Effects of increased potassium in scala tympani on auditory nerve sensitivity.

Raising the K+ concentration in scala tympani of the guinea-pig cochlea generally caused a substantial increase in the spontaneous firing rate of single auditory nerve fibres. This effect was not accompanied by any observed reduction in the threshold sensitivity of these fibres. These findings cast doubt on current theories of cochlear transduction.     

Effects of increased potassium in scala tympani on auditory nerve sensitivity

Summary Raising the K⁺ concentration in scala tympani of the guinea-pig cochlea generally caused a substantial increase in the spontaneous firing rate of single auditory nerve fibres. This effect was not accompanied by any observed reduction in the threshold sensitivity of these fibres. These findings cast doubt on current theories of cochlear transduction.G. Leng was supported by the S.R.C.     

The effect of stimulus frequency on transmission in ganglia of Remak's nerve in the chicken

Summary Electrical stimulation of side branches of Remak's nerve evoked a synaptically-mediated spike discharge at the oral end of the nerve which increased in amplitude in response to successive stimuli. The maximum amplitude of the synaptic component was attained at a frequency of about 3 Hz but was almost completely absent at 31 Hz.     

The conduction velocity, number, and diameter of unmyelinated fibers in Remak's nerve

Remak's nerve in the chicken was examined ultrastructurally and electrophysiologically to determine the characteristics of fibers in the nerve trunk. The ration of unmyelinated fibers to myelinated ones was 111:1. The mean number of unmyelinated fibers was 3555 plus/minus 232 (SEM, n=5) and they had a mean diameter of 0.502 plus/minus 0.034 (SEM) micron. The compound action potential consisted almost entirely of a large diphasic waveform which had a mean peak conduction velocity of 0.62 plus/minus 0.031 (SEM, n=5) m.s-1 at 37 degrees C.     

Synkinesis in hemifacial spasm: results of recording intracranially from the facial nerve

Summary We show evidence that the motonucleus of the facial nerve is involved in producing the synkinesis in patients with hemifacial spasm. These results were obtained by recording from the intracranial portion of the facial nerve and from the orbicularis oculi muscle in patients operated upon for hemifacial spasm during electrical stimulation of the mandibular branch of the facial nerve. Also, the electromyographic response from the same muscle was recorded when the facial nerve was electrically stimulated at a location near the brainstem. The results show that it is unlikely that the symptoms of patients with hemifacial spasm can be explained on the basis of ephaptic transmission at the site of lesion of the facial nerve.     

Synkinesis in hemifacial spasm: results of recording intracranially from the facial nerve

We show evidence that the motonucleus of the facial nerve is involved in producing the synkinesis in patients with hemifacial spasm. These results were obtained by recording from the intracranial portion of the facial nerve and from the orbicularis oculi muscle in patients operated upon for hemifacial spasm during electrical stimulation of the mandibular branch of the facial nerve. Also, the electromyographic response from the same muscle was recorded when the facial nerve was electrically stimulated at a location near the brainstem. The results show that it is unlikely that the symptoms of patients with hemifacial spasm can be explained on the basis of ephaptic transmission at the site of lesion of the facial nerve.     

The action of the cholecystokinin-A receptor antagonist,devazepide, on the digestive system of the chicken

The influence of the cholecystokinin (CCK)-A receptor antagonist, devazepide (DVZ), on the chicken digestive tract was investigated. The passage of food from the crops of birds treated with DVZ was not significantly different from that of the control. DVZ treatment did not inhibit the biliary flow stimulated by the CCK analogue, caerulein. Dispersed chicken pancreatic acini stimulated with CCK were treated with various concentrations of DVZ. At 10^–5 M, DVZ completely inhibited amylase release; this concentration was much higher than those reported to have similar effects in mammals. The results suggest that the action DVZ as a CCK antagonist in the chicken is very weak.     

Botulinum toxin as a carrier for oral vaccines

Botulinum toxin is an unusually potent substance that acts on the nervous system to produce the clinical outcome of flaccid paralysis. To produce this effect, the toxin ordinarily proceeds through two separate but essential sequences of events. During the first, the toxin is ingested, it traverses a portion of the gastrointestinal system and then it is transcytosed from the lumen of the gut to the general circulation. During the second, circulating toxin binds to peripheral cholinergic nerve endings, it is endocytosed and then it acts as a metalloendoprotease to cleave polypeptides that are essential for exocytosis. Although botulinum toxin is antigenic, it ordinarily does not evoke an immune response during or after cases of oral poisoning. This is due to the fact that the dose of toxin that produces flaccid paralysis—and potentially death—is less than the dose needed to evoke an antibody response. In the recent past, the techniques of molecular biology have been used to generate an expression product of botulinum toxin that retains the ability to escape the gut and reach the general circulation, retains the ability to evoke an immune response, but has lost the ability to produce neurotoxicity. This modified toxin may have two clinical applications. The expression product itself may have utility as an oral vaccine against botulism. Beyond this, the modified toxin, or a truncation mutant of the toxin, may have utility as a carrier in the construction of other oral vaccines. Both potential applications could lead to the expression of oral vaccines in common foods. Received 29 December 1998; received after revision 22 March 1999; accepted 24 March 1999     

Demilune cells of the cat submandibular gland; an unlikely source of kallikrein

The functional significance of kallikrein in the salivary gland remains unclear partially because of uncertainty over its precise cellular localization. Kallikrein was thought to originate in acinar cells, until recent evidence from cat and rat localized it primarily to the ducts. The possibility that salivary kallikrein may also be located in demilune cells was investigated in this study. - The total kallikrein content of cat submandibular glands was found to be substantially reduced by sampathetic nerve stimulation; whereas parasympathetic stimulation had no significant effect. These biochemical findings did not correlate with morphological studies that revealed almost complete depletion of the demilune cells secretory granules after stimulation of either division of the autonomic nerve supply. This lack of correlation makes it unlikely that kallikrein is present in the demilune cell secretory granules.     

Identification of chicken lysozyme <Emphasis Type="Italic">g</Emphasis>2 and its expression in the intestine

Lysozyme is an important component of the innate immune system, protecting the gastrointestinal tract from infection. The aim of the present study was to determine if lysozyme is expressed in the chicken (Gallus gallus) intestine and to characterise the molecular forms expressed. Immunohistochemical staining localised lysozyme to epithelial cells of the villous epithelium along the length of the small intestine. There was no evidence for lysozyme expression in crypt epithelium and no evidence for Paneth cells. Immunoblots of chicken intestinal protein revealed three proteins: a 14-kDa band consistent with lysozyme c, and two additional bands of approximately 21 and 23 kDa, the latter consistent with lysozyme g. RT-PCR analyses confirmed that lysozyme c mRNA is expressed in 4-day, but not older chicken intestine and lysozyme g in 4- to 35-day chicken intestine. A novel chicken lysozyme g2 gene was identified by in silico analyses and mRNA for this lysozyme g2 was identified in the intestine from chickens of all ages. Chicken lysozyme g2 shows similarity with fish lysozyme g, including the absence of a signal peptide and cysteines involved in disulphide bond formation of the mammalian and bird lysozyme g proteins. Analyses using SecretomeP predict that chicken lysozyme g2 may be secreted by the non-classical secretory pathway. We conclude that lysozyme is expressed in the chicken small intestine by villous enterocytes. Lysozyme c, lysozyme g and g2 may fulfil complimentary roles in protecting the intestine.Received 4 August 2004; received after revision 1 September 2004; accepted 7 September 2004     

The conduction velocity,number and diameter of unmyelinated fibers in Remak's nerve

Summary Remak's nerve in the chicken was examined ultrastructurally and electrophysiologically to determine the characteristics of fibers in the nerve trunk. The ratio of unmyelinated fibers to myelinated ones was 1111. The mean number of unmyelinated fibers was 3555±232 (SEM, n=5) and they had a mean diameter of 0.502±0.034 (SEM) m. The compound action potential consisted almost entirely of a large diphasic waveform which had a mean peak conduction velocity of 0.62±0.031 (SEM, n=5) m·s^–1 at 37°C.     

Analysis of vasodilatation in the submaxillary gland using potentiators of acetylcholine and kinins

Zusammenfassung Nachweis, dass bei Reizung des N. chorda lingualis der Katze ein Blutdruckeffekt ausbleibt, wenn ein Bradykinin potenzierender Faktor (Präparat BPF) zuvor gegeben wurde.

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Acknowledgments. We are greatly indepted to Dr.J. Stewart of the University of Colorado and to Dr.L. Greene of Brookhaven National Laboratories, New York, for kind gifts of synthetic bradykinin potentiators.

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This work was supported by grants from the Medical Research Council of Canada and the Alberta Heart Foundation.     

Development of the innervation of the urogenital complex in the fetal mouse

Summary The developing urogenital complex of the fetal mouse was studied by means of silver impregnation and electron microscopy. These studies showed that: 1) the mesonephric field is innervated during prenatal stages (Wolffian nerve); 2) nerve penetration precedes the differentiation of the gonads and related ducts; and 3) the Wolffian nerve arises during the earliest stages from the first pair of abdominal rami communicantes. The identity between the fetal Wolffian nerve and the nerve of the suspensory ligament (higher pathway) of the adult is discussed.     

Development of the innervation of the urogenital complex in the fetal mouse

The developing urogenital complex of the fetal mouse was studied by means of silver impregnation and electron microscopy. These studies showed that: 1) the mesonephric field is innervated during prenatal stages (Wolffian nerve); 2) nerve penetration precedes the differentiation of the gonads and related ducts; and 3) the Wolffian nerve arises during the earliest stages from the first pair of abdominal rami communicantes. The identity between the fetal Wolffian nerve and the nerve of the suspensory ligament (higher pathway) of the adult is discussed.     

Demilune cells of the cat submandibular gland; an unlikely source of kallikrein

Summary The functional significance of kallikrein in the salivary gland remains unclear partially because of uncertainty over its precise cellular localization. Kallikrein was thought to originate in acinar cells, until recent evidence from cat and rat localized it primarily to the ducts. The possibility that salivary kallikrein may also be located in demilune cells was investigated in this study. — The total kallikrein content of cat submandibular glands was found to be substantially reduced by sampathetic nerve stimulation; whereas parasympathetic stimulation had no significant effect. These biochemical findings did not correlate with morphological studies that revealed almost complete depletion of the demilune cells secretory granules after stimulation of either division of the autonomic nerve supply. This lack of correlation makes it unlikely that kallikrein is present in the demilune cell secretory granules.Acknowledgment. This study is made possible through the Dean's MRC grant number MD-3489 to the College of Dentistry, University of Saskatchewan.Authors wish to thank Mr. D. Duncan, Dept. of Oral Biology and D. Mandeville of Medical Photographic Services for technical assistance.     

Invasive properties of the ovarian cortex in birds

Summary In quail/chicken ovarian cortex associations, grown on chicken chorioallantoic membrane (CAM), epithelial and/or germ cells from the quail ovary may invade the cortical rim of the chicken ovary. In certain experimental conditions, ovarian cortical cells may leave a transplanted ovary and grow over or invade the mesenchyme of the surrounding CAM. So a germinal epithelium completely free from other ovarian cell groups can be obtained.The author is very grateful to Prof. Dr L. Vakaet, R.U.C.A., Antwerp, for his valuable suggestions and to Mrs S. De Wolf-Van Rompaey, for her excellent technical assistance.     

Homology of L-gulonolactone oxidase of species belonging to Mammalia, Aves, and Amphibia

Immunological cross-reactivity of L-gulonolactone oxidase of different species (rat, chicken, and bullfrog) was tested by the Ouchterlony technique. Antiserum directed against the enzyme from chicken kidney reacted with rat liver enzyme as well as with bullfrog kidney enzyme. This finding suggests that there is, at least partly, sequence homology among the enzyme from species belonging to the three classes, Mammalian, Aves, and Amphibia.     

Homology of L-gulonolactone oxidase of species belonging to Mammalia,Aves, and Amphibia

Summary Immunological cross-reactivity of L-gulonolactone oxidase of different species (rat, chicken, and bullfrog) was tested by the Ouchterlony technique. Antiserum directed against the enzyme from chicken kidney reacted with rat liver enzyme as well as with bullfrog kidney enzyme. This finding suggests that there is, at least partly, sequence homology among the enzymes from species belonging to the three classes, Mammalia, Aves, and Amphibia.     

Sur les interactions entre l'axe embryonnaire normal et les formations secondaires produites par la centrifugation de la blastula et de la gastrula chez les Amphibiens

Summary The complexes of organs induced by centrifugation of Amphibia blastulas or gastrulas interfere with the primary axis of the embryo: (a) explantates of centrifugated ectoblast are always poorer in differentiation than the same ectoblast leftin situ; (b) the complexes arising in the ventral part of the embryo have the tendency to elongate parallel to the main axis of the embryo and become connected with the head of the primary embryo; (c) grafts made on Axolotl eggs show that, when the reaction is poor, it cannot express itself except in cases of close contact with the normal organizer; (d) reciprocally, implants of strongly reacting centrifugated ectoblast placed on the ventral part of a normal gastrula of Pleurodeles induce modifications of the primary organs, viz. the transformation of the first somites into chorda.These facts lead to the conclusion that quantitative factors—and not qualitative—are effective in the differentiation of the embryo.     

Gene conversion in the chicken immunoglobulin locus: A paradigm of homologous recombination in higher eukaryotes

Gene conversion was first defined in yeast as a type of homologous recombination in which the donor sequence does not change. In chicken B cells, gene conversion builds the antigen receptor repertoire by introducing sequence diversity into the immunoglobulin genes. Immunoglobulin gene conversion continues at high frequency in an avian leukosis virus induced chicken B cell line. This cell line can be modified by homologous integration of transfected DNA constructs offering a model system for studying gene conversion in higher eukaryotes. In search for genes which might participate in chicken immunoglobulin gene conversion, we have identified chicken counterparts of the yeastRAD51, RAD52, andRAD54 genes. Disruption and overexpression of these genes in the chicken B cell line may clarify their role in gene conversion and gene targeting.