An E-band multi-channel Doppler backscattering system on EAST

An E-band (60-90 GHz) multi-channel Doppler backscattering (DBS) system with X-mode polarization has been installed on the Experimental Advanced Superconducting Tokamak (EAST), which can measure the turbulence at five different radial locations simultaneously. This system can launch 31 fixed microwave frequencies in the range of 60-90 GHz with a 1 GHz interval into the plasma, and five probing signals are selected by employing a reference signal and multiple filters. During experiments, the frequency of the reference signal is tunable in the E-band, and the selected probing signals can be changed as needed without any other adjustments, which can be performed in one shot or between shots. Furthermore, the incident angle can be adjusted from -10° to 20°, and the wavenumber range is 4-25 cm-1 with a wavenumber resolution of Δk/k ≤ 0.35. Ray tracing simulations are employed to calculate the scattering locations and the perpendicular wavenumber. In this article, the hardware design, ray tracing, and initial results obtained from the EAST plasma will be presented.

A Functional Polymorphism in HIF-3α Is Related to an Increased Risk of Ischemic Stroke

Hypoxia-inducible factor-3α (HIF-3α), a member of HIF family, can mediate adaptive responses to low oxygen and ischemia. It is believed that HIF plays crucial roles in stroke-related diseases. However, there are no reports on the association between HIF-3α genetic variants and ischemic stroke (IS) susceptibility. Therefore, we examined the association between HIF-3α gene polymorphisms (rs3826795, rs2235095, and rs3764609) and IS risk. The study population included 302 controls and 310 patients with ischemic stroke. Three polymorphisms in HIF-3α (rs3826795, rs2235095, and rs3764609) were genotyped using SNPscan technique. Our study showed a strong association of rs3826795 in HIF-3α with the risk of IS. The genotype and allele frequencies were shown to differ between the two groups. The rs3826795 in an intron of HIF-3α was related to a prominent increased IS risk (AA vs GG adjusted odd ratio [OR], 2.21; 95% confidence intervals [95% CI], 1.10-4.44; P = 0.03; AA vs AG/GG OR = 1.74, 95% CI, 1.02-2.97, P = 0.04; A vs G OR = 1.48, 95% CI, 1.05-2.07, P = 0.02). Logistic regression analysis suggested that rs3826795 posed a risk factor for IS in addition to common factors. Furthermore, when compared to controls, increased levels of homocysteic acid and level of non-esterified fatty acid were found in the cases (P < 0.01). However, no significant association was found between rs2235095 or rs3264609 and IS risk. These findings indicated that the rs3826795 polymorphism may be a potential target for predicting the risk of IS.

[Establishment of the classified evaluation system on the levels of influenza epidemics through a synthetic index method, in Beijing]

Objective: To establish a classified evaluation system for recognizing the levels of influenza epidemics and to explore the new reporting system on influenza epidemics. Methods: The following 3 indicators, including 1) the number of influenza-like illness, 2) positive rate of detection on influenza virus nucleic acids, and 3) the number of influenza outbreaks were chosen to calculate the synthetic index and to classify the grades of evaluation. Results: 209 weeks during 2013-2017 were classified into 5 grades: Grade 1 were 110 weeks (52.63%), Grade 2 were 47 weeks (22.49%), Grade 3 were 44 weeks (21.05%), Grade 4 were 8 weeks (3.83%), and Grade 5 were 0 week. Conclusion: This classified evaluation system provided simple, comprehensive and comparable reference indicators and used for the evaluation on influenza epidemics, also providing suggestions for influenza prevention and control accordingly.

[Study on the super-antigen genes of group A Streptococcus pyogenes strains isolated from patients with scarlet fever and pharyngeal infection, in Beijing, 2015-2017]

Objective: To analyze the characteristics of super-antigen (SAg) of group A Streptococcus pyogenes (GAS), isolated from patients with scarlet fever or pharyngeal infections in Beijing between 2015-2017. Methods: Throat swab specimens from patients with scarlet fever or pharyngeal infections were collected and tested for GAS. Eleven currently known SAg genes including SpeA, speC, speG, speH, speI, speJ, speK, speL, speM, smeZ and ssa were tested by real-time PCR while M protein genes (emm genes) were amplified and sequenced by PCR. Results: A total of 377 GAS were isolated from 6 801 throat swab specimens, with the positive rate as 5.5%. There were obvious changes noticed among speC, speG, speH and speK in three years. A total of 45 SAg genes profiles were observed, according to the SAgs inclusion. There were significant differences appeared in the frequencies among two of the highest SAg genes profiles between emm1 and emm12 strains (χ(2)=38.196, P<0.001; χ(2)=72.310, P<0.001). There also appeared significant differences in the frequencies of speA, speH, speI and speJ between emm1 and emm12 strains (χ(2)=146.154, P<0.001; χ(2)=52.31, P<0.001; χ(2)=58.43, P<0.001; χ(2)=144.70, P<0.001). Conclusions: Obvious changes were noticed among SAg genes including speC, speG, speH and speK from patients with scarlet fever or pharyngeal infections in Beijing between 2015-2017. SAg genes including speA, speH, speI and speJ appeared to be associated with the emm 1 and emm 12 strains. More kinds of SAg genes profiles were isolated form GAS but with no significant differences seen in the main SAg genes profiles, during the epidemic period.

[The epidemiological characteristics and drug resistance of mycoplasma pneumoniae in patients with community-acquired pneumonia during 2011-2015 in 5 sentinel hospitals in Beijing]

Objective: To analyze the prevalence and drug resistance of mycoplasma pneumoniae in patients with community-acquired pneumonia during 2011-2015 in Beijing. Methods: Totally 2 272 mycoplasma pneumoniae samples were collected from patients with community-acquired pneumonia in 5 sentinel hospitals during 2011-2015. Mycoplasma pneumoniae were detected by real-time PCR. 142 copies of positive samples with Ct value under 30 were cultured to get the strains so that the genotypes based on the P1 gene sequence and the drug resistance based on the in vitro drug resistance test could be conducted. χ(2) test was used to compare the detection rates of mycoplasma pneumoniae among different age groups and different onset-phase. Results: The positive rate of mycoplasma pneumoniae was 13.6%(308 cases). The positive rate in groups aging (5-14), (15-24) and ≥60 years old were separately 24.4% (67/275), 24.4% (38/156) and 3.9% (28/727) (χ(2)=1.22, P<0.001). The annual detection rate of mycoplasma pneumoniae in 2011-2015 were 14.6% (73/501), 10.2% (36/353), 26.4% (101/383), 10.3% (41/398), 9.0% (57/637),respectively (χ(2)=72.65, P<0.001). Seasonally, the peak of positive rate was between October and December (17.5%, 122/699) and the lowest positive rate was between April and June (8.6%, 43/502). 36 strains were isolated from 142 swabs and 23 (63.9%) were P1-Ⅰ and 13 (36.1%) were P1-Ⅱ by genotyping. All isolates were susceptible to the fluoroquinolones (levofloxacin, ciprofloxacin, and gatifloxacin) and tetracycline. All P1-Ⅱ strains were susceptible to macrolides while most of the P1-Ⅰ strains (22 strains) were macrolide-resistant. Conclusion: People aging (5-14) and (15-24) years old were more susceptible to mycoplasma pneumoniae in patients with community-acquired pneumonia in Beijing between 2011 and 2015. The highest positive rate of mycoplasma pneumoniae was in 2013 and the case distributed in all seasons. The major popular genotype was P1-Ⅰ, whose strains were mostly macrolide-resistant.

Prognostic significance of neutrophil to lymphocyte ratio in pancreatic cancer: A meta-analysis

AIM: To conduct a meta-analysis evaluating the association between the peripheral blood neutrophil to lymphocyte ratio (NLR) and the outcome of patients with pancreatic cancer.

METHODS: Studies evaluating the relationship between the peripheral blood NLR and outcome of patients with pancreatic cancer published up to May 2014 were searched using electronic databases, including PubMed, Web of Science, Embase and Ovid. A meta-analysis was performed to pool the hazard ratios (HRs) or odds ratios (ORs) and their 95% confidence intervals (CIs) using either a fixed-effects model or a random-effects model to quantitatively assess the prognostic value of NLR and its association with clinicopathological parameters.

RESULTS: Eleven studies containing a total of 1804 patients were eligible according to our selection criteria, and combined hazard ratios indicated that high NLR was a poor prognostic marker for pancreatic cancer patients because it had an unfavorable impact on the overall survival (OS) (HR = 2.61, 95%CI: 1.68-4.06, P = 0.000) and cancer specific survival (HR = 1.66, 95%CI: 1.08-2.57, P = 0.021). Subgroup analysis revealed that high NLR was associated with poor OS in patients with mixed treatment (HR = 4.36, 95%CI: 2.50-7.61, P = 0.000), chemotherapy (HR = 2.08, 95%CI: 1.49-2.9, P = 0.000), or surgical resection (HR = 1.2, 95%CI: 1.00-1.44, P = 0.048). Additionally, high NLR was significantly correlated with tumor metastasis (OR = 1.69, 95%CI: 1.10-2.59, P = 0.016), poor tumor differentiation (OR = 2.75, 95%CI: 1.19-6.36, P = 0.016), poor performance status (OR = 2.56, 95%CI: 1.63-4.03, P = 0.000), high cancer antigen 199 (OR = 2.62, 95%CI: 1.49-4.60, P = 0.000), high C-reactive protein (OR = 4.32, 95%CI: 2.71-6.87, P = 0.000), and low albumin (OR = 3.56, 95%CI: 1.37-9.27, P = 0.009).

CONCLUSION: High peripheral blood NLR suggested a poor prognosis for patients with pancreatic cancer, and it could be a novel marker of survival evaluation and could help clinicians develop therapeutic strategies for pancreatic cancer patients.

Eight-year survival of AIDS patients treated with Chinese herbal medicine

Treatment of acquired immunodeficiency syndrome (AIDS) currently relies on the use of antiretroviral drugs. Little is known about Chinese herbal medicine (CHM) outcomes in patients living with AIDS. We conducted a cohort study to investigate long-term survival among CHM-treated AIDS patients. Patients were poor farmers who contracted HIV-1 infection when selling blood in the 1990s. Symptoms of AIDS included recurring respiratory tract infections with a clinical diagnosis of pneumonia, swollen lymph nodes and weight loss. 385 patients with AIDS were included and 165 of them used a 16-herb formula for 14 days to 9 months. The eight-year survival rate was 87% for the CHM users and 34% for the non-users (increased survival probability for CHM user, 9.6; 95% CI = 6.0-15.4; p < 0.0001). Survival probability further increased 14.6-fold (95% CI = 8.2-26.1), when excluding the users who received CHM for less than three months. Zero deaths were found in patients who used CHM for six to nine months. All the survivors regained their body weight and none of them experienced a relapse of AIDS or any severe adverse events. After the CHM treatment for an average of 3.6 months, the plasma HIV load was 74.7% lower (paired t-test, p = 0.151) and the number of blood CD4+ lymphocytes increased from 253 to 314 (paired t-test, p = 0.021). Without life-long medication, CHM may be beneficial for long-term survival of AIDS patients.

Optimization of complex conditions by response surface methodology for APAM-oil/water emulsion removal from aqua solutions using nano-sized TiO2/Al2O3 PVDF ultrafiltration membrane

This paper studies the cumulative effect of various parameters, namely anionic polyacrylamide (APAM) concentration, oil concentration, pH, trans-membrane pressure (TMP), and total dissolved solid (TDS), and obtains optimal parameters for the minimum relative flux (J/J(0)) declining in aqueous solutions with response surface methodology (RSM). In order to analyze the mutual interaction and optimal values of parameters affecting ultrafiltration, a central composite rotatable design (CCRD), one method of RSM, was employed. The analysis of variance (ANOVA) of the cubic polynomial model demonstrated that this model was highly significant and reliable. The results show that the effect of APAM and oil on J/J(0) has an inverse trend with pH value increasing. Moreover, the mutual interaction of initial APAM (oil) concentration (C(APAM(oil))) and pH (TMP) were negligible, while the mutual interaction of C(APAM) and C(oil) has an obvious effect, i.e. the effect of initial feed C(APAM) became more important at higher values of initial feed C(oil), and the J/J(0) was only about 4%. The favorable operate conditions in this ultrafiltration process were at low C(APAM), C(oil), pH, and TMP, which agreed with the conclusions of many authors, while considering water production, C(APAM) and C(oil) < 50 mg/L, pH < 4, and TMP < 0.075 MPa could be accepted.

Isotherm and kinetic behavior of adsorption of anion polyacrylamide (APAM) from aqueous solution using two kinds of PVDF UF membranes

To determine the isotherm parameters and kinetic parameters of adsorption of anion polyacrylamide (APAM) from aqueous solution on PVDF ultrafiltration membrane (PM) and modified PVDF ultrafiltration membrane (MPM) is important in understanding the adsorption mechanism of ultrafiltration processes. Effect of variables including adsorption time, initial solution concentration, and temperature were investigated. The Redlich-Peterson equation of the five different isotherm models we chose was the most fitted model, and the R(2) was 0.9487, 0.9765 for PM and MPM, respectively; while, the pseudo-first-order model was the best choice among all the four kinetic models to describe the adsorption behavior of APAM onto membranes, suggesting that the adsorption mechanism was a chemical and physical combined adsorption on heterogeneous surface. The thermodynamic parameters were also calculated from the temperature dependence (Δ(r)G(m)(θ), Δ(r)H(m)(θ), Δ(r)S(m)(θ)), which showed that the process of adsorption is not spontaneous but endothermic process and high temperature favors the adsorption.

Characterization and anti-fouling performance of nano-Al₂O₃/PVDF membrane for Songhua river raw water filtration

Polyvinylidene fluoride (PVDF) flat ultrafiltration membranes modified by nano-sized alumina (Al₂O₃) particles were prepared by phase inversion process and their properties and anti-fouling performances were examined. The influence of three types of natural organic matters on the modified membrane fouling was also studied. Raw water was taken from two different locations, i.e., Harbin and Zhaoyuan, of Songhua River. Dissolved organic compounds in the raw water were fractionated using XAD resins into three fractions, i.e., hydrophobic fraction, transphilic fraction, and hydrophilic fraction (HPI). The three adsorbed compounds were further eluted and dissolved into distilled water respectively to prepare the feed for the fouling tests. All solutions were adjusted to a concentration of 10.6 mg C/L, which equals to the total organic carbon (TOC) of the raw water. Results show that the addition of nano-Al₂O₃ particulars did not affect the inherent traits of the PVDF membranes, however, its surface hydrophilic properties were improved significantly with the addition of nanoparticles and anti-fouling performance was enhanced as well. The HPIs in the Songhua River were the main foulant, causing more fouling to membrane than hydrophobic and transphilic matters.

[Study of chigger communities on major species of rodents in Yunnan Province]

OBJECTIVE

To understand the characteristics of the chigger communities on the major species of rodent hosts.

METHODS

Rats were captured in 16 counties (or towns) of Yunnan. All the mites on the two auricles of the host were collected and identified. Shannon-Weiner's indices (H,E), the richness indices and dominance indices were adopted to judge the diversity and community structure of chiggers on their hosts (7 species of rodents).

RESULTS

From the 7 species of dominant rodent hosts, 131 species of chiggers were identified, belonging to 17 genera of Trombiculidae. Among them, abundant individuals were collected from 6 species which were considered to be dominant chigger species. Shannon-Weiner's indices (H) of the chigger communities showed the following sequence: Rattus norvegicus>Apodemus chevrieri>Eothenomys miletus>Mus pahari>Rattus nitidus>Rattus flavipectus>Mus caroli, and the richness indices were similar to this tendency. The niche breadth of the 6 dominant chigger species showed the following tendency: Herpetacarus hastoclavus>Leptotrombidium scutellare>Leptotrombidium sinicum>Helenicula siena>Leptotrombidium hiemalis>Leptotrombidium eothenomydis. There was a wide niche overlap between any two chigger species with all indices beyond 0.76. Slight positive association existed between each two dominant species of chigger mites by the coefficient of association (V).

CONCLUSION

The community structure of chigger mites on the 7 major species of rodent hosts is complex, reflecting a high diversity of mite species. The niche breadth of the 6 dominant chigger species is different with a wide niche overlap.

A novel HLA allele, DRB1*1609, identified in the Chinese Han population*

A novel human leucocyte antigen-DRB1*16 (HLA-DRB1*16) allele (DRB1*1609) has been identified by sequencing-based typing (SBT) in Chinese Han population. This new allele has identical nucleotide sequence to DRB1*160101 in exon 2, except for a single-nucleotide substitution from A to T at position 127. This change leads to an amino acid change from tyrosine to phenylalanin at residue 47 (Y47F). SBT was performed for cloned DRB1*16-specific polymerase chain reaction fragment. The serological phenotype of DRB1*1609 is equivalent to DR16 antigen.

Identification of an HLA-B*07 allele variant (B*0740) in the Chinese Han population

A novel HLA-B*07 allele, B*0740, has been identified by sequence-based typing (SBT) in the Chinese Han population. This new allele is identical to B*0705 and B*0706 for exons 2, 3, and 4, except for a single nucleotide at position 605 of codon 202 in exon 3 (AAG-->ATG) leading to an amino acid change from lysine to methionine. SBT was performed following allele separation using the Haploprep method. The serological equivalence of B*0740 to the B7 antigen did not change.

Dynamic modulation of NMDA-induced responses by ifenprodil in rat prefrontal cortex

Ifenprodil is known to inhibit channel opening of NMDA receptors containing the NR2B subunit. However, it has also been shown to increase NMDA receptor affinity for glutamate-site agonists, including NMDA. The coexistence of the two opposing effects may explain why ifenprodil can either enhance or suppress an NMDA response depending on the level of NMDA binding and thus the NMDA concentration. Using whole cell recordings in rat prefrontal cortical slices, we report here that the effect of ifenprodil also depends on the speed and the direction of change of NMDA concentration. As shown previously, ifenprodil increased the inward current induced by low concentrations of NMDA applied through a local Y-tube perfusion system. However, the rising phase of the current was less enhanced compared to the falling phase. Increasing the speed of rising of NMDA concentration further reduced the enhancing effect of ifenprodil. When pressure ejection was used to produce even faster NMDA responses, the entire rising phase including the peak of the response was suppressed by ifenprodil, while the falling phase remained enhanced. These results are consistent with the suggestion that ifenprodil decreases both the association and dissociation rates of NMDA from NMDA receptors, and suggest that ifenprodil affects slow and fast NMDA responses in different manners. In particular, this study suggests that ifenprodil inhibits the rising phase of a fast NMDA response by suppressing both channel opening and the association of NMDA with NMDA receptors and that this inhibition can occur even when the level of NMDA binding is low.

Anatomic basis of sequence-dependent predictability exhibited by nigral dopamine neuron firing patterns

Interspike intervals (ISIs) of dopamine (DA) neurons recorded in the substantia nigra are predicted partially by their immediate prior history. This study was designed to assess neuroanatomic origins of these sequential relationships. ISI data recorded from three groups of nigral DA neurons were studied: 1) 16 neurons recorded in unlesioned animals, 2) 14 neurons recorded after forebrain hemisection, 3) 12 neurons recorded after partial forebrain hemisection that reproduced nonspecific effects of the surgical lesion while leaving forebrain connections intact. As predicted, DA neurons recorded after full forebrain hemisection yielded statistically significant reductions in sequential predictability relative to control neurons and neurons recorded following partial hemisection. These data support the hypothesis that the sequence-dependent behavior of DA neurons arise in part from interactions with forebrain structures. ISI sequences recorded from unlesioned rats demonstrated maximum predictability when an average of 3.7 prior events were incorporated into the forecasting algorithm, thereby suggesting a physiological process whose "depth" of history-dependence is approximately 600-800 msec. Additional studies examining the functional significance of sequence-dependent ISI structure exhibited by nigral DA neurons are indicated.

Enhancement of NMDA-induced current by the putative NR2B selective antagonist ifenprodil

Ifenprodil has been widely used as an antagonist selective for NMDA receptors containing the NR2B subunit. Evidence suggests, however, that ifenprodil also increases NMDA receptor affinity. Using rat brain slices, we found that ifenprodil enhanced NMDA-induced current in both cortical and subcortical areas examined. To test whether the effect is due to an increase in NMDA receptor affinity, we compared the effect of ifenprodil on currents induced by different concentrations of NMDA. Consistent with the hypothesis, the enhancing effect (percent increase) was relatively constant at low NMDA concentrations. As NMDA concentration increased, however, the effect decreased. To test whether the effect is blocked when NMDA binding sites are saturated with NMDA, high concentrations of NMDA were applied. To partially block Ca(2+) influx and prevent cells from deteriorating, the experiments were performed in the presence of either MK801 or kynurenate, two noncompetitive antagonists. Under such conditions, ifenprodil not only failed to potentiate NMDA currents, but consistently suppressed the current. When the same concentration of NMDA was applied in the presence of the competitive antagonist CGP37849, ifenprodil regained its ability to potentiate NMDA currents. Furthermore, the higher the concentration of CGP37849 the more the NMDA current was potentiated by ifenprodil. These results, combined with previous studies, suggest that the enhancing effect is due to an increase in NMDA receptor affinity and is specific for responses induced by low NMDA concentrations. As NMDA concentration increases, the affinity-enhancing effect decreases. Consequently, the channel-suppressing effect becomes more prominent.

Dual effects of D-amphetamine on dopamine neurons mediated by dopamine and nondopamine receptors

By increasing dopamine (DA) release and activating feedback mechanisms, amphetamine and related psychostimulants are known to inhibit DA cell firing. Here, we report that D-amphetamine also has an excitatory effect on DA cells, which under control conditions, is masked by the inhibitory effect of D-amphetamine and is revealed when D2-like receptors are blocked. Thus, using in vivo single-unit recording in rats, we found that the selective D2 antagonist raclopride not only blocked the inhibition induced by D-amphetamine but also enabled D-amphetamine to excite DA cells. The excitation, expressed as an increase in both firing rate and bursting, persisted when both D1- and D2-like receptors were blocked by SCH23390 and eticlopride, suggesting that it is not mediated by DA receptors. The norepinephrine uptake blocker nisoxetine mimicked the effect of D-amphetamine, especially the increase in bursting, whereas the 5-HT uptake blocker fluoxetine produced no significant effect. Adrenergic alpha1 antagonists prazosin and WB4101 and the nonselective alpha antagonist phenoxybenzamine completely blocked increase in bursting induced by D-amphetamine and partially blocked the increase in firing rate. The alpha2 antagonist idazoxan and the beta antagonist propranolole, however, failed to prevent D-amphetamine from producing the excitation. Thus, revising the traditional concept, this study suggests that D-amphetamine has two effects on DA cells, a DA-mediated inhibition and a non-DA-mediated excitation. The latter is mediated in part through adrenergic alpha1 receptors.

[The development of a multifunctional molecular electrophoretograms processing system]

This paper presents to you the principles, composition and features of the multifunctional molecular electrophoretograms processing system.

Endogenous DA-mediated feedback inhibition of DA neurons: involvement of both D(1)- and D(2)-like receptors

To investigate the role of D(1)-like receptors in endogenous dopamine (DA)-mediated feedback control of DA neurons in vivo, single unit recordings were made from rat nigral DA cells using low cerveau isolé preparations. The D(2) antagonist raclopride, but not the D(1) antagonist SCH23390, increased baseline activity of DA neurons, suggesting that spontaneously released DA acts primarily through D(2)-like receptors to inhibit DA cells. However, feedback inhibition induced by an increased DA release by D-amphetamine (1 mg/kg, i.v.) was partially reversed by SCH23390. The same inhibition, on the other hand, was always completely reversed by raclopride, suggesting that the D(1)-mediated portion of the inhibition depends upon co-activation of D(2)-like receptors. In rats with forebrain hemitransections, D-amphetamine-induced inhibition was markedly decreased and the remaining inhibition was not blocked by SCH23390, supporting the suggestion that D(1)-D(2) co-activation-induced inhibition is mediated through long feedback pathways. In chloral hydrate-anesthetized rats, D-amphetamine-induced inhibition was also insensitive to SCH23390; however, the degree of the inhibition was not reduced. Combined with previous studies, these data suggest that chloral hydrate not only inactivates the D(1) feedback pathway but also enables the D(2) feedback pathway to operate independently of D(1)-like receptors. Conversely, in parkinsonian animals D(1) receptor activation alone has been reported to inhibit DA cells. Taken together, these results suggest that a major portion of endogenous DA-mediated feedback inhibition is due to concurrent activation of D(1)- and D(2)-like receptors. However, this D(1)-D(2) interdependence may alter under certain conditions and may play a role in the pathophysiology of Parkinson's disease.

Dendritic glutamate-induced bursting in prefrontal pyramidal cells: role of NMDA and non-NMDA receptors

AIM

To investigate whether in the prefrontal cortical (PFC) pyramidal cells, focal glutamate application to the apical dendrite induces bursting and whether the effect of glutamate involves activation of both NMDA and non-NMDA receptors.

METHODS

Pyramidal cells in layers V and VI of the PFC were visualized in rat brain slices using infrared videomicroscopy and recorded with whole-cell electrodes. Glutamate and its agonists were focally applied to the apical dendrite and the soma using microiontophoresis.

RESULTS

Dendritic glutamate application (0-20 nA, 10 mmol/L) induced repetitive bursts in most cells tested (12/17). In the same cells, somatic glutamate (5-20 nA, 10 mmol/L) induced only regular spiking. The bursting effect is likely to be direct since applications 5 microns away from the dendrite resulted in either a much reduced effect or no effect. Both CGP 37849 1 mumol/L and NBQX 1 mumol/L reduced the effect, suggesting an involvement of both NMDA and non-NMDA receptors. However, when non-NMDA receptors were selectively activated using AMPA (2-50 nA, 10 mmol/L), only regular spiking was observed. In contrast, selective NMDA receptor activation (NMDA 1.3-25 nA, 100 mmol/L) reliably induced bursting.

CONCLUSION

In most PFC pyramidal cells tested, dendritic glutamate application induces repetitive bursting, whereas somatic glutamate application induces only regular spiking. Both NMDA and non-NMDA receptors are activated during dendritic glutamate application. However, bursting is primarily mediated by NMDA receptors.

Opposite modulation of cortical N-methyl-D-aspartate receptor-mediated responses by low and high concentrations of dopamine

To examine whether dopamine modulates cortical N-methyl-D-aspartate receptor-mediated glutamate transmission, whole-cell recordings were made from identified pyramidal cells located in layers V and VI of the medial prefrontal cortex of the rat using a slice preparation. In the presence of tetrodotoxin and the absence of Mg2+, a brief local application of N-methyl-D-aspartate evoked an inward current which was blocked by the N-methyl-D-aspartate antagonist dizocilpine maleate but not affected by the non-N-methyl-D-aspartate antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline, suggesting that the observed current is mediated by N-methyl-D-aspartate receptors located on recorded cells. Bath application of dopamine produced opposite effects on the N-methyl-D-aspartate current depending on the concentrations of dopamine applied. At low concentrations (<50 microM), dopamine enhanced the N-methyl-D-aspartate current, whereas at higher concentrations, dopamine suppressed the current. The same concentrations of dopamine did not significantly affect the inward current induced by the non-N-methyl-D-aspartate agonist alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid. The enhancing effect of dopamine on the N-methyl-D-aspartate response was mimicked by the D1 agonist SKF38393 and blocked by the D1 antagonist SCH31966, whereas the suppressing effect was mimicked by the D2 agonist quinpirole and blocked by the D2 antagonist eticlopride. The above results suggest that dopamine at low concentrations acts preferentially on D1-like receptors to promote N-methyl-D-aspartate receptor-mediated transmission, while at high concentrations dopamine also activates D2-like receptors, leading to a suppression of the N-methyl-D-aspartate function. This differential modulation of N-methyl-D-aspartate function may have significant implications for understanding behaviors and disorders involving both cortical dopamine- and glutamate-mediated neurotransmission.

Induction of sialic acid 9-O-acetylation by diverse gene products: implications for the expression cloning of sialic acid O-acetyltransferases

Sialic acids can be modified by O-acetyl esters at the 7- and/or 9-position, altering recognition by antibodies, lectins and viruses. 9(7)-O-acetylation is mediated by a sialic acid-specific O-acetyltransferase, which has proven difficult to purify. Two groups have recently isolated cDNAs possibly encoding this enzyme, by expression cloning of human melanoma libraries in COS cells expressing the substrate ganglioside GD3. Pursuing a similar approach, we have isolated additional clones that can induce 9-O-acetylation. One clone present in a melanoma library encodes a fusion protein between a bacterial tetracycline resistance gene repressor and a sequence reported to be part of the P3 plasmid. Expression of the open reading frame is necessary for inducing 9-O-acetylation, indicating that this is not a reaction to the introduction of bacterial DNA. Another clone from a rat liver cDNA library induced 9-O-acetylation on COS cells expressing alpha2-6-linked sialic acids, and encodes an open reading frame identical to the Vitamin D binding protein. However, truncation at the 5' end eliminates the amino-terminal hydrophobic signal sequence, predicting cytosolic hyperexpression of a truncated protein. Thus, diverse types of cDNAs can indirectly induce sialic acid 9-O-acetylation in the COS cell system, raising the possibility that the real enzyme may be composed of multiple subunits which would not be amenable to expression cloning. Importantly, the cDNAs we isolated are highly specific in their ability to induce 9-O-acetylation either on alpha2-6-linked sialic acids of glycoproteins (truncated vitamin D binding protein) or on the alpha2-8-linked sialic acids of gangliosides (Tetrfusion protein). These data confirm our prior suggestion that a family of O-acetyltransferases with distinctive substrate specificities exists in mammalian systems.

D1-D2 interaction in feedback control of midbrain dopamine neurons

Dopamine (DA) D1-like receptors are present in pathways implicated in feedback control of midbrain DA neurons. However, stimulation of these receptors either produces no effect on DA cells, or the effect is inconsistent. It is possible that the expression of a D1 feedback effect requires co-activation of D2-like receptors. To test this hypothesis, we recorded extracellularly the spontaneous activity of nigral DA cells in a low cerveau isolé rat preparation. SKF38393 and dyhydrexidine, two D1 agonists, were administered systemically to animals pretreated with different doses of the D2 agonist quinpirole. Supporting the hypothesis, the two D1 agonists consistently inhibited DA cells in animals given high doses of quinpirole (>/=40 microg/kg, i.v.). However, no significant D1 effect was observed in animals pretreated with only low doses (</=20 microg/kg) of quinpirole. Because low doses of D2 agonists preferentially act on DA autoreceptors, and because the D1 inhibition persisted in animals whose DA autoreceptors were blocked by intranigral application of raclopride, our results suggest that the expression of D1 feedback inhibition requires co-activation of D2-like receptors on DA target neurons, instead of DA neurons themselves. These results, together with the finding that chloral hydrate completely blocked the D1 inhibition, may explain why previous studies have failed to show a consistent D1 effect on DA cells and suggest that drugs designed to act specifically on one subtype of DA receptor may, via feedback pathways, influence the action of endogenous DA on other DA receptor subtypes as well.

Characterization of dopamine-induced depolarization of prefrontal cortical neurons

Dopamine (DA) has been reported to depolarize neurons in the prefrontal cortex (PFC). To further characterize this effect of DA, we made whole cell recordings from PFC pyramidal cells in rat brain slices. As reported previously, DA depolarized most PFC cells tested. This effect of DA was concentration-dependent and persisted in the presence of synaptic blockade, indicating a direct effect of DA on the recorded cell. During DA-induced depolarization, PFC neurons consistently showed an increase in excitability, suggesting that the depolarization is not directly related to DA-induced inhibition of PFC neurons previously observed in vivo. Surprisingly, the effect of DA was not mimicked or blocked by several commonly used DA agonists and DA antagonists. The alpha and beta antagonists phentolamine and alprenolol and the atypical antipsychotic drug clozapine also showed no significant effect on DA-induced depolarization. These results suggest that DA-induced depolarization may be mediated by a nonspecific mechanism. However, it remains possible that there exists a new type of DA receptors in the PFC not sensitive to classical DA agonists and antagonists, particularly given the fact that DA applied in the same manner depolarized only PFC neurons but not those in the striatum or the substantia nigra.

Regulation of sialic acid 9-O-acetylation during the growth and differentiation of murine erythroleukemia cells

Sialic acids are typically found at the terminal position on vertebrate oligosaccharides. They are sometimes modified by an O-acetyl ester at the 9-position, potentially altering recognition of sialic acid by antibodies, lectins, and viruses. 9-O-Acetylation is known to be selectively expressed on gangliosides in melanoma cells and on N-linked chains in hepatocytes. Using a recently developed probe, we show here that in murine erythroleukemia cells, this modification is selectively expressed on another class of oligosaccharides, O-linked chains carried on cell surface sialomucins. These cells also express 9-O-acetylation on the ganglioside GD3, but this modification appears to be undetectable on the cell surface. Increasing cell density in culture is associated with a decrease in cell surface 9-O-acetylation of sialomucins. This change correlates with the spontaneous differentiation toward a mature erythroid phenotype. This down-regulation upon differentiation and entry into the G0/G1 stage of the cell cycle is confirmed by differentiation-inducing agents. In contrast, cells arrested in G2/M by the microtubule depolymerizing agent nocodazole show increased expression of cell surface 9-O-acetylated sialomucins (but not the 9-O-acetylated ganglioside). However, the microtubule stabilizer taxol does not induce this increase, showing that the nocodazole effect is independent of cell cycle stage. Indeed, direct analysis showed no correlation of 9-O-acetylation with cell cycle stage in rapidly growing cells, and shorter treatments with nocodazole also increased expression. Western blots of cell extracts confirmed that changes caused by differentiation and nocodazole are not due to redistribution of molecules from the cell surface. Indeed, following selective removal of 9-O-acetyl groups from the cell surface by a specific esterase, the recovery of expression is mediated by new synthesis rather than by redistribution from an internal pool. Thus, 9-O-acetylation on these sialomucins appears to be primarily regulated by the rate of synthesis, and the increase with nocodazole treatment is likely due to the inhibition of turnover of cell surface molecules. These data show that 9-O-acetylation of sialic acids in murine erythroleukemia cells is a highly regulated modification, being selectively expressed in a cell type-specific manner on certain classes of oligosaccharides and differentially regulated with regard to subcellular localization and to the state of cellular differentiation.

Sialic acid 9-O-acetylation on murine erythroleukemia cells affects complement activation, binding to I-type lectins, and tissue homing

O-Acetylation of the 9-hydroxyl group of sialic acids has been suggested to modify various recognition phenomena involving these molecules, but direct proof has been lacking in most situations. In the accompanying paper (Shi, W.-X., Chammas, R., and Varki, A. (1996) J. Biol. Chem. 261, 31517-31525), we report that the extent of 9-O-acetylation of cell surface sialic acids on murine erythroleukemia (MEL) cells can be modified by various manipulations, including differentiation, nocodazole treatment, and 9-O-acetyl esterase treatment. We have used this system to explore the putative roles of 9-O-acetylation in modulating alternative pathway complement activation, I-type lectin binding, and tissue homing. MEL cells are shown to be sensitive to lysis in vitro by the alternative pathway of human complement. Induced differentiation of the MEL cells causes resistance to lysis, and this correlates directly with extent of decrease in 9-O-acetylation. A similar resistance to alternative pathway lysis can be obtained by selective enzymatic removal of 9-O-acetyl groups from sialic acids. Conversely, the increase in cell surface 9-O-acetylation caused by nocodazole treatment correlates with increased sensitivity to alternative pathway lysis. Thus, a 9-O-acetyl group added to the side chain of cell surface sialic acids may abrogate its normal function in restricting alternative pathway activation. Indeed, the binding of human complement factor H, a negative regulator of the alternative pathway, is shown to be blocked by O-acetylation of the sialic acids on MEL cells. MEL cells are also shown to have cell surface ligands for the I-type lectins sialoadhesin and CD22. Sialoadhesin (but not CD22) binding is selectively enhanced by differentiation-induced loss of cell surface 9-O-acetylation and by direct enzymatic removal of the ester groups. Thus, some sialoadhesin ligands are masked by 9-O-acetylation, presumably because the side chain is required for recognition. Since sialoadhesin is expressed on some macrophages in vivo, we reasoned that tissue homing of MEL cells might be affected by O-acetylation. Indeed, enzymatic removal of cell surface 9-O-acetyl groups alters the tissue distribution of intravenously injected cells. In particular, de-O-acetylation caused significant increase in homing to the liver and spleen. These data demonstrate that cell surface 9-O-acetylation can affect a variety of biological recognition phenomena and provide a system for further exploration of the specific molecular mechanisms involved.

Presence of antibodies to heat stress proteins and its possible significance in workers exposed to high temperature and carbon monoxide

Antibodies to the ubiquitous group of stress proteins known as heat shock proteins (Hsps) have been found to be associated with a number of diseases in humans. Hsps are known to be induced by certain xenobiotics, some of which are common in the working environment. The biological significance of the presence of such autoantibodies is presently unclear. In the present study, we used immunoblotting to investigate the presence of antibodies against the different stress proteins, Hsp27, Hsp60, Hsp71, Hsc (heat shock cognate) 73 and Hsp89 alpha and beta in groups of workers exposed to high temperature or carbon monoxide. These data were related to a detailed clinical evaluation and to various laboratory measurements including electrocardiogram (ECG), B echogram, white blood cell counts and typing, the activity of alanine aminotransferase (ALT), acid phosphatase (ACP) and alkaline phosphatase (ALP) and lymphocyte DNA damage. Antibodies to Hsp27 and Hsp71 were found more frequently in the high temperature and carbon monoxide-exposed groups than in controls (P < 0.05). The carbon monoxide-exposed group showed the highest incidence of anti-Hsp antibodies. Anti-Hsp60 antibodies were only detected in workers exposed to high temperature or carbon monoxide. The percentage of workers with abnormal ECG, B echogram changes and displaying hepatitis B antigen (HBsAg) was higher in the carbon monoxide group than in the control group (P < 0.05). There was a significant increase in the activity of ALT in the high temperature and carbon monoxide groups and in the activities of ACP and ALP in the carbon monoxide group (P < 0.05). The extent of DNA damage measured in lymphocytes was higher in workers from the high temperature and carbon monoxide-exposed groups. We suggest that the increased frequency of antibodies to Hsps is the result of these damages of the release of denatured Hsps and of a decrease in the phagocytic ability of macrophages in these workers. The data gathered in the present study show a statistical relation between the occurrence of antibodies against Hsps and the frequency of health problems in workers and suggest a potential role for the antibodies as useful biomarkers to assess whether workers are experiencing environmental stress.

Effects of lesions in the medial prefrontal cortex on the activity of midbrain dopamine neurons

To determine whether lesions in the prefrontal cortex (PFC) alter the activity of midbrain dopamine (DA) neurons, single unit recordings were made from DA neurons in control and lesioned rats. PFC lesions, obtained by local injection of ibotenic acid into the medial PFC, had no effect on either firing rate or bursting activity of DA neurons in the ventral tegmental area (VTA). However, the number of spontaneously active DA neurons in the VTA was significantly decreased. In the substantia nigra (SN), the same lesions increased the firing rate and had no effect on either the bursting activity of the number of active DA cells. These results suggest that PFC lesions alter the activity of DA neurons. However, VTA and SN DA neurons may respond differently to PFC lesions.

Chronic morphine induces visible changes in the morphology of mesolimbic dopamine neurons

The mesolimbic dopamine system, which arises in the ventral tegmental area (VTA), is an important neural substrate for opiate reinforcement and addiction. Chronic exposure to opiates is known to produce biochemical adaptations in this brain region. We now show that these adaptations are associated with structural changes in VTA dopamine neurons. Individual VTA neurons in paraformaldehyde-fixed brain sections from control or morphine-treated rats were injected with the fluorescent dye Lucifer yellow. The identity of the injected cells as dopaminergic or nondopaminergic was determined by immunohistochemical labeling of the sections for tyrosine hydroxylase. Chronic morphine treatment resulted in a mean approximately 25% reduction in the area and perimeter of VTA dopamine neurons. This reduction in cell size was prevented by concomitant treatment of rats with naltrexone, an opioid receptor antagonist, as well as by intra-VTA infusion of brain-derived neurotrophic factor. In contrast, chronic morphine treatment did not alter the size of nondopaminergic neurons in the VTA, nor did it affect the total number of dopaminergic neurons in this brain region. The results of these studies provide direct evidence for structural alterations in VTA dopamine neurons as a consequence of chronic opiate exposure, which could contribute to changes in mesolimbic dopamine function associated with addiction.

Linkage-specific action of endogenous sialic acid O-acetyltransferase in Chinese hamster ovary cells

9-O-Acetylation of sialic acids shows cell type-specific and developmentally regulated expression in various systems. In a given cell type, O-acetylation can also be specific to a particular type of glycoconjugate. It is assumed that this regulation is achieved by control of expression of specific 9-O-acetyltransferases. However, it has been difficult to test this hypothesis, as these enzymes have so far proven intractable to purification or molecular cloning. During a cloning attempt, we discovered that while polyoma T antigen-positive Chinese hamster ovary cells (CHO-Tag cells) do not normally express cell-surface 9-O-acetylation, they do so when transiently transfected with a cDNA encoding the lactosamine-specific alpha2-6-sialyltransferase (Galbeta1-4GlcNAc:alpha2-6-sialyltransferase (ST6Gal I); formerly ST6N). This phenomenon is reproducible by stable expression of ST6Gal I in parental CHO cells, but not upon transfection of the competing lactosamine-specific alpha2-3-sialyltransferase (Galbeta1-(3)4GlcNAc:alpha2-3-sialyltransferase; (ST6Gal III) formerly ST3N) into either cell type. Further analyses of stably transfected parental CHO-K1 cells indicated that expression of the ST6Gal I gene causes selective 9-O-acetylation of alpha2-6-linked sialic acid residues on N-linked oligosaccharides. In a similar manner, while the alpha2-3-linked sialic acid residue of the endogenous GM3 ganglioside of CHO cells is not O-acetylated, transfection of an alpha2-8-sialyltransferase (GM3:alpha2-8-sialyltransferase (ST8Sia I); formerly GD3 synthase) caused expression of 9-O-acetylation of the alpha2-8-linked sialic acid residues of newly synthesized GD3. These data indicate either that linkage-specific sialic acid O-acetyltransferase(s) are constitutively expressed in CHO cells or that expression of these enzymes is secondarily induced upon expression of certain sialyltransferases. The former explanation is supported by a low level of background 9-O-acetylation found in parental CHO-K1 cells and by the finding that O-acetylation is not induced when the ST6Gal I or ST8Sia I cDNAs are overexpressed in SV40 T antigen-expressing primate (COS) cells. Taken together, these results indicate that expression of sialic acid 9-O-acetylation can be regulated by the action of specific sialyltransferases that alter the predominant linkage of the terminal sialic acids found on specific classes of glycoconjugates.

Ritanserin, a 5-HT2A/2C antagonist, reverses direct dopamine agonist-induced inhibition of midbrain dopamine neurons

Ritanserin (RIT), widely-used as a selective 5-HT2A/2C receptor antagonist, has been reported to produce significant therapeutic effects on the negative symptoms of schizophrenia and to improve extrapyramidal side effects induced by neuroleptics. Because midbrain dopamine (DA) systems are believed to be the major site of action for many antipsychotic drugs, the effect of RIT on substantia nigra DA neurons was examined in chloral hydrate-anesthetized rats using single unit recording techniques. Systemic injection of RIT (0.1-6.4 mg/kg, i.v.) had no consistent effect on basal firing rate but significantly reversed the inhibition induced by both direct and indirect DA agonists. However, our data suggest that this effect of RIT is largely mediated by a mechanism independent of 5-HT. Thus the 5-HT2A/2C agonist 1(2,5 dimethyoxy-4-iodophenyl)-2-aminopropane showed no effect on either basal firing rate or the inhibition induced by the direct DA agonist quinpirole. Neither the selective 5-HT2A antagonist MDL 100907 nor depletion of endogenous 5-HT using p-chlorophenylalanine mimicked the effect of RIT (i.e., attenuated quinpirole-induced inhibition). Furthermore, the effect of RIT persisted in animals pretreated with p-chlorophenylalanine. Because RIT is known to bind D2-like receptors and because the inhibition of DA neurons induced by low doses of a direct DA agonist is believed to be mediated by DA autoreceptors, these results suggest that RIT may act on DA autoreceptors directly as a DA antagonist. Since similar doses of RIT were reported to have no significant effect on postsynaptic D2 receptors in the striatum, it is possible that RIT at the doses used may selectively block DA autoreceptors.

Nonlinear sequence-dependent structure of nigral dopamine neuron interspike interval firing patterns

Firing patterns of 15 dopamine neurons in the rat substantia nigra were studied. These cells alternated between two firing modes, single-spike and bursting, which interwove to produce irregular, aperiodic interspike interval (ISI) patterns. When examined by linear autocorrelation analysis, these patterns appeared to reflect a primarily stochastic or random process. However, dynamical analysis revealed that the sequential behavior of a majority of these cells expressed "higher-dimensional" nonlinear deterministic structure. Dimensionality refers to the number of degrees of freedom or complexity of a time series. Bursting was statistically associated with some aspects of nonlinear ISI sequence dependence. Controlling for the effects of nonstationarity substantially increased overall predictability of ISI sequences. We hypothesize that the nonlinear deterministic structure of ISI firing patterns reflects the neuron's response to coordinated synaptic inputs emerging from neural circuit interactions.

A mannose-specific lectin from Vicia villosa seeds

A lectin specific to mannose has been purified from Vicia villosa seed by (NH4)2SO4 fractionation, GalNAc-Sepharose and Man-Sepharose affinity chromatography. It was defined as VVLM, which showed a single band on an acidic-PAGE stained with Coomassie brilliant blue. The molecular weight of VVLM was 50 kDa as determined by gel filtration on Biogel P-100 column. The VVLM molecule consists of 2 distinct subunits with apparent molecular weight of 30 kDa and 22 kDa determined by SDS-PAGE. VVLM has at least four isolectins with similar haemagglutinating activity. Its extinction coefficient is calculated as A1(1cm) = 16.4 at 280 nm. Sugars could not be detected by phenol-sulfuric acid method. The circular dichroism analysis at far UV indicated that VVLM was a beta-sheet-rich protein, and gave no alpha-helix, 69% beta-sheet, 14% beta-turn by Provencher and Glockner method. The lectin was inhibited by alpha-methyl-D-mannose at 12.5 mM and glucose or GlcNAc at 50 mM. The carbohydrate binding specificity of VVLM was investigated by using affinity chromatography on a VVLM-Sepharose column. Among various Asn-linked oligosaccharides, core structure Man alpha 1-->3(Man alpha 1-->6)Man beta 1-->4GlcNAc beta 1-->4GlcNAcOT were found to have high affinity for VVLM-Sepharose. The antisera of VVLM did not produce precipitin line with VVLG in agar double diffusion plate indicating no serological relationship between VVLM and VVLG. However VVLM showed similar immunodeterminants of some other lectins of mannose specificity such as Con A, PSL, LCA and VFL.

GABA synapses formed in vitro by local axon collaterals of nucleus accumbens neurons

GABAergic medium-spiny neuron axons not only form the principal projections of the nucleus accumbens (nAcc) but also branch locally in a dense network overlapping their own dendrites, suggesting that their recurrent synapses mediate the major information processing functions of the nAcc. We used postnatal nAcc cultures to study these synapses individually. In culture, as in the intact nAcc, medium-spiny neurons account for over 95% of the cells and are GABAergic. Strikingly, these neurons showed a spike afterhyperpolarization (AHP) that was largely blocked by the GABAA antagonist bicuculline. The bicuculline-sensitive AHP occurred without or with latency, and met criteria for monosynapticity; consistent with this, dye fills showed the presence of recurrent axons and a low incidence of dye coupling. Blockade of Ca2+ influx eliminated this autaptic PSP, while TTX almost completely eliminated it, indicating that it is due to exocytic GABA release principally at axodendritic contacts. While blocking GABAB receptors had no direct effect on the autaptic PSP, activating these receptors with baclofen produced presynaptic inhibition, as well as directly mediated hyperpolarization; together, these actions increased the signal-to-noise ratio in the cellular response to synaptic inputs. Bicuculline also increased the signal-to-noise ratio; in addition, it induced burst firing and depolarization inactivation. In contrast, the indirect GABA agonist flurazepam and the GABA uptake blocker nipecotic acid each enhanced autaptic PSPs. Since autapses formed in vitro appear to be functionally equivalent to synapses between neighboring medium-spiny neurons that receive similar inputs, these results bear on the function of intrinsic GABA synapses in the intact nAcc. Thus, intrinsic GABA synapses are likely to regulate the signal-to-noise ratio in nAcc information processing and may be important targets for the modulatory actions of endogenous neurotransmitters and drugs.

Conformation and activity of Phaseolus coccineus var. rubronanus lectin

The conformation of native and denatured Phaseolus coccineus var. rubronanus lectin was studied by circular dichroism (CD) and correlated to the hemagglutinating activity. The far-UV CD spectrum at 25 degrees C showed a broad, negative band around 223 nm and a positive one at 196 nm. CD data analysis of the lectin indicated a beta-sheet-rich protein. At high temperatures, the spectrum was blue-shifted with increasing magnitude; these changes correlated well with the loss of the activity. The conformation of lectin between pH 2 and 10 remained essentially unchanged. At pH 13 the CD spectrum resembled that of unordered form with a negative band near 200 nm and the activity was completely lost. The denatured lectin in 6 M guanidine hydrochloride would be renatured upon diluting the denaturant to 0.75 M; the changes in CD spectrum again correlated well with the loss of the activity. The effect of sodium dodecyl sulfate on the lectin was drastic; it sharply increased the alpha-helix at the expense of the beta-sheet and reduced the activity; the changes reached a plateau above 20 mM surfactant.

Conformation and activity of mannose- and N-acetylgalactosamine-specific lectins from Vicia villosa seeds

The conformation of two Vicia villosa lectins specific for mannose and N-acetylgalactosamine, respectively, was studied by circular dichroism. Both showed a broad negative CD band around 220 nm and a positive one above 190 nm. CD data analysis indicated that they were rich in beta-sheet. However, they differed in conformational stability against extreme pH, at elevated temperature, and in guanidine hydrochloride and sodium dodecyl sulfate solutions. The unusual feature was that the conformation of N-acetylgalactosamine-specific lectin was virtually unaltered in 6 M guanidine hydrochloride and 7.5 mM surfactant.

Identified postnatal mesolimbic dopamine neurons in culture: morphology and electrophysiology

To examine the intrinsic properties of postnatal mesolimbic dopamine (DA) neurons, we dissociated the ventral tegmental area (VTA) from postnatal rats, enriched for DA neurons by microdissection or gradient purification, and grew the cells in culture. In these cultures, up to 50% of neurons were dopaminergic. DA neurons resembled their in vivo counterparts in soma shapes, and in showing two levels of tyrosine hydroxylase (TH) expression, axodendritic differentiation, two sizes of synaptic vesicles, nest-like synaptic arrangements with non-DA cells, and synaptic specializations. Electrophysiologically, however, they could not be distinguished from non-DA cells, which could be consistent with heterogeneity in cell properties. To examine a functional subset of VTA DA neurons, we retrogradely labeled VTA neurons projecting to the nucleus accumbens. These mesoaccumbens neurons were 86% TH positive, 56% cholecystokinin positive, and 0% neurotensin positive; they also displayed the soma shapes characteristic of DA neurons more generally and two levels of TH expression. Like their in vivo counterparts, mesoaccumbens cells generally fired single broad spikes that were triggered by slow depolarizations and had robust spike afterhyperpolarizations, low- and high-threshold Ca2+ spikes, rapid accommodation of firing, time-dependent anomalous rectification, and hyperpolarizing autoreceptor responses. Strikingly, the expression of these active properties did not change with time in culture. Mesoaccumbens DA cells could be identified by a distinctive subset of properties that made up an electrophysiological signature; however, unlike their in vivo counterparts, they were less often spontaneously active and never fired in bursts. These results suggest that most DA cell properties are intrinsic to the cells, including a significant heterogeneity that is maintained in postnatal culture; their level and mode of activity, however, appear to require afferent input. Culturing identified postnatal VTA DA neurons now makes possible examination of the impact of their individual properties on synaptic function.

Actions of neurotensin: a review of the electrophysiological studies

Three effects of NT were observed on midbrain DA cells. The modulatory effect of NT, that is, the attenuation of DA-induced inhibition, has been most extensively examined. Studies indicate that this effect of NT was not simply due to a nonspecific excitation. NT selectively attenuated DA-induced inhibition without affecting either GABA-induced inhibition or glutamate-induced excitation of the same cells, and the attenuation of DA-induced inhibition could be observed at the doses at which the basal activity of DA cells was not changed by NT. The attenuation of DA-induced inhibition by NT is also unlikely to result from the formation of a DA-NT complex, since neuromedin N, which competes with NT for the same receptor but does not bind to DA, mimicked the effects, and neurotensin(1-11), which forms a complex with DA but is inactive in competing for NT receptors, did not. The similarities between the effects of NT and those of 8-bromo-cAMP and forskolin suggest that intracellular cAMP and protein kinase A may be involved. This suggestion was supported by the findings that IBMX (an inhibitor of phosphodiesterases) potentiated the effect of NT; and SQ22536 (an inhibitor of adenylate cyclase) and H8 (an inhibitor of protein kinase A) antagonized it. Phorbal-12,13-dibutyrate (an activator of protein kinase C) did not mimic the effect of neurotensin, and H7 (an inhibitor of protein kinase C) did not reduce the effect, suggesting that protein kinase C is unlikely to be involved in the modulatory effect of neurotensin. Experiments in vitro indicated that the excitatory effect of NT on DA cells occurred at higher concentrations (> 10 nM) than those needed for producing the modulatory effect. Its persistence during DA receptor blockade by sulpiride suggests that this effect was not entirely mediated by an attenuation of the inhibition induced by endogenously released DA. At even higher concentrations (> 100 nM), a sudden cessation of cell activity preceded by an increase in firing rate was observed. Whether this effect of NT was due to depolarization inactivation or a toxic effect of the peptide at high concentrations remains to be determined. In most other areas studied, the excitatory effect of NT was most commonly observed. In many areas, this excitatory effect was apparently a direct postsynaptic effect of NT. However, different mechanisms may be involved (see Table 1). For example, in some areas NT acted through a decrease in membrane conductance, while in others no change or an increase in the membrane conductance was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Roles of intracellular cAMP and protein kinase A in the actions of dopamine and neurotensin on midbrain dopamine neurons

The role of intracellular cAMP and protein kinase A in dopamine-induced inhibition of dopamine neurons and the attenuation of this inhibition by neurotensin were studied in rat midbrain slices. Spontaneous activity of dopamine cells was recorded extracellularly from both the ventral tegmental area and the substantia nigra. Perfusion of the slices with 8-bromo-cAMP and forskolin significantly attenuated dopamine-induced inhibition, but neither blocked the inhibition completely. Neither SQ22536, an inhibitor of adenylate cyclase, nor H8, an inhibitor of protein kinase A, mimicked the inhibitory effect of dopamine on dopamine neurons, although they potentiated dopamine's effect. These results indicate that dopamine-induced inhibition of dopamine neurons can be affected by intracellular cAMP levels, but is unlikely to be mediated solely by inhibition of adenylate cyclase. The similarities between the effects of neurotensin and those of 8-bromo-cAMP and forskolin suggest that intracellular cAMP may be involved in the actions of neurotensin. This suggestion is supported by our findings that isobutyl-methylxanthine (an inhibitor of phosphodiesterases) potentiated the effect of neurotensin and SQ22536 and H8 antagonized it. Phorbol-12,13-dibutyrate (an activator of protein kinase C) did not mimic the effect of neurotensin, and H7 (an inhibitor of protein kinase C) did not reduce the effect, suggesting that protein kinase C is unlikely to be involved in the modulatory effect of neurotensin.

Effects of neurotensin on midbrain dopamine neurons: are they mediated by formation of a neurotensin-dopamine complex?

The effects of neurotensin on midbrain dopamine neuron activity were studied in brain slices using single-unit recording techniques. At low concentrations (0.2-10 nM), neurotensin attenuated dopamine-induced inhibition without a significant effect on the basal firing rate. At higher concentrations (greater than 10 nM), however, it consistently caused an increase in cell activity. At even higher concentrations (greater than 100 nM), a sudden cessation of cell activity preceded by an increase in firing rate was observed. Whether this effect of neurotensin was due to depolarization inactivation or to a toxic effect of the peptide at high concentrations remains to be determined. To determine whether the effects of neurotensin were mediated by formation of a neurotensin-dopamine complex, several neurotensin analogues were studied. Neurotensin (8-13), which binds to both neurotensin receptors and dopamine, mimicked the effects of native neurotensin. Neuromedin N, which competes with neurotensin for the same receptor but does not bind to dopamine, also mimicked the effects. However, neurotensin (1-11), which forms a complex with dopamine but is inactive in competing for neurotensin receptors, was ineffective. In addition, the excitatory effect of neurotensin was not attenuated in the presence of dopamine receptor blockade by sulpiride. These results suggest that formation of a neurotensin-dopamine complex may not account for the action of neurotensin on dopamine cells. When combined with the fact that there is a high density of neurotensin receptors on dopamine cells, our results support the suggestion that the observed effects of neurotensin on dopamine neurons are most likely mediated by an activation of neurotensin receptors.

Neurotensin modulates autoreceptor mediated dopamine effects on midbrain dopamine cell activity

Interactions of neurotensin (NT) with midbrain dopamine (DA) neurons were studied in rats using microiontophoretic techniques. Local ejection of NT significantly increased (greater than 30%) the firing rate of a few DA cells (12/106). In most cases, however, iontophoretic NT produced no significant change in spontaneous activity. On the other hand, in these same cells, NT significantly attenuated the inhibition induced by either DA or quinpirole, a specific D2 agonist. Inhibition induced by DA was not attenuated by either glutamate or cholecystokinin, although both of them increase the firing rate of DA cells. The effect of NT appears to be selective as NT attenuated DA-induced inhibition without a measurable effect on either GABA-induced inhibition or glutamate-induced excitation of the same DA cells. Combined, these results suggest that NT's effect on DA cell activity is primarily a neuromodulatory one. As both NT and D2 receptors in midbrain DA cell areas are primarily located on DA cells, the above results also suggest that the observed interaction between NT and DA occurred at the DA cell level.

HLA-A, -B, -DR, -DQ antigens in black North Americans

HLA antigens of black North Americans are not as well-characterized as those of other ethnic groups. We present results from HLA typing of black Americans using the 10th International Histocompatibility Workshop (IHW) sera. 1502 black Americans are typed for HLA-A, -B antigens. 128 black Americans are typed for HLA-DR, -DQ antigens. New specificities and splits established by the 10th IHW are identified in our data. Antigen frequency, gene frequency and haplotype frequency are computed for each phenotype observed. Haplotype A30--Bw42--DRw18--DQw4 and haplotype Aw36--Bw53 in strong linkage disequilibrium is characteristic of this black population. DR and DQ association patterns are similar to those of white North Americans. A major difference is the association of DRw8 with DQw7 in blacks versus an association of DRw8 with DQw4 in whites.

A small volume chamber for electrical recording from submerged brain slices and a pulse-free medium supply system using a peristalic pump

A small volume chamber for recording from submerged brain slices is described. In the chamber, the slice is covered on all sides by a thin layer of moving medium. The chamber is simple and easy to construct. The small volume of the chamber allows fast exchange of the medium solution surrounding the slice and reduces the complications induced by long time exposure of slices to certain drugs (eg. desensitization). Along with this small volume chamber, a medium supply system is also described, which is composed of a peristaltic pump and a pulse dampener. This pulse-free medium supply system allows cells to be held for up to 8 h with solution changes as frequently as every 10-20 min.

A simple and effective method for preventing the formation of salt bridges between barrels of a multibarrel microiontophoresis electrode

Several kinds of multibarrel glass blanks are available commercially for making a multibarrel microiontophoresis electrode. Among them are the ones that consist of fused straight lengths of tubing available in three to nine barrels. Although they enjoy many advantages over the other kinds of assemblies, salt bridges form easily between the barrels of the electrodes made from these blanks. These bridges, when they form, render the multibarrel pipette unusable. Here, we describe a simple and effective way to prevent the formation of salt-bridge by coating the end of the barrels with paraffin. The paraffin coated electrode exhibits excellent recording properties which are equivalent to those made from more expensive blanks.

Tetrahydroprotoberberine--a new chemical type of antagonist of dopamine receptors

In rats lesioned by unilateral micro-injection of 6-OHDA into substantia nigra, the apomorphine-induced contralateral rotation and the amphetamine-induced ipsilateral rotation were antagonized by THB, l-THP and haloperidol. Scopolamine reversed the antagonistic effect of THB against amphetamine. Thus, THB and l-THP exhibited the DA-receptor antagonistic property which was similar to that of haloperidol. l-SPD (10 mg/kg), however, only antagonized the amphetamine-challenged rotational response, while it could not antagonize, but potentiate, the apomorphine-challenged rotational response. So, l-SPD might be a partial agonistic antagonist of DA-receptors, and its effect was more potent than that of THB and l-THP. l-SPD would be ascertained further in clinic trial. From these results and others, the authors suggest that THPB is a new chemical type of antagonist of brain DA-receptors.