Mechanisms of chloride transport in crayfish stretch receptor neurones and guinea pig vas deferens: implications for inhibition mediated by GABA

Since activation of GABAA receptors is believed to open an associated Cl- channel, the intracellular Cl- activity (aiCl) must be lower than that predicted from a passive distribution, to account for hyperpolarizing responses, or higher, to account for depolarizing responses. The physiological and pharmacological properties of the implied Cl- extruding and accumulating mechanisms have been investigated by direct measurements of aiCl. A coupled K+-Cl- co-transport has been found in crayfish stretch receptor neurones and a predominating Cl(-)HCO3(-) exchange in guinea pig vas deferens. From the different ionic mechanisms involved in Cl- extrusion and accumulation, it is proposed that drugs which affect Cl- transport mechanisms will reduce GABA responses of both polarities only if their action is via interference with the Cl- recognition site, but not if it is via interference with the co- or counter-ion recognition site.     

Excitatory effect of adenosine on neurotransmission in the slices of superior colliculus and hippocampus of guinea pig

Postsynaptic potential (PSP) was recorded from the CA3 region of the pyramidal cell layer of hippocampal slices and from the superficial gray layer of superior collicular slices from guinea pigs. In the hippocampal slices, application of adenosine to the perfusion medium at a concentration of 10 nM to 1 μM enhanced the amplitude of the PSP and at concentrations greater than 10 μM it depressed the PSP. The dose-response curve of the effect of adenosine on neurotransmission in the hippocampus thus showed an excitatory and inhibitory biphasic pattern according to the concentrations applied. However, in superior collicular slices, application of adenosine at concentrations of more than 10 nM enhanced the amplitude of the PSP and there was no inhibition by adenosine even at a concentration of 1 mM.     

Effect of the mono- and tetra-sialogangliosides, GM1 and GQ1b, on long-term potentiation in the CA1 hippocampal neurons of the guinea pig

 Effects of the mono- and tetra-sialogangliosides, GM1 and GQ1b, on long-term potentiation (LTP) were investigated in the CA1 neurons of guinea-pig hippocampal slices. The magnitude of LTP induced by a strong tetanus (100 Hz, 100 pulses) was not significantly affected by application of either ganglioside. In contrast, when LTP was induced by a weak tetanus (100 Hz, 4 pulses), a significantly greater LTP was induced in the presence of either ganglioside. Similarly, when slices were incubated in low-Ca²⁺ (1.0–1.1 mM) medium for more than 2 h, the LTP was usually small or absent, but showed a significant increase in amplitude of population spike (A-PS) when the slices were incubated with either GM1 or GQ1b (4–5 μg/ml). In addition, the application of GQ1b (4 μg/ml) reversed the blocking effect of an NMDA-receptor antagonist, APP-5 (10 μM), on the induction of LTP and resulted in forming LTP. Based on these findings, we conclude that GM1 and GQ1b exert positive modulatory effects on the induction of LTP in hippocampal CA1 neurons and suggest that GM1 and GQ1b may participate in the induction of LTP as donors of Ca²⁺ ions. Received: 21 April 1998 / Accepted: 5 May 1998     

Prolactin reception and its effect on ACTH binding in human and guinea pig adrenocortical cells

Laboratory of Hormonal Regulation of Metabolism, Kiev Research Institute of Endocrinology and Metabolism. (Presented by Academician of the Academy of Medical Sciences of the USSR Yu. A. Pankov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 108, No. 8, pp. 177–179, August, 1989.     

The effect of elevated outflow pressure on flow resistance and the transfer of THO,albumin and glucose in the isolated guinea pig placenta

In the isolated, artificially perfused guinea pig placenta the relationship between arterial pressures, venous pressures and the relative transfer of 3H2O, D-glucose and albumin was studied at constant arterial perfusion rates. The results were as follows: A. Elevation of the fetal venous pressure induces an increase of flow resistance at the maternal side. Fetal perfusion resistance is raised by elevated pressure in the uterine vein also, the effect is much more pronounced, however. B. When the outflow resistance increases, a net transfer of water especially from the fetal to the maternal side can be observed. The relationship between the venous pressure difference and the rate of filtration is non-linear. C. The fetomaternal transfer of 131J-albumin and of 3H2O resp. D-glucose is influenced by fetomaternal filtration to a different degree. Whereas the albumin transfer increases strongly, the transfer rates of tritiated water and glucose change little.     

Kinetics of the effect of a single dose of cyclosporin-A on antibody and cell mediated immune responses in the guinea pig

The effect of 100 mg/kg cyclosporin-A (CS-A), given as a single dose either before or after immunization, on antibody levels and skin test reactivity was investigated. CS-A was found to suppress both primary and secondary anti-hapten and anti-carrier IgG1 and IgG2 antibodies. However, CS-A was also capable of inducing enhanced anti-hapten antibodies. CS-A showed a similar effect on contact sensitivity reactions to 2,4-dinitrofluorobenzene (DNFB) as has been shown for cyclophosphamide (CY) in that, given before sensitization, skin reactions were enhanced, whereas given after sensitization they were suppressed. However, the effect of CS-A on the T-cell proliferation in the lymph node, draining the site of sensitization to DNFB, differed from that of CY. Although CS-A induced a depression of T-cell proliferation, this suppression was more prolonged than that found in CY treated animals. Also, these draining lymph nodes never showed increased T-cell proliferation as did those in animals treated with CY before sensitization. This work demonstrates that a single dose of CS-A can both suppress or enhance antibody production and delayed hypersensitivity. The timing of the dose of CS-A in relation to the time of primary immunization is important. However, both IgG1 and IgG2 primary and secondary antibody responses can be altered. Comparison with the effect of CY on antibody levels and contact sensitivity would indicate that in some ways CS-A reacts similarly to antimitotic agents and in other ways is different.     

Tyrosine hydroxylase-immunoreactivity and its relations with gonadotropin-releasing hormone and neuropeptide Y in the preoptic area of the guinea pig

The present study examines the distribution of tyrosine hydroxylase (TH) immunoreactivity and its morphological relationships with neuropeptide Y (NPY)- and gonadoliberin (GnRH)-immunoreactive (IR) structures in the preoptic area (POA) of the male guinea pig. Tyrosine hydroxylase was expressed in relatively small population of perikarya and they were mostly observed in the periventricular preoptic nucleus and medial preoptic area. The tyrosine hydroxylase-immunoreactive (TH-IR) fibers were dispersed troughout the whole POA. The highest density of these fibers was observed in the median preoptic nucleus, however, in the periventricular preoptic nucleus and medial preoptic area they were only slightly less numerous. In the lateral preoptic area, the density of TH-IR fibers was moderate. Two morphological types of TH-IR fibers were distinguished: smooth and varicose. Double immunofluorescence staining showed that TH and GnRH overlapped in the guinea pig POA but they never coexisted in the same structures. TH-IR fibers often intersected with GnRH-IR structures and many of them touched the GnRH-IR perikarya or dendrites. NPY wchich was abundantly present in the POA only in fibers showed topographical proximity with TH-IR structures. Althoug TH-IR perikarya and fibers were often touched by NPY-IR fibers, colocalization of TH and NPY in the same structures was very rare. There was only a small population of fibers which contained both NPY and TH. In conclusion, the morphological evidence of contacts between TH- and GnRH-IR nerve structures may be the basis of catecholaminergic control of GnRH release in the preoptic area of the male guinea pig. Moreover, TH-IR neurons were conatcted by NPY-IR fibers and TH and NPY colocalized in some fibers, thus NPY may regulate catecholaminergic neurons in the POA.     

The effects of microiontophoretically applied capsaicin and substance P on single neurones in the rat and cat brain

Microiontophoretically applied capsaicin (10–480 nA) excited neurones in trigeminal nucleus caudalis (ntV) or potentiated their amino acid-induced excitation (20 of 23 neurones); inhibited one neurone; and had no effect on 2 neurones. Substance P (SP) excited 8 of 9 ntV neurones, and of these 8 neurones 6 were excited, one was depressed, and one was unaffected by capsaicin. Of 13 cerebellar neurones, 5 were depressed by capsaicin and 8 were unaffected. SP excited 3 of 5 cerebellar neurones. It is concluded that the excitatory action of capsaicin in ntV may be due to release of SP from neuronal structures and that the lack of excitatory effects seen in the cerebellum may reflect the absence of SP-containing neurones in this structure [2].     

The lack of an effect of applied d.c. electric fields on peripheral nerve regeneration in the guinea pig.

This study was undertaken to provide evidence of enhanced regeneration of mammalian peripheral nerves in response to applied d.c. electric fields. Peroneal nerves of adult guinea-pigs were crushed or transected and anastomosed. Constant current d.c. stimulators (20 microA) were implanted in the flank with platinum/iridium electrodes routed to the ankles. Animals with crush lesions were tested for toe spreading ability from the 14th to the 23rd day following the lesion. Animals with transection lesions were allowed to recover for 40 days and isometric force measurements of toe abduction and foot flexion were made. Both myelinated and unmyelinated fiber densities were determined. There proved to be no difference between legs treated with an anode, a cathode, or a sham electrode as evaluated by: the time to return of the toe spreading reflex, the isometric force of either twitches or tonic contractions, the latency between stimulation and contraction, or the number or density of either myelinated or unmyelinated fibers. These negative results are at variance with other studies that have reported beneficial effects of d.c. electric fields on peripheral nerve regeneration. The stimulation and analysis techniques used in this study were well within the variety of protocols that have yielded reports of highly significant positive effects with smaller numbers of animals than used in this study. The conclusion is that either there is a subtle but highly specific and critical difference between the present protocol and others, or the other studies need to be reevaluated. In either case, it seems that the ability of applied d.c. fields to enhance peripheral nerve regeneration in vivo remains open to question.     

Intranasal TRPV1 agonist capsaicin challenge and its effect on c-fos expression in the guinea pig brainstem

Central neuronal interaction seems to play a role in pathogenesis of upper airway cough syndrome. In the guinea pig model we used the method c-fos expression to identify neurons involved in processing of nociceptive nasal stimuli and their contribution to enhancement of cough. 21 spontaneously breathing, urethane anaesthetized animals were used. The controls received intranasal saline, stimulation group received capsaicin (15 μl, 50 μM), and not-treated group was free of nasal challenge. After 2 h animals were deeply anaesthetized, exsanguinated and transcardially perfused with saline and paraformaldehyde. The brainstems were removed, post-fixed, and slices were processed immunohistochemically for c-fos. In capsaicin group the FLI was detected in the nTs 0.5 mm caudal, 1.5 mm lateral to the obex, the area postrema, LRN and VRG. Intensive FLI was identified in trigeminal nuclear complex. Mean number of FOS positive neurons per section was significantly higher in capsaicin group than that in no-treatment controls or saline controls at the level of obex (p < 0.01). Neurons of nTs and VRG clearly activated after nasal provocation may participate in enhancement of cough.     

Membrane capacitance increases induced by histamine and cyclic AMP in single gastric acid-secreting cells of the guinea pig

Summary During acid secretion, gastric parietal cells undergo profound morphological changes including formation of the apical secretory membrane. To examine the mechanism of histamine-induced increases in the apical membrane area at the single cell level, we monitored the membrane capacitance by applying a time-resolved phase-sensitive detection method to singly isolated parietal cells of guinea pig. A real-time increase in the membrane capacitance was detected within several min after stimulation with histamine. An H2-blocker (cimetidine), but not an H1-blocker (pyrilamine), inhibited the histamine response. Dibutyryl cyclic AMP mimicked the histamine effect. The capacitance response to histamine was sensitive to cytosolic Ca²⁺, temperature and N-ethylmaleimide. The histamine response was inhibited by intracellular application of a non-hydrolyzable ATP analog (AMP-PNP) and an isoquinolinesulfonamide derivative that works as an inhibitor of protein kinase A (H-8). These results indicate that in parietal cells, elevation of intracellular cyclic AMP induces exocytotic insertion of intracellular membranes into the plasma membrane, presumably by activating protein kinase A.     

Effects of the antidiuretic hormone,arginine vasotocin,theophylline, filipin and A23187 on cyclic AMP in isolated frog skin epithelium (Rana temporaria)

A method for measuring cAMP in frog skin epithelium was developed. The epithelia were isolated after collagenase-treatment. cAMP was extracted by boiling water and the extract was purified on dry AI₂O₃. The change with time of the cAMP level after addition of arginine vasotocin (AVT) was studied. The hormone caused a rapid increase in cAMP level with a maximum after 3–5 min, whereafter the cAMP level declined. Incubation with AVT made the epithelia refractory to a second dose of AVT, which indicates that the decline in cAMP level was caused by a feedback mechanism and not by inactivation of the hormone. cAMP appeared evenly distributed in all cell-layers of the epithelia both before and after stimulation with AVT. Theophylline caused a rapid increase in the cAMP level, which remained elevated for at least 45 min. Addition of the ionophore A23187 or of filipin had no effect on the cAMP level. However, in the presence of theophylline, A23187 enhanced the cAMP level, whereas filipin had no effect. Therefore the involvement of cAMP in the action of A23187 has to be considered.     

A comparative study on the uptake and subsequent decarboxylation of monoamine precursors in cerebral microvessels

The endothelial cells and pericytes of brain microvessels (capillaries and small veins) are equipped with an enzymatic barrier, impeding the passage of circulating amino acids, such as amine precursors, into the brain. The properties of this mechanism was studied in brain slices and isolated microvessels from various species including man and also fetal material, following incubation in dihydroxyphenylalanine (DOPA), 5-hydroxytryptophan (5-HTP) and dihydroxyphenylserine (DOPS). A stereospecific, energy-dependent uptake leading to accumulation in the brain microvessel walls was found in all species studied; this process was found to exist already prenatally. The capacity of decarboxylation, the second step in the trapping mechanism at the blood-brain interphase, showed considerable species variation. The enzyme was present also in fetal brain microvessels. Inhibition experiments provided support for the presence of monoamine oxidase, but absence of catechol-O-methyl transferase, in the microvessel walls.     

Altering the blood-brain barrier in the rat by intracarotid infusion of polycations: a comparison between protamine,poly-L-lysine and poly-L-arginine

To evaluate the role of surface charge for the blood-brain barrier permeability, the albumin content was determined in the cerebrospinal fluid and in the brain 1 h after intracarotid infusion of protamine sulphate, a natural polycationic protein with a high content of arginine (mol. wt 4000–4400), poly-L-arginine (mol. wt 11600) or poly-L-lysine (mol. wt 10200). Five milligrams (4 ± 10^-4 mmol) poly-L-arginine increased the albumin content in the brain IS times more than S mg (5 ± 10^-4 mmol) poly-L-lysine (P < 0.001) and 3.5 times more than 5 mg (1 times 10^-3 mmol) protamine (P < 0.001); the difference between protamine and poly-L-lysine was also significant (P < 0.05). After 0.5 mg (4 ± 10^-4 mmol) poly-L-arginine the albumin extravasation was still higher than after 5 mg protamine (P < 0.01) and 5 mg poly-L-lysine (P < 0.001). Cisternal albumin increased from control values 0.08 mg ml^-1 to 0.30, 0.46 and 1.21 mg ml^-1 in rats given 5 mg poly-L-lysine, protamine and poly-L-arginine, respectively (P < 0.01 for difference between arginine and the other two substances). The higher mol. wt and positive charge of poly-L-arginine may at least in part explain the more pronounced albumin leakage after arginine than after protamine. However, the difference between poly-L-arginine and poly-L-lysine suggests that other factors, possibly related to the guanidino groups, contribute to the blood-brain barrier opening by poly-L-arginine.     

The effect of high ascorbic acid doses on the course of pregnancy in the guinea pig and on the progeny

Summary The work is a continuation of investigations made earlier by the author (Bull. of Exp. Biol. and Med. No. 10, 1962) on the effect of ascorbic acid on the function of the genital organs of female guinea pigs. This work contains data on the effect produced by ascorbic acid excess on the course of pregnancy and on the progeny.It was shown that prolonged (during the whole course of pregnancy) daily per oral administration of ascorbic acid to female guinea pigs (high doses –500 mg per animal, and physiological doses 50 mg per animal) led to pathology of pregnancy and of the progeny.This pathology is manifested by a considerable percentage of abortions at various periods, as well as by stillbirths and by birth of nonviable progeny. Histomorphological examination of internal organs of stillborn and nonviable animals revealed marked tissue hypoxia.Presented by Active Member A. P. Nikolaeva AMN SSSR Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 57, No. 4, pp. 105–108, April, 1964     

TPA对离体豚鼠心脏收缩性及对氯仿致小鼠心律失常保护作用的研究

目的 :观察TPA的强心作用及抗心律失常作用。方法 :Langendorff灌流离体豚鼠心脏 ,观察药物对心脏收缩力及心率的影响 ;用氯仿致小鼠心律失常 ,观察TPA对心脏的保护作用。结果 :1 0 3mol·L 1TPA二甲亚砜液、1 0 3mol·L 1盐酸TPA液都能非常显著地加强心脏收缩力 ,增幅分别达 1 86± 40 % (P <0 .0 1 ,n =8)、1 64± 3 1 % (P <0 .0 1 ,n =9) ,其强心作用与阳性对照 (7.0 6× 1 0 6 mol·L 1毒毛旋花甙K ,增幅 1 94± 42 % ,n =6)相比无显著性差异彩 ;TPA对心率及心跳节律影响较小。TPA有抗氯仿致小鼠室颤的作用 ,3 0mg·kg 1TPA组室颤发生率 (3 8% ,n =2 1 )与阴性对照发生率 (88% ,n =1 6)相比有非常显著的差异 (P <0 .0 1 )。结论 :TPA有较强增强心肌收缩力作用及抗心律失常作用 ,有进一步研究的价值     

Detection of immunoglobulin determinants on lymphocytes of the rabbit, mouse, guinea pig and chicken by the mixed antiglobulin reaction: effect of pretreating the lymphocytes with formaldehyde

The mixed antiglobulin reaction given by circulating and lymph node lymphocytes from a number of laboratory animals has been examined.In previous experiments on human lymphocytes stored at ?180°C it was found that cells from human patients with chronic lymphatic leukaemia, unlike those from normal persons, showed a reactivity that increased with increasing concentration of sensitized indicator erythrocytes. In the present work, lymphocytes from the rabbit, mouse and guinea pig, tested by the mixed antiglobulin reaction in the same way, showed no such dose-dependency, and thus resembled lymphocytes from normal persons. Cells from the chicken showed much greater variability in numbers of reacting lymphocytes over the range of indicator cells used, but usually showed peak reactivity with 0.6% indicator cells.Further experiments showed that suspensions of mouse, guinea pig and chicken lymphocytes yielded higher numbers of detectable Ig-bearing cells after treatment with formaldehyde than did untreated suspensions tested fresh or after storage either at 4°C or at ?180°C. The reactivity of rabbit lymphocytes, however, was not always increased by formaldehyde-treatment. The question of the specificity of the enhanced mixed antiglobulin reaction given by cells treated with formaldehyde is discussed.