Acquisition of contextual Pavlovian fear conditioning is blocked by application of an NMDA receptor antagonist D,L-2-amino-5-phosphonovaleric acid to the basolateral amygdala

Rats, with chronic cannula placed bilaterally in the amygdala, received infusions of the N-methyl-D-aspartate (NMDA) receptor antagonist D,L-2-amino-5-phosphonovaleric acid (APV) before contextual Pavlovian fear conditioning. Administration of APV to the basolateral nucleus prevented acquisition of fear. Central nucleus infusions had no effect. It is concluded that an NMDA-mediated process near the basolateral region of the amygdala (e.g., lateral or basolateral nucleus) is essential for the learning of fear.

Determinants of potency and temperature-dependent function in the Aplysia bag cell peptides

Structure-activity relationships were determined for the natural bag cell peptides (BCPs) and for a series of synthetic analogues in terms of their ability to stimulate (at 30 degrees C) and to inhibit (at 15 degrees C) bag cell adenyl cyclase. We found that the core RLRF motif shared by all these peptides is active in this assay, and is stimulatory. The histidine residue C-terminal to this motif in beta-BCP is superfluous in this respect. An electronegative residue C-terminal to RLRF is sufficient to induce temperature-dependent function. The Ala-Pro pair that is N-terminal to this motif in alpha-BCP increases potency, but does not alter function.

Pharmacists' views on health care reform

This study explored pharmacists' opinions on a reformed health care system. Questionnaires were mailed to 523 pharmacists about the structure, funding, cost control mechanisms, benefits, and features to be covered by a national health plan; 57.2% responded. The pharmacists showed no consensus regarding the basic structure of a national health plan. They favored increased taxes on alcohol and cigarettes to fund the plan and adamantly opposed increased individual income or employer payroll taxes. Pharmacists were not convinced that plan costs could be controlled. They strongly supported benefits for preventive services; however, they ranked coverage of outpatient prescription drugs relatively low. Pharmacists' opinions on health care reform differed according to position (e.g., owner or staff) and age.

PKC gamma mutant mice exhibit mild deficits in spatial and contextual learning

We are undertaking a genetic approach to investigate the role that synaptic modulation in the mammalian central nervous system plays in learning and memory and to identify relevant molecular components. We have generated mice deficient in the gamma isoform of protein kinase C (PKC gamma), an enzyme that has previously been implicated in both long-term potentiation (LTP) and learning and memory. These mice have a modified LTP of synaptic transmission in the hippocampus. We demonstrate that PKC gamma-mutant mice can learn to carry out hippocampus-dependent tasks, although mild deficits are evident. Thus, hippocampal CA1 LTP induced by the conventional tetanic stimulation is not essential for the mice to exhibit spatial and contextual learning. Furthermore, the modification of hippocampal synaptic plasticity correlates with the learning deficits we observe.

Calcitonin gene-related peptide-like immunoreactive (CGRPI) elements in the circadian system of the mouse: an immunohistochemistry combined with retrograde transport study

This study was based on immunohistochemical detection of calcitonin gene-related peptide-like immunoreactive (CGRPI) neurons and fibers in the suprachiasmatic nucleus (SCN) and intergeniculate leaflet (IGL) of the mouse. CGRPI neurons and fibers were found within the ventrolateral part of the SCN, in the whole extent of IGL and sparsely distributed in ventral lateral geniculate body. The presence of CGRPI structures in the SCN and IGL of the mouse further supports the hypothesis of differences in the content of neuroactive substances in the circadian clock between mammalian species. Fluorogold retrograde transport combined with CGRP immunofluorescence demonstrates that CGRPI neurons in the IGL constitute a part of IGL reciprocal connections.

Effects of amygdala, hippocampus, and periaqueductal gray lesions on short- and long-term contextual fear

The effects of amygdala, hippocampus, and periaqueductal gray (PAG) lesions on contextual fear conditioning in rats were examined. Freezing behavior served as the measure of conditioning. Unlesioned control animals showed reliable conditional freezing in the testing chamber when observed both immediately and 24 hr after footshocks. In contrast, rats with amygdala or ventral PAG lesions exhibited a significant attenuation in freezing both immediately and 24 hr after the shocks. Dorsal PAG lesions had no effect on freezing at either time. Animals with hippocampal lesions displayed robust freezing behavior immediately following the shock, even though they showed a marked deficit in freezing 24 hr after the shock. These results indicate that there are anatomically dissociable short- and long-term conditional fear states.

Necrotizing periorbital cellulitis

We report traumatic necrotizing periorbital cellulitis attributed to group A beta-hemolytic streptococci in a 4-year-old child. The infection was successfully treated via surgical cleansing, drainage, and grafting. The virulence of this organism requires an aggressive approach to the patient with periorbital cellulitis, which is refractory to intravenous antibiotics. Early treatment may limit extensive eyelid necrosis, the resultant secondary deformity, and the need for multiple reconstructive procedures.

A rare disease-associated mutation in the medium-chain acyl-CoA dehydrogenase (MCAD) gene changes a conserved arginine, previously shown to be functionally essential in short-chain acyl-CoA dehydrogenase (SCAD)

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a serious and potentially fatal inherited defect in the beta-oxidation of fatty acids. Approximately 80% of patients with MCAD deficiency are homozygous for a single disease-causing mutation (G985). The remaining patients (except for a few cases worldwide) are compound heterozygous with G985 in one allele. By sequencing of cloned PCR-amplified MCAD cDNA from a G985 compound heterozygous patient, we identified a C-to-T transition at position 157 as the only change in the entire coding sequence of the non-G985 allele. The presence of the T157 mutation was verified in genomic DNA from the patient and her mother by a PCR-based assay. The mutation changes conserved arginine at position 28 (R28C) of the mature MCAD protein. The effect of the T157 mutation on MCAD protein was investigated by expression of mutant MCAD cDNA in COS-7 cells. On the basis of knowledge about the three-dimensional structure of the MCAD protein, we suggest that the mutation destroys a salt bridge between arginine28 and glutamate86, thereby affecting the formation of enzymatically active protein. Twenty-two additional families with compound heterozygous patients were tested in the PCR-based assay. The T157 mutation was identified in one of these families, which had an MCAD-deficient child who died unexpectedly in infancy. Our results indicate that the mutation is rare. It is, however, noteworthy that a homologous mutation has previously been identified in the short-chain acyl-CoA dehydrogenase (SCAD) gene of a patient with SCAD deficiency, suggesting that the conserved arginine is crucial for formation of active enzyme in the straight-chain acyl-CoA dehydrogenases.

Crystal structures of medium-chain acyl-CoA dehydrogenase from pig liver mitochondria with and without substrate

The three-dimensional structure of medium-chain acyl-CoA dehydrogenase from pig mitochondria in the native form and that of a complex of the enzyme and a substrate (product) have been solved and refined by x-ray crystallographic methods at 2.4-A resolution to R factors of 0.172 and 0.173, respectively. The overall polypeptide folding and the quaternary structure of the tetramer are essentially unchanged upon binding of the ligand, octanoyl (octenoyl)-CoA. The ligand binds to the enzyme at the rectus (re) face of the FAD in the crevice between the two alpha-helix domains and the beta-sheet domain of the enzyme. The fatty acyl chain of the thioester substrate is buried inside of the polypeptide and the 3'-AMP moiety is close to the surface of the tetrameric enzyme molecule. The alkyl chain displaces the tightly bound water molecules found in the native enzyme and the carbonyl oxygen of the thioester interacts with the ribityl 2'-hydroxyl group of the FAD and the main-chain carbonyl oxygen of Glu-376. The C alpha--C beta of the fatty acyl moiety lies between the flavin and the gamma-carboxylate of Glu-376, supporting the role of Glu-376 as the base that abstracts the alpha proton in the alpha--beta dehydrogenation reaction catalyzed by the enzyme. Trp-166 and Met-165 are located at the sinister (si) side of the flavin ring at the surface of the enzyme, suggesting that they might be involved in the interactions with electron transferring flavoprotein. Lys-304, the prevalent mutation site found in patients with medium-chain acyl-CoA dehydrogenase deficiency, is located approximately 20 A away from the active site of the enzyme.

Profile of Fos-like immunoreactivity induction by light stimuli in the intergeniculate leaflet is different from that of the suprachiasmatic nucleus

Light stimuli induce Fos-like immunoreactivity (FLI) in suprachiasmatic nucleus (SCN) and intergeniculate leaflet (IGL). Short pulses of light stimuli that synchronize the circadian rhythms induce FLI in SCN. The characteristics of light induction of FLI in the IGL were studied using immunohistochemistry. In the IGL, at least 2 h of sustained light stimuli were necessary to show an increase of FLI. This FLI persisted while the light was turned on. FLI induction in the IGL by light stimuli was not circadian time specific response. These findings imply that the functional significance of Fos activation on circadian rhythms and mechanism of FLI induction in IGL would be different from that in SCN.

Immediate and one-year results of percutaneous mitral balloon valvuloplasty using Inoue and double-balloon techniques

Many investigators have reported the results of percutaneous mitral valvuloplasty (PMV) using the Inoue or double-balloon technique, but to date, the immediate and long-term follow-up results of the 2 different procedures have not been compared in a prospective study. Therefore, a prospective, randomized trial was performed in 120 consecutive patients who underwent PMV using Inoue (n = 59; group I) or double (n = 61; group D) balloons. The success rate was 83% in group I, and 89% in group D. The magnitude of changes in mitral valve area and hemodynamic variables was the same in both groups. Immediately after dilation, the long diameter changes of the mitral orifice was greater in group D, and the increase in ejection fraction slope was significantly greater in group D. The duration of the total procedure, and the fluoroscopic time was significantly shorter in group I. The incidence of left-to-right shunt at the atrial level (Qp/Qs > 1.5) was 3.4% in group I and 4.9% in group D. Severe mitral regurgitation (grade > or = 3) occurred in 2 patients in each group. At follow-up, the mitral valve area had significantly decreased at 6 months, but no further changes occurred at 1-year follow-up in both groups. The long diameter of the mitral orifice was greater in group D until 6 months after PMV, but the difference was not apparent at 1-year follow-up. In conclusion, the Inoue and double-balloon techniques obtained equivalent results in the success rate and frequency of complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Distorted distribution of nicotinamide-adenine dinucleotide phosphate-diaphorase neurons in temporal lobe of schizophrenics implies anomalous cortical development

The distribution of neurons expressing the enzyme nicotinamide-adenine dinucleotide phosphate-diaphorase (NADPH-d) in the lateral and medial temporal lobes of schizophrenic and matched control brains was investigated in a systematic blind analysis. Schizophrenics had significantly lower numbers of NADPH-d neurons in the hippocampal formation and in the neocortex of the lateral temporal lobe but significantly greater numbers of NADPH-d neurons in the white matter of the lateral temporal lobe and a tendency toward greater numbers in parts of the parahippocampal white matter. The distorted distribution of NADPH-d neurons in the lateral temporal lobe, which may be explained by developmental disturbances, such as impaired neuronal migration or an alteration in the death cycle of transitory subcortical neurons, is similar to that found in the prefrontal cortex of schizophrenics. Alterations of cortical ontogenesis, as reflected in the distribution of NADPH-d neurons, appear to be widespread among neocortical association fields in schizophrenics and may provide a clue to the cause of the disease.

Null subjects: comments on Valian (1990)

In this paper, I do not claim that any particular parameter-setting approach is correct, or even provide a characterization of subjectless sentences in children's speech. The only point of this paper is to show that Valian's argument that single-value solutions for setting the null subject parameter have insoluble problems is incorrect. Valian is correct that being able to analyze and interpret triggering data is a prerequisite for setting parameters, but a single-value solution of the sort described in this paper (and implicitly assumed in parameter-setting acquisition theories) is sufficient to do so; there is no need to invoke the dual-value solution that Valian argues is necessary. Furthermore, I argue that the single-value solution should be preferred on the grounds that (i) the mechanism I propose maintains many of the niceties of idealized parameter-setting acquisition theories whereas Valian's approach explicitly gives up on these attractive features of standard parameter-setting models, and (ii) it follows from dual-value theories but not single-value theories (depending on the nature of parameters and how many parameters there are) that parsing and speech production involve over-whelmingly difficult computations for children.

Mammalian brain substrates of aversive classical conditioning

In this review, we have examined recent studies that have successfully identified neural circuits necessary for nonspecific and specific conditioned responses. This success is due in large part to the advantages of the classical conditioning paradigm for controlling stimuli and responses. Clearly, this research does not attempt to account for all forms of memory. The power of this approach is demonstrated by the distinction between essential and nonessential memory traces or engrams. Essential memory traces represent the circuitry responsible for forming the association in classical conditioning. Nonessential memory traces do not represent the essential association, but they are important for facilitating, adapting, and modifying the final performance of the learned behavior. The search for the engram for any learned behavior has been viewed with skepticism by some investigators who quote Karl Lashley: "This series of experiments has yielded a good bit of information about what and where the memory is not. It has discovered nothing directly of the real nature of the engram" (1950, pp. 477-78). However, these authors neglect to quote Lashley fully, for even he was less pessimistic about that search than in normally recognized. He continued, "I sometimes feel, in reviewing the evidence on the localization of the memory trace, that the necessary conclusion is that learning just is not possible. It is difficult to conceive of a mechanism which can satisfy the conditions set for it. Nevertheless, in spite of such evidence against it, learning does sometimes occur" (1950, pp. 477-78, emphasis added). Learning does indeed occur, and its neurobiological substrates can be localized.

Effect of exogenous sialylation of the lipooligosaccharide of Neisseria gonorrhoeae on opsonophagocytosis

Serum-sensitive Neisseria gonorrhoeae strains become serum resistant when grown in the presence of a sialic acid precursor, cytidine monophospho-N-acetylneuraminic acid. We examined the abilities of human neutrophils to phagocytose sialylated and nonsialylated gonococci and observed a decrease in the complement-dependent phagocytosis of sialylated gonococci compared with that of nonsialylated gonococci (50.7 versus 25.9% survival at 30 min). This decrease in opsonophagocytosis after sialylation may contribute to the pathogenicity of gonococcal infections.

Selective impairment of long-term but not short-term conditional fear by the N-methyl-D-aspartate antagonist APV

Previous research has indicated that the competitive N-methyl-D-aspartate (NMDA) antagonist APV (DL-2-amino-5-phosphonovalerate) prevents the Pavlovian conditioning of fear to contextual stimuli when tested 24 hr, but not immediately, after training. The present study investigated this differential time-dependent effect of APV on fear conditioning. Rats were given either APV or saline and presented with 3 footshocks in a distinctive chamber. Promptly after the shock, rats that had received APV exhibited a species-typical fear response-freezing. However, the freezing lasted for only a short period of time (less than 3 min) compared with that of controls. An immediate-shock procedure showed that freezing was entirely a conditional response to the chamber. In addition, the results of a savings test suggest that APV impairs storage rather than retrieval processes. These results indicate that there are two temporally distinct associative fear processes, a short-term NMDA-independent conditional fear and a long-term NMDA-dependent conditional fear.

Modality-specific retrograde amnesia of fear

Emotional responses such as fear are rapidly acquired through classical conditioning. This report examines the neural substrate underlying memory of acquired fear. Rats were classically conditioned to fear both tone and context through the use of aversive foot shocks. Lesions were made in the hippocampus either 1, 7, 14, or 28 days after training. Contextual fear was abolished in the rats that received lesions 1 day after fear conditioning. However, rats for which the interval between learning and hippocampal lesions was longer retained significant contextual fear memory. In the same animals, lesions did not affect fear response to the tone at any time. These results indicate that fear memory is not a single process and that the hippocampus may have a time-limited role in associative fear memories evoked by polymodal (contextual) but not unimodal (tone) sensory stimuli.

Structural organization and regulatory regions of the human medium-chain acyl-CoA dehydrogenase gene

Medium-chain acyl-CoA dehydrogenase (MCAD) is a highly regulated mitochondrial flavo-enzyme that catalyzes the initial reaction in fatty acid beta-oxidation. Deficiency of MCAD is a common inherited defect in energy metabolism. We have previously shown that the mRNA encoding MCAD in an MCAD-deficient child is homozygous for the point mutation A985 to G [Kelly et al. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 9236-9420]. To define the molecular basis of MCAD deficiency and as an initial step in the study of the regulation of MCAD gene expression, we determined the structure and organization of the human MCAD gene. The gene is comprised of 12 exons which span 44 kb of DNA. Comparison of the MCAD gene to MCAD mRNAs from the MCAD-deficient child revealed that missplicing was common, resulting in a variety of exon deletions and intron insertions. The MCAD gene promoter region is extremely GC-rich and lacks prototypical TATA and CAAT boxes. Several regions upstream of the promoter are homologous with mitochondrial enhancers purportedly involved in coordinate expression of nuclear genes encoding mitochondrial proteins. Transfection of chimeric plasmid constructs with 299 bp of upstream sequence into HepG2 cells revealed high-level transcriptional activity. We conclude that the precursor MCAD mRNA is misspliced to a high degree and complexity in association with the G985 mutation and the MCAD gene contains a strong promoter which shares some structural features with other "housekeeping" genes encoding mitochondrial proteins.

The benzodiazepine inverse agonist DMCM as an unconditional stimulus for fear-induced analgesia: Implications for the role of GABAA receptors in fear-related behavior

When the benzodiazepine inverse agonist DMCM (6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylic acid methyl ester) occupies the benzodiazepine recognition site on the GABAA receptor complex, the inhibitory action of gamma-aminobutyric acid (GABA) is attenuated. DMCM acted as an unconditional stimulus for one response associated with fear or anxiety, analgesia, as indicated by a dose-dependent (0.25-1.0 mg/kg) suppression of rats' responses to a formalin injection. This was accompanied by other fearlike responses (defecation and urination). The opioid antagonist naltrexone (1.75-14 mg/kg) did not affect these behaviors. Environmental cues associated with DMCM provoked analgesia and defecation in the absence of the drug. The conditional analgesia was reversed by naltrexone (7 mg/kg). DMCM functions as an unconditional fear stimulus by eliciting fear-related behaviors and conditioning those responses to neutral stimuli. The neural circuitry underlying fear conditioning appears to involve tonically inhibitory GABAergic synapses.

Selective impairment of long-term but not short-term conditional fear by the N-methyl-D-aspartate antagonist APV

Previous research has indicated that the competitive N-methyl-D-aspartate (NMDA) antagonist APV (DL-2-amino-5-phosphonovalerate) prevents the Pavlovian conditioning of fear to contextual stimuli when tested 24 hr, but not immediately, after training. The present study investigated this differential time-dependent effect of APV on fear conditioning. Rats were given either APV or saline and presented with 3 footshocks in a distinctive chamber. Promptly after the shock, rats that had received APV exhibited a species-typical fear response-freezing. However, the freezing lasted for only a short period of time (less than 3 min) compared with that of controls. An immediate-shock procedure showed that freezing was entirely a conditional response to the chamber. In addition, the results of a savings test suggest that APV impairs storage rather than retrieval processes. These results indicate that there are two temporally distinct associative fear processes, a short-term NMDA-independent conditional fear and a long-term NMDA-dependent conditional fear.

Accumulation of Scoparone in Heat-Treated Lemon Fruit Inoculated with Penicillium digitatum Sacc

Phytoalexin scoparone (6,7-dimethoxycoumarin) generally was not detected in noninoculated lemon fruit (Citrus limon [L.] Burm., cv Eureka) but accumulated in fruit after inoculation with Penicillium digitatum Sacc. A much greater increase in the amount of scoparone was found in fruit exhibiting an incompatible response to Penicillium after heat treatment at 36 degrees C for 3 days. Heat treatment prevented development of decay in the inoculated fruit. The concentration of the compound after inoculation continued to increase during and after the heat treatment period, reaching 178 micrograms per gram fresh weight of the flavedo 6 days after the heat treatment. Changes in scoparone concentration in fruit were closely correlated with the changes in the antifungal activity of the fruit extract. A low concentration of the phytoalexin was detected in fruit injured mechanically. Scoparone also accumulated in the fruit following ultraviolet illumination; the concentration of the compound was dose-dependent. Median effective dose values of the inhibition of germ tube elongation and spore germination of P. digitatum were 29 and 46 micrograms per milliliter, respectively. Our findings suggest that the rapid increase in scoparone concentration plays an important role in the increased resistance of heat-treated lemon fruit to infection by P. digitatum.

A cultural psychiatric study on tattoos of young Korean males

In 2, 178 tattooed male conscripts in ages of 19-24 years, the most frequent tattoo was a heart mark or a mark of heart and arrow. The Chinese characters which mean "one mind," eagles, dragons, some of 12 zodiacal animals, flowers, and flowers and butterflies or birds were also frequent. The ten Korean symbols of long life and symbols which have been traditionally believed as having evil-repelling powers, for example, blue dragon or white tiger were also found. The frequency of images were different between the provinces with different historical and cultural backgrounds. Data was obtained through interviews with 781 tattooed males. Analysis of the data revealed the following. The prevalence of tattooing was 5.6%. The most prevailing motivation to having tattoos was a contemporary group craze or fashion. Of the 781 tattooed men, 62% had tattoos on their forearms, 34.2% had self-injured scars on their bodies, and 18.6% had criminal convictions. The results of MMPI showed high scores in items of psychopathic deviate and schizophrenia. This suggests that those with tattoos were impulsive, hostile and were prone to delinquent behavior. These results indicate that selection of the image to be tattooed is heavily influenced by inner needs and the cultural background of individuals.

Differential effects of selective opioid peptide antagonists on the acquisition of pavlovian fear conditioning

Pretreatment with opioid antagonists enhances acquisition of Pavlovian fear conditioning. The present experiments attempted to characterize the type of opioid receptor responsible for this effect using a procedure that assessed the fear of rats to a chamber previously associated with electric shock (1 mA, 0.75 s). Freezing, a species-typical immobility, was employed as an index of fear. Two mu opioid antagonists, CTOP (40 ng) and naloxonazine (10 micrograms), enhanced conditioning. On the other hand, the kappa antagonist nor-binaltorphimine reduced conditioning. Two delta antagonist treatments (16-methyl cyprenorphine and naltrindole) had no reliable effect on acquisition. Thus the enhancement of conditioning appears to be mediated by mu receptors. Previous research has shown that the conditional fear produced by these procedures caused an analgesia that is also mediated by mu receptors. It is argued that the enhancement effect occurs because of an antagonism of this analgesia and that the analgesia normally acts to regulate the level of fear conditioning.

Endogenous sialylation of the lipooligosaccharides of Neisseria meningitidis

Monoclonal antibodies (MAb) 3F11 and 06B4 recognize epitopes that are conserved on gonococcal lipooligosaccharides (LOS), present on some meningococcal LOS, and conserved on human erythrocytes. LOS of some group B and C prototype meningococcal LOS strains (LOS serotypes L1 to L8) treated with neuraminidase showed increased expression of the 3F11 and 06B4 MAb-defined epitopes. Neuraminidase-treated LOS separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver stained showed a shift in migration from a component with a mass of approximately 4.8 kDa to a component with a mass of between 4.5 and 4.6 kDa. The same strains grown in medium with excess CMP-N-acetylneuraminic acid had LOS that shifted in migration to a slightly higher component (mass, approximately 4.8 kDa). Chemical analysis of the neuraminidase-digested products from one LOS indicated it contained approximately 1.5% sialic acid. Covalent linkage between sialic acid and the LOS was confirmed by analysis of de-O-acylated and dephosphorylated LOS by liquid secondary ion mass spectrometry. Three studies show that some meningococci contain sialic acid in their LOS, that the sialic acid is cleaved and lost in conventional acetic acid hydrolysis, and that the sialic acid alters the expression of MAb-defined epitopes.

Trabecular smooth muscle modulates the capacitor function of the penis. Studies on a rabbit model

We investigated the role of trabecular smooth muscle tone in regulation of intracavernosal pressure, venous outflow resistance, and penile capacitance. In an isolated rabbit whole penis model, corpora cavernosa were infused with either contracting (high K(+)-norepinephrine combination) or relaxing (no added Ca(2+)-papaverine combination) physiological salt solutions while intracavernosal pressure was recorded. An infusion pump regulated by an intracavernosal pressure feedback mechanism enabled the measurement of flow necessary to maintain intracavernosal pressures at 30, 60, 90, 120, and 150 mmHg under steady-state conditions (inflow = outflow). These experiments allowed resistance to outflow from corpora to be calculated when trabecular smooth muscle was either constricted or relaxed. Decay in intracavernosal pressure over time from various predetermined intracavernosal pressures (150, 120, 90, 60, and 30 mmHg) was studied under conditions of zero inflow following contraction or relaxation of trabecular smooth muscle. This permitted calculation of the time constant, which together with the outflow resistance, permitted the calculation of penile capacitance. When smooth muscle is relaxed, venous outflow resistance is high, constant, and independent of intracavernosal pressure. Furthermore, relaxation of smooth muscle allows expansion of corpora with accumulation of volume under pressure, enabling the penis to act as a capacitor. This capacitor function is limited in the presence of constant high outflow resistance by stiffness of the fibroelastic elements of penis, tunica, and fibroelastic frame, which exhibit nonlinear deflection trends. Analysis of these variables has led us to propose a model for penile erection.

N-methyl-D-aspartate receptor antagonist APV blocks acquisition but not expression of fear conditioning

The role of N-methyl-D-aspartate (NMDA) receptors in Pavlovian fear conditioning was examined using the NMDA antagonist DL-2-amino-5-phosphonovaleric acid (APV). Either APV (5 micrograms/rat) or saline was administered before the training phase, the testing phase, or both. APV completely blocked acquisition but not expression of fear conditioning. The L enantiomer of APV did not affect the acquisition of conditional fear. To separate encoding from consolidation processes, APV was administered either before or immediately after the footshock unconditional stimulus (US) during the training phase. The results indicate that APV must be present during the US to produce its effects on fear conditioning. The behavioral effect of the drug is not due to analgesic action because APV did not alter pain sensitivity. The data suggest that NMDA receptors are critical for the acquisition but not expression of fear conditioning. These effects on fear conditioning are parallel to the in vitro effects of APV on the acquisition but not expression of long-term potentiation (LTP) and suggest that endogenously generated NMDA-dependent LTP participates in the neural plasticity underlying fear conditioning.

N-methyl-D-aspartate receptor antagonist APV blocks acquisition but not expression of fear conditioning

The role of N-methyl-D-aspartate (NMDA) receptors in Pavlovian fear conditioning was examined using the NMDA antagonist DL-2-amino-5-phosphonovaleric acid (APV). Either APV (5 micrograms/rat) or saline was administered before the training phase, the testing phase, or both. APV completely blocked acquisition but not expression of fear conditioning. The L enantiomer of APV did not affect the acquisition of conditional fear. To separate encoding from consolidation processes, APV was administered either before or immediately after the footshock unconditional stimulus (US) during the training phase. The results indicate that APV must be present during the US to produce its effects on fear conditioning. The behavioral effect of the drug is not due to analgesic action because APV did not alter pain sensitivity. The data suggest that NMDA receptors are critical for the acquisition but not expression of fear conditioning. These effects on fear conditioning are parallel to the in vitro effects of APV on the acquisition but not expression of long-term potentiation (LTP) and suggest that endogenously generated NMDA-dependent LTP participates in the neural plasticity underlying fear conditioning.

Meningococcal molecular mimicry and the search for an ideal vaccine

The carbohydrates expressed on the surface of meningococcal strains of groups B and C mimic those commonly found on human cells and thus are not functionally antigenic in infancy. In order to develop an effective vaccine, it will be necessary to find ways of circumventing this molecular mimicry. Three possible ways of achieving this are discussed. (i) The surface polysaccharides can theoretically present conformationally different epitopes, some of which might be recognized as antigenic by the host. Experimental evidence is presented that such differences do indeed exist; what is needed is to determine which of these conformations are unique to the organism and hence potentially antigenic. (ii) Precursors of the surface lipooligosaccharides may be unable to mimic human antigens, and so may be potential candidates for vaccine development. (iii) Natural immunity to some strains of meningococci develops in young children who are colonized with strains of Neisseria lactamica, and it is possible that its development could be enhanced by widespread intentional colonization by N. lactamica strains that are particularly efficient inducers of broad immunity.

Selectivity of phospholipase C phosphorylation by the epidermal growth factor receptor, the insulin receptor, and their cytoplasmic domains

Phosphatidylinositol-specific phospholipase C isozyme gamma (PLC-gamma, Mr 145,000) is an excellent substrate for the epidermal growth factor (EGF) receptor both in vivo and in vitro. PLC-beta-1, another PLC isozyme, is a poor substrate for the EGF receptor. We examined the relative phosphorylation of PLC-gamma and PLC-beta-1 by the 170-kDa native EGF receptor molecule, the 66-kDa cytoplasmic kinase domain of the EGF receptor (Arg647-Ala1186), the alpha 2 beta 2 native insulin receptor, and the 48-kDa cytoplasmic kinase domain of the insulin receptor beta subunit (Gly947-Ser1343). Similar to the intact EGF receptor, the cytoplasmic kinase domain of the EGF receptor preferentially phosphorylated PLC-gamma. High-performance liquid chromatographic comparison of tryptic phosphopeptides from PLC-gamma phosphorylated by both forms of the EGF receptor kinase indicated similar patterns of multiple tyrosine phosphorylations. These results imply that substrate selectivity, at least in terms of PLC isozymes, is independent of the extracellular ligand-binding and membrane anchor domains of the EGF receptor. In comparison, neither the intact insulin receptor nor the beta-chain kinase domain was able to phosphorylate PLC-gamma to a significant extent. Also, insulin failed to stimulate the phosphorylation of PLC-gamma in NIH 3T3/HIR cells, which overexpress the human insulin receptor. Thus PLC-gamma is not a phosphorylation substrate for the insulin receptor in vitro or in the intact cell.

Interactions of water-soluble porphyrins with hexadeoxyribonucleotides: resonance raman, UV-visible and 1H NMR studies

The interactions of the water-soluble porphyrins M(TMpy-P4) [M = H2, Cu(II), Ni(II), and Co(III); TMpy-P4 = tetrakis(4-N-methylpyridyl)porphyrinato ion], with the hexadeoxyribonucleotides d(CGTACG)2, d(TACGTA)2, d(GCATGC)2, d(TGTGCA)2, and d(CTATAG)2 have been investigated by resonance Raman and/or UV-visible spectroscopy. The results indicate that all hexamers containing the 5'CG3' as well as the 5'GC3' site, and also the mismatched hexamer d(TGTGCA)2, are capable of intercalating the H2, Cu(II) and Ni(II) porphyrins. 1H nuclear magnetic resonance spectra of d(CGTACG)2 mixed with Cu(TMpy-P4) have provided further evidence for the intercalation. For the other cases, outside binding by localized electrostatic interaction is suggested. There is no evidence of groove binding to any of the hexamers. Possible reasons for different binding properties of long and short helices are discussed.

Cough syncope caused by sinus arrest in a patient with sick sinus syndrome

Cough syncope is a syndrome in which dizziness or syncope occurs after prolonged bouts of cough. This paper presents a case of 63-year-old man with recurrent dizziness and syncope. The 24-hour ambulatory electrocardiogram and intracardiac electrogram showed sinus node dysfunction with sinus arrest, both spontaneous and inducible by voluntary cough. Sinus arrest was sometimes associated with dizziness. A permanent VVI pacemaker was implanted and no further cough syncope has occurred. We suggest that sinus arrest may play a role as a mechanism of cough syncope in a patient with sick sinus syndrome.

Neisseria lactamica and Neisseria meningitidis share lipooligosaccharide epitopes but lack common capsular and class 1, 2, and 3 protein epitopes

Neisseria lactamica, a common human pharyngeal commensal, contributes to acquired immunity to Neisseria meningitidis. To define the surface antigens shared between these two species, we used monoclonal antibodies (MAbs) to study 35 N. lactamica strains isolated in various parts of the world for cross-reactivity with meningococcal capsules, outer membrane proteins, and lipooligosaccharides (LOS). No N. lactamica strain reacted significantly with MAbs specific for capsular group A, B, C, Y, or W, and we were unable to extract capsular polysaccharide from them. Only 2 of 33 strains reacted weakly with MAbs against class 2 serotype proteins P2b and P2c. None reacted with MAbs specific for meningococcal class 1 protein P1.2 or P1.16 or class 2/3 serotype protein P2a or P15. Most N. lactamica strains (30 of 35) bound one or more of seven LOS-specific MAbs. Two LOS epitopes, defined by MAbs O6B4 and 3F11, that are commonly found on pathogenic Neisseria species were found on 25 of 35 N. lactamica. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting showed that the LOS of N. lactamica are composed of multiple components that are physically and antigenically similar to the LOS of pathogenic Neisseria species. Among four other commensal neisserial species, only Neisseria cinerea shared LOS epitopes defined by MAbs O6B4 and 3F11. Previous studies have shown that pharyngeal colonization with N. lactamica induces bactericidal antibodies against the meningococcus. We postulate that shared N. lactamica and meningococcal LOS epitopes may play an important role in the development of natural immunity to the meningococcus.

Electromorphic characterization and description of conserved epitopes of the lipooligosaccharides of group A Neisseria meningitidis

We studied the lipooligosaccharides (LOS) of 28 group A Neisseria meningitidis of epidemiologically diverse origins to investigate whether each of the LOS serotypes found in serogroup A could be identified physically as well as antigenically. Using a dot blot assay with LOS-specific monoclonal antibodies (MAbs), we identified four epitopes that were serotype specific. The LOS from strains of each serotype were electromorphically and antigenically distinct when analyzed by silver-stained sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. The LOS of L8 strains contained a 3,600-Mr component that bound the L8 MAb. The LOS of L9 strains contained two major components of 4,500 and 4,200 Mr. They bound the L9 MAb to the larger component. The LOS of L10 strains had a single major component of 4,000 Mr that bound the L10 MAb. The LOS of L11 strains contained a major 3,600-Mr component that could not be distinguished from the 3,600-Mr LOS of L8 strains by SDS-PAGE but that bound the L11 MAb. LOS of group A strains contained a highly conserved epitope in addition to a serotype-specific epitope. This was identified by a MAb that bound to all the strains on dot-blots and to multiple LOS components of various Mrs on immunoblots. We conclude that the LOS which bear the L9, L10, and L11 determinants are physically distinct and can be identified by SDS-PAGE or MAb binding or both. L8 and L11 are both borne on a 3.6-kilodalton LOS and can only be distinguished serologically.

Structure of the medium-chain acyl-CoA dehydrogenase from pig liver mitochondria at 3-A resolution

The three-dimensional structure of the medium-chain acyl-CoA dehydrogenase (EC 1.3.99.3) from pig liver mitochondria has been determined to 3.0-A resolution by the x-ray diffraction method. The enzyme is a tetramer of four identical 43-kDa subunits and contains one equivalent of flavin adenine dinucleotide (FAD) per subunit. The polypeptide is folded into three domains. The N-terminal and the C-terminal domains are composed mainly of alpha-helices, and the middle domain is packed with orthogonal beta-sheets. The FAD has an extended conformation: the flavin ring lies between the N-terminal and the beta-sheet domains, and the adenine moiety is found at the junction between the C-terminal and the beta-sheet domains of one subunit and the C-terminal domain of a neighboring subunit. The polypeptide chain folding near the FAD binding site is different from those observed in other flavoproteins, such as glutathione reductase and glycolate oxidase.

Lipooligosaccharides: the principal glycolipids of the neisserial outer membrane

The outer-membrane glycolipids of bacteria that colonize mucosal surfaces that are not routinely bathed by bile acids often lack the long, hydrophilic and neutral polysaccharides that protect the lipid membranes of enteric bacteria from dispersal. The glycolipid from these organisms is properly termed a lipooligosaccharide. A Neisseria strain makes from two to six lipooligosaccharide molecules that range in Mr from 3,150 to 7,100. Different species of Neisseria commonly make lipooligosaccharides of identical Mr and epitope content. Differences in oligosaccharides account for most of the observed physical heterogeneity. Oligosaccharides consist of (1) partially conserved and highly substituted basal oligosaccharides that branch at heptose residues; (2) a linear segment consisting of (hexose)n residues that determines the length of the oligosaccharide; and (3) terminal sequences that are similar to those of glycosphingolipids. Epitope expression is linked to physical heterogeneity and is modified by the molecular environment of the outer membrane. Serotype epitopes are present only on lipooligosaccharides of a certain Mr. Certain lipooligosaccharides regulate complement activation onto the bacterial surface and, hence, immune lysis.

Temporal behavior of the intensity-dependent absorption in photorefractive BaTiO(3)

We report measurements of response time for the intensity-dependent absorption in a single BaTiO(3) crystal under conditions in which no photorefractive effect can be observed. The speed of response is found to increase with increasing intensity but in a sublinear fashion similar to that observed for photorefractive decay. This experiment provides unambiguous evidence for the intensity-dependent absorption in BaTiO(3) crystals.

Binding of calcium to glycosaminoglycans: an equilibrium dialysis study

Binding of calcium to the glycosaminoglycans (GAGs) heparin, chondroitin sulfate (CS), keratan sulfate (KS), and hyaluronic acid (HA) has been studied by equilibrium dialysis using exclusion of sulfate to correct for Gibbs-Donnan effects. Calcium binding occurs to all of these GAG species, suggesting that both sulfate and carboxylate groups are involved in cation binding. For all GAGs, the binding stoichiometry is consistent with a calcium-binding "site" consisting of two anionic groups. The order of calcium binding affinities is heparin greater than CS greater than KS greater than HA, and is critically dependent upon charge density; heparin binds calcium with 10-fold higher affinity than CS. The mode of calcium binding to GAGs is consistent with a recently proposed mechanism of growth plate calcification which states that cartilage proteoglycan functions as a reservoir of calcium for calcification of epiphyseal cartilage.

Chronic amphetamine alters D-2 but not D-1 agonist-induced behavioral responses in rats

In two experiments, using different drug doses and periods of drug administration, rats were given amphetamine (AMPH) either continuously (via slow-release pellets), or intermittently (via injections). In both experiments, only the rats pretreated with intermittent AMPH subsequently showed heightened responsivity to the selective D-2 dopamine agonist LY171555 but not to SKF38393 (a D-1 agonist). This altered response to LY171555 was still present 30 days after the AMPH withdrawal, implying that D-2 dopamine receptors at least partially mediate AMPH inverse tolerance effects. The behavioral response to the D-2 agonist was clearly different in animals receiving high versus low doses of AMPH, suggesting that different drug-state learning may have occurred during pretreatment. In a third experiment, in which rats were given repeated daily injections of either the D-1 or the D-2 agonist, only rats pretreated with the D-2 agonist and subsequently injected with the D-2 agonist clearly showed heightened responsivity. These data imply an important role of D-2 receptors in the AMPH inverse tolerance effect.

Stimulated emission in optically pumped atomic-copper vapor

We have observed, for the first time to our knowledge, stimulated emission in atomic-copper vapor that is excited by a resonant tunable laser beam. One of the important and interesting results obtained in this experiment is that excitation of the (2)P(1/2) level of the copper atoms generates strong amplified spontaneous emission (ASE) for both(2)P(1/2)-(2)D(3/2) and (2)P(3/2)-(2)D(5/2) transitions. This is the first reported direct experimental evidence observed for collisional mixing between the (2)P(1/2) and (2)P(3/2) levels in a copper-vapor laser. Excitation of the (2)P(3/2) level induces substantially weaker ASE for the (2)P(1/2)-(2)D(3/2) transition. In addition, we observed collision-induced ASE for both transitions over a wide range of detuning of the pump frequency. The preliminary results of the experiment are presented, and the implications of the results for high-pressure copper-vapor lasers are discussed.

The immunochemistry of neisserial LOS

The outer membrane glycolipids of Neisseria lack long polysaccharides and are properly termed lipooligosaccharides (LOS). A Neisseria strain makes from two to six LOS of Mr 3150-7100. Different species commonly make LOS of identical Mr and epitope content. Oligosaccharide (OS) differences account for physical heterogeneity. OS consist of a conserved triantenary basal oligosaccharide, two linear segments of (n) hexose residues that determine OS mass, and terminal sequences similar to those of glycosphyngolipids. Epitope expression is linked to physical heterogeneity and conditioned by the molecular environment of the outer membrane. Serotype epitopes are expressed on Mr-restricted LOS. LOS regulate complement activation onto the bacterial surface and, hence, immune lysis.