensive investigations including hypothesis-generating interviews, matched case-control studies, cohort studies in embedded outbreaks, shopping list analyses, analyses of food samples from patient's homes, trace-back analyses and extensive microbiological analysis of products have not provided clear indications of a specific source of infection but the main hypothesis is that the vehicle of the outbreak are different pork products. In addition to the large U292 outbreak, at least four other S. Typhimurium outbreaks (caused by phage types U288, DT120, DT3 and DT135) have been investigated in Denmark in 2008.

Large ongoing outbreak of infection with Salmonella Typhimurium U292 in Denmark, February-July 2008

Denmark is currently experiencing an unusually large outbreak of gastrointestinal illness caused by Salmonella Typhimurium, phage type U292. The outbreak was discovered in early April by molecular typing (MLVA typing) of S. Typhimurium isolates at the Statens Serum Institut (SSI); the first patients reported onset on illness in February, but the number of reported cases has been particularly high in May and June (Figure 1). There are currently (as of 7 July) 366 confirmed cases, effectively making this the largest outbreak of salmonella infections in Denmark since 1993 [1].

Outbreak of Salmonella Weltevreden infections in Norway, Denmark and Finland associated with alfalfa sprouts, July-October 2007

Between 10 and 15 October 2007, the national reference laboratory at the Norwegian Institute of Public Health detected Salmonella Weltevreden in samples from four gastroenteritis patients.

Growth inhibitory factors in bovine faeces impairs detection of Salmonella Dublin by conventional culture procedure

AIMS

To analyse the relative importance of different biological and technical factors on the analytical sensitivity of conventional culture methods for detection of Salmonella Dublin in cattle faeces.

METHODS AND RESULTS

Faeces samples collected from six adult bovines from different salmonella-negative herds were split into subpools and spiked with three strains of S. Dublin at a concentration level of c. 10 CFU g(-1) faeces. Each of the 18 strain-pools was divided into two sets of triplicates of four volumes of faecal matter (1, 5, 10 and 25 g). The two sets were pre-enriched with and without novobiocin, followed by combinations of culture media (three types) and selective media (two types). The sensitivity of each combination and sources of variation in detection were determined by a generalized linear mixed model using a split-plot design.

CONCLUSIONS

Biological factors, such as faecal origin and S. Dublin strain influenced the sensitivity more than technical factors. Overall, the modified semi-solid Rappaport Vassiliadis (MSRV)-culture medium had the most reliable detection capability, whereas detection with selenite cystine broth and Mueller Kauffman tetrathionate broth combinations varied more in sensitivity and rarely reached the same level of detection as MSRV in this experiment.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study showed that for MSRV-culture medium and xylose lysine decarboxylase agar as the indicative medium, the sensitivity of the faecal culture method may be improved by focusing on the strain variations and the ecology of the faecal sample. Detailed investigation of the faecal flora (pathogens and normal flora) and the interaction with chemical factors may result in developing an improved method for detection of S. Dublin.

Outbreak with multi-resistant Salmonella Typhimurium DT104 linked to carpaccio, Denmark, 2005

We report an outbreak with Salmonella Typhimurium DT104 resistant to six different antibiotic classes. The outbreak occurred in Denmark in July/August 2005 and was traced to a single restaurant. In addition to patient interviews, an important tool in the investigation of this outbreak was comparison by multi-locus variable number of tandem repeat analysis (MLVA) typing of patient strains with strains from the food surveillance system. This showed that the source of the outbreak was imported beef served as carpaccio. Carpaccio, thinly sliced raw fillet of beef, has not previously been associated with outbreaks, but should be considered a high-risk food item. This outbreak was one of two in different European Union (EU) countries traced back to beef from one company in a third EU country. This underscores the importance of efficient international Salmonella surveillance and food-safety control systems enabling timely interventions within the EU.

A regional outbreak of S. Typhimurium in Denmark and identification of the source using MLVA typing

In Denmark, as part of the national laboratory-based surveillance system of human enteric infections, all S. Typhimurium isolates are currently sub-typed using phage typing, antibiogram typing, and pulsed-field gel electrophoresis (PFGE). However, the discriminatory ability of PFGE is not always high enough to discriminate within certain phage types, and it is not always possible to separate unrelated and related isolates. We have therefore applied multiple locus variable number of tandem repeats analysis (MLVA) for surveillance typing of S. Typhimurium since 2004. In May and June 2005, an outbreak with 26 cases of S. Typhimurium infection was identified by MLVA. The isolates were fully sensitive and had one of the most frequently occurring Danish phage types (DT12) and PFGE types. S. Typhimurium DT12 isolates from routine surveillance of animals and food were typed using MLVA and PFGE for comparison with the human isolates. The typing results revealed that an isolate from a pig herd and its corresponding slaughterhouse located in the same geographic region as the outbreak had the same PFGE and MLVA type as the human isolates. In contrast, all other DT12 isolates investigated, which had the same PFGE profile, had different MLVA types. The conclusion that the pig herd was the source of the human infections was supported by patient information, and pork from the herd stopped entering the market on 29 June. MLVA may contribute significantly to both surveillance and outbreak investigations of S. Typhimurium, as without MLVA typing this outbreak would not have been found nor its origin traced.

Prolonged restaurant-associated outbreak of multidrug-resistant Salmonella Typhimurium among patients from several European countries

This report concerns a prolonged restaurant-associated outbreak of infection caused by a multidrug-resistant (ASSuT) strain of Salmonella Typhimurium, phage-type U302, which took place during July and August 2003 and affected people from Denmark and neighbouring countries who had attended a specific restaurant. The outbreak comprised 67 laboratory-verified cases and ten probable cases; however, the actual number of patients was estimated to be more than 390. The outbreak strain was isolated from a buffet which was probably contaminated by an assistant chef who was found to excrete the epidemic strain. An attack rate of 7.3% was estimated and long incubation periods were observed, including one extreme instance of 27 days. This outbreak underscores the importance of conscientious personal hygiene, including frequent washing of hands, for professionals handling food.

Addition of Novobiocin in pre-enrichment step can improve Salmonella culture protocol of modified semisolid Rappaport–Vassiliadis

The aim was to investigate the effect of addition of Novobiocin to the non-selective buffered peptone water (BPW) for pre-enrichment of Salmonella in connection with plating on modified semisolid Rappaport-Vassiliadis (MSRV). In a semi-quantitative study, the level of Salmonella following pre-enrichment of 32 presumably naturally contaminated swine fecal samples were assessed for BPW with and without addition of Novobiocin (22 microg/ml). In another experiment, a total of 400 swine fecal samples were screened for the presence of Salmonella spp., in order to compare the performance of the non-selective pre-enrichment broth with BPW made semi-selective by addition of Novobiocin. The semi-quantitative assessment of the Salmonella level showed that addition of Novobiocin in the pre-enrichment step on average increased the level of Salmonella 1.2 log dilution steps. When growth was scored at five levels, 90 samples opposed to 50 yielded a strong positive reading (+++) when Novobiocin was applied. Growth was on average 0.3 scores higher when pre-enriched with Novobiocin. The difference in growth score medians of the two methods was highly significant (Sign test; p<0.001). Despite the increased sensitivity, 13 culture-positive samples were missed when using the Novobiocin-containing BPW. In conclusion, a simple addition of Novobiocin in the BPW pre-enrichment step of fecal samples may facilitate reading and thereby detection of Salmonella on MSRV. The increase of Salmonella in the semi-quantitative study may be caused by a reduction in the number of competitive microorganisms.

Molecular cloning of a functional allatostatin gut/brain receptor and an allatostatin preprohormone from the silkworm Bombyx mori

The cockroach-type or A-type allatostatins are inhibitory insect neuropeptides with the C-terminal sequence Tyr/Phe-X-Phe-Gly-Leu-NH(2). Here, we have cloned an A-type allatostatin receptor from the silkworm Bombyx mori (BAR). BAR is 361 amino acid residues long, has seven transmembrane domains, shows 60% amino acid residue identity with the first Drosophila allatostatin receptor (DAR-1), and 48% identity with the second Drosophila allatostatin receptor (DAR-2). The BAR gene has two introns and three exons. These two introns coincide with and have the same intron phasing as two introns in the DAR-1 and DAR-2 genes, showing that the three receptors are not only structurally but also evolutionarily related. Furthermore, we have cloned a Bombyx allatostatin preprohormone that contains eight different A-type allatostatins. Chinese hamster ovary cells permanently transfected with BAR DNA react on the addition of 4 x 10(-9)M Bombyx A-type allatostatins with a second messenger cascade (measured as bioluminescence), showing that BAR is a functional A-type allatostatin receptor. Southern blots suggest that Bombyx has at least one other BAR-related gene in addition to the BAR gene described in this paper. Northern blots and quantitative reverse transcriptase-polymerase chain reaction of different larval tissues show that BAR mRNA is mainly expressed in the gut and to a much lesser extent in the brain. To our knowledge, this is the first report on the molecular cloning and functional expression of an insect gut/brain peptide hormone receptor.

Evaluation of quality changes in walnut kernels (Juglans regia L.) by Vis/NIR spectroscopy

Storage of walnut kernels in light and at room temperature, as is common practice, is detrimental to their sensory quality and shelf life. This study demonstrates that Vis/NIR spectroscopy, in combination with multivariate data analysis (chemometrics), is a most capable rapid method for monitoring the overall quality deterioration of walnut kernels. Spectral predictions of the sensory attributes nutty and rancid tastes by partial least-squares regression (PLSR) resulted in correlations (r(2)) of 0.77 and 0.86, respectively, whereas with PLSR prediction of the chemical parameter hexanal content a correlation (r(2)) of 0.72 was obtained. The study further establishes that storage in light results in pronounced oxidative changes, especially in walnuts stored at 21 degrees C, whereas dark storage at 5 degrees C results in walnuts without any trace of rancid taste during 25 weeks of storage at accelerated storage conditions (50% oxygen).

[The self-regulation process, adjustment and defense. Interdisciplinary study]

The study of the processes of self-regulation and defense may serve as an example illustrating the interdisciplinary research in psychiatry. Belying on the topography of mental disturbance as described by the systemal method, this study can profit from the findings of animal ethology and oceanographyt++ and thus conceive of the diversity and integration of the defense mechanisms of living systems beloging to different levels in the hierarchy of species. These insights may contribute to a refinement of the analysis of the human defense mechanisms met in psychiatry. As an example of this an analysis of phobic avoidance is related.

Stereotyped behaviour in animals induced by stimulant drugs or by a restricted cage environment: relation to disintegrated behaviour, brain dopamine and psychiatric disease

Stereotyped behaviour can be produced in animals both by stimulant drugs (amphetamine, methamphetamine, cocaine, etc.) and by a restricted cage environment. Strong evidence indicates that the effect of stimulant drugs is mediated through a primary effect on brain dopamine, and further knowledge is now being acquired through studies on dopamine receptors, tolerance and reverse tolerance to amphetamines and the neural connections of dopaminergic sub-systems with other sub-systems in the brain. The forms of stereotypy induced by a restricted cage environment have been compared with other effects of this type of environment on behaviour and general health. This has led to a hypothesis that stereotyped behaviour may function as a survival (or defence) strategy in an unfavourable milieu. Some evidence indicates that brain dopamine is also involved in the mediation of stereotyped behaviour induced by the environment. The relevance of these results in clinical psychiatry is discussed. Stereotypy (and related disintegrated behaviour) is a well known feature of several mental diseases.

Stereotyped behaviour, hyperaggressiveness and "tyrannic" hierarchy induced in bank voles (Clethrionomys glareolus) by a restricted cage milieu

This investigation was originally conceived as a further development of studies made with the "amphetamine model" of psychosis. Since amphetamine itself seemed to be the most important flaw in this model, it was judged promising to study abnormal behaviour in animals elicited without the use of drugs. Bank voles were placed in two different cage milieux, a restricted milieu approaching usual laboratory conditions for experimental animals, and an enriched milieu offering opportunities for satisfaction of natural behavioural (ethological) needs. During an experimental period of 6 months normal behaviours (known from the ethogram of the bank vole) and abnormal behaviours were recorded in eight 5-min observation periods of each cage. Social structure (hierarchy) was studied by the intruder method and social function (peaceful or tyrannic hierarchy) by inspection of the subordinate voles for wounds. Stereotypies, hyperaggressive behaviour and tyrannic hierarchy, replacing normal behaviour and social structure, were seen frequently in the restricted milieu, but only occasionally in the enriched milieu (differences highly significant). It is concluded that these findings indicate possibilities for further development of the basic studies of abnormal behaviour made by means of the "amphetamine model" of psychosis. Opportunities exist for investigation of the interaction of milieu factors with genetic, pharmacological and other factors relevant to the development, prevention and treatment of abnormal behaviour and mental disease.

Relationship between penicillinase production and the in-vitro activity of methicillin, oxacillin, cloxacillin, dicloxacillin, flucloxacillin, and cephalothin against strains of Staphylococcus aureus of different phage patterns and penicillinase activity

A total of 157 strains of Staphylococcus aureus of different phage patterns and penicillinase production were investigated for their susceptibility to methicillin, oxacillin, cloxacillin, dicloxacillin, flucloxacillin and cephalothin by an agar dilution method. Only strains of the 52, 52A, 80, 81 complex had significantly higher IC-50 values than the rest of the strains. No correlation was found between penicillinase production and the IC-50 values. Penicillinase susceptibility divided the antibiotics into two groups: one including methicillin, oxacillin and cephalothin, and the other included dicloxacillin, cloxacillin and flucloxacillin. Nineteen strains of S. aureus which existed in both a penicillinase producing and a penicillinase non-producing form were examined for susceptibility to the six antibiotics. The difference between penicillinase positive and penicillinase negative variants was especially marked for flucloxacillin and cephalothin. Methicillin induction prior to susceptibility testing had only a minor influence on the results. Investigation of the stability of methicillin and the four isoxazolyl penicillins against penicillinase production by 37 strains of S. aureus showed methicillin to be the most stable antibiotic. This was followed by dicloxacillin, cloxacillin, flucloxacillin, and oxacillin in that order. The order of stability was identical and independent of phage pattern and quantitative penicillinase production.

Rare Gas Diffusion in NaCl

The mobility (diffusion and trapping) of the heavy rare gases Kr, Xe, and Rn in pure and doped NaCl single crystals was measured following ion bombardment to various integrated doses (108 to 2X1016 ions/cm2) and at energies between 30 and 500 keV. No obvious effect of doping on release was found. At low gas concentrations, release was compatible with volume diffusion yielding an acti­vation enthalpy, ΔH, of 1.5 ±0.2 eV. This value was obtained for both very low and very high bombardment energies (≈ 1 and 500 keV) thus indicating that the same release mechanism is operative near the surface and in the bulk material. For this release mechanism, a mobility in small vacancy clusters was suggested. At higher gas concentrations, the release was shifted towards higher temperatures. This retarded release was explained by transient trapping, i. e. by gas-gas or gas-damage interactions, and was shown to have a partially single jump character. Again, the result was the same for low and high bombardment energies.