Sox2 is required for olfactory pit formation and olfactory neurogenesis through BMP restriction and Hes5 upregulation

The transcription factor Sox2 is necessary to maintain pluripotency of embryonic stem cells, and to regulate neural development. Neurogenesis in the vertebrate olfactory epithelium persists from embryonic stages through adulthood. The role Sox2 plays for the development of the olfactory epithelium and neurogenesis within has, however, not been determined. Here, by analysing Sox2 conditional knockout mouse embryos and chick embryos deprived of Sox2 in the olfactory epithelium using CRISPR-Cas9, we show that Sox2 activity is crucial for the induction of the neural progenitor gene Hes5 and for subsequent differentiation of the neuronal lineage. Our results also suggest that Sox2 activity promotes the neurogenic domain in the nasal epithelium by restricting Bmp4 expression. The Sox2-deficient olfactory epithelium displays diminished cell cycle progression and proliferation, a dramatic increase in apoptosis and finally olfactory pit atrophy. Moreover, chromatin immunoprecipitation data show that Sox2 directly binds to the Hes5 promoter in both the PNS and CNS. Taken together, our results indicate that Sox2 is essential to establish, maintain and expand the neuronal progenitor pool by suppressing Bmp4 and upregulating Hes5 expression.

Summary: Analysis of Sox2 mutant mouse and Sox2 CRISPR-targeted chick embryos reveals that Sox2 controls the establishment of sensory progenitors in the olfactory epithelium by suppressing Bmp4 and upregulating Hes5 expression.

Cux2 acts as a critical regulator for neurogenesis in the olfactory epithelium of vertebrates

Signaling pathways and transcription factors are crucial regulators of vertebrate neurogenesis, exerting their function in a spatial and temporal manner. Despite recent advances in our understanding of the molecular regulation of embryonic neurogenesis, little is known regarding how different signaling pathways interact to tightly regulate this process during the development of neuroepithelia. To address this, we have investigated the events lying upstream and downstream of a key neurogenic factor, the Cut-like homeodomain transcription factor-2 (Cux2), during embryonic neurogenesis in chick and mouse. By using the olfactory epithelium as a model for neurogenesis we have analyzed mouse embryos deficient in Cux2, as well as chick embryos exposed to Cux2 silencing (si) RNA or a Cux2 over-expression construct. We provide evidence that enhanced BMP activity increases Cux2 expression and suppresses olfactory neurogenesis in the chick olfactory epithelium. In addition, our results show that up-regulation of Cux2, either BMP-induced or ectopically over-expressed, reduce Delta1 expression and suppress proliferation. Interestingly, the loss of Cux2 activity, using mutant mice or siRNA in chick, also diminishes neurogenesis, Notch activity and cell proliferation in the olfactory epithelium. Our results suggest that controlled low levels of Cux2 activity are necessary for proper Notch signaling, maintenance of the proliferative pool and ongoing neurogenesis in the olfactory epithelium. Thus, we demonstrate a novel conserved mechanism in vertebrates in which levels of Cux2 activity play an important role for ongoing neurogenesis in the olfactory epithelium.

Progressive effects of N-myc deficiency on proliferation, neurogenesis, and morphogenesis in the olfactory epithelium

N-myc belongs to the myc proto-oncogene family, which is involved in numerous cellular processes such as proliferation, growth, apoptosis, and differentiation. Conditional deletion of N-myc in the mouse nervous system disrupted brain development, indicating that N-myc plays an essential role during neural development. How the development of the olfactory epithelium and neurogenesis within are affected by the loss of N-myc has, however, not been determined. To address these issues, we examined an N-myc^Foxg1Cre conditional mouse line, in which N-myc is depleted in the olfactory epithelium. First changes in N-myc mutants were detected at E11.5, with reduced proliferation and neurogenesis in a slightly smaller olfactory epithelium. The phenotype was more pronounced at E13.5, with a complete lack of Hes5-positive progenitor cells, decreased proliferation, and neurogenesis. In addition, stereological analyses revealed reduced cell size of post-mitotic neurons in the olfactory epithelium, which contributed to a smaller olfactory pit. Furthermore, we observed diminished proliferation and neurogenesis also in the vomeronasal organ, which likewise was reduced in size. In addition, the generation of gonadotropin-releasing hormone neurons was severely reduced in N-myc mutants. Thus, diminished neurogenesis and proliferation in combination with smaller neurons might explain the morphological defects in the N-myc depleted olfactory structures. Moreover, our results suggest an important role for N-myc in regulating ongoing neurogenesis, in part by maintaining the Hes5-positive progenitor pool. In summary, our results provide evidence that N-myc deficiency in the olfactory epithelium progressively diminishes proliferation and neurogenesis with negative consequences at structural and cellular levels. © 2013 The Authors. Developmental Neurobiology Published by Wiley Periodicals, Inc. Develop Neurobiol 74: 643–656, 2014

Anti-Müllerian hormone may regulate the number of calbindin-positive neurons in the sexually dimorphic nucleus of the preoptic area of male mice

Background

The male brain is putatively organised early in development by testosterone, with the sexually dimorphic nucleus of the medial preoptic area (SDN) a main exemplifier of this. However, pubescent neurogenesis occurs in the rat SDN, and the immature testes secrete anti-Müllerian hormone (AMH) as well as testosterone. We have therefore re-examined the development of the murine SDN to determine whether it is influenced by AMH and/or whether the number of calbindin-positive (calbindin^+ve) neurons in it changes after pre-pubescent development.

Methods

In mice, the SDN nucleus is defined by calbindin^+ve neurons (CALB-SDN). The number and size of the neurons in the CALB-SDN of male and female AMH null mutant (Amh^-/-) mice and their wild-type littermates (Amh^+/+) were studied using stereological techniques. Groups of mice were examined immediately before the onset of puberty (20 days postnatal) and at adulthood (129–147 days old).

Results

The wild-type pre-pubertal male mice had 47% more calbindin^+ve neurons in the CALB-SDN than their female wild-type littermates. This sex difference was entirely absent in Amh^-/- mice. In adults, the extent of sexual dimorphism almost doubled due to a net reduction in the number and size of calbindin^+ve neurons in females and a net increase in neuron number in males. These changes occurred to a similar extent in the Amh^-/- and Amh^+/+ mice. Consequently, the number of calbindin^+ve neurons in Amh^-/- adult male mice was intermediate between Amh^+/+ males and Amh^+/+ females. The sex difference in the size of the neurons was predominantly generated by a female-specific atrophy after 20 days, independent of AMH.

Conclusions

The establishment of dimorphic cell number in the CALB-SDN of mice is biphasic, with each phase being subject to different regulation. The second phase of dimorphism is not dependent on the first phase having occurred as it was present in the Amh^-/- male mice that have female-like numbers of calbindin^+ve neurons at 20 days. These observations extend emerging evidence that the organisation of highly dimorphic neuronal networks changes during puberty or afterwards. They also raise the possibility that cellular events attributed to the imprinting effects of testosterone are mediated by AMH.

The bed nucleus of the stria terminalis has developmental and adult forms in mice, with the male bias in the developmental form being dependent on testicular AMH

Canonically, the sexual dimorphism in the brain develops perinatally, with adult sexuality emerging due to the activating effects of pubescent sexual hormones. This concept does not readily explain why children have a gender identity and exhibit sex-stereotypic behaviours. These phenomena could be explained if some aspects of the sexual brain networks have childhood forms, which are transformed at puberty to generate adult sexuality. The bed nucleus of stria terminalis (BNST) is a dimorphic nucleus that is sex-reversed in transsexuals but not homosexuals. We report here that the principal nucleus of the BNST (BNSTp) of mice has developmental and adult forms that are differentially regulated. In 20-day-old prepubescent mice, the male bias in the principal nucleus of the BNST (BNSTp) was moderate (360 ± 6 vs 288 ± 12 calbindin(+ve) neurons, p < 0.0001), and absent in mice that lacked a gonadal hormone, AMH. After 20 days, the number of BNSTp neurons increased in the male mice by 25% (p < 0.0001) and decreased in female mice by 15% (p = 0.0012), independent of AMH. Adult male AMH-deficient mice had a normal preference for sniffing female pheromones (soiled bedding), but exhibited a relative disinterest in both male and female pheromones. This suggests that male mice require AMH to undergo normal social development. The reported observations provide a rationale for examining AMH levels in children with gender identity disorders and disorders of socialization that involve a male bias.

[The first clinical use of an Dynamic Registration Tool for Navigation in FESS]

BACKGROUND

The effective register accuracy in an situs issues a challenge to the employment of instrument navigation in the ENT Surgery. The idea of the initially determined process Dynamic Registration Supply (DRS) is to improve the register accuracy by the automatic, and interoperability of the register.

MATERIALS AND METHODS

The aim was to determine clinical use of DRS. Opto-electrical system Navigation Panel Unit, vs. 4.0.0 with the functionality DRS was used. Experiments were carried out on 95 patients who had so called FESS. The data of a control group were available to researchers. The measuring log includes among other things following parameters: retooling time, cutting-suture time, frequency of use of the navigated pointer, frequency of additional registration.

RESULTS

At least once during the procedure DRS has been activated in 85 of 95 interventions (89.5). The time required increased by 15% accumulated 189 s per intervention. The most frequently used additional registration was in the region of sphenoid sinus. The surgeons underlined that out of 95 surveys in 75 cases the DRS rendered the instrument navigation more precise, while 1% of 93 cases considered this function as unwanted.

CONCLUSION

The first clinical study for use of an automatic algorithm for recognition and reduction of faulty registration of a CT, navigation was successful. The findings suggest that by using automatic intraoperative registration DRS consisting inaccuracy can be reduced. In practice this means an efficient quality improvement of the Navigation.

The male bias in the number of Purkinje cells and the size of the murine cerebellum may require Müllerian inhibiting substance/anti-Müllerian hormone

There is a male bias in the size of the cerebellum, with males, on average, having more Purkinje cells than females. The critical periods in cerebellum development occur when the immature testes secrete Müllerian inhibiting substance (MIS; synonym anti-Müllerian hormone) but only trace levels of testosterone. This suggests that the male bias in the cerebellum is generated by a different mechanism to the testosterone-sensitive reproductive nuclei. Consistent with this, in the present study, we report that Purkinje cells and other cerebella neurones express receptors for MIS, and that MIS(-/-) male mice have female-like numbers of Purkinje cells and a female-like size to other parts of their cerebellum. The size of the cell bodies of Purkinje cells was also dimorphic, although only a minority of this was a result of MIS. This suggests that MIS induces the initial male bias in the cerebellum, which is then refined by pubescent testosterone and/or other sex-specific factors.

Endogenous dynorphin in epileptogenesis and epilepsy: anticonvulsant net effect via kappa opioid receptors

Neuropsychiatric disorders are one of the main challenges of human medicine with epilepsy being one of the most common serious disorders of the brain. Increasing evidence suggest neuropeptides, particularly the opioids, play an important role in epilepsy. However, little is known about the mechanisms of the endogenous opioid system in epileptogenesis and epilepsy. Therefore, we investigated the role of endogenous prodynorphin-derived peptides in epileptogenesis, acute seizure behaviour and epilepsy in prodynorphin-deficient mice. Compared with wild-type littermates, prodynorphin knockout mice displayed a significantly reduced seizure threshold as assessed by tail-vein infusion of the GABA(A) antagonist pentylenetetrazole. This phenotype could be entirely rescued by the kappa receptor-specific agonist U-50488, but not by the mu receptor-specific agonist DAMGO. The delta-specific agonist SNC80 decreased seizure threshold in both genotypes, wild-type and knockout. Pre-treatment with the kappa selective antagonist GNTI completely blocked the rescue effect of U-50488. Consistent with the reduced seizure threshold, prodynorphin knockout mice showed faster seizure onset and a prolonged time of seizure activity after intracisternal injection of kainic acid. Three weeks after local injection of kainic acid into the stratum radiatum CA1 of the dorsal hippocampus, prodynorphin knockout mice displayed an increased extent of granule cell layer dispersion and neuronal loss along the rostrocaudal axis of the ipsi- and partially also of the contralateral hippocampus. In the classical pentylenetetrazole kindling model, dynorphin-deficient mice showed significantly faster kindling progression with six out of eight animals displaying clonic seizures, while none of the nine wild-types exceeded rating 3 (forelimb clonus). Taken together, our data strongly support a critical role for dynorphin in the regulation of hippocampal excitability, indicating an anticonvulsant role of kappa opioid receptors, thereby providing a potential target for antiepileptic drugs.

Y1-receptors regulate the expression of Y2-receptors in distinct mouse forebrain areas

Y-receptor-knockout mice have become an important tool to elucidate specific physiological roles of individual Y-receptors. However, their phenotypes are not always confirmatory to results obtained by pharmacological investigations in vivo or in vitro. These discrepancies may, at least in part, be due to compensatory changes in the expression of remaining Y-receptor types. To determine whether deletion of individual Y-receptors results in altered mRNA expression and/or binding toward other Y-receptor types, we applied in-situ hybridization and radioligand-binding studies on brain slices of Npy1r-, Npy2r- or Npy5r-knockout mice. Significant changes were seen in Y1-receptor-deficient mice. Thus, Y2-receptor mRNA and (125)I-peptide YY(3-36) binding in the hippocampus proper were increased by up to 55% and 89%, respectively. Similar increases in (125)I-peptide YY(3-36) binding were observed in the caudo-dorsal extension of the lateral septum, an area heavily targeted by hippocampal projections and involved in Y1-receptor-regulated anxiety. Increased (125)I-peptide YY(3-36) binding and Y2-receptor mRNA levels were also observed in the medial amygdaloid nucleus. In contrast, (125)I-peptide YY(3-36) binding was reduced in the central amygdaloid nucleus. Y2-receptor mRNA in the intermediate part of the lateral septum was reduced by 42%. Only minimal changes were observed in Y2- or Y5-receptor-deficient mice. Our results demonstrate that compensatory changes in the expression of Y2-receptors occur in Y1-receptor-deficient mice. These adaptations are likely to contribute to changed physiological function. Thus, alterations in Y2-receptors have to be taken in account upon discussion of Y1-receptor function, especially in emotional aspects like anxiety and aggression, but also alcoholism.

Y1 receptors regulate aggressive behavior by modulating serotonin pathways

Neuropeptide Y (NPY) is pivotal in the coordinated regulation of food intake, growth, and reproduction, ensuring that procreation and growth occur only when food is abundant and allowing for energy conservation when food is scant. Although emotional and behavioral responses from the higher brain are known to be involved in all of these functions, understanding of the coordinated regulation of emotion/behavior and physiological functions is lacking. Here, we show that the NPY system plays a central role in this process because ablation of the Y1 receptor gene leads to a strong increase in territorial aggressive behavior. After exposure to the resident-intruder test, expression of c-fos mRNA in Y1-knockout mice is significantly increased in the medial amygdala, consistent with the activation of centers known to be important in regulating aggressive behavior. Expression of the serotonin [5-hydroxytryptamine (5-HT)] synthesis enzyme tryptophan hydroxylase is significantly reduced in Y1-deficient mice. Importantly, treatment with a 5-HT-1A agonist, (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin hydrobromide, abolished the aggressive behavior in Y1-knockout mice. These results suggest that NPY acting through Y1 receptors regulates the 5-HT system, thereby coordinately linking physiological survival mechanisms such as food intake with enabling territorial aggressive behavior.

[Severe hypoglycemia in diabetics with impaired renal function]

BACKGROUND AND OBJECTIVE

Reduction of renal function in patients with type 1 or type 2 diabetes is associated with a clearly increased risk of hypoglycemia. Main causes are an altered pharmacokinetics of insulin and oral antidiabetics and/or impaired renal glucose production. A knowledge of renal function is, therefore, essential for preventing hypoglycemia caused by antidiabetic treatment. But serum creatinine, most commonly used in general practice, is an imprecise indication of renal function. This investigation assessed the significance of a false estimation of renal function as a partial cause of severe hypoglycemia.

PATIENTS AND METHODS

The study group consisted of 35 diabetics (21 females, 14 males; average age 61 years) who had been hospitalized because of an episode of severe hypoglycemia accompanied by loss of consciousness. Renal function was measured by serum creatinine and by creatinine clearance as calculated by the formula of Cockcroft and Gault. Also taken into account were HBA1c the antidiabetic treatment before and after discharge, and any additional medication.

RESULTS

Impaired renal function was established by the serum creatinine level in 9 patients and by calculated creatine clearance in 24. Compared with patients with normal renal function, those with renal failure were older (74.3 vs. 32.8 years), had more rarely undergone intensive insulin treatment (5 of 24 vs. 9 of 11) and had more commonly received ACE inhibitors (10/24 vs. 1/11). The insulin dosage at discharge had been reduced in 16 off 22 insulin-dependent patients in renal failure, and long-acting sulfonylurea preparation were discontinued or changed to gliquidone in the others.

CONCLUSION

This investigation indicates that false estimation of renal function from the level of serum creatinine is an important partial cause of hypoglycemia requiring treatment, especially in elderly persons with reduced muscle mass in whom renal function should be determined by calculating or measuring creatinine clearance.

Reduction of intracellular pH inhibits constitutive expression of Cyclooxygenase-2 in human colon cancer cells

Cyclooxygenase-2 (COX-2) over-expression is critically involved in tumor formation. Intracellular pH (pHi) has been shown to be alkaline in cancer cells, and to be an important trigger for cell proliferation. This study therefore analyzed the relationship between pHi and COX-2 expression. HRT-18 and Caco-2 cells cultured in medium with bicarbonate maintained a pHi of approximately 7.6, which is higher than that of non-neoplastic cells. Cells grown in bicarbonate-free medium with a pH at 6.8 showed a reduction in pHi to approximately 7.0. Importantly, reduction of pHi resulted in a complete inhibition of COX-2 mRNA and protein expression. When cells were grown in bicarbonate-supplemented medium at pH 6.8, pHi maintained at approximately 7.6 and COX-2 expression was not inhibited. Additionally, analysis utilizing protein synthesis inhibitor cycloheximide demonstrated that pHi mediated inhibition of COX-2 mRNA expression requires de novo protein synthesis of regulatory protein(s). These data strongly suggest that an alkaline pHi is an important trigger for constitutive COX-2 expression. Defining pHi-mediated mechanisms that govern the constitutive COX-2 expression may help in developing new strategies to block COX-2 over-expression in cancer cells.

Mast- und Schlachtleistung sowie Fleisch- und Fettqualität von Pietrain-Schweinen unterschiedlichen MHS-Genotyps und Geschlechts – 2. Mitteilung: Fettsäurenmuster der Depotfette Rückenspeck, Flomen und intermuskuläres Fett sowie der Gesamt- und Phospholipide des &lt;i&gt;M. long, dorsi&lt;/i&gt;

Abstract. Title of the Paper: Fattening and carcass Performance and meat- and fat quality of Pietrain pigs of different MHS-genotype and sex. II. Fatty acid pattern of the adipose tissues back fat, leaf fat and intermuscular fat and of the total- and phospholipids of the M. long, dorsi In this investigation the fatty acid pattern of the adipose tissues back fat (devided in dorsal and ventral compartment), leaf fat and intermuscular and the total and phospholipids of the M. long, dorsi of different MHSgenotypes and sexes of the Piétrain race have been compared. There were available 60 animals with equal numbers of the three MHS-genotypes (NN, Np, pp) and both sexes (castrates, gilts) (liveweight at the end of fattening: 150 kg). The decreasing presence of the stress allele p (pp > Np > NN) as well the castrates compared with the gilts were combined with increasing content of saturated and monounsaturated fatty acids and decreasing content of polyunsaturated fatty acids in all adipose tissues and in the total and phospholipids of the M. long, dorsi and thus with better technological quality. The results should additionally cause the selection stress resistent pigs of the Piétrain race.

Mast- und Schlachtleistung sowie Fleisch- und Fettqualität von Piarain-Schweinen unterschiedlichen MHS-Genoryps und Geschlechts – 1. Mitteilung: Mast- und Schlachtleistung sowie Fleischqualität

Abstract. Title of the Paper: Fattening and carcass Performance and meat- and fat quality of Pietrain pigs of different MHS-genotype and sex. I. Fattening and carcass Performance and meat quality For the purpose of the comparison of the fattening and carcass Performance and meat quality of different MHS-genotypes and sexes of the Pietrain race 60 fattening pigs with equal numbers of the three MHS-genotypes (NN, Np, pp) and both sexes (castrates, gilts) had been gone in the fattening and carcass Performance testing of a litter testing Station. The animals had been fattened from 30 to 105 kg. With decreasing presence of the stress allele p (pp > Np > NN) as well in the castrates compared with the gilts there could be shown increasing growth rates combined with decreasing feed conversion, decreasing carcass quality that is higher degree of fatness and lower lean meat content of the carcass, more advantageous meat quality and a higher intramusculare fat content. Aecording to the results a general selection for stress-resistance of the Pietrain race is recommended

Evidence for impaired glucose effectiveness in cirrhotic patients after liver transplantation

To evaluate the impact of acute and chronic liver disease and single immunosuppression (cyclosporine A [CSA] or FK506) on insulin sensitivity and glucose effectiveness in liver-grafted patients, we performed a frequently sampled intravenous glucose tolerance test (FSIGTT) in nondiabetic patients after orthotopic liver transplantation (OLT) with acute liver failure ([ALF] group, n = 9, with CSA therapy), in patients after OLT with chronic liver disease (CSA group, n = 8; FK506 group, n = 8), and in 9 healthy control subjects. Insulin sensitivity and glucose effectiveness were determined by analyzing glucose and insulin data from the FSIGTT with Bergman's minimal model technique for glucose. The intravenous glucose tolerance index ([KG] ie, the slope of the regression of the logarithm of blood glucose concentration) was not different between the ALF group (2.17 +/- 0.16 min(-1)) and controls (2.29 +/- 0.13 min(-1)), but was lower (P < .05) in both groups with chronic liver disease (CSA group, 1.46 +/- 0.1; FK506 group, 1.61 +/- 0.11 min(-1)) compared with the ALF group (P < .05). A positive relation for the KG and glucose effectiveness was found in all liver-grafted patients and controls. Insulin sensitivity was not different between all liver-grafted patients and controls. The body mass index (BMI) was the overall determinant of insulin sensitivity in all groups. Single immunosuppressive therapy does not impair insulin sensitivity in liver-grafted patients. The lower glucose effectiveness in liver-grafted patients with chronic liver disease but not in patients after ALF points to a defect in the regulation of glucose-mediated glucose uptake in peripheral tissue.

Einfluß des MHS-Genotyps auf die Mast- und Schlachtleistung von Piétrainschweinen und PI x DL-Mastendprodukten in der Stationsprüfung

Abstract. Title of the paper: The influence of MHS-genotypes on fattening and carcass Performance traits of purebred Piétrain pigs and PI x DL slaughter pigs at testing station For the comparison of fattening and carcass performance traits as well as the meat quality of different MHSgenotypes, one Pietrain group with 434 and another one of 64 PI x DL animals of both sexes were evaluated. The LSQ-means from an animal model showed in tendency a lower fattening Performance of the stresssusceptible genotypes. Significant differences were found for higher fat layers and fat surfaces and for lower meat surfaces and percentage of lean meat in NP- and NN-genotypes as compared to the PP-animals. The differences between the MHS-genotypes of the PI x DL animals were similar to those of the Pietrain animals. Both Statistical models confirmed a better meat quality already in the NP-genotypes. With respect to lower loss rates, reduction of insufficient meat qualities (PSE, DFD) and a still high proportion of lean meat of the NP- and NN- animals, a selection ofthe Pidtrain race for stress-resistance should be suitable.

The legacy of Friedrich Loeffler--the Institute on the Isle of Riems

When starting the experiments on foot and mouth disease on the Isle of Riems in October 1910, Friedrich Loeffler could continue investigations that had been interrupted in 1907 by ministerial order. Loeffler's appointment to Berlin in 1913 and his sudden death in 1915 lead to the temporary cessation of work on the Riems. With high personal creativity and many years of seminal influence, Otto Waldmann carried Loeffler's ideas further, in the selection of themes and research strategy, making the Riems a world famous place of research. Some essential elements have determined life and research on the island for decades: the development of measures against epidemics, the conception of their application, the extension of research to new diseases of economic significance, the close contacts with the veterinary practice at all times, the presentation of results to experts and the stimulating discussions in the laboratory. I will try to briefly draw a bow covering the decades of different social conditions to the present and to suggest that Loeffler's ideas, which have been improved with the years, can affect many a current decision, even though differentiated individually.

[Immunization of young cattle with gp51 of the bovine leukosis virus and the subsequent experimental infection]

Calves were immunised by means of a native Al(OH)3-absorbed gp51-preparation which had been obtained from a foetal lamb kidney cell line, following bovine leucosis virus (BLV) infection. 9 animals were immunised 3 times, using 300 micrograms gp51. 7 animals underwent test infection, using 2.5 x 10(3) or 2.5 x 10(4) BLV-infected lymphocytes. Serological and virological reactions of all animals, including 3 calves which had received only test infections, were followed up through 40 weeks by means of immunodiffusion test, enzyme-immuno-assay, gp51 antibody radio-immuno-assay, reverse transcriptase test, syncytial test, competitive p24 radio-immuno-assay, and by transmission of whole blood in animal experiments. The results obtained from virological testing showed that 1 animal had been protected by preceding immunisation. 4 in 7 immunised and test-infected animals exhibited transient BLV values, between the 7th and 16th weeks from infection. Typical leucosis infection had been induced to 2 animals. The above findings are discussed and are compared to similar results recorded by other working groups.

[The reasons for the occurrence of non-specific reactions in the immunodiffusion test for enzootic bovine leukosis]

A batch of enzootic bovine leucosis antigen earmarked for immunodiffusion testing exhibited unspecific responses to cattle sera, which prompted an investigation of the underlying causes. Evidence was produced, for the first time ever, that such reactions were attributable to an antigen-antibody reaction caused by Mycoplasma arginini.