Classical conditioning modifies cytochrome oxidase activity in the auditory system

The effects of excitatory classical conditioning on cytochrome oxidase activity in the central auditory system were investigated using quantitative histochemistry. Rats in the conditioned group were trained with consistent pairings of a compound conditional stimulus (a tone and a light) with a mild footshock, to elicit conditioned suppression of drinking. Rats in the pseudorandom group were exposed to pseudorandom presentations of the same tone, light and shock stimuli without consistent pairings. Untrained rats in a naive group did not receive presentations of the experimental stimuli. The findings demonstrated that auditory fear conditioning modifies the metabolic neuronal responses of the auditory system, supporting the hypothesis that sensory neurons are responsive to behavioural stimulus properties acquired by learning. There was a clear distinction between thalamocortical and lower divisions of the auditory system based on the differences in metabolic activity evoked by classical conditioning, which lead to an overt learned behavioural response versus pseudorandom stimulus presentations, which lead to behavioural habituation. Increases in cytochrome oxidase activity indicated that tone processing is enhanced during associative conditioning at upper auditory structures (medial geniculate nucleus and secondary auditory cortices). In contrast, metabolic activation of lower auditory structures (cochlear nuclei and inferior colliculus) in response to the pseudorandom presentation of the experimental stimuli suggest that these areas may be activated during habituation to tone stimuli. Together these findings show that mapping the metabolic activity of cytochrome oxidase with quantitative histochemistry can be successfully used to map regional long-lasting effects of learning on brain systems.     

An ultrathin frozen section is suitable for demonstrating cytochrome c oxidase activity at electron microscopic level

Multiple factors influence the outcome of in vitro fertilisation and embryo transfer (IVF-ET). In our prospective study different factors have been subject of examination concerning their effect on the outcome of in vitro fertilisation and embryo transfer. 1237 couples undergoing 1675 consecutive treatment cycles between 1.1.1990-31.12.1991 were included in this study. Prior to treatment, couples were divided into "good" and "poor" prognosis groups. Cycles were prospectively labelled as carrying a potentially "poor prognosis", if one or more of the following factors were noted: 1) female age > 35; 2) an existence of male factor; 3) couples with more than 3 previous unsuccessful treatment cycles. Couples with none of these factors were assigned to the "good" prognosis group. The pregnancy rate per cycle in the "poor" prognosis group was 5.96%, compared with 17.92% per cycle in the "good" prognosis group (p < 0.001). The most important factors determining pregnancy rates were female age and male factor, and we observed that the rate of pregnancy declined after the third treatment cycle. An explanation may be seen in lower fertilisation rates after the age of 35 and cases of poor semen quality. Both will result in poor embryo quality.     

Contributions of regularly and irregularly discharging vestibular-nerve inputs to the discharge of central vestibular neurons in the alert squirrel monkey

The discharge of neurons in the vestibular nuclei was recorded in alert squirrel monkeys while they were being sinusoidally rotated at 2 Hz. Type I position-vestibular-pause (PVP I) and vestibular-only (V I) neurons, as well as a smaller number of other type I and type II eye-plus-vestibular neurons were studied. Many of the neurons were monosynaptically related to the ipsilateral vestibular nerve. Eye-position and vestibular components of the rotation response were separated by multiple regression. Anodal currents, simultaneously delivered to both ears, were used to eliminate the head-rotation signals of irregularly discharging (I) vestibular-nerve afferents, presumably without affecting the corresponding signals of regularly discharging (R) afferents. R and I inputs to individual central neurons were determined by comparing rotation responses with and without the anodal currents. The bilateral currents, while reducing the background discharge of all types of neurons, did not affect the mean vestibular gain or phase calculated from a population of PVP I neurons or from a mixed population consisting of all type I units. From this result, it is concluded that I inputs are canceled at the level of secondary neurons. The cancellation may explain why the ablating currents do not affect the gain and phase of the vestibulo-ocular reflex. While cancellation was nearly perfect on a population basis, it was less so in individual neurons. For some neurons, the ablating currents decreased vestibular gain, while for other neurons the vestibular gain was increased. The former neurons are interpreted as receiving a net excitatory (I-EXC) I input, the latter neurons, a net inhibitory (I-INH) input. When compared with the corresponding R inputs, the I inputs were usually small and phase advanced. Phase advances were larger for I-EXC than for I-INH inputs. The sign and magnitude of the I inputs were unrelated to other discharge properties of individual neurons, including discharge regularity and the phase of vestibular responses measured in the absence of the ablating currents. Unilateral currents were used to assess the efficacy of ipsilateral and contralateral pathways. Ipsilateral pathways were responsible for almost all of the effects seen with bilateral currents. The results suggest that the vestibular signals carried by central neurons, even by those neurons receiving a monosynaptic vestibular-nerve input, are modified by polysynaptic pathways.     

Effect of infants on adult social relations in the squirrel monkey (Saimiri Sciureus)

7 groups of squirrel monkeys were observed to assess the effect of infants on social interactions and interanimal distances among adult members of their natal groups. Each group contained one or two infants, 5 to 7 months of age at the start of the study. Infants initiated affiliative and playful interactions with all adults, whereas adults directed few mostly antagonistic, interactions toward infants. Following the removal of infants from groups, distances between adults decreased and adult affiliative interactions increased more than 100%. The results indicate that infants within the age range examined can have a pervasive, primarily inhibitory, influence on adult social relationships.     

Effect of posterior parietal and frontal neocortical lesions in the squirrel monkey.

2 groups of squirrel monkeys with frontal or parietal cortical lesions and an unoperated control group (N = 12) received the following in the order mentioned: brightness discrimination; 3 forms of a spatial pattern discrimination in which the essential cue and site of reinforcement were separated (SSP); delayed response; form discrimination; and 3 forms of a spatial pattern discrimination in which the essential cue and site of reinforcement were identical. Ss with frontal lesions were impaired on delayed response, and those with parietal lesions were impaired on form and SSP discriminations. Neither group was impaired on brightness discrimination. Results confirm and extend previous findings that the posterior parietal cortex of nonhuman primates is critically involved in visually guided spatial discriminations when the primary cue and the site of reinforcement are separated. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increment-threshold spectral sensitivity in the squirrel monkey.

Measured the spectral sensitivity of 5 adult squirrel monkeys and 2 human males in an increment-threshold context. Under conditions of dark adaptation the spectral sensitivity of the squirrel monkey was closely similar to that of man. For conditions of light adaptation, the squirrel monkey showed maximal sensitivity at 540 nm. with subsidiary peaks at 600 and 440 nm. Relative to man, the squirrel monkey was considerably less sensitive to wavelengths longer than 580 nm. For this species there are substantial differences between the spectral sensitivity functions determined by increment-threshold methods and those obtained using critical flicker frequency (CFF) techniques. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Salivary cortisol: a non-invasive measure of hypothalamo-pituitary-adrenocortical activity in the squirrel monkey, Saimiri sciureus

STUDY OBJECTIVES: To study the in vitro effects of the serotonin2 (5-HT2) receptor agonist 1-(2.5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) in skeletal muscle specimens from malignant hyperthermia-susceptible (MHS) and normal (MHN) patients following pretreatment with the 5-HT2 receptor antagonist ritanserin. DESIGN: Prospective study. SETTING: Malignant hyperthermia (MH) laboratory at a university hospital. PATIENTS: 41 patients undergoing in vitro contracture test for diagnosis of MH susceptibility. INTERVENTIONS: Skeletal muscle biopsies in adult patients were performed with a 3-in-1 nerve block with 40 ml prilocaine 1%. In children, general anesthesia was induced with 50 micrograms/kg alfentanil intravenously (i.v.) and 2 to 2.5 micrograms/kg propofol i.v. and maintained with a continuous infusion of propofol (< or = 150 micrograms/kg/min) and nitrous oxide (66%) in oxygen. MEASUREMENTS AND MAIN RESULTS: Patients were first classified as MHS or MHN by the in vitro contracture test according to the European MH protocol. Surplus muscle specimens of 21 MHS and 20 MHN patients were used in this study. At first, DOI was added to the organ bath at a concentration of 0.02 mM. In the second part of the study, muscle specimens were preincubated with ritanserin 0.01 mM for 10 minutes before DOI 0.02 mM was added to the bath. Muscle specimens from all patients developed contractures after administration of DOI. The onset of contractures was significantly faster in MHS muscles, and the magnitude of contracture was significantly greater than in MHN. The muscle twitch decreased significantly in both groups after DOI. After pretreatment with ritanserin, start of contracture was significantly delayed in MHS muscles. MHN muscles failed to develop contractures. The maximum level of contracture was significantly reduced in MHS. Muscle twitch decreased also in both MHS and MHN groups. CONCLUSIONS: The findings may indicate that stimulation of 5-HT2 receptors is involved in MH induction. Furthermore, 5-HT2 receptor antagonists could possibly be effective in preventing MH. Additional studies are required to determine if administration of 5-HT2 receptor antagonists could be of additional value in the treatment or prevention of anesthetic-induced MH.     

Neural conduction velocity of the human auditory nerve: bipolar recordings from the exposed intracranial portion of the eighth nerve during vestibular nerve section

We measured the conduction velocity of the intracranial portion of the auditory nerve in 3 patients undergoing vestibular nerve section to treat Ménière's disease. The conduction velocity varied from patient to patient, with an average value of 15.1 m/sec. The latency of peak III of the brain-stem auditory evoked potentials (BAEPs) increased by an average of 0.5 msec as a result of exposure of the eighth nerve, and if that increase is assumed to affect the entire length of the auditory nerve (2.6 cm) evenly, then the corrected estimate of conduction velocity would be 22.0 m/sec. Estimates of conduction velocity based on the interpeak latencies of peaks I and II of the BAEP, assuming that peak II is generated by the mid-portion of the intracranial segment of the auditory nerve, yielded similar values of conduction velocities (about 20 m/sec).     

Mitochondrial fixation for the detection of cytochrome oxidase activity using microwave irradiation

We examined cell fixation with microwave irradiation (MWI) used in cytochemistry. MWI was applied to blocks of about 1 mm3 of mouse parotid glands at 500 W for about 5 sec in a fixative at 37 degrees C. The activities of endogenous peroxidase and mitochondrial cytochrome oxidase were demonstrated by using the DAB method with 3,3'-diaminobenzidine (DAB) and 0.01% H2O2. Under electron microscopy, peroxidase activity was localized in the nuclear envelope, endoplasmic reticulum and secretory granules. However, mitochondria cytochrome oxidase activity seemed to be rather weak against the MWI at 37 degrees C. Moreover, suspension of isolated hamster liver mitochondria was fixed by MWI and also demonstrated cytochrome oxidase activity by using the cytochemical methods with DAB, cytochrome c, catalase and sucrose. Such mitochondrial fractions were subjected to 6-second MWI given 10 or 18 times with an interval of 10 seconds with and without a chilled water bath. The final temperature of each fixative was kept at about 10 degrees C or rose to about 37 and 55 degrees C. When we took care to keep the temperature below 10 degrees C, the DAB reaction products accumulated in the mitochondrial intermembrane-intracristal space. No mitochondrial deposits were observed when the temperatures of the fixatives rose to 37 and 55 degrees C. These results indicated that peroxidase was very resistant to the heat with MWI fixation. Cytochrome oxidase is sensitive to the heat with MWI, so, a chilled water bath had to be used.     

Lipid peroxidation and changes in cytochrome c oxidase and xanthine oxidase activity in organophosphorus anticholinesterase induced myopathy

The data gained from clinical studies in the past years have indicated that the thrombolytic therapy (TL) has favourable effect on patients with acute myocardial infarction (AMI). It is aimed at reperfusion in the ischaemic area, a decrease in the extent of infarction site and a decrease in mortality. TL administered within the initial hours after the onset of AMI leads to better results than when administered after several hours. Currently, TL is not limited by age. The patients who were given streptokinase (SK) or anistreplase (APSAC) prior to more than 4 days, if necessary, urokinase or alteplase (rt-PA) should be given. There are differences in the opinions as to the optimal selection of thrombolytic drugs. However, all currently used drugs lead to a significant decrease in mortality due to AMI. The preferential use of accelerated administration of rt-PA in contrast to SK is justified in younger patients with extensive AMI of the anterior wall, in whom the therapy has begun within 4 hours since its onset. The occurrence of severe bleeding indicates that TL should be halted and coagulation factors should be replaced by freshly frozen plasma or fibrinogen concentrate, if necessary, transfusion of full blood should take place. If the severe bleeding occurs shortly after the administration of SK, the persisting plasminaemia can be arranged by antifibrinolytic drugs. An improvement in TL results can be achieved by adjuvant antithrombotic therapy. At the same time, in addition to acetylsalicylic acid, the patient treated with rt-PA should be given heparin. Heparin administration is not necessary in patients treated with SK or APSAC. However, heparin is indicated in patients at risk due to systemic embolization in congestive heart disease, extensive infarction or atrial fibrillation. (Tab. 1, Ref. 28.)     

Thermodynamic volume cycles for electron transfer in the cytochrome c oxidase and for the binding of cytochrome c to cytochrome c oxidase

Determining the way in which deleterious mutations interact in their effects on fitness is crucial to numerous areas in population genetics and evolutionary biology. For example, if each additional mutation leads to a greater decrease in log fitness than the last (synergistic epistasis), then the evolution of sex and recombination may be favored to facilitate the elimination of deleterious mutations. However, there is a severe shortage of relevant data. Three relatively simple experimental methods to test for epistasis between deleterious mutations in haploid species have recently been proposed. These methods involve crossing individuals and examining the mean and/or skew in log fitness of the offspring and parents. The main aim of this paper is to formalize these methods, and determine the most effective way in which tests for epistasis could be carried out. We show that only one of these methods is likely to give useful results: crossing individuals that have very different numbers of deleterious mutations, and comparing the mean log fitness of the parents with that of their offspring. We also reconsider experimental data collected on Chlamydomonas moewussi using two of the three methods. Finally, we suggest how the test could be applied to diploid species.     

Functional properties of retinal ganglion cells during optic nerve regeneration in the goldfish

Perfringolysin O (theta-toxin) is a cholesterol-binding and pore-forming toxin that shares with other thiol-activated cytolysins a highly conserved sequence, ECTGLAWEWWR (residues 430-440), near the C-terminus. To understand the membrane-insertion and pore-forming mechanisms of the toxin, we evaluated the contribution of each Trp to the toxin conformation during its interaction with liposomal membranes. Circular dichroism (CD) spectra of Trp mutant toxins indicated that only Trp436 has a significant effect on the secondary structure, and that Trp436, Trp438, and Trp439 make large contributions to near-UV CD spectra. Quenching the intrinsic Trp fluorescence of the wild-type and mutant toxins with brominated lecithin/cholesterol liposomes revealed that Trp438 and probably Trp436, but not Trp439, contributes to toxin insertion into the liposomal membrane. Near-UV CD spectra of the membrane-associated mutant toxins indicated that both Trp438 and Trp439 are required for the CD peak shift from 292 to 300 nm, a signal related to theta-toxin oligomerization and/or pore formation, suggesting a conformational change around Trp438 and Trp439 in these processes.     

Mercury accumulation in the squirrel monkey eye after mercury vapour exposure

Squirrel monkeys were exposed to mercury vapour at different concentrations and for different numbers of days. The calculated total mercury absorption ranged between 1.4-2.9 mg (range of daily absorption 0.02-0.04 mg). The monkeys were killed at different intervals after the end of exposure (range 1 month - 3 years) and the eyes were enucleated. Eyes from four un-exposed monkeys were used as control material. Mapping of the mercury distribution in the eye revealed that the non-myelin-containing portion of the optic disc was densely loaded with mercury deposits, which are mostly confined to the capillary walls and the glial columns. The white matter of the brain does not accumulate mercury at these exposure levels, which might suggest that the myelinization process inhibits the accumulation of mercury. The pigmented epithelium of the pars plicata of the ciliary body and of the retina contained a considerable amount of mercury. This finding indicates that mercury is trapped within the melanocytes, which keeps potentially dangerous material from reaching the neural retina. In addition, the retinal capillary walls were densely loaded with mercury deposits, even 3 years after exposure. It was also found that the inner layers of the retina accumulated mercury during a 3-year period. It is known that the biological half-time of mercury in the brain may exceed years. This seems also to be the case for the ocular tissue.     

A microtiter plate assay for cytochrome c oxidase in permeabilized whole cells

A new mouse retinal degeneration that appears to be an excellent candidate for modeling human retinitis pigmentosa is reported. In this degeneration, called rd-3, differentiation proceeds postnatally through 2 weeks, and photoreceptor degeneration starts by 3 weeks. The rod photoreceptor loss is essentially complete by 5 weeks, whereas remnant cone cells are seen through 7 weeks. This is the only mouse homozygous retinal degeneration reported to date in which photoreceptors are initially normal. Crosses with known mouse retinal degenerations rd, Rds, nr, and pcd are negative for retinal degeneration in offspring, and linkage analysis places rd-3 on mouse chromosome 1 at 10 +/- 2.5 cM distal to Akp-1. Homology mapping suggests that the homologous human locus should be on chromosome 1q.     

Isolation and characterization of Rhodobacter capsulatus mutants affected in cytochrome cbb3 oxidase activity

We describe a log-linear method for analysis of case-parent-triad data, based on maximum likelihood with stratification on parental mating type. The method leads to estimates of association parameters, such as relative risks, for a single allele, and also to likelihood ratio chi2 tests (LRTs) of linkage disequilibrium. Hardy-Weinberg equilibrium need not be assumed. Our simulations suggest that the LRT has power similar to that of the chi2 "score" test proposed by Schaid and Sommer and that both can outperform the transmission/disequilibrium test (TDT), although the TDT can perform better under an additive model of inheritance. Because a restricted version of the LRT is asymptotically equivalent to the TDT, the proposed test can be regarded as a generalization of the TDT. The method that we describe generalizes easily to accommodate maternal effects on risk and, in fact, produces powerful and orthogonal tests of the contribution of fetal versus maternal genetic factors. We further generalize the model to allow for effects of parental imprinting. Imprinting effects can be fitted by a simple, iterative procedure that relies on the expectation-maximization algorithm and that uses standard statistical software for the maximization steps. Simulations reveal that LRT tests for detection of imprinting have very good operating characteristics. When a single allele is under study, the proposed method can yield powerful tests for detection of linkage disequilibrium and is applicable to a broader array of causal scenarios than is the TDT.     

Behavioral thermoregulation in the squirrel monkey when response effort is varied.

Three adult male squirrel monkeys controlled the air temperature within their test chamber by pulling a chain to select between 2 preset air temperatures, 10 and 50Deg.C. When the force required to pull the chain was increased in steps from 2.94 to 6.86 N, interresponse interval increased, resulting in wider air temperature swings within the chamber. The average air temperature selected became progressively lower, producing a concomitant fall in skin temperature. However, internal body temperatures (rectal and brainstem) remained nearly constant due to a compensatory increase in metabolic heat production. By allowing a cooler, rather than warmer, environment to result from a decreased response rate, Ss guarded against hyperthermia, which they were ill equipped to handle autonomically. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of feedback from peripheral movements on neuron activity in the aplysia abdominal ganglion

We have made reasonably comprehensive measurements of action potential activity in the Aplysia californica abdominal ganglion to determine the amount of feedback the central nervous system (CNS) receives from a movement which it initiates. Voltage-sensitive dye measurements of action potential activity of cells in the ganglion were made during the gill-withdrawal reflex elicited by siphon stimulation. We compared recordings in two situations which differed dramatically in the amount the gill moved. In the control sea water, the gill withdrawal was normal; in low-Ca2+, high-Mg2+ sea water, the gill movement was blocked. Both the timing and the number of spikes of the individual neurons were similar in the two situations. Histograms of the summed spike activity versus time and histograms of the number of active neurons versus time in the two conditions were also similar. Finally, two numerical measures of trial-to-trial differences, a paired t-test and a measure we named fractional similarity, did not indicate larger differences between two trials in the different sea waters than two trials in the same sea water. Feedback from sensory neurons activated by the gill movement itself does not make a large contribution to the spike activity in the abdominal ganglion. Apparently the Aplysia CNS issues the command for the withdrawal and does not make adjustments for the magnitude of the actual withdrawal. It may not even receive the information necessary for such adjustments to be made. A second motivation for these experiments was to test whether removing the feedback might simplify the neuronal activity that occurs during the gill-withdrawal reflex. This did not occur.