Retinal and cortical nonlinearities combine to produce masking in V1 responses to plaids

The visual response of a cell in the primary visual cortex (V1) to a drifting grating stimulus at the cell’s preferred orientation decreases when a second, perpendicular, grating is superimposed. This effect is called masking. To understand the nonlinear masking effect, we model the response of Macaque V1 simple cells in layer 4Cα to input from magnocellular Lateral Geniculate Nucleus (LGN) cells. The cortical model network is a coarse-grained reduction of an integrate-and-fire network with excitation from LGN input and inhibition from other cortical neurons. The input is modeled as a sum of LGN cell responses. Each LGN cell is modeled as the convolution of a spatio-temporal filter with the visual stimulus, normalized by a retinal contrast gain control, and followed by rectification representing the LGN spike threshold. In our model, the experimentally observed masking arises at the level of LGN input to the cortex. The cortical network effectively induces a dynamic threshold that forces the test grating to have high contrast before it can overcome the masking provided by the perpendicular grating. The subcortical nonlinearities and the cortical network together account for the masking effect. Melinda Koelling is formerly from Center for Neural Science and Courant Institute, New York University.     

Detection of sinusoidal gratings by pattern-specific detectors: further evidence for the correlation principle in human vision

 The detection of compound sinusoidal gratings of various spatial frequency separations and four different grating sizes has been studied using the summation-to-threshold paradigm. Contrast interrelation functions have been measured and spatial frequency tuning estimates, based on the slope of the contrast interrelation function at two definite points, were derived using the “negative gradient technique” proposed by Logvinenko [Logvinenko (1995) Biol Cybern 73: 547–552]. It is shown that compound grating detection can be modelled by assuming pattern-specific sensory mechanisms for each of the spatial frequency components, which adapt to the periodicity and the size of the stimulus but not to its envelope function. Further, it is shown that relative sensitivity for a given spatial frequency separation can be predicted with good accuracy by the correlation of the grating components used for superposition. It is suggested that the most plausible implementation of the pattern correlation principle in human grating detection is the “grating cell” model. Received: 10 March 2000 / Accepted in revised form: 4 December 2000     

Recognition by human Vγ9/Vδ2 T cells of melanoma cells upon fusion with Daudi cells

 Daudi Burkitt’s lymphoma cells, unlike other tumor cell lines, stimulate human T cells coexpressing the variable (V) region genes TCRG-V9 and V TCRD-V2 to proliferate and secrete lymphokines. Hybrids, derived by the fusion of Daudi cells with the human melanoma cell line MZ2-MEL 2.2, retain the morphology of melanoma cells. Unlike the parental melanoma cell line, these Daudi × MZ2-MEL 2.2 hybrids stimulate secretion of tumor necrosis factor (TNF) and granulocyte/macrophage colony stimulating factor (GM-CSF) by CD4-positive Vγ9/Vδ2 T-cell clones. Whereas the stimulator phenotype of Daudi cells behaves as a dominant trait in Daudi × melanoma hybrids, the expression of B-cell differentiation markers is suppressed. Thus, the γ/δ T-cell ligand expressed by Daudi cells behaves as a dominant tumor antigen in Daudi × melanoma hybrids and is unrelated to the differentiated B-cell phenotype. Dominant expression of the Daudi ligand for human Vγ9/Vδ2 T cells in these hybrids may provide a basis for defining the stimulatory principle at the molecular level. Received: 2 May 1996 / Revised: 15 July 1996     

Neural assemblies and laminar interactions in the cerebral cortex

 Neural assemblies are assumed to become organized and to operate within the cerebral cortex, and so must be constrained by the cytological and physiological properties of this laminated structure. A hypothesis of such assemblies is presented, based on important details of neuronal architecture and physiology in different cortical laminae. Laminae II, III and VI, which are the origin and termination of most cortico-cortical projections, are regarded as the site of storage of most of the information encoded by assemblies – a neuronal ‘library’. Laminae II and III are the most sensitive coincidence detectors, and therefore probably initiate the process of assembly formation. However, these three laminae have very low levels of spontaneous activity in the waking state, and so active cell assemblies cannot base their functioning on these laminae alone. Lamina V pyramidal cells have a much higher level of spontaneous activity. Thus, indirect pathways between ‘library’ cells, via lamina V pyramidal cells, are likely to be more secure than direct ones. It is proposed that direct links between ‘library’ cells become stabilized by Hebbian strengthening, once the recipient ‘library’ cell has been ‘primed’ by neural activity transmitted indirectly via lamina V neurones. Thus lamina V neurones could catalyse the process of assembly formation. Given this proposal, lamina V cells, in their interaction with ‘library’ cells, would code information in terms of precisely timed individual impulses, but would employ a code based on slower frequency changes in their descending influences upon neural centres in the brainstem and spinal cord. Predictions for single unit and electrographic experiments are discussed. Received: 30 November 1995/Accepted in revised form: 3 June 1996     

Computational models of visual neurons specialised in the detection of periodic and aperiodic oriented visual stimuli: bar and grating cells

Computational models of periodic- and aperiodic-pattern selective cells, also called grating and bar cells, respectively, are proposed. Grating cells are found in areas V1 and V2 of the visual cortex of monkeys and respond strongly to bar gratings of a given orientation and periodicity but very weakly or not at all to single bars. This non-linear behaviour, which is quite different from the spatial frequency filtering behaviour exhibited by the other types of orientation-selective neurons such as the simple cells, is incorporated in the proposed computational model by using an AND-type non-linearity to combine the responses of simple cells with symmetric receptive field profiles and opposite polarities. The functional behaviour of bar cells, which are found in the same areas of the visual cortex as grating cells, is less well explored and documented in the literature. In general, these cells respond to single bars and their responses decrease when further bars are added to form a periodic pattern. These properties of bar cells are implemented in a computational model in which the responses of bar cells are computed as thresholded differences of the responses of corresponding complex (or simple) cells and grating cells. Bar and grating cells seem to play complementary roles in resolving the ambiguity with which the responses of simple and complex cells represent oriented visual stimuli, in that bar cells are selective only for form information as present in contours and grating cells only respond to oriented texture information. The proposed model is capable of explaining the results of neurophysiological experiments as well as the psychophysical observation that the perception of texture and the perception of form are complementary processes. Received: 4 June 1996 / Accepted in revised form: 7 October 1996     

The Detection of Orientation Continuity and Discontinuity by Cat V1 Neurons

The orientation tuning properties of the non-classical receptive field (nCRF or “surround”) relative to that of the classical receptive field (CRF or “center”) were tested for 119 neurons in the cat primary visual cortex (V1). The stimuli were concentric sinusoidal gratings generated on a computer screen with the center grating presented at an optimal orientation to stimulate the CRF and the surround grating with variable orientations stimulating the nCRF. Based on the presence or absence of surround suppression, measured by the suppression index at the optimal orientation of the cells, we subdivided the neurons into two categories: surround-suppressive (SS) cells and surround-non-suppressive (SN) cells. When stimulated with an optimally oriented grating centered at CRF, the SS cells showed increasing surround suppression when the stimulus grating was expanded beyond the boundary of the CRF, whereas for the SN cells, expanding the stimulus grating beyond the CRF caused no suppression of the center response. For the SS cells, strength of surround suppression was dependent on the relative orientation between CRF and nCRF: an iso-orientation grating over center and surround at the optimal orientation evoked strongest suppression and a surround grating orthogonal to the optimal center grating evoked the weakest or no suppression. By contrast, the SN cells showed slightly increased responses to an iso-orientation stimulus and weak suppression to orthogonal surround gratings. This iso-/orthogonal orientation selectivity between center and surround was analyzed in 22 SN and 97 SS cells, and for the two types of cells, the different center-surround orientation selectivity was dependent on the suppressive strength of the cells. We conclude that SN cells are suitable to detect orientation continuity or similarity between CRF and nCRF, whereas the SS cells are adapted to the detection of discontinuity or differences in orientation between CRF and nCRF.     

The bovine T cell receptor alpha/delta locus contains over 400 V genes and encodes V genes without CDR2

αβ T cells and γδ T cells perform nonoverlapping immune functions. In mammalian species with a high percentage of very diverse γδ T cells, like ruminants and pigs, it is often assumed that αβ T cells are less diverse than γδ T cells. Based on the bovine genome, we have created a map of the bovine TRA/TRD locus and show that, in cattle, in addition to the anticipated >100 TRDV genes, there are also >300 TRAV or TRAV/DV genes. Among the V genes in the TRA/TRD locus, there are several genes that lack a CDR2 and are functionally rearranged and transcribed and, in some cases, have an extended CDR1. The number of bovine V genes is a multiple of the number in mice and humans and may encode T cell receptors that use a novel way of interacting with antigen. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The emerging <Emphasis Type="Italic">Fusarium</Emphasis> toxin enniatin B: in-vitro studies on its genotoxic potential and cytotoxicity in V79 cells in relation to other mycotoxins

The Fusarium metabolite enniatin B is now recognized as a frequent contaminant of grains used for human foods and animal feeds. Yet, so far very limited data are available on its toxicity and that of other emerging Fusarium mycotoxins (Jestoi M, 2008, Crit Rev Food Sci Nutr 48:21-49). Thus, the mutagenic/genotoxic potential of enniatin B was investigated in a battery of short-term tests, and its cytotoxicity compared with that of several other mycotoxins. No mutagenicity was detected in the Ames assay with four Salmonella typhimurium strains, and in the HPRT (hypoxanthine guanine phosphoribosyl transferase) assay with V79 cells, in either the presence or absence of an external metabolizing enzyme system (rat liver S9). For other types of genotoxicity, i.e., clastogenicity and chromosomal damage, studied in V79 cells by means of alkaline single-cell gel electrophoresis (Comet) assay and micronucleus assay, no significant genotoxic potential of enniatin B was revealed. However, the Fusarium metabolite exerts pronounced time- and concentration-dependent cytotoxic effects in V79 cells as determined by Alamar Blue reduction and by neutral red uptake assays. For instance, IC₂₀ and IC₅₀ values determined for enniatin B by neutral red assay for 48-h exposure are 1.5 μM and 4 μM. These values are higher than those of the more potent Fusarium toxin deoxynivalenol (IC₂₀ 0.7 μM, IC₅₀ of 0.8 μM), but clearly lower than the IC values of several other mycotoxins tested in parallel. Their ranking of cytotoxicity in V79 cells was as follows: deoxynivalenol > enniatin B > patulin > ochratoxin A > zearalenone > citrinin. Moreover, enniatin B was found to induce nuclear fragmentation, a sign of apoptosis, already at low submicromolar concentrations. In summary, despite an apparent lack of mutagenic and genotoxic activity, enniatin B can cause pronounced cytotoxicity in mammalian cells, detectable at low micromolar concentrations.     

A Basic Study on the Biological Monitoring for Vanadium—Effects of Vanadium on Vero Cells and the Evaluation of Intracellular Vanadium Contents

A high concentration of vanadium (V) has toxic effects on human and animals and is one of environmental pollutants. In the present study, we have conducted a fundamental study using cultured Vero cells from monkey kidney for the future environmental monitoring. Orthovanadate (VAN), one of V compounds, of 10⁻¹⁰ and 10⁻⁸ M did not affect the cell growth although the higher concentration of above 10⁻⁶ M VAN inhibited the cell growth accompanied with the decrease in cell numbers and morphological changes. Given that the washing method with ice-cold Li is also effective for determination of the cellular Na content, we used this method for the determination of the V content of the Vero cells. The V distributions in Vero cell; in the 10⁻³ M VAN solution, extracellular and intracellular were obtained as 1:0.564:0.036 and 1:0.662:0.098 at 60 and 120 min after the treatment of VAN. The intracellular V content was 10% of the applied concentration of VAN. Consequently, it was suggested that V concentration of 10⁻⁷ and 10⁻⁶ M in the tissue and environment, respectively, might become the threshold concentration; a criterion of the environmental contamination when we carry out environmental monitoring.     

Effects of Mutating Leucine to Threonine in the M2 Segment of α1 and β1 Subunits of GABAAα1β1 Receptors

The conserved leucine residues at the 9′ positions in the M2 segments of α₁ (L264) and β₁ (L259) subunits of the human GABA_A receptor were replaced with threonine. Normal or mutant α₁ subunits were co-expressed with normal or mutant β₁ subunits in Sf9 cells using the baculovirus/Sf9 expression system. Cells in which one or both subunits were mutated had a higher ``resting' chloride conductance than cells expressing wild-type α₁β₁ receptors. This chloride conductance was blocked by 10 mm penicillin, a recognized blocker of GABA_A channels, but not by bicuculline (100 μm) or picrotoxin (100 μm) which normally inhibit the chloride current activated by GABA: nor was it potentiated by pentobarbitone (100 μm). In cells expressing wild-type β₁ with mutated α₁ subunits, an additional chloride current could be elicited by GABA but the rise time and decay were slower than for wild-type α₁β₁ receptors. In cells expressing mutated β₁ subunits with wild-type or mutated α₁ subunits (αβ(L9′T) and α(L9′T)β(L9′T)), no response to GABA could be elicited: this was not due to an absence of GABA_A receptors in the plasmalemma because the cells bound [³H]-muscimol. It was concluded that in GABA_A channels containing the L9′T mutation in the β₁ subunit, GABA-binding does not cause opening of channels, and that the L9′T mutation in either or both subunits gives an open-channel state of the GABA_A receptor in the absence of ligand. Received: 17 April 1996/Revised: 5 July 1996     

Structured illumination microscopy of a living cell

Due to diffraction, the resolution of imaging emitted light in a fluorescence microscope is limited to about 200 nm in the lateral direction. Resolution improvement by a factor of two can be achieved using structured illumination, where a fine grating is projected onto the sample, and the final image is reconstructed from a set of images taken at different grating positions. Here we demonstrate that with the help of a spatial light modulator, this technique can be used for imaging slowly moving structures in living cells. This article has been submitted as a contribution to the Festschrift entitled “Uncovering cellular sub-structures by light microscopy” in honour of Professor Cremer’s 65th birthday.     

Modeling the Current-Voltage Characteristics of Chara Membranes: I. The Effect of ATP Removal and Zero Turgor

We have obtained and modeled the electrical characteristics of the plasma membrane of Chara internodal cells: intact, without turgor and perfused with and without ATP. The cells were voltage and space-clamped to obtain the I/V (current-voltage) and G/V (conductance-voltage) profiles of the cell membrane. The intact cells yielded similar I/V characteristics with resting p.d.s of −221 ± 12 mV (cytoplasmic clamp, 5 cells) and −217 ± 12 mV (vacuolar clamp, 5 cells). The cut unperfused cells were depolarized at −169 ± 12 mV (7 cells) compared to the vacuole-clamped intact cells. The cells perfused with ATP fell into three groups: hyperpolarized group with resting p.d. −175 ± 12 mV (4 cells) and I/V profile similar to the intact and cut unperfused cells; depolarized group with resting p.d. of −107 ± 12 mV (6 cells) and I/V profiles close to linear; and excited cells with profiles showing a negative conductance region and resting p.d. at −59 ± 12 mV (5 cells). The cells perfused with medium containing no ATP showed upwardly concave I/V characteristics and resting p.d. at −81 ± 12 mV (6 cells). The I/V curves were modeled employing the ``Two-state' model for the H<sup>+</sup> pump (Hansen et al., 1981). The inward and outward rectifiers were fitted to exponential functions and combined with a linear background current. The excitation state in perfused cells was modeled by including an inward current, i <sub>excit</sub>, with p.d.-dependence described by a combination of hyperbolic tangent functions. An inward current, i <sub>no-ATP</sub>, with a smaller amplitude, but very similar p.d.-dependence was also included in the simulation of the I/V curves from cells without ATP. This approach avoided I/V curve subtraction. The modeling of the total I/V and G/V characteristics provided more information about the parameters of the ``Two-state' pump model, as well as more quantitative understanding of the interaction of the major transport systems in the plasmalemma in generation of the resting potential under a range of circumstances. ATP had little effect on nonpump currents except the excitation current; depolarization profoundly affected the pump characteristics. Received: 23 January/Revised: 10 October 1995     

Electrochemical prevention of marine biofouling on a novel titanium-nitride-coated plate formed by radio-frequency arc spraying

We have developed a new method for forming titanium-nitride(TiN)-coated plates using radio-frequency arc spraying (RFAS). A TiN coating formed by RFAS has been used for electrochemical prevention of marine biofouling. X-ray diffraction and X-ray photoelectron spectroscopy indicate that a TiN composite film containing Ti was formed on a polyethylene terephthalate plate surface when Ti was sprayed by RFAS under atmospheric pressure. A cyclic voltammogram (scan rate 20 mV/s) of the TiN formed by RFAS revealed no oxidative and reductive peak currents in the range −0.6 V to 1.2 V against a saturated silver/silver chloride (Ag/AgCl) electrode. When a potential of 1.0 V against Ag/AgCl was applied to the electrode in seawater, no dissolved Ti was detected. Changes in pH and the chlorine concentration were not observed in this range. In all, only 4.5% of the Vibrio alginolyticus cells attached to the electrode survived when a potential of 0.8 V against Ag/AgCl was applied in seawater for 30 min. In field experiments, attachment of the organisms to the TiN electrode was inhibited by applying an alternating potential of 1.0 V and −0.6 V against Ag/AgCl. The TiN film can be formed by RFAS on large and intricately shaped surfaces, and it is a practical electrode for the electrochemical prevention of fouling of various marine structures. Received: 17 April 1998 / Received revision: 5 June 1998 / Accepted: 19 June 1998     

Abscisic acid metabolism and lipid accumulation of a cell suspension culture of <Emphasis Type="Italic">Lesquerella fendleri</Emphasis>

Lesquerella fendleri (commonly known as “Fendler’s bladderpod” or “yellowtop”) is a member of the Brassicaceae and is an important seed oil-producing plant. The lipid profile of L. fendleri seed indicates potential for producing a high quality replacement for castor oil. In this work, characterization of the lipid content of a suspension cell culture, derived from seedlings of L. fendleri, is provided. Under the described suspension cell culture conditions, 16:0, 18:1Δ9, 18:2 Δ9, Δ12 and 18:3 Δ9, Δ12, Δ15 fatty acids were found to accumulate in the cells, while 16:0, 26:0 and 28:0 fatty acids were predominant in the culture medium. Subsequently, the effect of application of abscisic acid (ABA), which modulates lipid accumulation, was assessed. Exogenously applied ABA was taken up by the cells and metabolized via the conjugation pathway, resulting in the accumulation of ABA-glucose ester. Preliminary tests demonstrate the cell line is responsive to exogenous ABA, resulting in increased cellular lipid content and increased accumulation of lipids in the culture medium. This novel L. fendleri suspension culture presents a valuable model system for efficient characterization of mechanisms associated with ABA-induced accumulation of lipids.     

Fluorometric observation of viable and dead adhering diatoms using TO-PRO-1 iodide and its application to the estimation of electrochemical treatment

A rapid method for the direct measurement of viable and dead adhering diatoms was developed using a fluorescent dye, TO-PRO-1 iodide. By staining the marine diatom, Nitzchia closterium, with TO-PRO-1 iodide, viable and dead cells were identified as red and yellow cells respectively, under an epifluorescence microscope employing blue excitation. Only dead cells were stained with TO-PRO-1 iodide. Viable cells were observed as red because of autofluorescence arising from intracellular chlorophyll, whereas dead cells were observed as yellow because of the fluorescence of TO-PRO-1 iodide. The percentage of TO-PRO-1-iodide-stained was correlated with the percentage of dead cells in N. closterium cells exposed to heat (60 °C, 15 min). Other microalgae containing intracellular chlorophyll could be also distinguished as viable or dead cells by this fluorometric staining method. This method was applied for the assessment of N. closterium cells killed by the electrochemical treatment and used to monitor biofouling populations and their viability directly on the electrode surface. When 1.0 V was applied against a saturated calomel electrode, 99% of the cells attached to graphite electrode were killed in 1 h. Received: 7 August 1998 / Received revision: 16 October 1998 / Accepted: 7 November 1998     

Estrogen mitogenic action. I. Demonstration of estrogen-dependent MTW9/PL2 carcinogen-induced rat mammary tumor cell growth in serum-supplemented culture and technical implications

Summary The MTW9/PL cell line was established by our laboratory in culture from the carcinogen-induced hormone-responsive MT-W9A rat mammary tumor of a Wistar-Furth (W/Fu) rat. This tumor formed estrogen, androgen, and progesterone responsive tumors in W/Fu rats (Sirbasku, D. A., Cancer Res. 38:1154–1165; 1978). It was later used to derive the MTW9/PL2 cell population which was also estrogen-responsive in vivo (Danielpour, D., et al., In Vitro Cell. Dev. Biol. 24∶42–52; 1988). In the study presented here, we describe serum-supplemented culture conditions in which the MTW9/PL2 cells demonstrate≥80-fold steroid hormone growth responses. All sera used were steroid hormone-depleted by charcoal-dextran treatment at 34°C. The studies were done with horse serum as well as serum from other mammalian species. The growth of the MTW9/PL2 cells was biphasic in response to hormone-depleted serum. Concentrations of ≤5% (v/v) promoted optimum growth. Above this concentration, serum was inhibitory. Concentrations ≥40% (v/v) inhibited growth altogether. Addition of 1.0×10⁻¹³−1.0×10⁻⁸ M 17β-estradiol (E₂) reversed the inhibition completely. At 1.0×10⁻⁸ M, estrone, estriol and diethylstilbestrol promoted growth as well as E₂. Testosterone and dihydrotestosterone promoted growth only at ≥10⁻⁷ M. Progesterone was effective only at≥10⁻⁶ M. Cortisol was ineffective. Labeled-hormone-binding analysis and Western immunoblotting documented that MTW9/PL2 cells had estrogen and progesterone receptors but not androgen or cortisol receptors. Estrogen treatment of MTW9/PL2 cells induced a concentration and time dependent increase in progesterone receptors. We conclude (1) the MTW9/PL2 population is the first highly steroid hormone-responsive rat mammary tumor cell line to be established in culture from a carcinogen-induced tumor, and (2) sera from a number of species including horse, rat and human contain an inhibitor which mediates estrogen sensitive MTW9/PL2 cell growth in culture.     

Characterization and optimization of a two-phase partitioning bioreactor for the biodegradation of phenol

An electrochemical reactor employing activated carbon fibers (ACF) was constructed for the disinfection of bacteria in drinking water. The application of an alternating potential of 1.0 V and −0.8 V versus a saturated calomel electrode, for disinfecting and desorbing bacteria, enabled reactor operation for 840 h. Drinking water was passed through the reactor in stop/flow mode: 300 ml/min flow for 12 h and no flow for 12 h, alternately. The bacterial cell density in treated water was always been less than 20 cells/ml. It was also found that the formation of biofilm on the ACF reactor caused an increase in current, enabling the self-detection of microbial fouling. Received: 19 February 1996 / Received last revision: 23 July 1996 / Accepted: 2 September 1996     

Proteomic approach for acute-phase proteins of hemolymph and muscles in Scylla serrata challenged by a pathogenic bacterium

Acute-phase response is documented to be a significant mechanism of innate immunity in vertebrates and invertebrates. In this study, proteomic methodologies were applied for different protein expressions in hemolymph of Scylla serrata challenged by Vibrio parahaemolyticus after immunization, and in muscles of the crabs separately challenged by V. parahaemolyticus, V. anguillarum and Aeromonas hydrophila. Up-regulated cryptocyanin is documented in the hemolymph and up-regulated calexcitin, wingless (fragment) and tachykinin-related peptide in the muscle as acute-phase proteins. All the four altered proteins were responsible for bacterial stress, but cryptocyanin seemed to be a memory response protein against the challenge by a live bacterium after immunization of the live cells. These up-regulated proteins can be indicative of an understanding of immunity of a crab. __________ Translated from Journal of Xiamen University (Natural Science), 2005, 44(4): 559–562, 44(Sup.): 191–194 [译自: 厦门大学学报(自然科学版), 2005, 44(4): 559–562, 44(增刊): 191–194]     

The expression patterns of β1,4 galactosyltransferase I and V mRNAs, and Galβ1-4GlcNAc group in rat gastrocnemius muscles post sciatic nerve injury

Glycosylation is one of the most important post-translational modifications. It is clear that the single step of β1,4-galactosylation is performed by a family of β1,4-galactosyltransferases (β1,4-GalTs), and that each member of this family may play a distinct role in different tissues and cells. β1,4-GalT I and V are involved in the biosynthesis of N-linked oligosaccharides and play roles in sciatic nerve regeneration after sciatic nerve injury. In the present study, the expression of β1,4-galactosyltransferase (β1,4-GalT) I, V mRNAs and Galβ1-4GlcNAc group were examined in rat gastrocnemius muscles after sciatic nerve crush and transection. Real time PCR revealed that β1,4-GalT I and V mRNAs expressed at a high level in normal gastrocnemius muscles and decreased gradually from 6 h, reached the lowest level at 2 weeks, then restored gradually to relatively normal level at 4 weeks after sciatic nerve crush. In contrast, in sciatic nerve transection model, β1,4-GalT I and V mRNAs decreased gradually from 6 h, and remained on a low level at 4 weeks in gastrocnemius muscles after sciatic nerve transection. In situ hybridization indicated that β1,4-GalT I and V mRNAs localized in numerous myocytes and muscle satellite cells under normal conditions and at 4 weeks after sciatic nerve crush, and in a few muscle satellite cells at 4 weeks after sciatic nerve transection. Furthermore, lectin blotting showed that the expression level of the Galβ1–4GlcNAc group decreased from 6 h, reached the lowest level at 2 weeks, and restored to relatively normal level at 4 weeks after sciatic nerve crush. RCA-I lectin histochemistry demonstrated that Galβ1–4GlcNAc group localized in numerous membranes of myocytes and muscle satellite cells in normal and at 4 weeks after sciatic nerve crush, and in a few muscle satellite cells at 2 and 4 weeks after sciatic nerve transection. These results indicated that the expressions of β1,4-GalT I, V mRNAs and Galβ1–4GlcNAc group were involved in the process of denervation and reinnervation, which suggests that β1,4-GalT I, V mRNAs and Galβ1-4GlcNAc group may play an important role in the muscle regeneration.     

Effect of masking the parietal eye on the diurnal activity and body temperature of two sympatric species of monitor lizards, Varanus s. salvator and Varanus b. nebulosus

 Five water monitor lizards, Varanus salvator salvator, and four clouded monitor lizards, Varanus bengalensis nebulosus, were caught on Tioman island in Malaysia. A radio-thermistor transmitter was implanted into the buccal cavity of each animal, and they were released into an enclosure measuring 5.5 × 6.5 metres. The lizards were observed for 9 and 8 days, respectively, before and after the parietal eye was covered with aluminium foil. With uncovered parietal eye, both species showed a clear diurnal rhythm, being active only during day time. After covering the parietal eye, the mean locomotor activity of five V. s. salvator decreased from 791 to 107 min · day^–1 but remained unchanged around 850 min · day^–1 for V. b. nebulosus. The mean duration of locomotor activity decreased in V. s. salvator and V. b. nebulosus after the parietal eye was covered, but V. b. nebulosus maintained its locomotor activity by increasing the number of locomotor bouts. The water monitor spent very little time on thermoregulation. Its body temperature ranged between 26.3 and 28.4 °C, which decreased after the parietal eye was covered. The clouded monitor thermoregulated around 28.8–36.0 °C, which remained unchanged after the parietal eye was covered. In both species, there was a strong correlation between body temperature and ambient temperature. Behavioural abnormalities were recorded among V. s. salvator with covered parietal eye. They were often observed to be active by night and often slept outside a burrow. The circadian rhythm of V. b. nebulosus appeared unaffected by shielding of its parietal eye. Captivity combined with shielded parietal eye induced agonistic behaviour in both species. Accepted: 11 September 1996