The Production of Nominal and Verbal Inflection in an Agglutinative Language: Evidence from Hungarian

The contrast between regular and irregular inflectional morphology has been useful in investigating the functional and neural architecture of language. However, most studies have examined the regular/irregular distinction in non-agglutinative Indo-European languages (primarily English) with relatively simple morphology. Additionally, the majority of research has focused on verbal rather than nominal inflectional morphology. The present study attempts to address these gaps by introducing both plural and past tense production tasks in Hungarian, an agglutinative non-Indo-European language with complex morphology. Here we report results on these tasks from healthy Hungarian native-speaking adults, in whom we examine regular and irregular nominal and verbal inflection in a within-subjects design. Regular and irregular nouns and verbs were stem on frequency, word length, and phonological structure, and both accuracy and response times were acquired. The results revealed that the regular/irregular contrast yields similar patterns in Hungarian, for both nominal and verbal inflection, as in previous studies of non-agglutinative Indo-European languages: the production of irregular inflected forms was both less accurate and slower than of regular forms, both for plural and past-tense inflection. The results replicate and extend previous findings to an agglutinative language with complex morphology. Together with previous studies, the evidence suggests that the regular/irregular distinction yields a basic behavioral pattern that holds across language families and linguistic typologies. Finally, the study sets the stage for further research examining the neurocognitive substrates of regular and irregular morphology in an agglutinative non-Indo-European language.     

Patients with impaired verb-tense processing: do they know that yesterday is past?

This paper begins with a focus on the task of stem inflection, where participants are given a verb stem and asked to produce the verb''s past-tense form, which can produce a neuropsychological double dissociation with respect to regular versus irregular verbs. Two differing theoretical interpretations are outlined: one is based on specifically morphological and separate brain mechanisms for processing regular versus irregular verbs; the other argues that the two sides of the dissociation can arise from one procedure, which is not specifically morphological, and which relies to differing extents on phonological versus semantic information for regular versus irregular verbs. We then present data from a different version of the task, in which patients were given past-tense forms and asked to produce the present-tense or stem forms (talked → talk and ate → eat). This change yielded a very different pattern of performance in four non-fluent aphasic patients as a function of the regular–irregular manipulation, an outcome which is argued to be more compatible with the single- than the dual-mechanism account. Finally, we present a small amount of data from a task in which the patient was asked to judge whether spoken regular and irregular verb stems and past-tense forms indicated actions occurring today or yesterday. This task produced an even more different and intriguing pattern of performance suggesting a deficit in morpho-syntactic knowledge: not how to produce past-tense forms but what such forms mean and how that understanding interacts with verb regularity. The paper concludes with a discussion of how the research field of acquired disorders of tense processing might advance as a result of new approaches, in particular those informed by studies of developmental disorders.     

Mechanisms of Reading in Persons with Different Levels of Written Text Comprehension

The aim of the present study was to investigate the reading mechanisms in adults (27 subjects; mean age, 19.5 ± 0.8 [SD] years) with different levels of written text comprehension using fMRI. The main objective was to analyze the basic brain mechanisms of verbal stimuli perception with and without semantic component during reading discrimination tasks. The BOLD signal changes during WORD and PSEUDOWORD reading comparing to GAZE FIXATION state were estimated using both analysis of whole brain activation and ROIs (structures connected with the brain system providing reading) in two groups of subjects, “good” and “poor” readers. It was revealed that activations were higher in “poor” readers in lingual gyrus, SMG, STG compared to “good” readers during PSEUDOWORD reading. It was supposed, that the strategies of words and pseudowords recognition differed in two groups of readers: “good” readers identified words or pseudowords already at the stage of visual analysis of “word” structure and demonstrated attempts to decode pseudowords (i.e., language lexical zones were not activated); “poor” readers, apparently, tried to read pseudowords using the same strategy as for the words reading referring to the lexicon, and after failure identified pseudowords as meaningless concepts. In that case, activations of both lexical “language” zones and visual word form area (VWFA) were observed.     

Irregular past tense forms in English: how data from children with specific language impairment contribute to models of morphology

Two cognitive models of inflectional morphology are widely debated in the literature—the Words and Rules model, whereby irregular forms are stored in the lexicon but regular forms are created by rule, and Single Mechanism models, whereby both regulars and irregulars form an associative network, with no rules. A newer model, the Computational Grammatical Complexity (CGC) model, recognises the contribution of hierarchical complexity in three components of the grammar, syntax, morphology and phonology, to the construction of morphologically complex forms. This model has previously been tested for regular past tense inflection in English, and in this study we test its predictions for the English irregular past tense, in four groups of children: a group with Grammatical Specific Language Impairment (G-SLI; aged 9;8–17;8), and three groups of typically developing children (aged 5;4–8;5). Children with G-SLI provide an important test case for the CGC model because they have deficits in syntax, morphology and phonology. As predicted, children with G-SLI produced fewer tense-marked irregulars than expected for their age, and fewer over-regularisations than their language-matched controls. The effect of verb-end phonology on over-regularisation and null-marking errors was the same for all groups: both G-SLI and typically developing children were more likely to over-regularise verbs ending in a vowel, and more likely to null-mark verbs ending in an alveolar consonant. We interpret these results as providing further support for the CGC model.     

SYMMETRY,LOCOMOTION, AND THE EVOLUTION OF AN ANTERIOR END: A LESSON FROM SEA URCHINS

Bilaterally symmetrical, “regular” sea urchins in the Family Echinometridae (Class Echinoidea; Phylum Echinodermata) were found to lack a locomotor anterior. Heterocentrotus mammillatus and Echinometra mathaei were observed while locomoting. Members of both ellipsoidal species were found to proceed with their short or long axis foremost with statistically equivalent frequencies. This finding demonstrates that the evolution of bilateral symmetry is not always accompanied by the evolution of a locomotor “anterior” end. The elliptical echinometrid sea urchins provide a particularly appropriate study group for investigating the relationship between the evolution of body form and locomotor behavior. Although the radially symmetrical regular sea urchins, from which the echinometrids sprang, lack a locomotor anterior, all “irregular” echinoids, which are also derived from a regular ancestor but are bilaterally symmetrical, possess an “obligate” locomotor anterior. The symmetry and behavior exhibited by the elliptical echinometrid sea urchins therefore demonstrates that the first irregular echinoids (which exhibit bilateral symmetry by definition) need not have possessed a locomotor anterior as they do today.     

Cognitive components of regularity processing in the auditory domain

Background

Music-syntactic irregularities often co-occur with the processing of physical irregularities. In this study we constructed chord-sequences such that perceived differences in the cognitive processing between regular and irregular chords could not be due to the sensory processing of acoustic factors like pitch repetition or pitch commonality (the major component of ‘sensory dissonance’).

Methodology/Principal Findings

Two groups of subjects (musicians and nonmusicians) were investigated with electroencephalography (EEG). Irregular chords elicited an early right anterior negativity (ERAN) in the event-related brain potentials (ERPs). The ERAN had a latency of around 180 ms after the onset of the music-syntactically irregular chords, and had maximum amplitude values over right anterior electrode sites.

Conclusions/Significance

Because irregular chords were hardly detectable based on acoustical factors (such as pitch repetition and sensory dissonance), this ERAN effect reflects for the most part cognitive (not sensory) components of regularity-based, music-syntactic processing. Our study represents a methodological advance compared to previous ERP-studies investigating the neural processing of music-syntactically irregular chords.     

Suppression of Homoeologous Pairing by <Emphasis Type="Italic">B</Emphasis> Chromosomes in a <Emphasis Type="Italic">Lolium</Emphasis> Species Hybrid

INTERSPECIFIC hybridization together with polyploidy has been an important force in the evolution of many of our graminaceous crop plants. Both wheat (Triticum aestivum) and oats (Avena sativa), for example, are natural allohexaploids derived in each case from the hybridization of three separate but related diploid species. The efforts of plant breeders to synthesize stable and fertile polyploids of this kind have, on the whole, been unsuccessful. The main reason for this is that whereas meiosis in natural allopolyploids such as wheat is extremely regular this is not the case with “synthetic” polyploids. In wheat precise control over pairing at meiosis is achieved by a gene or a cluster of genes on chromosome SB. The gene acts by restricting the pairing to homologous chromosomes with the result that only bivalents are formed, disjunction is regular and inheritance is completely disomic^1,2. In the artificial polyploids at pachytene there is pairing between both homologous chromosomes (from the same species) and “corresponding” homoeologous chromosomes (from different species). The result is an extremely irregular metaphase 1 comprising multivalents and univalents as well as bivalents. Segregation is irregular and a certain degree of infertility is inevitable.     

Grip Force Is Part of the Semantic Representation of Manual Action Verbs

Motor actions and action verbs activate similar cortical brain regions. A functional interference can be taken as evidence that there is a parallel treatment of these two types of information and would argue for the biological grounding of language in action. A novel approach examining the relationship between language and grip force is presented. With eyes closed and arm extended, subjects listened to words relating (verbs) or not relating (nouns) to a manual action while holding a cylinder with an integrated force sensor. There was a change in grip force when subjects heard verbs that related to manual action. Grip force increased from about 100 ms following the verb presentation, peaked at 380 ms and fell abruptly after 400 ms, signalling a possible inhibition of the motor simulation evoked by these words. These observations reveal the intimate relationship that exists between language and grasp and show that it is possible to elucidate online new aspects of sensorimotor interaction.     

Conformational studies of alanine oligopeptides by nuclear magnetic resonance.

We have studied the nmr spectra of the series of alanine oligopeptides containing a methoxyethoxyethoxyacetyl blocking group on the N-terminal residue and a morpholino blocking group on the C-terminal residue. Spectra were measured in chloroform–trifluoroacetic acid solvent systems. For oligomers with chain lengths of five or more, “double peaks” are observed for the α-CH protons. Addition of trifluoroacetic acid causes the peaks to coalesce. The amount of trifluoroacetic acid necessary for coalescence increases from the pentamer to the nonamer. These findings are general since alanine oligomers with different blocking groups exhibit similar “double peak” phenomena. We explain the “double peak” phenomenon in terms of specific folded forms of the oligopeptides which arise from intramolecular hydrogen bonding. Additional evidence for such hydrogen bonding is presented based upon infrared studies. Slight aggregation probably occurs for the pentamer and hexamer which may stabilize the folded forms.     

The quantitative analysis of chromosome pairing and chiasma formation based on the relative frequencies of M I configurations. II. Primary trisomics

On an earlier occasion the estimation of the “crossing-over potentials” of the two arms of a chromosome from the relative frequencies of the different types of bivalent was discussed. When in normal diploids the bivalents in M I can not be distinguished from each other, primary trisomics may be used to mark particular chromosomes. For the estimation of the “crossingover potentials” of the two arms the only type of configuration available (trivalent) is not sufficient. The required additional information may be obtained from the average probability (b) of the chromosome arms to be bound. Using the satellite chromosome trisomic ofSecale cereale it is shown that the use ofb introduces an excessive error, especially with highb values. Consequently, the primary trisomics can not be recommended for the estimation of the “crossing-over potentials” of the two arms of particular chromosomes. The telocentric trisomics permit the recognition of more configurations and are to be preferred. Partner exchange and nucleolus may both interfere with chiasma formation. The data suggest that the three homologous chromosomes may not be equal in respect to pairing and chiasma formations. There are indications that the initiation of pairing is localized in one locus on each arm.     

Variation of hamstrings lengths and velocities with walking speed

Crouch gait, one of the most prevalent movement abnormalities among children with cerebral palsy, is frequently treated with surgical lengthening of the hamstrings. To assist in surgical planning many clinical centers use musculoskeletal modeling to help determine if a patient’s hamstrings are shorter or lengthen more slowly than during unimpaired gait. However, some subjects with crouch gait walk slowly, and gait speed may affect peak hamstring lengths and lengthening velocities. The purpose of this study was to evaluate the effects of walking speed on hamstrings lengths and velocities in a group of unimpaired subjects over a large range of speeds and to determine if evaluating subjects with crouch gait using speed matched controls alters subjects’ characterization as having “short” or “slow” hamstrings. We examined 39 unimpaired subjects who walked at five different speeds. These subjects served as speed-matched controls for comparison to 74 subjects with cerebral palsy who walked in crouch gait. Our analysis revealed that peak hamstrings length and peak lengthening velocity in unimpaired subjects increased significantly with increasing walking speed. Fewer subjects with cerebral palsy were categorized as having hamstrings that were “short” (31/74) or “slow” (38/74) using a speed-matched control protocol compared to a non-speed-matched protocol (35/74 “short”, 47/74 “slow”). Evaluation of patients with cerebral palsy using speed-matched controls alters and may improve selection of patients for hamstrings lengthening procedures.     

Menstrual irregularities in adolescents: hormonal pattern and ovarian morphology

The endocrine pattern and ovarian characteristics of 110 healthy adolescents with menstrual irregularities were investigated during the early follicular and premenstrual phases and were compared to those of 14 adolescents with regular menstrual cycles and 20 adults. Over a period of six gynecological years a low ovulation rate (49%) was found in the group of subjects with irregular cycles and regular ovulation was noted in only a few subjects. Slight differences in endocrine pattern and ovarian morphology were observed between the group of adolescents with regular cycles and the group of adults. In contrast, adolescents with irregular menses had higher mean values of luteinizing hormone (LH), testosterone (T), and androstenedione (A) in comparison with the other two groups both in follicular and premenstrual phases. Nearly 35% of the subjects with irregular cycles had levels of T, A and LH which were higher than the upper limit of the adult normal range. Lower progesterone (P), 17P and oestradiol values were observed in the premenstrual phase. Within the group of subjects with irregular menses, LH levels were higher in anovulatory than in ovulatory cycles, in both phases of the cycle, while T and A levels were higher and prolactin levels were lower in the premenstrual phase of anovulatory cycles. Unlike irregular anovulatory cycles, irregular ovulatory cycles showed a hormonal pattern similar to that found in the adult group. By ultrasound evaluation, a high percentage of subjects with irregular menses had multicystic ovaries (57.9%) and the mean (+/- SEM) ovarian volume was higher (10.6 +/- 0.5 cm3) than that found in adolescents with regular menses (6.7 +/- 0.8 cm3) and in the adult group (7.7 +/- 0.3 cm3). With the increase in frequency and continuity of ovulation an improvement in the direction of adult volume and ovarian structure was observed. Besides the endocrine similarity the data emphasize the striking similarity, already documented by histological studies, between pubertal ovaries and those seen in micropolycystic ovary syndrome. These endocrine and ovarian characteristics are typical of a large number of adolescents with irregular menstrual cycles: these features may be representative of a developmental step toward adult normality, although the possibility of a pathological evolution for some subjects cannot be excluded.     

The evolution of pattern camouflage strategies in waterfowl and game birds

Visual patterns are common in animals. A broad survey of the literature has revealed that different patterns have distinct functions. Irregular patterns (e.g., stipples) typically function in static camouflage, whereas regular patterns (e.g., stripes) have a dual function in both motion camouflage and communication. Moreover, irregular and regular patterns located on different body regions (“bimodal” patterning) can provide an effective compromise between camouflage and communication and/or enhanced concealment via both static and motion camouflage. Here, we compared the frequency of these three pattern types and traced their evolutionary history using Bayesian comparative modeling in aquatic waterfowl (Anseriformes: 118 spp.), which typically escape predators by flight, and terrestrial game birds (Galliformes: 170 spp.), which mainly use a “sit and hide” strategy to avoid predation. Given these life histories, we predicted that selection would favor regular patterning in Anseriformes and irregular or bimodal patterning in Galliformes and that pattern function complexity should increase over the course of evolution. Regular patterns were predominant in Anseriformes whereas regular and bimodal patterns were most frequent in Galliformes, suggesting that patterns with multiple functions are broadly favored by selection over patterns with a single function in static camouflage. We found that the first patterns to evolve were either regular or bimodal in Anseriformes and either irregular or regular in Galliformes. In both orders, irregular patterns could evolve into regular patterns but not the reverse. Our hypothesis of increasing complexity in pattern camouflage function was supported in Galliformes but not in Anseriformes. These results reveal a trajectory of pattern evolution linked to increasing function complexity in Galliformes although not in Anseriformes, suggesting that both ecology and function complexity can have a profound influence on pattern evolution.     

Electrical activity of the brain and oxygen supply for cognitive-mnestic activity in humans under different degrees of hypoxia

Comparative analysis of the indices of oxygen supply for the body and the brain and the functional state of the brain was carried out in three experimental situations: performance of cognitive-mnestic tests under normoxic (TN) and hypoxic conditions (TH) and exposure to hypoxia in the absence of cognitive tasks (H). Each subject participated in all of the experiments. Hypoxic conditions were created by breathing of a hypoxic gas mixture (HGM) consisting of oxygen and nitrogen for 25 min. The first group (eight subjects) was exposed to moderate hypoxia, with the gas mixture containing 12% O₂ (HGM-12); the second group (eight subjects) was exposed to severe hypoxia, with the gas mixture containing 8% O₂ (HGM-8). The cognitive-mnestic activity (CMA) under both normoxia and hypoxia was continuous and included the following tests: “Arithmetic calculations,” “Memory for numerals,” “Colored figures”, and “Sensorimotor response time.” The CMA efficiency was significantly impaired only under severe hypoxia (HGM-8). The CMA efficiency was higher in some subjects of the first group (HGM-12) in the TH series as compared to that in the TN series. The EEG spectral power (SP) during CMA was decreased as compared to the background in all subjects in the TN series and in most subjects of the first group, exposed to HGM-12, whereas it was increased in all subjects of the second group, exposed to HGM-8. The EEG SP was lower in most subjects of both groups studied in the TH series as compared to that found in the H series. The rheographic index of cerebral blood flow rate was not changed compared to the background in the TN series and was increased in the H and TH series during HGM-8 treatment. The increase in cerebral blood flow was less pronounced in the TH series as compared to the H series in most subjects of the second group (HGM-8). Oxygen consumption by the body was elevated by 10–20% in the TN series. A significant increase in oxygen consumption was found in the subjects of both groups studied during hypoxia treatment (H), and it was greater in HGM-12. The following differences were found between the subjects of the two experimental groups: the increase in oxygen consumption in most subjects of the first group (HGM-12) was higher in the TH series as compared to the H series, whereas, in most subjects of the second group (HGM-8), the increase in oxygen consumption was higher in the H series. The data are discussed from the point of view of synergic and concurrent relationships between different forms of energy expenditure on structural and functional reorganization and organ-specific functions.     

Communication and collective action: language and the evolution of human cooperation

All social species face various “collective action problems” (CAPs) or “social dilemmas,” meaning problems in achieving cooperating when the best move from a selfish point of view yields an inferior collective outcome. Compared to most other species, humans are very good at solving these challenges, suggesting that something rather peculiar about human sociality facilitates collective action. This article proposes that language — the uniquely human faculty of symbolic communication — fundamentally alters the possibilities for collective action. I explore these issues using simple game-theoretic models and empirical evidence (both ethnographic and experimental). I review several standard mechanisms for the evolution of cooperation — mutualism, reciprocal altruism, indirect reciprocity and signaling — highlighting their limitations when it comes to explaining large-group cooperation, as well as the ways in which language helps overcome those limitations. Language facilitates complex coordination and is essential for establishing norms governing production efforts and distribution of collective goods that motivate people to cooperate voluntarily in large groups. Language also significantly lowers the cost of detecting and punishing “free riders,” thus greatly enhancing the scope and power of standard conditional reciprocity. In addition, symbolic communication encourages new forms of collectively beneficial displays and reputation management — what evolutionists often term “signaling” and “indirect reciprocity.” Thus, language reinforces existing forces that favor the evolution of cooperation, as well as creating new opportunities for collective action not available even to our closest primate relatives.     

Bemerkungen zur Evolution von., Sprachen bei Säugetieren1 Zur Variabilität innerartlicher Kommunikation bei Caniden

Remarks on the evolution of “languages” of mammals. The variability of the intraspecific communication of canids The canid species mainly considered in this study, the golden jackal (Canis aureus), the cojote (Canis latrans), and especially the wolf (Canis lupus) have an extremely variable species-specific intraspecific communication. Communities, but also differences between the species become evident; the wolf with its distinct social behavior has the greatest differentiation. These results make also clear, that forms of communication in mammals develop in evolutionary processes and events. A safe statement on the beginning of the forms of communication in canids cannot be given so far. This is also true for humans. The ideas of Lenneberg (1967) of the parallel and disjunct origin of the forms of communication in mammals has a high probability for higher systematic units, but on lower systematic level a gradual change can be observed. The forms of communication in mammals are highly differentiated structures, where specific pecularities of the brain are of a special importance. The observations on the variability of intraspecific communication of canids, representing nonhuman mammals, suggest to define “language” in a very general form. In this way, similarities, analogies, and differences between the species of mammals, inclusive man, can be seen more clearly. In only this way the material can be gained to answer the question, if the language of man has in principle exceptional position biologically. It is important for the valuation of forms of intraspecific communication, the “languages”, of mammals not to choose human theory of life and human thinking as a basis, but to start with the biological pecularities of the species. Also canids, as higher mammals, have the ability to abstract, a form of thinking. In their special, species-specific way also non-human mammals arrange their area of experience and thinking. They form for themselves a species-specific “theory of live”. This will of course be different from the human one, according to the systematic position and the biological environment of the species. It is generally accepted that man has special abilities of thinking, he possesses an extraordinary developed brain, compared to all other mammals. This must effect his communication, his language, and result in differences to other mammal species. Gipper (1977) pointed out especially these differences, but they should not be interpreted as differences in principle. Canids use different gestures and sounds for communication within the species; dialog relations can be observed. Different connections of gestures and sounds have different contents of information. It is remarkable that canids do not use their total abilities in using the means of communication in the same way. This is very striking in the change from the wolf, as the only ancestor, to the domestic dog. It is evident that the brain has a greater importance in developing intraspecific communication, than do the peculuarities of organs causing the understanding. A dependanc of intraspecific communication from the environment can be observed either in differences of wird species of canids as well as in the domestication. In the domestic dog, but also in other domestic animals, there is an increase in vocalisations. But the content of information of sounds and gestures decreases in domestication, expressions of arousal become more important. A remarkable plasticity of intraspecific communication becomes evident by domestication. The transformations can be evaluated in the sense of Kosswig (1963, 1965) as first stages of a regressive evolution. Experiments of cross-breeding canid species show exemplarily that forms of communication within these mammal species have a highly polygene regulation, and that processes of learning have an influence. Also from this point of view, no basic differences between nonhuman mammals and humans can be assured, especially when taking into account the facts and thoughts described by Lenneberg. The findings in the canids give useful hints for a better understanding of the human language and its relations to the forms of communication in other mammals. Altogether one can conclude that genetic variability, numerous recombinations, the synorganisation of the processes caused in this way, and natural selection plays definite role in the evolution of “languages”.     

AN ACTIGRAPHIC STUDY COMPARING COMMUNITY DWELLING POOR SLEEPERS WITH NON-DEMENTED CARE HOME RESIDENTS

Sleep disturbances are a common problem among institutionalized older people. Studies have shown that this population experiences prolonged sleep latency, increased fragmentation and wake after sleep onset, more disturbed circadian rhythms, and night-day reversal. However, studies have not examined the extent to which this is because of individual factors known to influence sleep (such as age) or because of the institutional environment. This article compares actigraphic data collected for 14 days from 122 non-demented institutional care residents (across ten care facilities) with 52 community dwelling poor sleepers >65 yrs of age. Four dependent variables were analyzed: (i) “interdaily stability” (IS); (ii) “intradaily variability” (IV); (iii) relative amplitude (RA) of the activity rhythm; and (iv) mean 24?h activity level. Data were analyzed using a fixed-effect, single-level model (using MLwiN). This model enables comparisons between community and institutional care groups to be made while conditioning out possible “individual” effects of “age,” “sex,” “level of dependency,” “level of incontinence care,” and “number of regular daily/prescribed medications.” After controlling for the effects of a range of individual level factors, and after controlling for unequal variance across groups (heteroscedascity), there was little difference between community dwelling older adults and institutional care residents in IS score, suggesting that the stability of day-to-day patterns (such as bed get-up, lunch times, etc.) is similar within these two resident groups. However, institutional care residents experienced more fragmented rest/wake patterns (having significantly higher IV scores and significantly lower mean activity values). Our findings strongly suggest that the institutional care environment itself has a negative association with older people's rest/wake patterns; although, longitudinal studies are required to fully understand any causal relationships. (Author correspondence: r.meadows@surrey.ac.uk)     

Pattern visual evoked potentials recorded from human occipital cortex with chronic subdural electrodes

Pattern evoked potentials to full- and partial-field stimulation were recorded simultaneously from scalp electrodes and from subdural electrodes located over the temporal and occipital cortex, including electrodes placed over or close to the lower lip of the calcarine fissure. High-amplitude pattern evoked potentials were recorded exclusively from electrodes localized in the vicinity of the calcarine fissure and showed a positive-negative deflection in phase with surface recordings, followed by a second negative peak phase reversed with respect to the major surface positive peak (“P100”). The findings suggest that the initial component is an expression of the afferent volley and that the second component (equivalent of the surface “P100”) is most probably generated as a dipole strictly localized to the visual cortex in close proximity of the calcarine fissure (area 17 and/or area 18).     

Changes in the motility patterns of spermatozoa from the rabbit epididymis as assessed by computer-aided sperm motion analysis

Sperm maturation in the epididymis includes changes in their potential for motility that enables spermatozoa to reach the egg and penetrate its investments. The motility characteristics of spermatozoa from the testis, the epididymis, and vas deferens of the rabbit were investigated by computer-assisted sperm analysis (CASA). Various forms of motility were displayed by sperm from different regions of the epididymis released into incubation medium Testicular sperm were motile, although nonprogressive. The maximum percentage motility was expressed by sperm in the proximal cauda epididymidis, and forward progression was developed by spermatozoa from the distal caput. Once forward progression was established, the curvilinear velocity was about the same for sperm from all regions of the tract, whereas straight-line velocity increased between the mid-corpus and cauda and paralleled the decline in lateral displacement of the head. The maintenance of motility in vitro was best maintained by sperm from the distal regions of the tract although sperm from the distal caput maintained motility better than sperm from the proximal and midcorpus regions. Analysis of the motile sperm cells revealed several types of trajectories (“irregular,” “small circular,” “large circular and arcs,” “jagged” and “straight-line”) that were analyzed by discriminant analysis using the variables generated by CASA. Accuracy of classification varied from 70% to 96%, depending on the type of track. The classification function was then applied to the changes that occurred during incubation and showed that irregular trajectories gave way to small and then large circular tracks and progressive forms as sperm matured. © 1996 Wiley-Liss, Inc.     

Reaction of ribosomal sulfhydryl groups with 5,5'-dithiobis(2-nitrobenzoic acid)

The number of sulfhydryl groups in the Escherichia coli ribosome has been measured by titration with 5,5′-dithiobis(2-nitrobenzoic acid). Under denaturing conditions, there are 38.8 ± 1.0 titratable thiols per 70 S ribosome and 22.8 ± 0.3 and 12.9 ± 0.3 titratable thiols per 50 S and 30 S subunits, respectively. Three categories of thiol groups can be distinguished in the native 70 S ribosome, a “fast reacting” class of about 3 residues, a “slow reacting” class of about 10 residues and a “buried” class including about 26 residues. The addition of polyuridylic acid to reaction mixtures protects a fast-reacting thiol in the 30 S subunit belonging to protein S1.The addition of urea to ribosome solutions makes the buried residues titratable. Denaturation occurs as a sharp transition at a urea concentration between 4 and 4.5 m. Urea does not fully dissociate the ribosome into RNA and protein. Instead, in the case of the 30 S subunit, a slowly sedimenting particle forms in the presence of urea, containing roughly 65% of the normal amount of protein.