Automated splitting into batches for observational biomedical studies with sequential processing

Experimental design usually focuses on the setting where treatments and/or other aspects of interest can be manipulated. However, in observational biomedical studies with sequential processing, the set of available samples is often fixed, and the problem is thus rather the ordering and allocation of samples to batches such that comparisons between different treatments can be made with similar precision. In certain situations, this allocation can be done by hand, but this rapidly becomes impractical with more challenging cohort setups. Here, we present a fast and intuitive algorithm to generate balanced allocations of samples to batches for any single-variable model where the treatment variable is nominal. This greatly simplifies the grouping of samples into batches, makes the process reproducible, and provides a marked improvement over completely random allocations. The general challenges of allocation and why good solutions can be hard to find are also discussed, as well as potential extensions to multivariable settings.

Extending protein interaction networks using proteoforms and small molecules

MOTIVATION

Biological network analysis for high-throughput biomedical data interpretation relies heavily on topological characteristics. Networks are commonly composed of nodes representing genes or proteins that are connected by edges when interacting. In this study, we use the rich information available in the Reactome pathway database to build biological networks accounting for small molecules and proteoforms modeled using protein isoforms and post-translational modifications to study the topological changes induced by this refinement of the network representation.

RESULTS

We find that improving the interactome modeling increases the number of nodes and interactions, but that isoform and post-translational modification annotation is still limited compared to what can be expected biologically. We also note that small molecule information can distort the topology of the network due to the high connectedness of these molecules, which does not necessarily represent the reality of biology. However, by restricting the connections of small molecules to the context of biochemical reactions, we find that these improve the overall connectedness of the network and reduce the prevalence of isolated components and nodes. Overall, changing the representation of the network alters the prevalence of articulation points and bridges globally but also within and across pathways. Hence, some molecules can gain or lose in biological importance depending on the level of detail of the representation of the biological system, which might in turn impact network-based studies of diseases or druggability.

AVAILABILITY AND IMPLEMENTATION

Networks are constructed based on data publicly available in the Reactome Pathway knowledgebase: reactome.org.

P17.10.B Identification of mechanisms involved in the recurrence of glioblastoma by transcriptomic, proteomic and spatial profiling analysis

Background

Glioblastoma (GBM) is the most aggressive and common brain tumor. Despite multimodal therapy which consists of complete tumor removal, chemo- and radiation therapy in most patients, the tumor recurs, and the overall survival of only 14 months remains very poor. To identify tumor-induced immune evasion and treatment resistance mechanisms induced during GBM recurrence, we aimed at characterizing the immunological/molecular changes in patient-matched treatment-naïve and recurrent GBM samples.

Material and Methods

Proteins and total RNA were extracted from 16 patient-matched treatment-naïve (primary) and recurrent GBM fresh frozen tumor samples. The expression of genes involved in brain immune responses were compared using Nanostring panels encompassing Cancer and Neuroinflammation genes. Proteomic was conducted using 6 patient-matched primary and recurrent tumor samples. Immunostaining was performed on a tissue microarray containing matched primary and recurrent tumor samples to identify tumor cells and microglia in order to assess spatial transcriptome of these specific cell types in situ using GeoMX technology. Moreover, correlation analysis of differentially genes and proteins with time to relapse was performed.

Results

Genes significantly differentially expressed between primary and recurrent tumors revealed genes overexpressed in recurrent tumors belonging to “FCGR-mediated Phagocytosis” and “synapse pruning” pathways. Proteomic confirmed the synaptic signalling considering overexpressed proteins. Correlation studies with the time to relapse indicated that higher expression of FCG receptors, complement molecules and synaptic components correlate with shorter time to relapse, sharing similarities with neurodegenerative/cognitive disorders such as schizophrenia and Alzheimer disease. The source for these molecules is under evaluation with the spatial transcriptomic analysis.

Conclusion

Upregulation of specific proteins such as FCG receptors, complement and synaptic components may result in more favourable conditions for tumor regrowth and may therefore be identified as negative predictors patient outcome. Interfering with these molecules may represent novel therapeutic options after initial GBM surgery.

Importance of Block Randomization When Designing Proteomics Experiments

Randomization is used in experimental design to reduce the prevalence of unanticipated confounders. Complete randomization can however create imbalanced designs, for example, grouping all samples of the same condition in the same batch. Block randomization is an approach that can prevent severe imbalances in sample allocation with respect to both known and unknown confounders. This feature provides the reader with an introduction to blocking and randomization, and insights into how to effectively organize samples during experimental design, with special considerations with respect to proteomics.

Detecting single amino acids and small peptides by combining isobaric tags and peptidomics

Single amino acids and small endogenous peptides play important roles in maintaining a properly functioning organism. These molecules are however currently only routinely identified in targeted approaches. In a small proof-of-concept mass spectrometry experiment, we found that by combining isobaric tags and peptidomics, and by targeting singly charged molecules, we were able to identify a significant amount of single amino acids and small endogenous peptides using a basic mass-based identification approach. While there is still room for improvement, our simple test indicates that a limited amount of extra work when setting up the mass spectrometry experiment could potentially lead to a wealth of additional information.

PathwayMatcher: proteoform-centric network construction enables fine-granularity multiomics pathway mapping

BACKGROUND

Mapping biomedical data to functional knowledge is an essential task in bioinformatics and can be achieved by querying identifiers (e.g., gene sets) in pathway knowledge bases. However, the isoform and posttranslational modification states of proteins are lost when converting input and pathways into gene-centric lists.

FINDINGS

Based on the Reactome knowledge base, we built a network of protein-protein interactions accounting for the documented isoform and modification statuses of proteins. We then implemented a command line application called PathwayMatcher (github.com/PathwayAnalysisPlatform/PathwayMatcher) to query this network. PathwayMatcher supports multiple types of omics data as input and outputs the possibly affected biochemical reactions, subnetworks, and pathways.

CONCLUSIONS

PathwayMatcher enables refining the network representation of pathways by including proteoforms defined as protein isoforms with posttranslational modifications. The specificity of pathway analyses is hence adapted to different levels of granularity, and it becomes possible to distinguish interactions between different forms of the same protein.

Analyzing the Structure of Pathways and Its Influence on the Interpretation of Biomedical Proteomics Data Sets

Biochemical pathways are commonly used as a reference to conduct functional analysis on biomedical omics data sets, where experimental results are mapped to knowledgebases comprising known molecular interactions collected from the literature. Due to their central role, the content of the functional knowledgebases directly influences the outcome of pathway analyses. In this study, we investigate the structure of the current pathway knowledge, as exemplified by Reactome, discuss the consequences for biological interpretation, and outline possible improvements in the use of pathway knowledgebases. By providing a view of the underlying protein interaction network, we aim to help pathway analysis users manage their expectations and better identify possible artifacts in the results.

A comparison of hydrological and topological watersheds

We introduce the hydrological watershed, a watershed where water can penetrate the soil, and compare it with the topological watershed for a two-dimensional landscape. For this purpose, we measure the fractal dimension of the hydrological watershed for different penetration depths and different grid sizes. Through finite size scaling, we find that the fractal dimension is 1.31 ± 0.02 which is significantly higher than the fractal dimension of the topological watershed. This indicates that the hydrological watershed belongs to a new universality class. We also find that, as opposed to the topological watershed, the hydrodynamic watershed can exhibit disconnected islands.

Novel TMC8 splice site mutation in epidermodysplasia verruciformis and review of HPV infections in patients with the disease

BACKGROUND

Epidermodysplasia verruciformis (EV) is a genodermatosis leading to infections with cutaneous HPV, persistent plane warts and a high rate of non-melanoma skin cancer (NMSC). Biallelic loss-of-function mutations in TMC6 and TMC8 are known to be causative.

OBJECTIVE

The aim of this study was to report EV-causing mutations in four patients with EV and to give an overview of all described patients with EV.

PATIENTS AND METHODS

We investigated four patients with classical features of EV from two families. All patients were affected by plane warts with typical EV histology since early childhood, and β-HPVs were detected on their skin. One patient had recurring cutaneous squamous cell carcinomas (cSCC) and carcinomas in situ (Bowen type). We sequenced both TMC6/8 for disease-causing mutations and quantified levels of gene expression. We also performed a systematic literature review to discuss these patients in the context of previously reported cases, mutations already identified, as well as HPV types.

RESULTS

Three patients of one family carried a homozygous splice site mutation in TMC8 resulting in aberrantly spliced transcripts that were not degraded. By contrast, no TMC6/8 mutation was detected in the patient from the other family. A systematic literature review revealed 501 described patients with EV. Around 40% of patients with EV analysed for genetic alterations carried no mutation in TMC6/8. While β-HPVs were identified in the majority of cases, α-HPVs were detected in several individuals.

CONCLUSION

The relatively high proportion of EV patients without mutation in TMC6/8 indicates the existence of EV-causing mutations in additional, presently unknown gene(s). However, a homozygous TMC8 splice site mutation in our patients resulted in aberrant transcripts which cannot retain the healthy phenotype. The literature review revealed that HPV-5 is the most commonly identified HPV in patients with EV, but HPV-3, HPV-14 and HPV-20 were unexpectedly identified more frequently than HPV-8.

What patients really think about asthma guidelines: barriers to guideline implementation from the patients' perspective

Background

Treatment of asthma does not always comply with asthma guidelines (AG). This may be rooted in direct or indirect resistance on the doctors’ and/or patients’ side or be caused by the healthcare system. To assess whether patients’ concepts and attitudes are really an implementation barrier for AG, we analysed the patients’ perspective of a “good asthma therapy” and contrasted their wishes with current recommendations.

Methods

Using a qualitative exploratory design, topic centred focus group (FG) discussions were performed until theoretical saturation was reached. Inclusion criteria were an asthma diagnosis and age above 18. FG sessions were recorded audio-visually and analysed via a mapping technique and content analysis performed according to Mayring (supported by MAXQDA®). Participants’ speech times and the proportion of time devoted to different themes were calculated using the Videograph System® and related to the content analysis.

Results

Thirteen men and 24 women aged between 20 and 77 from rural and urban areas attended five FG. Some patients had been recently diagnosed with asthma, others years previously or in childhood. The following topics were addressed: (a) concern about or rejection of therapy components, particularly corticosteroids, which sometimes resulted in autonomous uncommunicated medication changes, (b) lack of time or money for optimal treatment, (c) insufficient involvement in therapy choices and (d) a desire for greater empowerment, (e) suboptimal communication between healthcare professionals and (f) difficulties with recommendations conflicting with daily life. Primarily, (g) participants wanted more time with doctors to discuss difficulties and (h) all aspects of living with an impairing condition.

Conclusions

We identified some important patient driven barriers to implementing AG recommendations. In order to advance AG implementation and improve asthma treatment, the patients’ perspective needs to be considered before drafting new versions of AG. These issues should be addressed at the planning stage.

Trial registration

DRKS00000562 (German Clinical Trials Registry).

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-016-0346-6) contains supplementary material, which is available to authorized users.

Epidermodysplasia verruciformis

Epidermodysplasia verruciformis (EV) is a rare genodermatosis that predisposes certain individuals to developing cutaneous malignancies caused by infectious agents. Mutations in the transmembrane channel gene TMC6 or TMC8 create patient susceptibility to infections by human papillomavirus (HPV) and the development of EV-typical plane warts. Mainly in the UV-exposed regions, affected individuals have a lifelong increased risk for the development of cutaneous malignancy, especially squamous cell carcinoma (SCC). EV is the first disease to correlate cancer and viral infection, therefore EV now serves as the cornerstone to our understanding of viral oncogenesis. The EV model of cutaneous SCC may be applied to the general population; it is suggested that the TMC mutations impair the immunity of the patients, supporting the amplification of specific HPV types. Despite several advances in our comprehension of EV, the pathogenesis of the disease is not well understood.

Influence of diet on calcium metabolism, tissue calcification and urinary sludge in rabbits (Oryctolagus cuniculus)

Rabbits absorb more calcium (Ca) from their diet than they require, and excrete surplus via urine, which therefore contains a typical 'sludge'. This makes rabbits susceptible to Ca-containing uroliths. But given the Ca content of diets of free-ranging specimens, and the limited reports of urinary sludge and Ca contents in free-ranging lagomorphs, we can suspect that rabbits are naturally adapted to high urinary Ca loads. We fed four groups of New Zealand hybrid rabbits [n = 28, age at start 5-6 weeks) pelleted diets consisting of lucerne hay only (L, Ca 2.32% dry matter (DM)], lucerne:oats 1:1 (LG, Ca 1.36%), grass hay only (G, Ca 1.04%), or grass:oats 1:1 (GG, 0.83%) for 25 weeks, with water available ad libitum. Diets were not supplemented with Ca, phosphorus, or vitamin D. Rabbits on diets LG and GG had lower food and water intakes, lower faeces and urine output, grew faster and had higher body mass at slaughter (mainly attributable to adipose tissue). Apparent Ca digestibility decreased in the order L-LG-G/GG. Rabbits on L had larger and heavier kidneys, more urinary sediment at sonography, and a higher urinary Ca content than the other groups. No animal showed signs of urolithiasis/calcinosis at X-ray, sonography, or gross pathology. Kidney/aorta histology only sporadically indicated Ca deposits, with no systematic difference between groups. Under the conditions of the experiment, dietary Ca loads in legume hay do not appear problematic for rabbits, and other factors, such as water supply and level of activity may be important contributors to urolithiasis development in veterinary patients. However, due to the lower Ca content of grass hay, the significantly lower degree of urinary sludge formation, and the significantly higher water intake related with grass hay feeding, grass hay-dominated diets are to be recommended for rabbits in which urolithiasis prevention is an issue.

Short Report: New use of current technology to measure rectal temperature and heart rate during endurance exerciseToEd

The technology necessary to log data remotely and independently has been available for some years. This technology has been applied mostly to environmental and natural sciences, however, and not in life sciences. This was due primarily to the cost of the technology and the small demand for it in the life sciences, especially in studies of exercise physiology. Our recent collaboration with a local technology company (SyGade Solutions (Pty) Ltd., Johannesburg) has resulted in the use of miniature data loggers to record rectal temperature, heart rate (HR), and altitude during road and cycle racing. This technology has the potential to measure these variables simultaneously and in a free-living situation and will therefore contribute to more innovative research. South African Sports Medicine Vol.17(1) 2005: 29-30

Short Report: New use of current technology to measure rectal temperature and heart rate during endurance exerciseToEd

The technology necessary to log data remotely and independently has been available for some years. This technology has been applied mostly to environmental and natural sciences, however, and not in life sciences. This was due primarily to the cost of the technology and the small demand for it in the life sciences, especially in studies of exercise physiology. Our recent collaboration with a local technology company (SyGade Solutions (Pty) Ltd., Johannesburg) has resulted in the use of miniature data loggers to record rectal temperature, heart rate (HR), and altitude during road and cycle racing. This technology has the potential to measure these variables simultaneously and in a free-living situation and will therefore contribute to more innovative research. South African Sports Medicine Vol.17(1) 2005: 29-30

Lipid peroxidation as additional marker in patients with colorectal cancer. Results of a preliminary study

BACKGROUND AND AIMS

Up to now, various tumor markers have been proposed for the detection of the onset of malignant cell transformation or the better follow-up of cancer patients. The aim of the present study is to investigate the diagnostic value of systemic lipid peroxidation as an additional evaluative tool in the follow-up of surgical patients with colorectal cancer in combination to the clinically routine tumor markers carcinoembryonic antigen (CEA) and carcinoantigen 19-9 (CA 19-9).

PATIENTS AND METHODS

36 patients with a colorectal carcinoma were included in this study. Blood samples were collected 1 day prior to the operation, 10 days and 1 year after the operation. Oxygen free radical mediated lipid peroxidation was determined by measurement of thiobarbituric acid-reactive substances in the same serum that were used for the determination of tumor markers.

RESULTS

Compared to control values, a highly significant increase of lipid peroxidation was found in the serum of all colorectal carcinoma patients up to the first 10 postoperative days. Differentiation of the patients, according to the T-stage, showed a marked and more obvious tendency towards higher serum lipid peroxides with increased tumor stage when compared to the conventional tumor markers. One year postoperatively the serum levels of lipid peroxidation returned to nearly normal values. Also the conventional tumor markers CEA and CA 19-9 showed a relative rise in the levels with the respective tumor stage, but differences were only statistically significant in the highest T-categories.

CONCLUSION

After curative resection of the tumor, the level of systemic lipid peroxides decreases to normal values. We conclude from these results that the tumor is the primary cause of the increased systemic lipid peroxides.

Prostate and sexuality: An overview

OBJECTIVE

Diseases of the prostate, prostatitis, prostatodynia, benign prostatic hyperplasia (BPH), and carcinoma of the prostate interfere with sexual function. Since the American Urological Association have issued their position statement in 1990 that male sexual dysfunction is a recognized disease entity, studies examined the interrelation between sexuality and the prostate. These studies were identified in our review.

METHOD

A computer- and hand-based search of the literature was conducted with the key words health-related quality of life, sexual function and the various disease states of the prostate, the drawback being that validated quality-of-life instruments have just recently and mostly nationally been validated.

RESULTS

Sexual function is a dimension of quality-of-life questionnaires with 1 up to 11 questions addressing sexuality. The effect of aging on male sexuality as determined in Sweden serves as an important background information. Whereas prostadynia and sexual dysfunction aggravate each other, BPH and its treatment influence only certain sexual functions. Carcinoma of the prostate, untreated or under observation, has the greatest impact on sexuality which is tolerated differently from country to country and depends upon the expectation of survival.

CONCLUSION

The impact of treatment of prostatic diseases on sexuality can now be studied easier in utilizing validated questionnaires. This update may serve as a base for these upcoming studies.

Formation of uniparental disomy 7 delineated from new cases and a UPD7 case after trisomy 7 rescue. Presentation of own results and review of the literature

Maternal uniparental disomy for the entire chromosome 7 (matUPD7) has been reported several times in Silver-Russell syndrome (SRS) and growth-restricted patients. Here we present our results from the analysis of an abortion with confined placental mosaicism (CPM) for trisomy 7 which showed a maternal meiotic origin of the trisomy in the placenta and rescue to maternal UPD7 in foetal membrane. Furthermore, two newly detected SRS cases with maternal UPD7 revealed isodisomy and partial heterodisomy, respectively. Summarising these results with those published previously on the origin of UPD7, similar numbers of isodisomy (n=11) and cases with complete or partial heterodisomy (n=12) have been reported. In respect to the different formation mechanisms of UPD, complete isodisomy should be the result of a post-zygotic mitotic segregation error, whereas heterodisomic UPDs should be caused by trisomic rescue after meiotic non-disjunction events. In maternal UPD7, 50% of cases seem to be caused by post-zygotic mitotic segregation errors, which is similar to the situation in trisomy 7. This result corresponds to the situation in trisomy 8 but is in contrast to observations in the frequent aneuploidies. Thus, the different findings in these aberrations reflect the presence of multiple factors that act to ensure normal segregation, varying in importance for each chromosome.

Long-term angiographic and clinical outcome after percutaneous transluminal coronary angioplasty and intracoronary radiation therapy in humans

BACKGROUND

Ionizing radiation has been shown to reduce neointimal formation after balloon angioplasty in experimental models of restenosis. This study was designed to evaluate the feasibility, safety, and effectiveness of intracoronary radiation therapy (ICRT) after percutaneous transluminal coronary angioplasty (PTCA) for preventing restenosis in human coronary arteries.

METHODS AND RESULTS

Twenty-one patients (22 arteries) with unstable angina underwent standard balloon angioplasty. ICRT was performed with the use of an 192Ir source wire that was hand delivered to the angioplasty site. Angiographic follow-up was performed at 24 hours, between 30 and 60 days, and at 6 months. Angioplasty was successful in 19 of 22 lesions, and insertion of the radioactive source wire was successful at all treated sites. Angiographic study at 24 hours demonstrated early late loss of the luminal diameter from 1.92+/-0.55 to 1.40+/-0.27 mm. Between 30 and 60 days, repeat angiography demonstrated total occlusion in 2 arteries, a new pseudoaneurysm in 1 artery, and significant dilatation at the treatment site in 2 additional vessels. At > or = 6 months' follow-up, all remaining arteries (n=20) maintained patent, with a mean lumen diameter of 1.65+/-0.8 mm. The calculated late lumen loss was 0.27+/-0.56 mm, and the late loss index was 0.19. Clinical events at 1 year included myocardial infarction in 1 patient, repeat angioplasty to the treated site in 3 patients, and persistent angina in 7 patients.

CONCLUSIONS

These preliminary results demonstrate that ICRT after coronary intervention is feasible and is associated with an acceptable degree of complications and lower rates of angiographic restenosis indexes.

The influence of maternal nicotine exposure on neonatal lung carbohydrate metabolism

The influence of maternal nicotine exposure (1 mg/kg body mass/day) during pregnancy and lactation on energy metabolism of lung tissue of neonatal rats were investigated. The glucose turnover of the lung tissue of the neonatal rats exposed to nicotine via the placenta and mother's milk was 86.4% higher than that of the controls. Glycolysis was however suppressed by 22.7% (P < 0.01). The adenine nucleotide pool (ATP+ADP+AMP) was 32.8% higher for the lungs of the 3 week old neonates exposed to nicotine than that of the control rat lung. After 4 weeks of nicotine withdrawal glycolysis of those animals exposed to nicotine were still inhibited to the same extent than during exposure. The adenine nucleotide pool was 69.95% higher than that of the controls. It is proposed that the inhibition of glycolysis was due to the high ATP/ADP ratio of the lungs of the nicotine exposed rats.

Dendritic transport: quantitative analysis of the time course of somatodendritic transport of recently synthesized RNA

We have previously reported that recently synthesized RNA is selectively transported into the dendrites of hippocampal neurons grown in culture (Davis et al., 1987). The present study provides further details about this transport process, focusing especially on the velocity of transport, by comparing the velocity of dendritic transport of RNA in neurons of different ages and in the branched and unbranched dendrites of individual neurons. In our previous study, we recognized that calculations of transport velocity could be compromised because transport was being evaluated in a population of dendrites of varying lengths. The present study uses a mathematical modeling approach to determine how the morphology of the population of dendrites would affect the analysis of transport velocity. Focusing first on a simple model, we compared the distribution of transported material at various times when all dendrites were of the same length and when the population included dendrites of different lengths. We found that the distance of labeling increased linearly over time when all dendrites were of the same length, but increased with a negatively accelerating curve when dendrites were of different lengths. We then determined the actual distribution of dendritic lengths in cultured hippocampal neurons, based on immunostaining with an antibody directed against the selective dendritic marker, microtubule-associated protein 2 (MAP2). Using a computer model, we calculated the mean distance of transport as a function of time in this population of dendrites, assuming different velocities of transport. The velocity that best fit the measured distances of RNA transport in both 7- and 15-d-old neurons was 11 microns/hr (0.26 mm/d). However, for the dendrites exhibiting the longest distance of labeling, the best-fitting curve assumed a velocity of 21 microns/hr in both 7- and 15-d-old neurons (0.50 mm/d). Comparisons of transport in branched and unbranched dendrites revealed that the distance of labeling over branched dendrites was consistently longer than over unbranched dendrites of individual neurons. However, neurons with a larger proportion of branched dendrites did not exhibit a greater mean distance of transport. The density of silver grains was higher over branched than over unbranched dendrites, suggesting that a greater amount of recently synthesized RNA may be transported into branched dendrites. Taken together, these results suggest that RNA transport into dendrites is regulated differentially in the dendrites of individual neurons.

Associative synaptic potentiation and depression: quantification of dissociable modifications in the hippocampal dentate gyrus favors a particular class of synaptic modification equations

This report further characterizes associative long-term synaptic modification of the ipsilateral and contralateral synapses formed by the bilateral entorhinal cortical (EC) projection to the dentate gyrus (DG). The experimental model is the anesthetized hooded rat. The quantitative results qualify this system as a model for studying the rules of associative synaptic modification formulated in terms of individual synapses. Bilateral DG microelectrodes recorded both ipsilateral and contralateral EC-DG responses before and after brief, high-frequency EC conditioning stimulation. The weak contralateral pathway received high-frequency conditioning before, during, or after similar conditioning of the strong, converging ipsilateral pathway. Statistical analyses revealed two types of significant, dissociated synaptic modifications, which depend on the relationship of the ipsilateral and contralateral afferents. First, contralateral EC-DG responses potentiated or depressed when the converging ipsilateral responses concurrently either potentiated or remained unchanged. Second, contralateral EC-DG responses potentiated, depressed, or showed no change when the collateral ipsilateral responses concurrently either potentiated or remained unchanged. Correlation and contingency table analyses indicated that changes in the contralateral synaptic responses are not well predicted by changes at either neighboring synapses of the converging ipsilateral pathway or at synapses of the collateral ipsilateral pathway. The contingencies of associated pre- and postsynaptic activation determined by the conditioning paradigm, however, accurately predicted the altered synaptic responses of both ipsilateral and contralateral EC-DG pathways. The results imply that associative synaptic modification in the EC-DG system is specific to individual synapses and requires both appropriate presynaptic and postsynaptic activation. Because this system provides suitable controls for nonspecific effects of conditioning stimulation and because modification of neighboring synapses is dissociable, the EC-DG system can be used to study further those rules of activity-dependent associative modification that are formulated in terms of individual synapses. The discussion briefly considers published rules of synaptic modification, pointing out several rules that are not consistent with the experimental observations and one that agrees with the present results.

Vitamin-K status beyond the neonatal period. A prospective study in normal breast-fed and formula-fed infants

Vitamin K-dependent clotting factors (FII, FVII, FX) and PT and TT were studied prospectively in 113 healthy newborns during the first 6 weeks of life. No vitamin K prophylaxis was given. Infants were divided into three groups: breast fed, formula fed or combination. The method of nutrition could not be found to influence the coagulation status.

Karyotyping, red blood cell and haemoglobin typing of the mithun (Bos frontalis), its wild ancestor and its hybrids

In Bhutan in remote parts of the Himalayas the mithun (Bos frontalis) has been used probably for centuries in an ingenious system for crossbreeding with domestic cattle which results in highly profitable hybrid females. The hybrid males are infertile and so far no stable crossbreed has been developed. Genetic analyses reported in this paper support the view that the gaur is the wild ancestor of the mithun. Both have only 58 chromosomes in contrast to 60 in cattle and also different, hitherto undescribed haemoglobins and blood groups which would justify the revision of the present classification of the subfamily Bovinae. If, with the aid of modern genetic methods, a stable crossbreed could be developed, dairy and beef production in Bhutan and many climatically similar areas could benefit greatly. Because of its remarkable size the mithun may, in the hands of enterprising breeders, also make a useful genetic contribution to beef production elsewhere.

The control of peroxidase-catalysed iodination and de-iodination

It has been demonstrated that the H2O2/l ratio is a critical factor in the control of iodination and de-iodination of covalently bound tyrosyl residues in proteins and free iodotyrosines by peroxidase enzymes. This has been shown for myeloperoxidase (MPO) isolated from normal human polymorphonuclear lymphocytes in particular, and also for peroxidase of animal origin such as thyroid peroxidase (TPO) and lactoperoxidase (LPO). It has been shown that the H2O2/l ratio exerts a controlling influence on MPO-catalysed reactions of fully iodinated tyrosines, e.g. di-iodotyrosine, and of partially and completely iodinated thyronines such as thyroxine and tri-iodothyronine. Using an in vivo model system it has been shown that MPO catalyses the sequential events of iodination, iodine exchange and de-iodination of tyrosines and, furthermore, that all three reactions are influenced by the rate of H2O2 generation and the iodide concentration of the reaction medium. The action of MPO on iodothyronine substrates only affects de-iodination irrespective of whether the iodothyronine is partially iodinated, as in tri-iodothyronine, or completely iodinated, as in thyroxine. This MPO-catalysed de-iodination of thyroxine and tri-iodothyronine can also be regulated by the H2O2/l ratio. Moreover, the results show that MPO-catalysed iodine exchange can only occur in completely iodinated tyrosines such as di-iodotyrosine (DIT). Iodine exchange in partially iodinated tyrosines such as mono-iodotyrosine (MIT) or in iodothyronines (T3 and T4) cannot be catalysed by MPO irrespective of the H2O2/l ratio. These results introduce a new concept which may be important in understanding the control of thyroid activity in thyroid disease and the control of MPO activity in biological defence mechanisms in man.

Left ventricular function in terminal uremia. A hemodynamic and echocardiographic study

14 patients with advanced uremia had a mean cardiac index (CI) of 4.37 +/- 0.25 liters/min/m2, a mean stroke work index (SWI) of 65.6 +/- 3.7 g/m/m2 and a mean left ventricular filling pressure (LVFP) of 16.3 +/- 2.1 mm Hg. The left ventricular performance was estimated to be normal when CI or SWI changes were correlated with simultaneous variation of the LVFP attained during peritoneal dialysis or afterload reduction. CI was high at a normal LVFP, it decreased at low or high LVFP. Guanidines retention, metabolic acidosis and hypocalcemia did not prevent the maintenance of a high CI or SWI. Out of 32 patients, left ventricular hypertrophy and pericardial effusion, conditions which may affect ventricular distensibility, were present in 25 and in 22 echocardiograms, respectively. We suggest that in uremic subjects, LVFP is primarily influenced by volume loads and by ventricular distensibility modifications.

Blockade and stimulation of renal, adrenal, and vascular angiotensin II receptors with 1-Sar, 8-Ala angiotensin II in normal man

We have assessed the capacity of an analogue of angiotensin II (A II), 1-Sar, 8-Ala A II (P113) in normal man to stimulate and block responses to A II in four systems: blood pressure was monitored directly from an arterial catheter, and renal blood flow was measured with 133Xe and arterial renin and aldosterone concentrations by radioimmunoassay. The 31 normal subjects were in balance on a daily intake of 200 meg sodium and 100 meq potassium to suppress endogenous renin. P113 administered intravenously induced a dose-related renal blood flow reduction, with a threshold dose of 0.1 mug/kg/min. This dose also induced a small but significant increase in arterial blood pressure and plasma aldosterone as well as a reduction in plasma renin activity. In contrast to its effect on the renal vasculature, no tendency to a progressive response in the latter three parameters was noted as the P113 dose was increased 30-fold, to 3.0 mug/kg/min. P113 also reduced the clearance of para-aminohippurate, creatinine, sodium, and potassium, a pattern similar to that induced by A II. P113 at 0.1 mug/kg/min reduced significantly the blood pressure and renal vascular and aldosterone responses to graded doses of A II. Higher P113 doses totally obliterated all three responses to A II infused at 10 ng/kg/min, a dose that provides arterial A II concentrations in the range found in angiotensin-mediated hypertension. When A II was infused first, to induce a pressor, renal vascular, and aldosterone response, P113 induced a dose-related reversal of the response in each system. In conclusion, P113 is a partial agonist in normal man, inducing an angiotensin-like response in settings in which endogenous A II is not playing a tonic role, and displaying dominant antagonist activity in settings in which A II is active. Moreover, the studies suggest that the receptors mediating the responses to A II are different in the renal vasculature and other systemic vascular beds. The adrenal receptor must also differ. This agent should be useful in dissecting the role of A II in diseases characterized by hypertension or abnormalities of renal and adrenal function.

Renal blood flow and its response to angiotensin II. An interaction between oral contraceptive agents, sodium intake, and the renin-angiotensin system in healthy young women

A variety of estrogen- and progestin-containing oral contraceptive agents reduced renal blood flow (RBF) significantly in 23 healthy, nonhypertensive young women, to a mean of 75 +/- 3.3% of the value expected for their age and dietary sodium intake (P less than 0.001). There was also significant activation of the renin-angiotensin system: renin substrate was increased approximately 3-fold in association with a striking increase in the circulating renin activity and angiotensin II levels in relation to sodium intake and excretion. Two observations suggest that the RBF reduction was directly mediated by angiotensin II. A correlation was demonstrable between circulating angiotensin II and RBF (P less than 0.01), and renal vascular responsiveness to angiotensin II infused into the renal artery was reduced significantly (P less than 0.001). Moreover, the oral contraceptive agents modified the basic relationship between sodium balance and vascular responsiveness to angiotensin II, suggesting that the agents acted through some mechanism other than alteration in the state of sodium balance. These observations provide further evidence for an important role of angiotensin II as a determinant of RBF. Renal vasoconstriction may contribute to the genesis of a number of complications, such as sodium retention and hypertension, associated with oral contraceptive use.