Collection and quality of rhesus monkey semen

Electroejaculation is an accepted method of semen collection from nonhuman primates. Although both penile and rectal probe stimulation techniques have been used, there has been a general lack of consistency and detail regarding their application. This report describes the collection, processing, and evaluation of rhesus monkey semen contrasting two methods of penile electroejaculation: 1) a constant-voltage method where stimulus current is a variable and 2) a constant-current method where stimulus current is operator-controlled. The constant-current method was the more efficient procedure, requiring a lower stimulus current for successful electroejaculation. The influence on semen quality of potentially toxic agents used in the procedure, surgical glove powder and electrolyte cream, was tested; both were detrimental as measured by motility loss. No correlation was found between coagula volume and sperm numbers. The intra- and interanimal variability in semen samples from six monkeys was also evaluated. Penile electroejaculation, combined with control of stimulus current, provides a consistent, successful, and humane method for the collection of semen in the rhesus monkey.     

Seasonal influence on semen traits and freezability from locally adapted Curraleiro bulls

Studies were conducted to characterize the effect of season of the year on testicular morphology, fresh and frozen/thawed semen quality from Curraleiro (Pé-duro) bulls in the Brazilian Central west region. Five adult, healthy bulls underwent an andrological examination and semen collection using an electroejaculator, once a month for a year. Fresh and thawed semen were evaluated for progressive sperm motility and sperm vigor, sperm morphology and acrosomal integrity. Testicular length and volume were less (P<0.05) in April than in the other months of the year. For fresh semen, the ejaculate in April had less volume and sperm concentration (P<0.05), while sperm vigor was less (P<0.05) in June, increasing in January and February. With the frozen/thawed semen, the proportion of sperm was greater (P<0.05) in April to July, decreasing from October to December. Semen collected in December had the greatest (P<0.05) proportion of major defects while that collected in February/March had the highest proportion of minor defects. The proportion of live intact sperm reduced progressively from December to April/May. The marginal influence of the time of the year on testicular biometry and fresh semen in Curraleiro bulls shows the adaptation of this breed to the environmental conditions in the region. Thus, reproduction with natural mating should be successful at any time of year. For frozen semen collection for conservation programs, the best time of year is from June to September.     

Sperm morphology is better in the second ejaculate than in the first in domestic cats electroejaculated twice during the same period of anesthesia

Several species produce ejaculates of inferior quality after a period of sexual abstinence, but the frequency of semen collection has thus far not been shown to affect sperm morphology in felids. The aim of this study was to determine whether sperm morphology and motility would differ between 2 ejaculates collected from the same cat within a short interval. Fifteen male domestic cats were anesthetized and then electroejaculated twice, with a 5- to 10-min interval between treatments. A standardized electroejaculation regimen was used with 80 stimuli, from 2 to 5 V, for each ejaculate. The first ejaculates contained significantly higher (P < 0.05) proportions of distal droplets, coiled tails and immotile spermatozoa than the second ejaculates, which contained significantly higher proportions of morphologically normal spermatozoa (40.9 vs 54.6%) but a lower sperm count (39.0 x 10(6) vs 5.2 x 10(6)). The higher proportions of defective spermatozoa and the lower motility in the first ejaculate than in the second were probably due to the aging of spermatozoa in the epididymis. These results show that the second ejaculate collected within a short interval has better sperm morphology and motility than the first and that this should be considered when evaluating semen quality in the domestic cat and when collecting cat semen to be used for artificial insemination or to be frozen for storage.     

Responses of simple and non-oriented cells to stimuli of variable duration in areas 17 and 18 of cat visual cortex.

Single unitresponses to photic stimuli of variable duration were studied in the cat visual areas 17 and 18. The closed-chamber technique was used to record extracellularly impulsive electrical activity in locally anaesthetized, Flaxedil-paralyzed and artificially ventilated cats. Stimulus duration ranges between 0.020 and 10 sec, the background luminance and the intensity of stimuli being constant. We found a first group of cells which fire independently of the stimulus duration; a second group which fire in close relation to the stimulus duration in a rather wide range of values, and a third group which fire monotonously as long as the stimulus goes on. The three groups of cells are supposed to be three functionally different types of cortical cells.     

Welfare aspects of theriogenology: investigating alternatives to electroejaculation of bulls

Evaluation of the breeding soundness of bulls is an important management tool. Electroejaculation has been a reliable method of obtaining a semen sample for the purpose of evaluating breeding soundness, but is considered by some to be inhumane on the grounds that it is painful. This paper provides a review of studies conducted to find ways to both measure, as well as lessen, pain associated with electroejaculation, and to explore alternatives to electroejaculation in bulls. Changes in heart rate, serum cortisol, serum progesterone, relative aversion, and degrees of vocalization, struggling and lying down have been used to assess the pain associated with electroejaculation. Transrectal massage and artificial vaginas, and oxytocin and cloprostenol have been investigated as alternatives to, and facilitators of electroejaculation, respectively. Epidural, intravenous and topical anesthetics have been used to ameliorate the pain associated with electroejaculation. Serum progesterone and degrees of vocalization are useful for measuring the pain associated with electroejaculation in bulls. Transrectal massage and artificial vaginas are not as efficacious as electroejaculation for obtaining a semen sample and drugs used to facilitate or decrease pain associated with electroejaculation have not been efficacious enough to warrant use. Transrectal massage of the ampullae may be of some use as an alternative to electroejaculation in docile bulls and may be also be used to decrease the duration of subsequent electroejaculation. Pain associated with electroejaculation may be influenced by operator technique; therefore, operators of electroejaculator equipment must strive to apply electrical stimulation as gently as possible.     

Stallion ejaculation induced by manual stimulation of the penis

This paper reports the use of a procedure for collection of semen from stallions by manual stimulation of the penis while the stallion is standing. Our use of this method with 18 stallions of various ages and types of semen collection experience indicates that this method may be an efficient alternative to traditional semen collection techniques using an artificial vagina and stimulus mare or dummy mount mare. Our observations, together with those of others who have tried the manual technique, suggest that both animals and handlers can be readily trained to use this method. Limited data suggests that semen samples obtained by manual stimulation are similar to those obtained using an artificial vagina.     

A model-based approach for the analysis of neuronal information transmission in multi-input and -output systems

We present a new method to characterize multi-input and output neuronal systems using information theory. To obtain a lower bound of transinformation we take three steps: (1) Estimation of the deterministic response to isolate components carrying stimulus information. The deviation of the original response from the deterministic estimate is defined as noise. (2) Coordinate transformation using PCA yields an uncorrelated representation. (3) Partial transinformation values are calculated independently either by Shannon's formula assuming normality or based on density estimation for arbitrary distributions. We investigate the performance of the algorithms using simulated data and discuss suitable parameter settings. The approach allows to evaluate the degree to which stimulus features are encoded. Its potential is illustrated by analyses of neuronal activity in cat primary visual cortex evoked by electrical retina stimulation.     

Use of oxytocin and cloprostenol to facilitate semen collection by electroejaculation or transrectal massage in bulls

Two experiments were conducted with 24 bulls in which semen collection was attempted by transrectal massage (RM) and electroejaculation (EE). In experiment 1, bulls received the following treatments on successive semen collection days: saline 10 min prior to electroejaculation (control); saline 10 min prior to 2 min of transrectal massage followed by electroejaculation; cloprostenol (CLO) 10 min prior to 2 min of transrectal massage followed by electroejaculation; oxytocin (OXY) 10 min prior to 2 min of transrectal massage followed by electroejaculation. Transrectal massage consisted of general, back and forth motion over the ampullae, prostate and urethra with a flattened hand.

In experiment 2, bulls received saline (control), oxytocin, or cloprostenol 10 min before attempting semen collection by transrectal massage. Massage was applied specifically to the ampullae for a maximum of 5 min or until a semen sample was obtained. Electroejaculation was attempted in all bulls following transrectal massage.

In experiment 1, semen was obtained in <1% of bulls by transrectal massage. However, by using an improved massage technique in experiment 2, semen was obtained in 97.2% of attempts. Semen was obtained in 96.9 and 98.9% of attempts by electroejaculation in experiments 1 and 2, respectively.

Oxytocin treatment increased the time to penile protrusion during electroejaculation in experiment 1 and during massage in experiment 2. In experiment 1, oxytocin decreased the time to semen emission and tended to decrease the number of electroejaculation stimuli to semen emission. Cloprostenol treatment, in experiment 1, resulted in an increased number of electroejaculation stimuli to penile protrusion, but did not affect the number of stimuli required for semen emission.

Massage of the ampullae prior to electroejaculation reduced both the time to semen emission and the number of electroejaculation stimuli required for semen emission. Transrectal massage of the ampullae was very effective in this experiment for producing semen emission, but quantity of semen samples was less than for electroejaculation. The usefulness of transrectal massage for semen collection in breeding soundness evaluations needs to be investigated further under field conditions.     

Assessing the encoding of stimulus attributes with rapid sequences of stimulus events

In a preceding paper (M. Eger and R. Eckhorn, J. Comput. Neurosci., 2002) we have published a three step method for the quantification of transinformation in multi-input and -output neuronal systems. Here we present an extension that applies to rapid series of transient stimuli and thus, fills the gap between the discrete and continuous stimulation paradigm. While the three step method potentially captures all stimulus aspects, the present approach quantifies the discriminability of selected attributes of discrete stimuli and thus, assesses their encoding. Based on simulated and recorded data we investigate the performance of the implemented algorithm. Our approach is illustrated by analyses of neuronal population activity from the visual cortex of the cat, evoked by electrical stimuli of the retina.     

Label-free electrical detection of DNA hybridization for the example of influenza virus gene sequences

Microarrays based on DNA-DNA hybridization are potentially useful for detecting and subtyping viruses but require fluorescence labeling and imaging equipment. We investigated a label-free electrical detection system using electrochemical impedance spectroscopy that is able to detect hybridization of DNA target sequences derived from avian H5N1 influenza virus to gold surface-attached single-stranded DNA oligonucleotide probes. A 23-nt probe is able to detect a 120-nt base fragment of the influenza A hemagglutinin gene sequence. We describe a novel method of data analysis that is compatible with automatic measurement without operator input, contrary to curve fitting used in conventional electrochemical impedance spectroscopy (EIS) data analysis. A systematic investigation of the detection signal for various spacer molecules between the oligonucleotide probe and the gold surface revealed that the signal/background ratio improves as the length of the spacer increases, with a 12- to 18-atom spacer element being optimal. The optimal spacer molecule allows a detection limit between 30 and 100 fmol DNA with a macroscopic gold disc electrode of 1 mm radius. The dependence of the detection signal on the concentration of a 23-nt target follows a binding curve with an approximate 1:1 stoichiometry and a dissociation constant of KD=13+/-4 nM at 295 K.     

Semen evaluation in the chamois of Abruzzi (Rupicapra pyrenaica ornata)

The chamois of Abruzzi (Rupicapra pyrenaica ornata) has been classified as endangered by the World Union for Conservation. The objective of this study was to analyze seasonal differences in the characteristics of various male reproductive organs and in semen quality. The study was conduced during 2004 in the reserve of Lama dei Peligni (Italy) on three chamois males aged between 2 and 5 years. Males were captured during March-May months and October-December months. Various testicular and scrotal measurements were taken and semen was collected using an electroejaculator. Sperm motility pattern was evaluated using computer assisted sperm analyzer, membrane integrity using differential staining and morphology with phase contrast microscopy. Testicular size, sperm motility membrane integrity and the percent of morphological normal spermatozoa were greater during October-December. The authors concluded that sperm characteristics are strongly influenced by season and that semen collected in this period (breeding season) has suitable quality for manipulation and long-term preservation.     

The age-related characteristics of the correlation of involuntary and voluntary analysis during image recognition]

An experimental paradigm was used, based on the stimuli presentation in the absence and presence of the attention, directed to them; it allowed to divide involuntary (automatic) and voluntary (controlled) processing levels of the analysis, functioning parallelly in the process of real image identification. In conditions of this paradigm the regional and hemispheric organization of the evoked electrical activity (ERP and differential curves) was studied in youths aged 16-17 (11 persons) and children aged 7 (15 persons). The analysis of the differential curves revealed periods of negativation and positivation, connected with the automatic (unattended stimuli) and controlled (attended stimuli) analysis of images. Correlation of the identification success and singled out periods of differential curves has shown that in children aged 7 sensory decisions achieved on the automatic level are a significant contribution to the identification of images. Attraction of the attention to the stimulus in children aged 7 intensifies its processing, observed already after making the main decision on the character of the stimulus. In youths the success of identification correlated mainly with the processes at the controlled level; in this case the integrating role of the left frontal area at the final stage of the analysis is singled out.     

Electroejaculation in chimpanzees and gorillas and artificial insemination in chimpanzees

Electroejaculation was performed in 3 chimpanzees, 1 pygmy chimpanzee, and 2 gorillas with an instrument that delivers a modified sine wave current with a frequency of 24 Hz. The current stimuli were applied by a rectal probe with longitudinal electrodes. The electrical parameters varied from 6 to 12 V and from 30 to 40 mA for response of erection and lay between 8 and 18 V and between 40 and 145 mA during semen emission. Eleven chimpanzee semen samples showed the following data (x ± SD): total volume 1.9 ± 1.3 ml, volume of the liquid fraction 0.3 ± 0.2 ml, spermatozoa per ejaculate 743 ± 376 × 10⁶, sperm motility 52.7 ± 9.6%, morphologically abnormal spermatozoa 12.2 ± 7.5%. From an adult gorilla, three semen samples were collected, in each case without spermatozoa. The electrostimulation of a 6-year-old gorilla led to an erection, but not to semen emission. Three female chimpanzees were inseminated with fresh or frozen semen, each of them within three different estrous cycles. None of these inseminations led to a pregnancy.     

Pregnancy in the domestic cat after artificial insemination with previously frozen spermatozoa

Methods for collection, freeze preservation and artificial insemination of domestic cat semen were developed. Total sperm count and pre-freeze and post-thaw percent motility were significantly greater (P is less than 0.05) for samples collected by an artificial vagina method than for those collected by electroejaculation. Although conception rate was low (10.6%), 6 pregnancies were achieved, 2 after hormonal induction of oestrus.     

Multimodal assessment of pain in the esophagus: a new experimental model

A new multimodal pain assessment model was developed integrating electrical, mechanical, cold, and warmth stimuli into the same device. The device, with a bag and electrodes for electrical stimulation, was positioned in the lower part of the esophagus in 11 healthy subjects. Mechanical stimuli were delivered with an impedance planimetric system. Thermal stimuli were performed by circulating water of different temperatures (5-50 degrees C) inside the bag. All subjects reported both nonpainful and painful local and referred sensations to all stimuli. Temporal summation to repeated electrical stimuli could be studied. For all stimuli, there was a relationship between stimulus intensity and pain intensity. The referred pain area increased with increasing intensity of the electrical and mechanical stimuli. There were several differences between the sensations evoked by the four stimulus modalities, indicating activation of different visceral nerve pathways. This model offers the possibility for controlled multimodal stimuli activating the superficial and deeper layers of the human gut and should be used in basic, clinical, and pharmacological pain studies.     

Temporal pattern sensitive and nonsensitive responses in the cat's retinal ganglion cells

In order to characterize temporal pattern sensitivity in the cat ganglion cells, a new analysis technique by semi-Markov models which was developed in the previous papers (Tsukada et al., 1975–1977) was applied to input-output relations of the receptive-field. Three types of statistical spot stimuli positioned in the center region of receptive fields were used. Each type of stimulus has an identical histogram in the inter-stimulus intervals and therefore the same mean and variance, but different correlations between adjacent inter-stimulus intervals (Type 1, positive; Type 2, negative; and Type 3, independent processes). From the output spike trains of cat retinal ganglion cells to each stimulus, mean, variance, and histogram were computed. As the result of investigating these data, we could draw the following conclusion from the resultant output interval histograms. The receptive-field-center responses of cat ganglion cells can be classified into two groups (Types L and N) according to the difference of responsiveness to the three types of statistical spot stimuli. A Type L response has the same histogram in interspike intervals for all three stimuli, and is not sensitive to the temporal pattern, while a Type N response has three different forms depending on each type of stimulus showing high sensitivity to the temporal pattern. These results were also simulated by the Markov chain model and discussed with relation to neural coding and classification of ganglion cell types.     

Rectal probe electroejaculation of primates.

The technique of rectal probe electroejaculation has been developed to permit collection of semen using equipment proven safe, simple, and effective on the 30 primate species so far tested. This paper provides information on the construction and operation of this equipment, together with electrical parameters applicable to primate species. Seminal emission or ejaculation occurs in all species when alternating current is delivered at 0.25 mA/mm2 electrode area. The most effective frequency is 20 Hz, and the most acceptable anesthetic is ketamine hydrochloride.     

Hippocampal representation of touch-guided behavior in rats: persistent and independent traces of stimulus and reward location

Understanding the mechanisms by which sensory experiences are stored remains a compelling challenge for neuroscience. Previous work has described how the activity of neurons in the sensory cortex allows rats to discriminate the physical features of an object contacted with their whiskers. But to date there is no evidence about how neurons represent the behavioural significance of tactile stimuli, or how they are encoded in memory. To investigate these issues, we recorded single-unit firing and local field potentials from the CA1 region of hippocampus while rats performed a task in which tactile stimuli specified reward location. On each trial the rat touched a textured plate with its whiskers, and then turned towards the Left or Right water spout. Two textures were associated with each reward location. To determine the influence of the rat's position on sensory coding, we placed it on a second platform in the same room where it performed the identical texture discrimination task. Over 25 percent of the sampled neurons encoded texture identity--their firing differed for two stimuli associated with the same reward location--and over 50 percent of neurons encoded the reward location with which the stimuli were associated. The neuronal population carried texture and reward location signals continuously, from the moment of stimulus contact until the end of reward collection. The set of neurons discriminating between one texture pair was found to be independent of, and partially overlapping, the set of neurons encoding the discrimination between a different texture pair. In a given neuron, the presence of a tactile signal was uncorrelated with the presence, magnitude, or timing of reward location signals. These experiments indicate that neurons in CA1 form a texture representation independently of the action the stimulus is associated with and retain the stimulus representation through reward collection.