Früherkennung von Typ-1-Diabetes durch Inselautoantikörper-Screening – ein Positionspapier der Fr1daPlex-Projektleiter und -Schulungszentren, des BVKJ Bayern und PaedNetz Bayern e.V

Dieses Positionspapier basiert auf der langjährigen klinischen Erfahrung und grundlagen-wissenschaftlichen Forschung der Autoren zur Diagnose und Behandlung von Kindern und Jugendlichen mit einem präsymptomatischen Frühstadium des Typ-1-Diabetes. Der Nutzen sowie potenzielle Nachteile der Früherkennung von Typ-1-Diabetes durch ein Inselautoantikörper-Screening werden kritisch diskutiert. Zudem werden die Perspektiven einer Verzögerung des Ausbruchs der klinischen Stoffwechselerkrankung durch eine Teplizumab-Behandlung adressiert. Wir sehen heute die Chance einer relevanten Verbesserung der therapeutischen Möglichkeiten und der Lebensperspektive betroffener Kinder und Jugendlicher. Wichtige nächste Schritte für die Implementierung eines Inselautoantikörper-Screenings in Deutschland sind die Fortbildung der Kinder- und Jugendärzte, die über das Screening aufklären sollen, die Etablierung von wenigen überregionalen Laboratorien, die die Testung durchführen, und die Ausweitung regionaler Kapazitäten für Schulung und Betreuung der Kinder mit einem Frühstadium des Typ-1-Diabetes. This position paper is based on the authors' many years of clinical experience and basic science research on the diagnosis and treatment of children and adolescents with a presymptomatic early stage of type 1 diabetes. The benefits as well as potential disadvantages of early detection of type 1 diabetes by islet autoantibody screening are critically discussed. In addition, the perspectives of delaying the onset of the clinical metabolic disease through treatment with teplizumab are addressed. Today, we see the chance of a relevant improvement in the therapeutic options and life perspectives of affected children and adolescents. Important next steps for the implementation of islet autoantibody screening in Germany are the training of pediatricians who should inform families about the screening, the establishment of a few transregional laboratories that carry out the test, and the expansion of regional capacities for the training and care of children with an early stage of type 1 diabetes.

SARS-CoV-2 Infections and Presymptomatic Type 1 Diabetes Autoimmunity in Children and Adolescents From Colorado, USA, and Bavaria, Germany

This study screens more than 50 000 youths in diverse populations of Colorado and Bavaria to assess whether previous SARS-CoV-2 infection was associated with autoimmunity, which predicts future type 1 diabetes.

Assessment of the quality of routine ambulatory healthcare for common disorders in children and adolescents in Germany: study protocol for a retrospective medical record review (QualiPäd)

INTRODUCTION

The quality of healthcare in childhood and adolescence is of key importance, in order to foster a healthy development and to avoid chronic health problems. Yet, data for Germany regarding the quality of healthcare for this patient group are lacking. The QualiPäd research project aims to estimate the quality of outpatient healthcare for children and adolescents in Germany, focusing on common psychiatric and physical disorders.

METHODS AND ANALYSIS

Quality indicators for seven common physical and mental childhood and adolescent clinical conditions (attention deficit/hyperactivity disorder, asthma, atopic dermatitis, depression, otitis media, conduct disorder/oppositional defiant disorder, tonsillitis) will be developed and ratified by experts, using the RAND/UCLA Appropriateness Method.Initially, 1400 medical records of children and adolescents with one of the aforementioned clinical conditions will then be randomly drawn from 40 outpatient practices in the German federal state of Hessen. The records will then be assessed regarding their adherence to the respective quality indicators. Based on this, the percentage of appropriate and inappropriate (eg, wasteful) healthcare of all clinical conditions (primary endpoint) will be estimated. Additionally, possible factors influencing the quality of care (eg, patient characteristics, type of condition, type of practice) will be identified using generalised estimation equation models.

ETHICS AND DISSEMINATION

This study will show for which of the studied clinical conditions and/or patients improvement of quality of care is necessary within the German health system. Also, the quality indicators designed for the study can afterwards be implemented in regular care and thus enable regular reporting of the outpatient care of this target group. The authors plan to disseminate their findings through international, peer-reviewed scientific publications, and through presentations at national and international paediatric and child psychiatric conferences.

TRIAL REGISTRATION NUMBER

DRKS00022408.

Symptoms, SARS-CoV-2 Antibodies, and Neutralization Capacity in a Cross Sectional-Population of German Children

Background: Children and youth are affected rather mildly in the acute phase of COVID-19 and thus, SARS-CoV-2 infection infection may easily be overlooked. In the light of current discussions on the vaccinations of children it seems necessary to better identify children who are immune against SARS-CoV-2 due to a previous infection and to better understand COVID-19 related immune reactions in children. Methods: In a cross-sectional design, children aged 1-17 were recruited through primary care pediatricians for the study (a) randomly, if they had an appointment for a regular health check-up or (b) if parents and children volunteered and actively wanted to participate in the study. Symptoms were recorded and two antibody tests were performed in parallel directed against S (in house test) and N (Roche Elecsys) viral proteins. In children with antibody response in either test, neutralization activity was determined. Results: We identified antibodies against SARS-CoV-2 in 162 of 2,832 eligible children (5.7%) between end of May and end of July 2020 in three, in part strongly affected regions of Bavaria in the first wave of the pandemic. Approximately 60% of antibody positive children (n = 97) showed high levels (>97th percentile) of antibodies against N-protein, and for the S-protein, similar results were found. Sufficient neutralizing activity was detected for only 135 antibody positive children (86%), irrespective of age and sex. Initial COVID-19 symptoms were unspecific in children except for the loss of smell and taste and unrelated to antibody responses or neutralization capacity. Approximately 30% of PCR positive children did not show seroconversion in our small subsample in which PCR tests were performed. Conclusions: Symptoms of SARS-CoV-2 infections are unspecific in children and antibody responses show a dichotomous structure with strong responses in many and no detectable antibodies in PCR positive children and missing neutralization activity in a relevant proportion of the young population.

Bacillus thuringiensis protein transfer between rootstock and scion of grafted poplar

Bacillus thuringiensis (Bt) Cry1Ac protein is a toxin against different leaf-eating lepidopteran insects that attack poplar trees. In the present study, the mode of migration of the Bt-Cry1Ac protein within poplar grafts was investigated. Grafting was done using Pb29 (transgenic poplar 741 with cry1Ac genes), CC71 (transgenic poplar 741 with cry3A genes), non-transgenic poplar 741 and non-transgenic Populus tomentosa, either as scion or as rootstock. In order to detect migration of Bt-Cry1Ac protein from one portion of the graft union to different tissues in the grafted plant, ELISA analysis was employed to assess the content of Bt-Cry1Ac protein in the phloem, xylem, pith and leaves of the grafted poplar. To further verify migration of Bt-Cry1Ac protein, Clostera anachoreta larvae, which are susceptible to Bt-Cry1Ac protein, were fed leaves from the control graft (i.e., graft portion that originally did not contain Bt-Cry1Ac protein). The results showed that Bt-Cry1Ac protein was transported between rootstock and scion mainly through the phloem. Migration of Bt-Cry1Ac protein in the grafted union was also evidenced in that the leaves of the control graft did have a lethal effect on C. anachoreta larvae in laboratory feeding experiments.

Bacillus thuringiensis protein transfer between rootstock and scion of grafted poplar

Bacillus thuringiensis (Bt) Cry1Ac protein is a toxin against different leaf-eating lepidopteran insects that attack poplar trees. In the present study, the mode of migration of the Bt-Cry1Ac protein within poplar grafts was investigated. Grafting was done using Pb29 (transgenic poplar 741 with cry1Ac genes), CC71 (transgenic poplar 741 with cry3A genes), non-transgenic poplar 741 and non-transgenic Populus tomentosa, either as scion or as rootstock. In order to detect migration of Bt-Cry1Ac protein from one portion of the graft union to different tissues in the grafted plant, ELISA analysis was employed to assess the content of Bt-Cry1Ac protein in the phloem, xylem, pith and leaves of the grafted poplar. To further verify migration of Bt-Cry1Ac protein, Clostera anachoreta larvae, which are susceptible to Bt-Cry1Ac protein, were fed leaves from the control graft (i.e., graft portion that originally did not contain Bt-Cry1Ac protein). The results showed that Bt-Cry1Ac protein was transported between rootstock and scion mainly through the phloem. Migration of Bt-Cry1Ac protein in the grafted union was also evidenced in that the leaves of the control graft did have a lethal effect on C. anachoreta larvae in laboratory feeding experiments.

Hospital separations indicate increasing need for prevention of diabetic foot complications in central Australia

The aim of this study was to guide service provision for prevention of diabetic foot complications through the analysis of hospital separation data for those with diabetes in central Australia. We reviewed the hospital separation data for central Australia from 1992 to 1997 for adults known to be diabetic and those with diabetic foot complications. Foot complications were identified from International Classification of Diseases-9th Revision (ICD-9) codes. Additionally, we assessed the proportion of cases with diabetic foot, identified by ICD-9 coding and confirmed by record review, that were identified by Australian National-Diagnostic Related Group-Version 3 (AN-DRG-3) coding. Separations with diabetes doubled from 352 in 1992 to 796 in 1997. This represents an increase from 1232 to 2521 separations per 100,000 people over 15 years of age. Separations with foot complications increased threefold from 28 in 1992 to 90 in 1997, a rate increase from 98 to 285 per 100,000 people over 15 years of age. The proportion of diabetes separations that had foot complications remained around 10% during the 6 year period. Aboriginal people made up 89% of the individuals with foot complications and 91% of separations for diabetic foot. Foot complications were predominantly of the more acute type (90%), amenable to early intervention. The AN-DRG-3 code for diabetic foot identified only 59% (37/63 in 1997) of the separations identified by the ICD-9 codes, and admitted primarily for foot complications in Alice Springs Hospital. The known burden of hospital care for diabetes and diabetic foot complications has increased markedly in recent years. A combination of changes in prevalence, primary care utilisation, detection, hospital access or re-admission rates may underlie the observed increases. As it is very unlikely that diabetes or diabetic foot complications are being over diagnosed, or that the hospitals are over utilised, this analysis shows there is an increasingly apparent need for improved prevention of diabetic foot complications. Therefore primary health care systems should ensure that they implement evidence-based care for preventing foot complications among people with diabetes.

Assessment of the nucleotide sequence variability in the bovine T-cell receptor alpha delta joining gene region

The sequence of 2,193 nucleotides from the bovine T-cell receptor alpha/delta joining gene region (TCRADJ) was determined and compared with the corresponding human and murine sequences. The identity was 75.3% for the comparison of the Bos taurus vs. the Homo sapiens sequence and 63.8% for the Bos taurus vs. the Mus musculus sequence. This comparison permitted the identification of the putatively functional elements within the bovine sequence. Direct sequencing of 2,110 nucleotides in nine animals revealed 12 variable sites. Estimates, based on direct sequencing in three Holstein Friesian animals, for the two measures of sequence variability, nucleotide polymorphism (u) and nucleotide diversity (p), were 0.00050 (60.00036) and 0.00077 (60.00056), respectively. The test statistic, Tajima's D, for the comparison of the two measures indicates that the difference between u and p is close to significance (P < 0.05), suggesting the possibility of selective forces acting on the studied genomic region. Allelic variation at 5 of the 12 variable sites was analysed in 359 animals (48 Anatolian Black, 56 Braunvieh, 115 Fleckvieh, 47 Holstein Friesian, 50 Simmental and 43 Pinzgauer) using the oligonucleotide ligation assay (OLA) in combination with the enzyme linked immunoabsorbant assay (ELISA). Nine unambiguous haplotypes could be derived based on animals with a maximum of one heterozygous site. Four to seven haplotypes were present in the different breeds. When taking into account the frequencies of the haplotypes in the different breeds, especially in Anatolian Black, an ancestral cattle population, we could establish the likely phylogenetic relationships of the haplotypes. Such haplotype trees are the basis for cladistic candidate gene analysis. Our study demonstrates that the systematic search of single nucleotide polymorphisms (SNPs) is useful for analysing all aspects of variability of a given genomic region.

Insulin-like growth factor I (IGF-I) and long R(3)IGF-I differently affect development and messenger ribonucleic acid abundance for IGF-binding proteins and type I IGF receptors in in vitro produced bovine embryos

The insulin-like growth factor (IGF) system is a complex network, including ligands (IGF-I and -II), binding proteins (IGFBP-1 to -6), and receptors, of which the type I IGF receptor (IGF-I-R) is important for transmission of most biological effects of IGFs. As IGFs are secreted in large amounts by the female reproductive tract, it has been hypothesized that maternal IGFs may affect embryonic growth and differentiation in a fine-tuned manner, involving modulation of IGF effects by embryonic IGFBP and IGF-I-R expression. To address this point, we cultured in vitro produced bovine embryos in a chemically defined culture system in the presence (100 ng/ml) of recombinant human IGF-I, long R(3)IGF-I (LR(3)), or without IGF supplementation (control). The affinity of LR(3) to IGFBPs measured by competition assays and Western ligand blots is at least 3 orders of magnitude lower than that of IGF-I. LR(3) was most efficient in stimulating early embryonic cleavage, whereas further development was most potently supported by IGF-I. Total cell numbers of blastocysts were highest in the presence of LR(3) (105 +/- 4), followed by IGF-I (96 +/- 5), and the control group (91 +/- 3; P < 0.05). Differential cell staining of blastocysts revealed that these differences were mainly represented by trophectoderm cell numbers. Analysis of messenger RNA (mRNA) expression for IGFBPs and IGF-I-R was performed by RT-real-time PCR, using expression of the nonregulated housekeeping gene glyceraldehyde-3-phosphate dehydrogenase for normalization. Embryonic IGFBP-2 mRNA levels in the LR(3) treatment group were 1.7-fold (P < 0.001) and 2.8-fold (P < 0.001) higher than those in the IGF-I and control groups, respectively. IGFBP-5 mRNA levels were about 2-fold (P < 0.001) elevated in both IGF treatment groups, with slightly (P < 0.05) higher levels in IGF-I- than in LR(3)-treated embryos. Similarly, IGFBP-3 mRNA abundance was increased (P < 0.05) in embryos from the IGF-I vs. the LR(3) culture system. IGF-I-R mRNA levels were reduced by IGF-I (80% of control; P < 0.01), but increased by LR(3) (1.3-fold vs. control; P < 0.001). These data show that the affinity for IGFBPs of IGF peptides is relevant for their effects on preimplantation embryos and affects different parameters, i.e. development, cell numbers, and mRNA expression for components of the IGF system, in different directions.

[Study on effect of ABA, PEG4000 and AgNO3 on number of somatic embryos of Larix Principis-Rupprechtii by 311-A regression design]

This paper, the effects of ABA, PEG400 and AgNO3 on the number of somatic embryos of Larix Principis-Rupprechtii were carried out by 311-A regression design. The regression equation was established which expresses the number of somatic embryos of Larix Principis-Rupprechtii as function, and the ABA, PEG400 and AgNO3 on as variable respectively. Using the regression equation, the single factor effect and mutual effect between the number of somatic embryos of Larix Principis-Rupprechtii and ABA, PEG400 and AgNO3 was studied; the optimum concentration recipes can be obtained by computer processing, that are ABA: 18.9138 mg/L, PEG400: 88.8007 g/L and AgNO3: 10.7513 mg/L, the target somatic embryos number is 107.5278 each gram callus. The results of experiment showed that this method is simple, practical and rapid for selecting several hormone category and concentration recipes media of conifer somatic embryogenesis.

[The somatic embryogenesis and establishment of transformation experiment system in Larix principis-Rupprechtii]

Larix principis-Rupprechtii is one of the superior afforestation forest trees growing in north China. Embryogenic cultures were initiated from immature zygotic embryos of Larix principis-Rupprechtii on S culture medium containing 2, 4-D 0-2.2 mg/L, KT and BA each at 0-0. 8 mg/L. Embryogenic calli were subcultured and multiplicated on S + B culture medium containing dropping off each hormone concentration. We set up 33 steady-going embryogenic cell lines; We studied on the growth stage and genotype differences of every embryogenic cell lines; and Finded more than 10 high-frequency somatic embryogenesis cell lines such as 2K, 2T, 2I, 2J, 3C etc.. The number of 2T somatic embryos reaches 314/per gram of embryogenic tissue and the number of 3C somatic embryos is 185/per gram of embryogenic tissue. The re-induction method of Larix principis-Rupprechtii from somatic embryos was used to produce renewable embryogenic cultures and steady-going embryogenic cell lines effectively. Mature somatic embryos can germinate and develop further into plantlets when they are isolated and cultured on a hormone-free WPM culture medium. The regeneration plantlets were obtained. Furthermore, the transformation with a truncated gene of Bacillus thuringensis (B. t) were carried out, the PCR showed positive results, because of this, embryogenic cell line of Larix principis-Rupprechtii can be used for transformation experiments to support further breeding in forestry.

Characterization and chromosomal localization of the chicken avidin gene family

Chicken avidin is a biotin-binding protein expressed under inflammation in several chicken tissues and in the oviduct after progesterone induction. The gene encoding avidin belongs to a family that has been shown to include multiple genes homologous to each other. The screening and chromosomal localization studies performed to reveal the structure and organization of the complete avidin gene family is described. The avidin gene family is arranged in a single cluster within a 27-kb genomic region. The cluster is located on the sex chromosome Z on band q21. The organization of the genes was determined and two novel avidin-related genes, AVR6 and AVR7, were cloned and sequenced.

Possible community immunity to small round structured virus gastroenteritis in a rural aboriginal community

In April 1998 an outbreak of gastroenteritis affected visitors, but none of the Aboriginal residents, at a Territory Health Services luncheon in a rural Aboriginal community in Central Australia. The epidemiological features and identification of Small Round Structured Virus (SRSV) from two participants suggest that this was an outbreak caused by a SRSV. The attack rate in the visitors who ate or drank food at the luncheon was 73% (11 of 15). Seventeen Aboriginal residents were interviewed, none had gastroenteritis. The community potable water supply was contaminated with faecal bacteria around the time of the outbreak. No particular food could be implicated and laboratory examination of foods was not possible. It is proposed that past exposure to SRSVs may have resulted in the Aboriginal residents developing clinical immunity to infection. The process and consequences of the investigation in this community are also discussed.

Construction and characterisation of a gridded chicken cosmid library with four-fold genomic coverage

Gridded genomic libraries are crucial for the positional candidate gene approach. For this purpose we constructed a gridded genomic library from a female chicken using the vector sCos 1. About 110,000 cosmid clones were grown and replicated in 384-well plates. An average insert size of 39 kb was calculated from the analysis of 68 randomly selected clones. No chimerism could be observed from 31 in situ hybridisations. One replica of the library (number 125) has been transferred to the Resource Centre/Primary Database (RZPD) of the German Human Genome Project (DHGP). The whole library was gridded onto four nylon filters at high density for efficient identification of cosmid clones by colony hybridisation. Twenty-two probes were used for screening the library and each of them gave at least one positive signal. This result is in good agreement with a four-fold coverage of the genome as estimated from the insert length and number of recombinant clones. This library provides a powerful tool for rapid physical mapping and complex analysis of the chicken genome.

Determination of fat in olestra-containing savory snack products by capillary gas chromatography

A quantitative method to determine fat in olestra-containing savory snack products was validated within the AOAC Peer-Verified Methods Program. The method may be used to demonstrate compliance with the guidelines of the U.S. Nutrition Labeling and Education Act for labeling products as "fat free" or "low fat." The method can measure total and saturated fat in savory snacks when present at levels of 0.2-10 g total fat and 0.1-3 g saturated fat per 30 g serving. The method is standardized to measure C6-C24 fatty acids. Extraction of olestra-containing savory snack samples with chloroform-methanol (modified AOAC Official Method 983.23) yields a lipid extract containing the total fat and olestra. The extracted lipid is hydrolyzed by lipase, yielding fatty acids and unreacted olestra. The fatty acids are precipitated as calcium soaps. Olestra is extracted from insoluble soaps with hexane and then discarded. The isolated soaps are converted back into fatty acids with hydrochloric acid and extracted with hexane. The isolated fatty acids are converted to methyl esters with boron trifluoride-methanol and quantitated by capillary gas chromatography using internal standard. Test samples were prepared by blending olestra-containing and full-fat (triglyceride) snacks to obtain 6 levels of spiking (0-10 g total fat added/30 g serving) in potato chips, potato crisps, cheese puffs, and nacho cheese-flavored corn chips. Results were linear (r2 > 0.997) between 0 and 10 g fat/30 g serving for each product matrix. Mean recovery was 101 +/- 6% standard deviation (SD) for total fat and 104 +/- 6% SD for saturated fat. Mean recovery by peer laboratory was 88 +/- 5% SD for total fat and 95 +/- 4% SD for saturated fat in potato chips (0-3 g total fat added/30 g serving). Two sets of 10 replicates of potato chips (0.5 g total fat/30 g serving and 0.16 g saturated fat/30 g serving) and potato crisps (0.5 g total fat/30 g serving and 0.16 g saturated fat/30 g serving) were analyzed by submitting and peer laboratories. Repeatability relative standard deviations ranged from 3.90 to 7.33% for total fat and from 4.01 to 11.53% for saturated fat. Reproducibility relative standard deviations were 7.33% (total fat, potato chips), 7.15% (total fat, potato crisps), 11.36% (saturated fat, potato chips), and 13.50% (saturated fat, potato crisps).

Malaria acquired in the Torres Strait

Two cases of Plasmodium vivax malaria acquired in the Torres Strait during 1997 are reported. The source of infection could not be firmly established but two possibilities are discussed. Anopheline mosquitoes are present in the Torres Strait, and malaria is frequently imported from Papua New Guinea (PNG), thus transmission by local mosquitoes poses an ongoing threat. However, in this particular location, Badu Island, no recent importation of malaria was identified and mosquito surveillance demonstrated low numbers of anopheline species at the time and for the preceding two years. These cases could also feasibly be explained by a variant of 'baggage malaria' in which mosquitoes already infected with the malaria parasite were imported from PNG in one of the small boats that regularly make this journey. These cases serve as a reminder to health care providers in northern Australia to consider the diagnosis of malaria in patients presenting with a febrile illness.

Biosynthesis of taxol: enzymatic acetylation of 10-deacetylbaccatin-III to baccatin-III in crude extracts from roots of Taxus baccata

The biosynthesis of taxol is a multistep process. One intermediate reaction is the acetylation of 10-deacetylbaccatin-III (10-DAB) to baccatin-III, an assumed precursor of taxol. Here we describe the cell free acetylation of 10-DAB in crude extracts from roots of Taxus baccata saplings using 14C-or 3H-labeled acetyl-coenzyme A as the acetyl donor. The reaction is strictly dependent on the addition of 10-DAB and is specific for the 10-hydroxyl group of the taxane ring. Formation of radiolabeled baccatin-III was confirmed by co-chromatography of the labeled product with authentic baccatin-III in different TLC-systems and HPLC. Furthermore, the acetylation product showed an identical UV spectrum as authentic baccatin-III. Crude extracts from cambium of stems yielded three- to fivefold lower activity. This is in agreement with our finding that the taxol titer in roots was considerably higher than that in cambium.

Time-sensitive reversal of hyperplasia in transgenic mice expressing SV40 T antigen

The role of viral oncoprotein expression in the maintenance of cellular transformation was examined as a function of time through controlled expression of simian virus 40 T antigen (TAg). Expression of TAg in the submandibular gland of transgenic mice from the time of birth induced cellular transformation and extensive ductal hyperplasia by 4 months of age. The hyperplasia was reversed when TAg expression was silenced for 3 weeks. When TAg expression was silenced after 7 months, however, the hyperplasia persisted even though TAg was absent. Although the polyploidy of ductal cells could be reversed at 4 months of age, cells at 7 months of age remained polyploid even in the absence of TAg. These results support a model of time-dependent multistep tumorigenesis, in which virally transformed cells eventually lose their dependence on the viral oncoprotein for maintenance of the transformed state.

Parasitological and serological studies on the prevalence of Echinococcus multilocularis Leuckart, 1863 in red foxes (Vulpes vulpes Linnaeus, 1758) in Switzerland

In the Canton of Zurich in Switzerland, 1,252 red foxes (Vulpes vulpes) were examined during 1990-1991 for intestinal stages of Echinococcus multilocularis using the mucosal smear technique. Special safety precautions were employed during examination. An average of 35% (432 foxes) were infected, mostly with low to medium numbers of gravid worms producing thick-shelled eggs. In the eleven districts of the Canton, prevalence rates varied between 13% and 57%. An average of 29% of the foxes had antibodies in serum or body fluid against a highly species-specific antigen of E. multilocularis (Em2-antigen). The fact that foxes with intestinal E. multilocularis infection have been found in all parts of the Canton of Zurich indicates a relatively high potential infection risk for humans, but apparently the risk is reduced by certain extrinsic or intrinsic factors which have yet to be determined.

Detection of Echinococcus coproantigens by enzyme-linked immunosorbent assay in dogs, dingoes and foxes

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of Echinococcus coproantigens in fecal samples from dogs, dingoes or foxes infected with either E. granulosus or E. multilocularis. The ELISA was based on protein-A-purified polyclonal antibodies [anti-E. granulosus excretory/secretory (E/S) antigens]. The specificity of the assay as determined in 155 samples derived from carnivores that were free of helminth infection (n = 37) or infected with non-Echinococcus cestodes (n = 76) or with various nematodes (n = 42) was found to be 98% overall. The diagnostic sensitivity was strongly dependent on the homologous worm burden. All 13 samples from foxes harboring greater than 1,000 E. multilocularis worms and 13 of 15 (87%) samples from dogs or dingoes containing greater than 200 E. granulosus worms were ELISA-positive, whereas 34 of 46 samples from foxes harboring less than 1,000 E. multilocularis and 9 of 10 samples from dogs or dingoes bearing less than 200 E. granulosus tested negative. Experimental prepatent infections of dogs with E. granulosus revealed positive ELISA reactions within the prepatent period (10-20 days post-infection) for six animals bearing greater than 1,000 E. granulosus each; a low worm burden (less than 1,000 tapeworms/animal) resulted in ELISA positivity in only 2 of 3 animals at 30 days post-infection at the earliest. All five dogs that had been experimentally infected with E. multilocularis tested positive in the coproantigen ELISA as early as on day 5 post-infection.

Kinetics of calcium-dependent inactivation of calcium current in voltage-clamped neurones of Aplysia californica

Ca currents flowing during voltage-clamp depolarizations were examined in axotomized Aplysia neurones under conditions that virtually eliminated other currents. Moderate to large currents exhibited a two-component time course of relaxation that can be approximated reasonably well by the sum of two exponentials. The rapid phase (tau 1 approximately equal to 70 ms at 0 mV) plus the slower phase (tau 2 approximately equal to 300 ms at 0 mV) ride upon a steady, non-inactivating current, I infinity. Conditions that diminish the peak current amplitude, such as reduced stimulus depolarization, inactivation remaining from a prior depolarization, or partial blockade of the Ca conductance by Cd, slowed both phases of inactivation, and all selectively eliminated the tau 1 phase, such that weak currents exhibited only the slower phase of decline. Injection of EGTA slowed both phases of inactivation, decreased the extent of the tau 1 phase, and increased the intensity of I infinity and of the current during the tau 2 phase. For a given voltage, the rate of inactivation increased as the peak current strength was increased, and decreased as the peak current strength was decreased. For a given peak current the rate of inactivation decreased as depolarization was increased. The relation of inactivation to prior Ca2+ entry was essentially linear for small currents, but decreased in slope with time during strong currents. The relation also became shallower with increasing depolarization, suggesting an apparent decrease in the efficacy of Ca in causing inactivation at more positive potentials. The basic kinetics of Ca current inactivation along with experimentally induced changes in those kinetics were simulated with a binding-site model in which inactivation develops during current flow as a function of the entry and accumulation of free Ca2+. This demonstrated that a single Ca-mediated process can account for the two-component time course of inactivation, and that the nearly bi-exponential shape need not arise from two separate processes. The two-component time course emerges as a consequence of a postulated hyperbolic reaction between diminishing probability of channels remaining open and the accumulation of intracellular free Ca2+. The occurrence of a single- or a two-component time course of inactivation thus appears to depend on the levels of internal free Ca2+ traversed during current flow.

Calcium tail currents in voltage-clamped intact nerve cell bodies of Aplysia californica

Calcium tail currents were measured in axotomized Aplysia neurones L2-L6 using a two-electrode voltage clamp and micro-electrodes of specially low resistance. Measurements were made at -40 mV following depolarizing pulses of 7 or 10 ms duration in the presence of 45 microM-tetrodotoxin and 200 mM-tetraethylammonium. Symmetrical currents were eliminated by addition of digitally stored current traces produced in response to equivalent hyperpolarizations. The remaining current, identified as a tail current, was blocked by replacement of extracellular calcium with cobalt or manganese. Computer fits showed that the tail current closely approximated the sum of two exponentially decaying components. The first had a time constant, tau 1, of 0.38 +/- 0.05 ms, which may have been frequency-limited by the speed of the clamp; the second had a time constant, tau 2, of 2.0 +/- 0.8 ms. A more slowly decaying third tail current component (tau 3 = 30 ms), which developed more slowly, may be related to the non-specific current rather than the calcium current. The tau 1 and tau 2 components of the tail current lost amplitude with increasing pulse duration along an approximately bi-exponential time course that resembled the time course of relaxation of the calcium current during a prolonged depolarization. The slow third component of the tail current showed no such inactivation. The amplitudes of the first and second components of the calcium tail current both increased as sigmoidal functions of the test pulse voltage, reaching half maximum at +20 mV and plateauing above +60 mV. The voltage dependencies of the two components were similar. The rate of decay of the tau 1 component increased with increasing temperature and with increasing negative potential, whereas tau 2 showed little dependence on these parameters. The rates of decay of neither the tau 1 nor the tau 2 component were affected by large changes in the amplitude of the test depolarization or in the amplitude of the tail current or by injection of calcium ions or EGTA. Thus, the kinetics of the tail current as resolved under our conditions appear to be virtually independent of calcium-mediated inactivation. Activation time constants (tau m) predicted from tau 1 are 3 to 5 times longer than the values of tau m determined from the half-time to peak of activation. These kinetics are slower than those reported for Limnaea by factors of 2.5 to 3.5.(ABSTRACT TRUNCATED AT 400 WORDS)

Cyclic AMP enhances calcium-dependent potassium current in Aplysia neurons

The effect on the Ca-dependent potassium current, IK(Ca), of procedures that increase intracellular cAMP levels was studied in Aplysia neurons using three different pharmacological approaches. Exposure to cAMP analogues which were either resistant to or protected from phosphodiesterase hydrolysis caused an increase in IK(Ca) from 30 to 50% in 10 min. The degree of reversibility of this effect varied from complete with db cAMP to very little with pcpt cAMP. Exposure to cholera toxin, which stimulates the synthesis of endogenous cAMP, increased IK(Ca) 25% in 10 min and the effect was not reversible. Both approaches were effective in all seven neuron types studied. Application of serotonin plus phosphodiesterase inhibitor caused an increase in IK(Ca) in neuron R15 but not in the other neuron types. Application of pentylene tetrazole (PTZ) led to a decrease in IK(Ca). It is proposed that elevation of cyclic AMP mediates an increased sensitivity of the IK(Ca) channel to Ca ions.

Inactivation of calcium conductance characterized by tail current measurements in neurones of Aplysia californica

Calcium tail currents, recorded at -40 mV after repolarization from 7 or 10 ms voltage-clamp depolarizations in axotomized Aplysia neurones in the presence of tetrodotoxin and tetraethylammonium, were used to investigate the inactivation of the calcium conductance without interference from contaminating potassium currents. Prior depolarization with a prepulse (V1) resulted in a reduction in size of the tail currents recorded following the test pulse (V2). The reduction occurred in both the fast (tau 1 less than 0.4 ms) and slow (tau 2 approximately equal to 2.0 ms) components of the tail current. The degree of inactivation remained constant when tail currents were measured at potentials ranging up to 30 mV on either side of the potassium equilibrium potential. Thus, any changes in potassium current must have contributed virtually nothing to the changes in tail current amplitude seen following presentation of the prepulse. Inactivation was greatest following prepulses to potentials (+10 to +40 mV) that produce maximal entry of calcium ions, and declined to about zero as the prepulse approached the calcium equilibrium potential. For V1 potentials above +50 mV, the prepulse caused an apparent short-term facilitation of V2 tail currents in EGTA-injected neurones. This effect, detected up to 50 ms following the pulse, is of uncertain origin. Pressure injection of calcium ions caused reduction in the size of the tail current, which was restored by subsequent injection of EGTA. Tail current amplitude was reduced by presentation of the prepulse for all test pulse voltages, but the measured inactivation declined exponentially towards a minimum with test pulses of increasingly positive potential. Removal of inactivation following a 200 ms prepulse was greatly accelerated by injection of EGTA. The EGTA-resistant inactivation remaining at short times decayed with a time constant of about 0.12 s. The relation of tail current reduction to prepulse voltage is consistent with the interpretation that the EGTA-resistant inactivation remaining at short times depends on entry of calcium ions during the prepulse, as does the EGTA-sensitive inactivation remaining at later times. It is proposed that the 'EGTA-resistant' phase of inactivation results from loading of EGTA with calcium ions near the inner surface of the membrane during sustained calcium entry, allowing the intracellular calcium concentration to rise. The results provide further evidence for a calcium-mediated inactivation of the calcium conductance.(ABSTRACT TRUNCATED AT 400 WORDS)

Residual calcium ions depress activation of calcium-dependent current

Calcium ions enter and accumulate during depolarization of some cells, activating a potassium current, IK(Ca), that depends on the cytoplasmic concentration of calcium ions, [Ca]i. However, elevation of [Ca]i can depress IK(Ca) elicited by a subsequent membrane depolarization. The depression of IK(Ca) is ascribed here to a [Ca]i-mediated inactivation of the voltage-gated calcium conductance, which causes a net reduction in calcium ions available for the activation of IK(Ca). This suggests that other processes dependent on gated calcium entry may also be depressed by small background elevations in cytosolic free calcium ions.