The Person Beneath the Hair: Hair Discrimination, Health, and Well-Being

Discrimination toward black hair is pervasive in today's society. Hair discrimination is negative bias manifested toward black natural or textured hair styles typically worn by persons of African descent. This commentary discusses the potential effects of hair discrimination on the health and well-being of persons of African descent. Specifically, it explores the mental and physical health implications of hair discrimination and situates it within the broader context of social determinants of health. The Creating a Respectful and Open World for Natural Hair Act has been recently passed in the United States House of Representatives, but more work is needed to eliminate hair discrimination and its negative effects.

Immunotherapy-induced neutralizing antibodies disrupt allergen binding and sustain allergen tolerance in peanut allergy

In IgE-mediated food allergies, exposure to the allergen activates systemic allergic responses. Oral immunotherapy (OIT) treats food allergies through incremental increases in oral allergen exposure. However, OIT only induces sustained clinical tolerance and decreased basophil sensitivity in a subset of individuals despite increases in circulating allergen-specific IgG in all treated individuals. Therefore, we examined the allergen-specific antibodies from 2 OIT cohorts of patients with sustained and transient responses. Here, we compared antibodies from individuals with sustained or transient responses and discovered specific tolerance-associated conformational epitopes of the immunodominant allergen Ara h 2 recognized by neutralizing antibodies. First, we identified what we believe to be previously unknown conformational, intrahelical epitopes using x-ray crystallography with recombinant antibodies. We then identified epitopes only recognized in sustained tolerance. Finally, antibodies recognizing tolerance-associated epitopes effectively neutralized allergen to suppress IgE-mediated effector cell activation. Our results demonstrate the molecular basis of antibody-mediated protection in IgE-mediated food allergy, by defining how these antibodies disrupt IgE-allergen interactions to prevent allergic reactions. Our approach to studying the structural and functional basis for neutralizing antibodies demonstrates the clinical relevance of specific antibody clones in antibody-mediated tolerance. We anticipate that our findings will form the foundation for treatments of peanut allergy using neutralizing antibodies and hypoallergens.

Human IgE monoclonal antibody recognition of mite allergen Der p 2 defines structural basis of an epitope for IgE cross-linking and anaphylaxis in vivo

Immunoglobulin E (IgE) antibody is a critical effector molecule for adaptive allergen-induced immune responses, which affect up to 40% of the population worldwide. Allergens are usually innocuous molecules but induce IgE antibody production in allergic subjects. Allergen cross-linking of IgE bound to its high affinity receptor (FcεRI) on mast cells and basophils triggers release of histamine and other mediators that cause allergic symptoms. Little is known about the direct allergen-IgE antibody interaction due to the polyclonal nature of serum IgE and the low frequency of IgE-producing B cells in blood. Here, we report the X-ray crystal structure of a house dust mite allergen, Der p 2, in complex with Fab of a human IgE monoclonal antibody (mAb) isolated by hybridoma technology using human B cells from an allergic subject. This IgE mAb, 2F10, has the correct pairing of heavy and light chains as it occurs in vivo. Key amino acids forming the IgE epitope on Der p 2 were identified. Mutation of these residues ablated their functional ability to cross-link IgE in a mouse model of passive systemic anaphylaxis. These analyses revealed an important conformational epitope associated with the IgE antibody repertoire to a major mite allergen.

Estimating methane coefficients to predict the environmental impact of traits in the Australian dairy breeding program

The dairy industry has been scrutinized for the environmental impact associated with rearing and maintaining cattle for dairy production. There are 3 possible opportunities to reduce emissions through genetic selection: (1) a direct methane trait, (2) a reduction in replacements, and (3) an increase in productivity. Our aim was to estimate the independent effects of traits in the Australian National Breeding Objective on the gross methane production and methane intensity (EI) of the Australian dairy herd of average genetic potential. Based on similar published research, the traits determined to have an effect on emissions include production, fertility, survival, health, and feed efficiency. The independent effect of each trait on the gross emissions produced per animal due to genetic improvement and change in EI due to genetic improvement (intensity value, IV) were estimated and compared. Based on an average Australian dairy herd, the gross emissions emitted per cow per year were 4,297.86 kg of carbon dioxide equivalents (CO₂-eq). The annual product output, expressed in protein equivalents (protein-eq), and EI per cow were 339.39 kg of protein-eq and 12.67 kg of CO₂-eq/kg of protein-eq, respectively. Of the traits included in the National Breeding Objective, genetic progress in survival and feed saved were consistently shown to result in a favorable environmental impact. Conversely, production traits had an unfavorable environmental impact when considering gross emissions, and favorable when considering EI. Fertility had minimal impact as its effects were primarily accounted for through survival. Mastitis resistance only affected IV coefficients and to a very limited extent. These coefficients may be used in selection indexes to apply emphasis on traits based on their environmental impact, as well as applied by governments and stakeholders to track trends in industry emissions. Although initiatives are underway to develop breeding values to reduce methane by combining small methane data sets internationally, alternative options to reduce emissions by utilizing selection indexes should be further explored.

Breeding for reduced methane emission and feed-efficient Holstein cows: An international response

Selecting for lower methane (CH₄) emitting animals is one of the best approaches to reduce CH₄ given that genetic progress is permanent and cumulative over generations. As genetic selection requires a large number of animals with records and few countries actively record CH₄, combining data from different countries could help to expedite accurate genetic parameters for CH₄ traits and build a future genomic reference population. Additionally, if we want to include CH₄ in the breeding goal, it is important to know the genetic correlations of CH₄ traits with other economically important traits. Therefore, the aim of this study was first to estimate genetic parameters of 7 suggested methane traits, as well as genetic correlations between methane traits and production, maintenance, and efficiency traits using a multicountry database. The second aim was to estimate genetic correlations within parities and stages of lactation for CH₄. The third aim was to evaluate the expected response of economically important traits by including CH₄ traits in the breeding goal. A total of 15,320 methane production (MeP, g/d) records from 2,990 cows belonging to 4 countries (Canada, Australia, Switzerland, and Denmark) were analyzed. Records on dry matter intake (DMI), body weight (BW), body condition score, and milk yield (MY) were also available. Additional traits such as methane yield (MeY; g/kg DMI), methane intensity (MeI; g/kg energy-corrected milk), a genetic standardized methane production, and 3 definitions of residual methane production (g/d), residual feed intake, metabolic BW (MBW), BW change, and energy-corrected milk were calculated. The estimated heritability of MeP was 0.21, whereas heritability estimates for MeY and MeI were 0.30 and 0.38, and for the residual methane traits heritability ranged from 0.13 to 0.16. Genetic correlations between different methane traits were moderate to high (0.41 to 0.97). Genetic correlations between MeP and economically important traits ranged from 0.29 (MY) to 0.65 (BW and MBW), being 0.41 for DMI. Selection index calculations showed that residual methane had the most potential for inclusion in the breeding goal when compared with MeP, MeY, and MeI, as residual methane allows for selection of low methane emitting animals without compromising other economically important traits. Inclusion of residual feed intake in the breeding goal could further reduce methane, as the correlation with residual methane is moderate and elicits a favorable correlated response. Adding a negative economic value for methane could facilitate a substantial reduction in methane emissions while maintaining an increase in milk production.

Genetic parameters for methane emission traits in Australian dairy cows

Methane is a greenhouse gas of high interest to the dairy industry, with 57% of Australia's dairy emissions attributed to enteric methane. Enteric methane emissions also constitute a loss of approximately 6.5% of ingested energy. Genetic selection offers a unique mitigation strategy to decrease the methane emissions of dairy cattle, while simultaneously improving their energy efficiency. Breeding objectives should focus on improving the overall sustainability of dairy cattle by reducing methane emissions without negatively affecting important economic traits. Common definitions for methane production, methane yield, and methane intensity are widely accepted, but there is not yet consensus for the most appropriate method to calculate residual methane production, as the different methods have not been compared. In this study, we examined 9 definitions of residual methane production. Records of individual cow methane, dry matter intake (DMI), and energy corrected milk (ECM) were obtained from 379 animals and measured over a 5-d period from 12 batches across 5 yr using the SF₆ tracer method and an electronic feed recording system, respectively. The 9 methods of calculating residual methane involved genetic and phenotypic regression of methane production on a combination of DMI and ECM corrected for days in milk, parity, and experimental batch using phenotypes or direct genomic values. As direct genomic values (DGV) for DMI are not routinely evaluated in Australia at this time, DGV for FeedSaved, which is derived from DGV for residual feed intake and estimated breeding value for bodyweight, were used. Heritability estimates were calculated using univariate models, and correlations were estimated using bivariate models corrected for the fixed effects of year-batch, days in milk, and lactation number, and fitted using a genomic relationship matrix. Residual methane production candidate traits had low to moderate heritability (0.10 ± 0.09 to 0.21 ± 0.10), with residual methane production corrected for ECM being the highest. All definitions of residual methane were highly correlated phenotypically (>0.87) and genetically (>0.79) with one another and moderately to highly with other methane candidate traits (>0.59), with high standard errors. The results suggest that direct selection for a residual methane production trait would result in indirect, favorable improvement in all other methane traits. The high standard errors highlight the importance of expanding data sets by measuring more animals for their methane emissions and DMI, or through exploration of proxy traits and combining data via international collaboration.

Mapping Human Monoclonal IgE Epitopes on the Major Dust Mite Allergen Der p 2

IgE Abs drive the symptoms of allergic disease upon cross-linking allergens on mast cells or basophils. If the IgE binding sites on the allergens could be identified, it may be useful for creating new forms of immunotherapy. However, direct knowledge of the human IgE (hIgE) epitopes is limited because of the very low frequency of IgE-producing B cells in blood. A new hybridoma technology using human B cells from house dust mite-allergic patients was used to identify four Der p 2-specific hIgE mAbs. Their relative binding sites were assessed and compared by immunoassays with three previously studied murine IgG mAbs. Immunoassays showed that the recognition of Der p 2 by the first three hIgE was inhibited by a single murine IgG, but the fourth hIgE recognized a different epitope from all the other mAbs. The functional ability of the hIgE that bind different epitopes to cross-link Der p 2 was demonstrated in a mouse model of passive systemic anaphylaxis. Nuclear magnetic resonance analyses of Der p 2 in complex with IgG and IgE Abs were used to identify specific residues in the epitopes. To our knowledge, the combination of immunoassays to distinguish overlapping epitopes and nuclear magnetic resonance analyses to identify specific residues involved in Ab binding provided the first epitope mapping of hIgE mAbs to an allergen. The technologies developed in this study will be useful in high-resolution mapping of human epitopes on other Ags and the design of improved therapeutics.

A Human IgE Antibody Binding Site on Der p 2 for the Design of a Recombinant Allergen for Immunotherapy

Der p 2 is one of the most important allergens from the house dust mite Dermatophagoides pteronyssinus Identification of human IgE Ab binding epitopes can be used for rational design of allergens with reduced IgE reactivity for therapy. Antigenic analysis of Der p 2 was performed by site-directed mutagenesis based on the x-ray crystal structure of the allergen in complex with a Fab from the murine IgG mAb 7A1 that binds an epitope overlapping with human IgE binding sites. Conformational changes upon Ab binding were confirmed by nuclear magnetic resonance using a 7A1-single-chain variable fragment. In addition, a human IgE Ab construct that interferes with mAb 7A1 binding was isolated from a combinatorial phage-display library constructed from a mite-allergic patient and expressed as two recombinant forms (single-chain Fab in Pichia pastoris and Fab in Escherichia coli). These two IgE Ab constructs and the mAb 7A1 failed to recognize two Der p 2 epitope double mutants designed to abolish the allergen-Ab interaction while preserving the fold necessary to bind Abs at other sites of the allergen surface. A 10-100-fold reduction in binding of IgE from allergic subjects to the mutants additionally showed that the residues mutated were involved in IgE Ab binding. In summary, mutagenesis of a Der p 2 epitope defined by x-ray crystallography revealed an IgE Ab binding site that will be considered for the design of hypoallergens for immunotherapy.

Cyclooxygenase-2 protein levels are independent of epidermal growth factor receptor expression or activation in operable non-small cell lung cancer

Both cyclooxygenase (COX)-2 and epidermal growth factor receptor (EGFR) are thought to play important roles in the pathogenesis of non-small cell lung cancer (NSCLC). A number of in vitro studies have postulated a link between EGFR activation and subsequent COX-2 upregulation. The relationship between these factors has not been established in patients with NSCLC. COX-2 and EGFR expression were studied in 172 NSCLC specimens using standard immunohistochemical techniques. Western blotting was used to determine COX-2 and EGFR levels in five NSCLC cell lines. The effect of treatment with EGF on COX-2 expression in A549 cells was assessed.

RESULTS

Both EGFR and COX-2 are overexpressed in NSCLC. The predominant pattern of COX-2 and EGFR staining was cytoplasmic. Membranous EGFR staining was seen in 23.3% of cases. There was no relationship between COX-2 and EGFR expression and survival or any clinicopathological features. No correlation was seen between EGFR expression and COX-2 expression in the immunohistochemical series or in the cell lines. Treatment with EGF did not upregulate COX-2 levels in A549 cells, either in serum free or serum-supplemented conditions.

CONCLUSIONS

Although COX-2 and EGFR are over-expressed in NSCLC neither was of prognostic significance in this series of cases. There is no correlation between these two factors in either tumour samples or cell lines. Although these factors show no correlation in NSCLC, they remain potential, though independent targets for treatment.

Excitatory effects of oxytocin and cholecystokinin on oxytocin neurones: differences between virgin, pregnant and lactating rats

Extracellular recordings were made from supraoptic oxytocin (OT) neurones in rat brain slices to investigate the effect of reproductive state on their excitation by OT and cholecystokinin (CCK). Stable background activity was induced by local glutamate application, and OT neurones were identified by their continuous firing and opioid inhibition. The excitatory effect of OT (indicated by percentage neurones excited, peak increment in firing, and response magnitude) was maximal in lactating rats, intermediate in virgin, and lowest in pregnant animals. Excitation by CCK was high in both lactating and virgin rats but, as with OT tests, was minimal in the pregnant group. These adaptations in the responses to OT and CCK may help to ensure that the firing of OT neurones is appropriately regulated to meet changing demands for OT release.

Epidermal growth factor receptors and cyclooxygenase-2 in the pathogenesis of non-small cell lung cancer: potential targets for chemoprevention and systemic therapy

The epidermal growth factor receptor (EGFR) is part of a family of plasma membrane receptor tyrosine kinases that control many important cellular functions, from growth and proliferation to cell death. Cyclooxygenase (COX)-2 is an enzyme which catalyses the conversion of arachidonic acid to prostagladins and thromboxane. It is induced by various inflammatory stimuli, including the pro-inflammatory cytokines, Interleukin (IL)-1beta, Tumour Necrosis Factor (TNF)-alpha and IL-2. Both EGFR and COX-2 are over-expressed in non-small cell lung cancer (NSCLC) and have been implicated in the early stages of tumourigenesis. This paper considers their roles in the development and progression of lung cancer, their potential interactions, and reviews the recent progress in cancer therapies that are directed toward these targets. An increasing body of evidence suggests that selective inhibitors of both EGFR and COX-2 are potential therapeutic agents for the treatment of NSCLC, in the adjuvant, metastatic and chemopreventative settings.

Percutaneous lung biopsies: a survey of UK practice based on 5444 biopsies

Percutaneous transthoracic lung biopsies are commonly performed for the investigation of lung masses. We describe current practice and complication rates in the UK. A postal questionnaire was sent to all centres in the British Thoracic Society directory. 157 replies (61% response rate) were received, providing data on 5444 biopsies. Mean number of biopsies performed per annum was 30.5 per centre; 8% of centres did not perform biopsies, 36% performed <25 biopsies per annum, 34% <50, 16% <100 and 6% >100. Consultant radiologists perform 91% of biopsies. Written consent was obtained at all centres. The operator obtained consent at 50% of centres. Written information for patients was provided at 35 (24%) centres. Biopsies are performed on a day case basis at 103 (71%) centres. Prior to biopsy the following were obtained routinely: CT scan (73% of centres), platelet count (73%), full clotting screen (70%), lung function (55%). Complications included pneumothorax (20.5% of biopsies), pneumothorax requiring chest drain (3.1%), haemoptysis (5.3%) and death (0.15%). The timing of post-procedure chest radiography was variable. Those centres that performed predominantly cutting needle biopsies had similar pneumothorax rates to centres performing mainly fine needle biopsies (18.9% vs 18.3%). There is great variation in practice throughout the UK. Most procedures are performed on a daycase basis. Small pneumothoraces are common but infrequently require treatment. National guidelines are needed to ensure consistency of standards.

Permissive effect of centrally administered oxytocin on the excitatory response of oxytocin neurones to ventral tegmental stimulation in the suckled lactating rat

The mesencephalic ventral tegmentum has been implicated in the milk-ejection reflex and modulation of inputs from this region could provide a mechanism whereby central oxytocin facilitates synchronous bursting of oxytocin neurones during suckling. Experiments were therefore undertaken to investigate the effect of intracerebroventricular (i.c.v.) oxytocin on the response of oxytocin neurones to ventral tegmental stimulation. Oxytocin neurones were recorded in the supraoptic nucleus of urethane-anaesthetized lactating rats during suckling, and their response to single shock stimulation of the ventral tegmentum was monitored using peri-stimulus time-interval histograms. Before i.c.v. oxytocin, oxytocin neurones were either unresponsive to ventral tegmental stimulation, or displayed a small inhibition. However, after administration of oxytocin (2.2 ng i.c.v.), seven out of eight neurones tested displayed a pronounced excitatory response (onset latency 78.4 +/- 4.8 ms, duration 73.4 +/- 8.3 ms). This permissive effect on the excitatory response was only observed in the presence of suckling, and followed the same time course as facilitation of the milk-ejection reflex, being maximal immediately before each facilitated bursting response in the oxytocin neurones. The response to ventral tegmental stimulation remained unaltered after intraperitoneal administration of hypertonic saline to cause a generalized increase in the excitability of the oxytocin neurones. Moreover, i.c.v. oxytocin had no effect on the response of oxytocin neurones to stimulation of a descending input from the medial septum. In conclusion, administration of i.c.v. oxytocin has a selective permissive effect on the excitation of oxytocin neurones from the ventral tegmentum, and this supports previous in vitro studies suggesting that centrally released oxytocin may act as a modulator of afferent transmission to the magnocellular nuclei. This effect on the afferent excitation of oxytocin neurones may provide a mechanism whereby i.c.v. oxytocin facilitates suckling-evoked bursting activity.

Rational design of femtomolar inhibitors of isoleucyl tRNA synthetase from a binding model for pseudomonic acid-A

This paper describes the design and characterization of novel inhibitors of IleRS, whose binding affinity approaches the tightest reported for noncovalent inhibition. Compounds were designed from a binding model for the natural product pseudomonic acid-A (PS-A) together with a detailed understanding of the reaction cycle of IleRS and characterization of the mode of binding of the reaction intermediate IleAMP. The interactions of the compounds with IleRS were characterized by inhibition of aminoacylation of tRNA or PP(i)/ATP exchange at supersaturating substrate concentration and by transient kinetics and calorimetry methods. A detailed understanding of the interaction of a comprehensive series of compounds with IleRS allowed the identification of key features and hence the design of exquisitely potent inhibitors. Predictions based on these results have been recently supported by a docking model based on the crystal structure of IleRS with PS-A [Silvian, L. F., Wang J. M., and Steitz T. A. (1999) Science 285 1074-1077].

Molecular recognition of tyrosinyl adenylate analogues by prokaryotic tyrosyl tRNA synthetases

Molecular modelling and synthetic studies have been carried out on tyrosinyl adenylate and analogues to probe the interactions seen in the active site of the X-ray crystal structure of tyrosyl tRNA synthetase from Bacillus stearothermophilus, and to search for new inhibitors of this enzyme. Micromolar and sub-micromolar inhibitors of tyrosyl tRNA synthetases from both B. stearothermophilus and Staphylococcus aureus have been synthesised. The importance of the adenine ring to the binding of tyrosinyl adenylate to the enzyme, and the importance of water-mediated hydrogen bonding interactions, have been highlighted. The inhibition data has been further supported by homology modelling with the S. aureus enzyme, and by ligand docking studies.

Treatment-resistant schizophrenic patients respond to clozapine after olanzapine non-response

BACKGROUND

Treatment-resistance in schizophrenia remains a public health problem. Clozapine has been shown to be effective in about one third of this population, but carries with it medical risks and weekly blood draws. As olanzapine is a drug with a very similar biochemical profile to clozapine, it is important to evaluate whether non-response to olanzapine predicts clozapine non-response.

METHODS

Forty-four treatment-resistant patients received eight weeks of olanzapine, either in a double-blind trial or subsequent open treatment at a mean daily dose of 25 mg/day. Two of 44 patients (5%) responded to olanzapine treatment. Patients who did not respond could then receive clozapine. Twenty-seven subsequently received an 8-week open trial of clozapine.

RESULTS

Patients who did and did not receive clozapine did not differ demographically or in psychopathology. Eleven of 27 (41%) met a priori response criteria during clozapine treatment (mean dose 693 mg/day) after failing to respond to olanzapine.

CONCLUSIONS

This study demonstrates that failure to respond to olanzapine treatment does not predict failure to clozapine. Treatment-resistant patients who fail on olanzapine may benefit from a subsequent trial of clozapine.

Supraoptic oxytocin and vasopressin neurones show differential sensitivity to the neurosteroid pregnenolone sulphate

The neurosteroid pregnenolone sulphate (PS) interacts allosterically with ionotropic glutamate receptors and thereby could be an important modulator of activity within the hypothalamic magnocellular nuclei. The present in-vitro study therefore examined the effect of perifusion of PS (100 microM) on activity of supraoptic oxytocin (OT) and vasopressin (VP) neurones, in which firing was stimulated by local application of glutamate, NMDA or AMPA. In the presence of locally applied glutamate, PS significantly potentiated firing in putative VP neurones, but had little effect on putative OT neurones. In both cell types, PS increased firing in the presence of NMDA and depressed firing in the presence of AMPA. The action of PS on glutamate- and NMDA-stimulated firing was unaffected by addition of the GABA(A) receptor antagonist, picrotoxin (50 microM). The suppressive action of PS on AMPA-stimulated firing was, however, reversed by picrotoxin and therefore probably requires intact GABAergic transmission for its expression. When putative VP neurones were stimulated by local application of K+, in the presence of picrotoxin, PS evoked a small increase in the ongoing activity, although this did not reach significance. When the glutamate receptor antagonists, NBQX (20 microM) and AP5 (40 microM), were included in the medium, no change in K+ -stimulated firing was observed. Hence PS has no effect on activity of putative VP neurones in the absence of exogenous and endogenous glutamate excitation. In conclusion, PS selectively potentiates glutamate-stimulated activity in putative VP neurones, probably via NMDA receptors, thus providing a mechanism whereby this neurosteroid might exert rapid non-genomic effects on VP secretion. The lack of effect of PS in putative OT neurones probably relates to the relatively small involvement of NMDA receptors in mediating glutamate excitation in this cell type.

Ethics and employee benefits

The following article attempts to bring to light the many questions and thoughts regarding ethical behavior as it relates to the employee benefits profession. Rather than dictating to the reader all the answers regarding ethics, the article demonstrates the different ways various situations can be interpreted. It leaves open the choices available to employee benefits professionals, while compelling us to confront the difficult decisions we must face when dealing with employees, employers and insurance companies.

ATP acting on P2Y receptors triggers calcium mobilization in Schwann cells at the neuroelectrocyte junction in skate

Schwann cells are integral cellular components of the dense cholinergic presynaptic plexus (nerve plate) which innervates each electrocyte in skate electric organ. Using the Ca2+-sensitive dye fura-2, we have followed the response in these cells to various chemical challenges. In K+ depolarized nerve plates nerve terminals consistently responded with a rapid and sustained Ca2+ signal. Schwann cell responses to depolarization were rarely seen but, when observed, were always delayed in onset when compared to nerve terminal response (6-10 s later). The possibility that these responses were triggered by mediators released from nerve terminals was tested by direct application of candidate substances. Schwann cells were found to respond to adenosine triphosphate and adenosine diphosphate with a biphasic increase of intracellular Ca2+ concentration, a rapid peak response being followed in the majority of cells by a sustained plateau phase. In the absence of external Ca2+ only the transient peak response was observed. Depletion of internal Ca2+ stores with thapsigargin completely inhibited the adenosine triphosphate-stimulated rise in Schwann cell Ca2+. The response to adenosine triphosphate was concentration-dependent (EC50 2.8 microM) and was reversibly blocked by two antagonists of P2 purinoceptors: suramin and reactive blue 2. Adenosine diphosphate and 2-methylthio-adenosine triphosphate were equipotent with adenosine triphosphate and at high concentrations (100 microM) diadenosine tetraphosphate produced responses comparable to low concentrations of adenosine triphosphate. Adenosine, adenosine monophosphate, the alpha beta-methylene analogues of adenosine triphosphate and adenosine diphosphate, uridine triphosphate, cytidine triphosphate and guanosine triphosphate were without significant effect. These results show that, in skate electric organ Schwann cells, the release of Ca2+ from intracellular stores is triggered by adenosine triphosphate acting on P(2gamma) receptors and suggest that Schwann cells may be targets for synaptically-released adenosine triphosphate in the electric organ model of the neuromuscular junction.

Glutamate excitation of oxytocin neurones in vitro involves predominantly non-NMDA receptors

Experiments were undertaken to compare effects of the NMDA and non-NMDA receptor antagonists, AP5 (40 microM) and NBQX (10 microM), on glutamate-induced firing in supraoptic oxytocin (OT) and vasopressin (VP) neurones in vitro. In putative OT neurones NBQX caused a significantly greater reduction in firing than AP5, whilst in putative VP neurones both antagonists reduced activity powerfully and to a similar extent. The relatively small effect of AP5 in putative OT neurones was unaffected by the removal of extracellular magnesium. These results suggest that glutamate-induced firing in putative OT neurones is predominantly controlled by non-NMDA receptors.

The neurosteroid pregnenolone sulphate enhances NMDA-induced phasic firing of vasopressin neurones in the rat supraoptic nucleus

The effect of the neurosteroid pregnenolone sulphate (PS) on N-methyl-D-aspartate (NMDA)-induced phasic firing of supraoptic vasopressin (VP) neurones was studied in rat hypothalamic slices in vitro. In VP neurones which were induced to fire phasically by continuous perifusion with NMDA (9-30 microM), addition of 100 microM PS to the incubation medium significantly increased overall spike frequency, with a rise in both proportion of time active and intraburst firing rate. A similar effect was seen during picrotoxin block of GABAergic transmission. No significant change in NMDA-induced phasic firing was observed with 100 microM dehydroepiandrosterone sulphate. VP neurones became silent in the absence of NMDA, and under these conditions PS had no effect. In conclusion, PS increases NMDA-induced phasic firing in VP neurones, providing a mechanism whereby this neurosteroid may participate in the regulation of VP secretion.

Photoperiod effect on bud burst in Prunus is phase dependent: significance for early photosynthetic development

A 16-h photoperiod stimulated bud burst in mature rooted cuttings of Prunus avium cv. Stella, but not in selfed Stella seedlings. However, in a 12-h photoperiod, bud burst occurred earlier in the seedlings than in the mature cuttings. In the 12-h photoperiod, production of polypeptides involved in carbon dioxide fixation and photosynthetic electron transport was higher in seedlings than in mature cuttings, whereas in the 16-h photoperiod, shoot development and polypeptide production were similar in seedlings and mature cuttings. In both photoperiods, the amount of large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase that was associated with thylakoid membranes in young leaves was higher in seedlings than in mature cuttings. Transcript levels of rbcL mRNA were influenced by photoperiod in mature cuttings but not in seedlings. In seedlings, early bud burst and development of the light harvesting apparatus would be an advantage at the start of the growing season, before the mature tree canopy reduces irradiances near the woodland floor.

Inhibition of acetylcholine release from presynaptic terminals of skate electric organ by calcium channel antagonists: a detailed pharmacological study

Release of acetylcholine (ACh) from the presynaptic terminals in skate electric organ was tested for its sensitivity to calcium channel antagonists. A pharmacological profile was established by measuring inhibition of K(+)-stimulated release of [3H]ACh from prelabelled tissue slices. Peptide antagonists of N-type (omega-conotoxins GVIA and MVIIA) and P-type (omega-agatoxin-IVA) channels had no effect, whereas both omega-conotoxins MVIIC and SVIB produced concentration-dependent inhibition and could completely block ACh release. omega-Conotoxin GVIA and omega-agatoxin IVA did not attenuate the block by omega-conotoxin MVIIC. The inorganic ions, Cd2+ and Ni2+, also produced a full inhibition of release (Cd2+ > > Ni2+) and Gd3+ a partial one. Drugs targeting L-type channels (diltiazem, nifedipine and verapamil) at low microM concentrations and a synthetic analogue of the polyamine toxin from funnel web spider venom (sFTX) at 1 mM were all non-inhibitory. Inhibition by omega-conotoxins MVIIC (IC50 25 nM) and SVIB (IC50 500 nM) was reversible and modulated by external concentrations of Ca2+. Inhibitory potency was increased by lowering and decreased by elevating external Ca2+. This "antagonistic" effect of Ca2+ was also seen with Cd2+ inhibition. The inhibitory potency of omega-conotoxin MVIIC was unaffected by predepolarisation. End plate potentials generated by release of endogenous ACh in electrically-stimulated slices were also reversibly blocked by Cd2+ and omega-conotoxins MVIIC and SVIB but were unaffected by omega-conotoxin GVIA and omega-agatoxin IVA. It is concluded that ACh release in skate electric organ depends on presynaptic calcium channels which have different pharmacological properties from established sub-types.

Novel pharmacological sensitivity of the presynaptic calcium channels controlling acetylcholine release in skate electric organ

The presynaptic terminals of skate (Raja montagui) electric organ were tested for their sensitivity to calcium channel antagonists. Acetylcholine (ACh) release and the elevation of intraterminal Ca2+ concentrations triggered by K+ depolarisation were studied. ACh release was measured as 3H efflux from slices of organ prelabelled with [3H]choline. Depolarisation caused a marked, Ca(2+)-dependent increase in 3H efflux that was completely blocked by 100 microM Cd2+ and by 300 nM omega-conotoxin-MVIIC (MVIIC). Inhibition by MVIIC was concentration dependent (IC50 of approximately 20 nM) and reversible. No inhibition was seen with nifedipine (5 microM) or the two other peptide antagonists studied: omega-conotoxin-GVIA (GVIA) at 5 microM and omega-agatoxin-IVA (Aga-IVA) at 1 microM. In a "nerve plate" preparation (a presynaptic plexus of nerve fibres, Schwann cells, and nerve terminals) changes in intraterminal Ca2+ concentrations were measured by microfluorimetry using fluo-3. An increase in fluorescence, indicating a rise in the free [Ca2+], rapidly followed K+ depolarisation, and this change was restricted to the nerve terminals. This response was insensitive to nifedipine (5 microM), GVIA (5 microM), and Aga-IVA (300 nM) but almost completely abolished by MVIIC (1 microM). MVIIC inhibition was concentration dependent and partially reversible. These results show that the nerve terminals in skate electric organ have calcium channels with a pharmacological sensitivity that is markedly different from the established L, N, and P types in other systems but shares some, but not all, of the features of the recently described Q type.

Unilateral periarcuate and posterior parietal lesions impair conditional position discrimination learning in the monkey

Monkeys were trained on a conditional position discrimination in which the conditional cue was a light blinking at two distinct rates and the discriminanda (illuminated buttons) appeared in varying symmetrical positions of eccentricity. Unilateral arcuate, posterior parietal, or principal sulcus lesions were performed at criterion. The monkeys were tested to recovery when a homologous lesion was made contralaterally. The first of two analyses examined a period of 4 weeks following each lesion; the unit of analysis was lesions. The arcuate and parietal lesions produced impairments on both widely eccentric and central discriminanda locations; initially, virtually all responses were deflected to the ipsilateral side. There was significant improvement after the arcuate and parietal lesions from weeks 1 to 4. An analysis of total trials to criterion showed major deficits from the second arcuate and parietal lesions, with the arcuate lesion impairment being particularly severe. These results establish that a spatial concept of left vs right is seriously deranged by unilateral lesions of cortical association areas involved in spatial orientation and discrimination.

Lateralization of emotionality in right parietal cortex of the rat

Lesions of right parietal cortex in the rat increase activity in the open field compared with left parietal lesions, especially after section of the corpus callosum. Left or right motor or medial frontal cortex lesions do not have a lateralized effect. This evidence of a localized asymmetry between the cerebral hemispheres strongly implies that right parietal cortex has a role in emotionality in this species. Our findings suggest a functional similarity to right parietal cortex in man.

Parietal and frontal eye field neglect in the rat

Rats were given unilateral aspiration lesions of parietal, medial frontal, or dorsolateral frontal (motor) cortex and then tested for visual, auditory and tactile neglect, and for circling. All medial frontal lesion animals showed contralateral neglect in each modality and circled ipsiversively. The parietal lesion rats initially displayed contralateral visual and auditory neglect as severe as that in the medial frontal group. Three weeks after the lesions, the parietal group had a smaller residual deficit on the visual test than the medial frontal group. In the first week, parietal animals responded less than the medial frontals to stroking the vibrissae but were more responsive to mild pinching of a toe contralateral to the lesion side. In striking contrast to the medial frontal animals, the parietal group circled strongly to the contralateral side. No rat with a motor cortex lesion neglected or circled preferentially. Like medial frontal cortex, unilateral parietal lesions also produce neglect and circling, but there are important features distinguishing unilateral lesion effects in these two regions.

Pineal lesion produces bilateral visual and auditory inattention in the rat

Unilateral lesions in such brain regions as medial frontal cortex and superior colliculus produce polysensory neglect contralateral to the lesion. Since the pineal gland is an unpaired brain structure, both electrophysiologically and hormonally responsive to visual and auditory stimulation, it may modulate bilateral sensory attention mechanisms. Long-Evans male rats were given pineal or sham lesions and were tested behaviourally. Sensory assessment revealed that in comparison to sham animals rats with pineal lesion exhibited unilateral visual and auditory neglect to stimuli presented on either side of the body. Animals with pineal lesions were more likely than sham-lesioned animals to demonstrate visual allesthesis and, compared to sham-lesioned rats, showed extinction on the left side to bilateral simultaneous visual stimulation. This is the first report that midline neuroendocrine damage can produce bilateral sensory inattention.

A method to section the corpus callosum in the rat

A simply constructed instrument and a surgical procedure are described for transecting the corpus callosum in the rat. The callosum can be cut in its entirety, or the cut can be limited to anterior or posterior halves. The procedure obviates lateralized incidental damage.

Evidence for biological activity of two N-terminal fragments of neurotensin, neurotensin1-8 and neurotensin1-10

Intracisternal (i.c.) administration of the endogenous tridecapeptide neurotensin (NT) has been previously shown to significantly reduce the incidence of cold-restraint stress (CRS)-induced gastric ulcers in rats. In this study we confirm the cytoprotective activity of central NT, and document structure-activity relationships for this effect of NT. When tested in a dose equimolar to 17.9 nmol of NT the NT analogs [Gln4]NT, D-Trp11-NT, and D-Arg8-NT were cytoprotective, whereas D-Arg9-NT was not. Gonadotropin-releasing hormone (Gn-RH) and melanocyte-stimulating hormone-release inhibiting factor (MIF-1), two oligopeptides structurally unrelated to NT exhibited no cytoprotective efficacy in this paradigm. The C-terminal fragments of NT, xenopsin and NT8-13, and the N-terminal fragment NT1-6 were completely ineffective. Finally, NT1-8 and NT1-10, two N-terminal fragments of NT produced significant cytoprotective activity at this dose level. The cytoprotection afforded by NT1-8 and NT1-10, like that of NT, was dose-dependent with ED50's similar to that of NT (NT = 16.2 nmol, NT1-8 = 17.8 nmol and NT1-10 = 19.9 nmol). In conclusion, we demonstrate that smaller molecular weight forms of NT thought to be degradation products of NT can effectively exert biological effects.

Brief deprivation of vision after unilateral lesions of the frontal eye field prevents contralateral inattention

Brief deprivation of vision after unilateral lesions of the frontal eye field prevents the appearance of contralateral inattention to visual, auditory, and somatosensory stimuli. The forced circling that accompanies inattention, however, is not affected. An equivalent preoperative period in the dark only partly reduces inattention symptoms. Visual deprivation does not reduce or prevent inattention resulting from lesions of the superior colliculus.