Functional electrical stimulation on chronic and acute hemiplegic shoulder subluxation

OBJECTIVE

The present study investigated and assessed the effectiveness of a functional electrical stimulation (FES) program in the management of acute and chronic shoulder subluxation.

DESIGN

By their postonset duration, hemiplegic subjects with subluxation participating in the study were placed into a short-duration group and a long-duration group. Subjects in each group were further assigned randomly to either a control subgroup or an experimental subgroup. The experimental subgroups of both short and long duration received FES therapy in which supraspinatus and posterior deltoid were induced to contract repetitively up to 6 hr/day for 6 wk. The duration of the FES session and muscle contraction/relaxation ratio were progressively increased as performance improved.

RESULTS

The experimental subgroup of short duration showed significant improvements in reducing subluxation as indicated by x-ray compared with the control subgroup of short duration after the first FES treatment. The same effect was not shown for the experimental subgroup of long duration. The second FES treatment program only resulted in an insignificant change of shoulder subluxation for both the short- and long-duration subgroups.

CONCLUSIONS

The present study suggests that hemiplegic subjects with short postonset duration are effectively trained for shoulder subluxation by the first FES treatment program. The same FES showed not to be effective when applied to the subjects with subluxation of > 1 yr.

Cytogenetic study of workers exposed to chromium compounds

The frequency of sister chromatid exchanges (SCEs), high SCE frequency cells (HFCs), and genetic polymorphism of genotypes glutathione S-transferase (GST) M1 and T1 were analyzed in peripheral lymphocytes of 35 workers occupationally exposed to chromium (Cr) and 35 matched control group. Results showed that workers exposed to Cr showed 6.07 SCE/cell, as compared to 4.76 SCE/cell for the control group (p<0.01). Smokers showed a statistically significant higher frequency of SCE than non-smokers in both groups. The work duration of Cr workers was an important factor. Workers exposed for more than 5 years showed a significantly higher level of SCEs (p<0.05). Workers exposed to Cr for 5 or more years had higher HFC rates (51.4%) than those exposed for less than 5 years (22.9%), with an odds ratio of 4.5 times than those exposed for less than 5 years. In HFC analysis, Cr workers who smoked showed a higher level of HFC (60%) than the control group (5.7%) and also had a higher odds ratio (60.4) compared with the control group. Among non-smokers, the odds ratio was 9.0. Another objective of this study is to investigate the relationship between SCE and genetic polymorphisms of GST M1 and T1 in Cr workers. The results showed that the incidence of GSTM1 null genotype was 60% in the control group and 77.1% in Cr workers, and percentages of GSTT1 deletion were 42.9% and 62.9% in control and exposed individuals, respectively. There was a slightly increased frequency of SCE among Cr workers with GSTM1 null genotype as opposed to non-null genotype individuals. A similar result was seen among the control group; however, there were no statistically significant differences. In conclusion, the current study found the positive induction of SCE in workers who smoked or/and were exposed to Cr. However, different GST genotypes did not influence the level of cytogenetic damage between groups. Despite slight variation in numbers, they all appear to be not different.

The effects of colchicine treatment on wound healing in a caustic murine injury model

OBJECTIVE

The present study determined the effects of colchicine on wound repair in a murine model of dermal chemical injury.

METHODS

Standardized 4.15 cm2 circular lesions were induced on the dorsum of adult male mice with NaOH. Five minutes of IN or 3N caused lesions of graded depth. Mice received colchicine (1 mg/kg) or phosphate-buffered saline intraperitoneally in equivalent volumes. Treatment began immediately postinjury and was continued on an alternating day schedule for 14 days. Wound size was measured every third day postinjury. On day 15 postinjury, wounds were histologically graded for depth of injury, degree of fibrosis, inflammatory cell response, and revascularization. All histological determinations and wound measurements were performed in a blinded fashion.

RESULTS

All mice had a similar initial wound size and completed the experimental protocol. In dermal wounds of superficial depth, colchicine-treated mice (n = 20) had a larger wound size during days 6 through 9 of the experimental trial when compared to phosphate-buffered saline-treated mice (n = 18). In the deeper wounds, there were no significant differences in wound size between colchicine and phosphate-buffered saline-treated groups. Colchicine (n = 54) did not affect the degree of fibrosis at all depths of injury vs phosphate-buffered saline treatment in mice (n = 55). The degree of wound revascularization was less in colchicine-treated mice (n = 54) than phosphate-buffered saline-treated mice (n = 55).

CONCLUSION

Colchicine did not improve wound healing in an alkaline-induced dermal injury.

Effects of thoraco-lumbar electric sensory stimulation on knee extensor spasticity of persons who survived cerebrovascular accident (CVA)

Spasticity is mostly due to an excess of impulses to alpha motor neurons partly resulting from a change of interneuron activity. Low threshold afferent has been reported to change the activity in interneuron. The purpose of this study is to investigate the effects of surface spinal paravertebral stimulation on knee extensor spasticity. Ten survivors of stroke, with knee extensor spasticity, received electric stimulation for five 45-minute periods through surface electrodes applied to the skin in the twelfth thoracic and first lumbar areas. The electric stimulations had an amplitude modulated alternating current (AC), with a carrier frequency of 2500 Hz, modulated to "beats" frequency of 20 Hz. Stimulation amplitude was raised to elicit sensory stimulation. The pre- and post-treatment evaluation included the modified Ashworth scale, active torque during controlled knee movements at various velocities, and electromyographic (EMG) activity during the torque measurements. Our results indicate that nine of ten subjects demonstrated a decrease in the modified Ashworth scale post-treatment. The EMG activity of the spastic quadriceps during active knee flexion was decreased post-treatment as compared with the value before treatment. The active torque value of knee flexion or extension at 30 degrees, 60 degrees, or 90 degrees/sec of angular velocity did not change significantly post-treatment. A trend of increasing spastic quadriceps EMG activity with respect to the angular velocity during an active knee flexion was established, with Ashworth scale considered. The level of EMG activity is higher when the Ashworth scale is higher. According to our results, the surface paravertebral sensory stimulation was effective in reducing quadriceps muscle spasticity of the subjects. Both the modified Ashworth scale and the EMG activity of spastic quadriceps during eccentric contraction are suggested as sensitive tools for measuring spasticity of persons who survived cerebrovascular accident (CVA).

Context of the coat protein DAG motif affects potyvirus transmissibility by aphids

Previous work with tobacco vein mottling virus (TVMV) has established that a highly conserved three amino acid motif, asp-ala-gly (DAG), located near the N terminus of the coat protein (CP), is important for aphid transmission. However, several other potyviruses which have motifs other than DAG are aphid-transmissible. Creation of these motifs in TVMV through site-directed mutagenesis failed to render TVMV aphid-transmissible from infected plants, and the creation of a putative complementary motif in the helper component did not restore transmissibility. In an isolate of tobacco etch virus (TEV) that contains two consecutive DAG motifs separated by a single ala, transmissibility was abolished or reduced by mutations affecting the first motif, whereas mutations in the second motif had little or no effect. In a TEV mutant made non-transmissible due to an altered first motif, substitution of val for ala in the position immediately before the second DAG restored transmissibility, whereas changing val to ala in the location prior to the first DAG resulted in reduced TEV transmissibility. In contrast, a val to ala change in the position preceding the single DAG motif of TVMV did not affect transmission. Creation of another DAG motif at the beginning of the TVMV CP core, in a position where certain other potyviruses have a second DAG motif, did not restore transmissibility. Our results suggest that the mere presence of a DAG motif does not guarantee transmissibility and that the context in which the DAG or equivalent motif is found plays a role in the process.

Spectral karyotypic study of the HL-60 cell line: detection of complex rearrangements involving chromosomes 5, 7, and 16 and delineation of critical region of deletion on 5q31.1

Interstitial deletions of the q arm of chromosome 5 have been associated with acute myelogenous leukemia (AML); therefore, accurate identification of rearrangements of this chromosome in a model cell line, HL-60, is important for understanding the critical genes involved in this disease. In this study, we employed a newly developed technology termed spectral karyotyping to delineate chromosomal rearrangements in this cell line. Our study revealed a derivative of chromosome 7 that resulted from translocations of chromosome arms 5q and 16q to 7q; that is, der(7)t(5;7)(?;q?)t(5;16)(?;q?). Interestingly, both chromosomes 5 and 7 were also involved in translocations with chromosome 16 in der(16) t(5;16)(q?;q?22-24) and der(16)t(7;16)(?;q?22-24), respectively. Other notable chromosomal abnormalities that were not previously reported in the HL-60 included an insertion of chromosome 8 in the q arm of chromosome 11, a translocation between chromosomes 9 and 14, and a translocation between chromosomes 14 and 15. In an attempt to define the loss of the 5q31.1 region in HL-60, we performed fluorescence in situ hybridization analysis by utilizing bacterial artificial chromosomes BAC1 and BAC2 that spanned the IL9 and EGR1 gene interval, which was previously shown to be a critical region of loss in AML. We showed that a copy of both BAC1 (spanning the D5S399 locus) and BAC2 (spanning the D5S393 locus centromeric to BAC1) were present in the normal chromosome 5, but a second copy of BAC1 was lost and a second copy of BAC2 was inserted in the der(16)t(7;16) chromosome. Thus, not only was this study the first to use the new 24-color karyotyping technique to identify several novel chromosomal rearrangements in HL-60, but it also narrowed the 5q31.1 critical region of deletion to the region represented by BAC1.

LSD and DOB: interaction with 5-HT2A receptors to inhibit NMDA receptor-mediated transmission in the rat prefrontal cortex

Both the phenethylamine hallucinogen (-)-1-2, 5-dimethoxy-4-bromophenyl-2-aminopropane (DOB), a selective serotonin 5-HT2A,2C receptor agonist, and the indoleamine hallucinogen D-lysergic acid diethylamide (LSD, which binds to 5-HT1A, 1B, 1D, 1E, 1F, 2A, 2C, 5, 6, 7, dopamine D1 and D2, and alpha1 and alpha2 adrenergic receptors), but not their non-hallucinogenic congeners, inhibited N-methyl-D-aspartate (NMDA)-induced inward current and NMDA receptor-mediated synaptic responses evoked by electrical stimulation of the forceps minor in pyramidal cells of the prefrontal cortical slices. The inhibitory effect of hallucinogens was mimicked by 5-HT in the presence of selective 5-HT1A and 5-HT3 receptor antagonists. The inhibitory action of DOB, LSD and 5-HT on the NMDA transmission was blocked by the 5-HT2A receptor antagonists R-(+)-alpha-(2, 3-dimethoxyphenil)-1-[4-fluorophenylethyl]-4-piperidineme thanol (M100907) and ketanserin. However, at low concentrations, when both LSD and DOB by themselves only partially depressed the NMDA response, they blocked the inhibitory effect of 5-HT, suggesting a partial agonist action. Whereas N-(4-aminobutyl)-5-chloro-2-naphthalenesulphonamide (W-7, a calmodulin antagonist) and N-[2-[[[3-(4'-chlorophenyl)- 2-propenyl]methylamino]methyl]phenyl]-N-(2-hydroxyethyl)-4'-methoxy-b enzenesulphonamide phosphate (KN-93, a Ca2+/CaM-KII inhibitor), but not the negative control 2-[N-4'methoxybenzenesulphonyl]amino-N-(4'-chlorophenyl)-2-propeny l-N -methylbenzylamine phosphate (KN-92), blocked the inhibitory action of LSD and DOB, the selective protein kinase C inhibitor chelerythrine was without any effect. We conclude that phenethylamine and indoleamine hallucinogens may exert their hallucinogenic effect by interacting with 5-HT2A receptors via a Ca2+/CaM-KII-dependent signal transduction pathway as partial agonists and modulating the NMDA receptors-mediated sensory, perceptual, affective and cognitive processes.

Characterization of the humoral and cellular immune responses against hepatitis C virus core induced by DNA-based immunization

Hepatitis C Virus (HCV) causes most cases of posttransfusion hepatitis. Chronic HCV infection is highly related to chronic hepatitis, cirrhosis and hepatocellular carcinoma. Current therapies are only minimally effective and no vaccine has been developed. DNA-based immunization could be of prophylactic and therapeutic value for HCV infection. By intramuscular inoculation in BALB/c mice with an HCV recombinant plasmid pCI-HCV-C, we found significant levels of IgM antibody, but no significant IgG rise. After boost the immunized mice with recombinant HCV-core protein (cp1-10; 1-164aa), the anticore IgG, verified by Western-blotting, rose rapidly, which was two weeks earlier than that with control plasmid. Spleen cells from pCI-HCV-C immunized mice gave higher proliferation index (PI) than control (P < 0.05). The PI of cp1-10 boosted mice was even higher. Proliferation blocking assay with mAb proved the responding cell to be of CD4+ CD8- phenotype, supporting specific priming of T helper cells. A 51Cr-releasing CTL assay specific for HCV-core was developed, and a specific CTL response against HCV-core was demonstrated in both pCI-HCV-C immunized mice and mice boosted with cp1-10. Strong cytotoxic activity against peptide-pulsed p815 cells (H-2d), but not EL-4 cells (H-2b), suggested MHC class I restriction of the CTL activity. Blocking of CTL with mAb proved the effector cells to be of CD4- CD8+. Three CTL epitopes in HCV-core protein were demonstrated. We failed to detect CTL when immunized only with core protein. The results suggested that vaccination with HCV-core derived DNA sequences could be an effective method to induce humoral and cellular immune responses to HCV.

A pre- and postsynaptic modulatory action of 5-HT and the 5-HT2A, 2C receptor agonist DOB on NMDA-evoked responses in the rat medial prefrontal cortex

Intracellular recordings were made from pyramidal neurons in layers V and VI of the rat medial prefrontal cortex in slice preparations to investigate the effect of the serotonin 5-HT2A,2C receptor agonist (-)-1-2,5-dimethoxy-4-bromophenol-2-aminopropane (DOB) and 5-hydroxytryptamine (5-HT) on N-methyl-D-aspartate (NMDA)-induced responses. Bath application of either DOB or 5-HT [in the presence of antagonists to 5-HT1A, 5-HT3 and gamma-aminobutytric acid (GABA) receptors] produced a concentration-dependent biphasic modulation of the NMDA responses. They facilitated and inhibited NMDA responses at low (</= 1 microM DOB and </= 50 microM 5-HT) and higher concentrations, respectively. Both the facilitating and inhibitory action were blocked by the highly selective 5-HT2A receptor antagonist R-(+)-alpha-(2, 3-dimethoxyphenil)-1-[4-fluorophenylethyl]-4-piperidineme thanol (M100907) and the 5-HT2 receptor antagonist ketanserin, thus indicating that both facilitation and inhibition were mediated by the activation of the 5-HT2A receptor subtype. However, the facilitating, but not inhibitory, action of DOB showed a marked desensitization, suggesting that the facilitation and inhibition of NMDA responses resulted from activation of different 5-HT2A receptor subtypes and/or signal-transduction pathways. Indeed, the selective PKC inhibitor chelerythrine and the Ca2+/CaM-KII inhibitor KN-93 prevented the facilitating and inhibitory action of DOB, respectively. We have generated several lines of evidence to indicate the following scenario. Low concentrations of DOB, at presynaptic nerve terminals, markedly enhance NMDA-induced release of excitatory amino acids (EAAs), which then act upon both NMDA and non-NMDA receptors to elicit inward current. The massive inward current masks the postsynaptic inhibitory action of DOB. At higher concentrations, DOB inhibits the release of EAAs and discloses the postsynaptic inhibitory action.

Purification and characterization of turnip mosaic virus helper component protein

ABSTRACT The helper component (HC) protein of turnip mosaic virus (TuMV) was concentrated by differential centrifugation followed by ammonium sulfate precipitation. The partially purified HC was then loaded onto a Ni(2+)-resin column that bound the HC; a histidine tag was not required for binding. The HC eluted from the column migrated as a band of about 50 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In its native state, the HC did not pass through an ultrafiltration membrane with a molecular mass cutoff of 100 kDa, which suggested that the HC is in a multimeric form when it is biologically active. The molecular mass of the multimeric form was determined by gel filtration to be approximately 145 kDa. Purified HC retained its activity for several months at -20 degrees C. Using a protein blotting-overlay protocol, purified HC interacted in vitro with an aphid-transmissible TuMV isolate, but not with a non-aphid-transmissible isolate.

pH-dependent cocaine-induced cardiotoxicity

Severe cocaine toxicity causes acidemia and cardiac dysfunction. These manifestations are described in 4 patients who presented with seizures, psychomotor agitation, and cardiopulmonary arrest. Their initial laboratory values demonstrated acidemia and electrocardiographic findings that included a prolonged QRS complex and QTc duration and a rightward T40 ms axis deviation. Treatment of the patients with hyperventilation, sedation, active cooling, and sodium bicarbonate infusion led to the normalization of their blood pHs and reversal of their cardiac conduction disorders. Acidemia can contribute to cocaine cardiac disorders by promoting conduction delays, dysrhythmias, and depressed myocardial contractility. Good supportive care corrects the blood pH and cardiac conduction disorders and remains the major focus in the management of patients with cocaine toxicity.

Clozapine, but not haloperidol, prevents the functional hyperactivity of N-methyl-D-aspartate receptors in rat cortical neurons induced by subchronic administration of phencyclidine

Repeated exposure of rats to the psychotomimetic drug phencyclidine (PCP) markedly increased the response of prefrontal cortical neurons to the glutamate agonist N-methyl-D-aspartate (NMDA) relative to agonist alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid. Moreover, acute challenge by PCP produced a significantly reduced block of NMDA-induced current. In addition, the subchronic administration of PCP reduced significantly the paired-pulse facilitation, accompanied by a significant increase of excitatory postsynaptic current variance. These results suggest that repeated exposure to PCP increased evoked release of excitatory amino acids. The enhanced release of excitatory amino acids evoked by NMDA could explain, at least partly, a hypersensitive response to NMDA and a reduced blockade of the NMDA responses by a PCP challenge in rats exposed repeatedly to PCP. Pretreatment with the atypical antipsychotic drug clozapine, but not the typical antipsychotic drug haloperidol, attenuates the repeated PCP-induced effect. Our results support the hypothesis that clozapine may facilitate NMDA receptor-mediated neurotransmission to improve schizophrenic-negative symptoms and cognitive dysfunction. This novel approach is useful for evaluating the cellular mechanisms of action of atypical antipsychotic drugs.

Biphasic modulatory action of the selective sigma receptor ligand SR 31742A on N-methyl-D-aspartate-induced neuronal responses in the frontal cortex

The technique of intracellular recording was used to assess the effect of SR 31742A, a selective sigma receptor ligand, on N-methyl-d-aspartate (NMDA) and (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor-mediated responses in pyramidal cells of the rat medial prefrontal cortex in vitro brain slice preparations. Bath application of SR 31742A produced a biphasic effect on NMDA responses: SR 31742A facilitated and inhibited NMDA-induced inward current at low (0.01, 0.05 and 0.1 microM) and higher (0.5, 1 and 10 microM) concentrations, respectively. The potentiating effect reached the peak (366%) at 0.1 microM, with an estimated EC50 value of 23 nM. Correspondingly, SR 31742A also produced a similar biphasic modulatory action on excitatory postsynaptic potentials or currents (EPSPs/EPSCs) evoked by electrical stimulation of the forceps minor. In contrast, SR 31742A produced a modest potentiation of AMPA responses at the concentrations from 0.01 to 1 microM. The potentiating action of SR 31742A on NMDA-receptor mediated neurotransmission may account for, at least partially, its antipsychotic and cognitive-enhancing potential, whereas the inhibitory action on NMDA responses at higher concentrations may be related to the purported neuroprotective action of sigma receptor ligands.

Herpes simplex type II and Mycoplasma genitalium as risk factors for heterosexual HIV transmission: report from the heterosexual HIV transmission study

OBJECTIVES

Two hundred twenty-four human immunodeficiency virus (HIV) discordant couples (one HIV negative, one HIV positive) were compared with 78 seroconcordant heterosexually infected couples with HIV with regard to sexually transmitted diseases.

METHODS

Serologic testing and cultures were used to determine exposure of participants to sexually transmitted pathogens. These data were compared with HIV concordance of partners to investigate possible risk factors for HIV transmission.

RESULTS

Syphilis, chlamydia, and hepatitis B virus (HBV) serologies did not distinguish between concordant and discordant couples nor did cultures for Neisseria gonorrhoeae and Trichomonas or Chlamydia enzyme immunoassay (EIA). Risk of transmission increased with positive serologies for herpes simplex virus (HSV)-2 (P = 0.002), cytomegalovirus (CMV) (P = 0.04), and Mycoplasma genitalium (P = 0.01), but not with Mycoplasma fermentans or Mycoplasma penetrans. Cytomegalovirus was not a significant risk factor when controlled for HSV-2 status. Examination by partner status showed increased risk of concordance with: HSV-2 positive serology in both partners (odds ratio [OR] = 3.14; confidence interval [CI] = 1.62-6.09; P = 0.007); HSV-2 in female secondary partner (OR = 2.10; CI = 1.12-3.93; P = 0.02) or the male primary partner (OR = 2.15; CI = 1.15-4.02; P = 0.017); M. genitalium antibody in both partners (OR = 3.44; CI = 1.68-7.04; P < 0.001); M. genitalium antibody in the primary male partner (OR = 2.51, CI = 1. 27-4.91; P = 0.008) and M. genitalium antibody in the secondary female partner (OR = 2.52; CI = 1.21-5.23; P = 0.01).

CONCLUSIONS

These data support the role of HSV-2 in transmission of HIV and, for the first time, suggest a role for M. genitalium as an independent risk factor.

Effects of surface spinal cord stimulation on spasticity and quantitative assessment of muscle tone in hemiplegic patients

Spasticity after a stroke interferes with the normal function of a limb. Electric stimulation has been used in a variety of ways to decrease spasticity. The purposes of this study were (1) to quantify the effectiveness of electric stimulation on decreasing ankle spasticity and (2) to develop a quantitative assessment of muscle tone, which could be replicated in the clinic. Ten patients with hemiparesis resulting from ischemic stroke participated in the study according to the selection criteria. Their mean age was 57 yr, with a mean stroke interval of 12.5 months. Patients received electric stimulation for 45 min through surface electrodes applied to the skin in the 12th thoracic and 1st lumbar areas. All patients received five electric stimulation treatment sessions. The electrical pulses were amplitude modulated frequency beat with a carry frequency of 2500 Hz and a stimulation frequency of 20 Hz. The stimulation intensity was adjusted to each patient to produce a sensory stimulation. The pre- and posttreatment evaluation included surface electromyography activity during passive ankle dorsiflexion, passive ankle dorsiflexion resistance at different angular velocities, as measured by an isokinetic machine and the modified Ashworth scale. Our results indicate that the surface spinal cord stimulation with middle frequency modulated to low frequency for sensory stimulation on the skin of 12th thoracic and first lumbar area is effective in reducing calf muscle spasticity of hemiplegic patients. The isokinetic torque measures for spasticity are a sensitive tool to document the effects of the treatment.

M100907 and clozapine, but not haloperidol or raclopride, prevent phencyclidine-induced blockade of NMDA responses in pyramidal neurons of the rat medial prefrontal cortical slice

In the present study, we demonstrate that, in a concentration-dependent manner, M100907 (formerly MDL 100907, a highly selective 5-HT2A receptor antagonist and a purported atypical antipsychotic drug [APD]), but not its much less active stereoisomer M100009, completely prevents or markedly reverses the phencyclidine (PCP)-induced blockade of N-methyl-D-aspartate (NMDA) responses in pyramidal neurons of the medial prefrontal cortex (mPFC). Furthermore, the atypical APD clozapine, but not the typical APD haloperidol or raclopride (a selective dopamine D2,3 receptor antagonist), mimicked the action of M100907, preventing the PCP-induced effect. These results suggest that M100907 might be an antidote for treating the PCP-induced psychotomimetic state that closely resembles schizophrenia; they could also account for the antipsychotic potential of M100907. Furthermore, our results suggest that the prototype (clozapine) and a candidate (M100907) atypical APDs might be effective in ameliorating schizophrenic symptoms including cognitive and neuropsychological deficits, which are induced in humans who abuse PCP. We hypothesize that the ability of M100907 and clozapine to prevent or reverse the PCP-induced blockade of the NMDA receptor channel is attributed to their 5-HT2A receptors antagonizing property. Therefore, with further systematic studies, the ability of compounds to prevent or reverse PCP's blockade of NMDA responses may prove to be an effective electrophysiological model for screening potential atypical APDs and predicting their therapeutic efficacy in cognitive deficits.

Inhibition of NMDA-receptor mediated response in the rat medial prefrontal cortical pyramidal cells by the 5-HT3 receptor agonist SR 57227A and 5-HT: intracellular studies

The techniques of intracellular recording and single-electrode voltage-clamp were used to study the effect of serotonin (5-HT) and the selective 5-HT3 receptor agonist SR 57227A on N-methyl-D-aspartic acid (NMDA)-evoked responses in pyramidal cells of the rat medial prefrontal cortex (mPFC) in in vitro brain slice preparations. Bath application of 5-HT or SR 57227A produced a concentration-dependent inhibition of NMDA-induced membrane depolarization, action potentials, and inward current. The depressant action of 5-HT and SR 57227A had a slow onset and showed no signs of receptor desensitization. This action was markedly attenuated or completely blocked by the selective 5-HT3 receptor antagonists granisetron and BRL 46470A, but not other receptor antagonists. In addition to inhibiting NMDA-evoked responses, SR 57227A also depressed significantly pharmacologically isolated, NMDA receptor-mediated, monosynaptic excitatory postsynaptic currents (EPSCs) elicited by electrical stimulation of the forceps minor; this inhibitory action was blocked by BRL 46470A but not other 5-HT receptor antagonists. Perfusion of Ca2+-free or low Ca2+ plus Cd2+ artificial cerebrospinal fluid prevented electrical stimulation-induced EPSCs, but did not affect the inhibitory action of 5-HT and SR 57227A. In conclusion, we demonstrate for the first time that 5-HT and SR 57227A interact with 5-HT3-like receptors to produce a direct inhibitory action on NMDA receptor-mediated response in pyramidal cells of the mPFC.

High-frequency DNA rearrangements in the chromosomes of clinically isolated Mycoplasma fermentans

Mycoplasma fermentans is currently being examined as an agent potentially associated with human disease. Several strains of M. fermentans were isolated from patients with respiratory tract disease and AIDS. Two of these clinical strains, M64 and SK6, were triple-filter-cloned and designated as the parental clones in this study. Genomic DNA of randomly picked subclones in four and five subsequent generations passed from the parental M64 and SK6 clones were analyzed by using a radiolabeled M. fermentans-specific insertion sequence (IS)-like element as the probe. The hybridization patterns of DNA restriction fragments revealed high frequencies of chromosomal changes accompanied with excision or new insertion of the IS-like element in M. fermentans chromosome. The findings indicate M. fermentans has an effective mechanism(s) to produce a rapid gene rearrangement that may be mediated by one or more copies of the IS-like element.

Role of the helper component in vector-specific transmission of potyviruses

Four aphid species were tested for their ability to transmit tobacco etch (TEV) and turnip mosaic (TuMV) potyviruses. Myzus persicae and Aphis gossypii transmitted both viruses efficiently from infected plants, whereas Lipaphis erysimi transmitted only TuMV and Myzus ascalonicus was a poor or non-transmitter of either virus. Similar electrically monitored probing patterns were produced by M. persicae, L. erysimi and M. ascalonicus, ruling out behavioural differences as the cause of differential transmission. Transmission results similar to those from infected plants were obtained when these aphids acquired homologous virus/helper component (HC) mixtures through membranes. With heterologous virus/HC mixtures, M. persicae remained a highly efficient vector and M. ascalonicus a non-vector, but L. erysimi became an efficient vector of TEV if acquired in the presence of TuMV HC and A. gossypii transmitted both viruses less efficiently when acquired with TuMV HC. Transmission was highly correlated with the retention of virus in the stylets, as determined by autoradiography of 125I-labelled virions. The results show that constituent(s) of or in the food canal of different aphid species differ in their ability to interact with specific HCs, leading to qualitative or quantitative differences in ability to retain and subsequently transmit specific potyviruses.

Delayed hypoglycemia in a child after ingestion of a single glipizide tablet

This is the first report to describe the delayed onset of hypoglycemia in a child after ingestion of one tablet of glipizide. A 2-year-old boy was observed to ingest 5 mg glipizide and 25 mg hydrochlorothiazide. Activated charcoal was administered within 35 minutes of ingestion. Hypoglycemia (serum glucose 49 mg/dL) developed 11 hours later. Emergency physicians must be aware of the potential for delayed hypoglycemia in children with single-tablet ingestions of glipizide. Prolonged monitoring of glucose levels is warranted.

Effects of aging on erythropoietin secretion in female rats

The secretion of erythropoietin (EPO) in old (22 25 months), middle (mid)-aged (15-17 months), adult (6-7 months), and young (3 months) female rats was studied. Rats of different ages were bled by cardiac puncture for measuring plasma EPO, estradiol, and progesterone levels. The metabolic clearance rate of EPO was determined by a single-injection method. The effects of ovariectomy and replacement of estradiol (E) and/or progesterone (P) on plasma EPO concentration were also investigated. Analysis of direct effects of E and/or P on EPO from kidney tissues was carried out in an in vitro study. Plasma EPO levels were higher in both mid-aged and old rats than in young rats (P < 0.01). The metabolic clearance rate of EPO was also greater in adult, mid-aged and old rats than in young rats (P < 0.01). Ovariectomy increased rat plasma EPO concentration which might be inhibited by E (P < 0.01), P (P < 0.01), or E and P (P < 0.05) replacement. Neither E (10(-10) or 10(-9) M) nor P (10(-8) or 10(-7) M) alone altered EPO release from kidney tissue in vitro. Combination of E (10(-10) M) and P (10(-8) x or 10(-7) M) stimulated the EPO release from kidney tissue (P < 0.01). These data suggest that the mechanism of the secretion of EPO by kidneys in female rats during aging is ovarian steroid hormones independent.

Mini-proinsulin and mini-IGF-I: homologous protein sequences encoding non-homologous structures

Protein minimization highlights essential determinants of structure and function. Minimal models of proinsulin and insulin-like growth factor I contain homologous A and B domains as single-chain analogues. Such models (designated mini-proinsulin and mini-IGF-I) have attracted wide interest due to their native foldability but complete absence of biological activity. The crystal structure of mini-proinsulin, determined as a T3R3 hexamer, is similar to that of the native insulin hexamer. Here, we describe the solution structure of a monomeric mini-proinsulin under physiologic conditions and compare this structure to that of the corresponding two-chain analogue. The two proteins each contain substitutions in the B-chain (HisB10-->Asp and ProB28-->Asp) designed to destabilize self-association by electrostatic repulsion; the proteins differ by the presence or absence of a peptide bond between LysB29 and GlyA1. The structures are essentially identical, resembling in each case the T-state crystallographic protomer. Differences are observed near the site of cross-linking: the adjoining A1-A8 alpha-helix (variable among crystal structures) is less well-ordered in mini-proinsulin than in the two-chain variant. The single-chain analogue is not completely inactive: its affinity for the insulin receptor is 1500-fold lower than that of the two-chain analogue. Moreover, at saturating concentrations mini-proinsulin retains the ability to stimulate lipogenesis in adipocytes (native biological potency). These results suggest that a change in the conformation of insulin, as tethered by the B29-A1 peptide bond, optimizes affinity but is not integral to the mechanism of transmembrane signaling. Surprisingly, the tertiary structure of mini-proinsulin differs from that of mini-IGF-I (main-chain rms deviation 4.5 A) despite strict conservation of non-polar residues in their respective hydrophobic cores (side-chain rms deviation 4.9 A). Three-dimensional profile scores suggest that the two structures each provide acceptable templates for threading of insulin-like sequences. Mini-proinsulin and mini-IGF-I thus provide examples of homologous protein sequences encoding non-homologous structures.

M100907, a selective 5-HT2A receptor antagonist and a potential antipsychotic drug, facilitates N-methyl-D-aspartate-receptor mediated neurotransmission in the rat medial prefrontal cortical neurons in vitro

The technique of intracellular recording was used to examine the effect of M100907 (formerly MDL 100907), a highly selective 5-HT2A receptor antagonist and a potential antipsychotic drug (APD), on N-methyl-D-aspartate (NMDA) and (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor-mediated responses in pyramidal cells of the rat medial prefrontal cortex in in vitro brain slice preparations. Bath administration of M100907, but not its inactive stereoisomer M100009, produced a 350% to 550% increase of NMDA-induced responses in a concentration-dependent manner with an EC50 value of 14 nmol/L, reminiscent of the action of clozapine. M100907 did not alter AMPA responses. Moreover, M100907 significantly increased the amplitude and duration of excitatory postsynaptic potentials and currents evoked by electrical stimulation of the forceps minor. We have generated several lines of evidence indicating that M100907 enhances glutamate receptor-mediated neurotransmission in pyramidal cells of the medial prefrontal cortex by facilitating NMDA-induced release of excitatory amino acids. The robust potentiation of NMDA receptor-mediated neurotransmission may explain, at least partly, the potential antipsychotic action of this compound. Furthermore, if M100907 proves to be an effective APD and if our findings can be extended to other atypical APDs, which are known to possess a relatively high affinity to 5-HT2A receptors, they may account for the purported efficacy of atypical APDs in alleviating some negative symptoms such as cognitive and executive functions.

Exaggerated precocious centromere separation in cells of a human breast cancer line treated with a green tea extract

In a breast cancer cell line, MDA-MB-468, established in our laboratory, an average of 3% of the mitotic cells exhibited a phenomenon known as centromere splaying, which is a characteristic feature of cells of patients with Roberts syndrome. However, centromere splaying in cells of Roberts syndrome patients is limited to i) the centromere region and ii) chromosomes with large amounts of heterochromatin. When the breast cancer cells were treated with an extract of green tea GTE-TP91, up to 45% of the metaphases were observed to exhibit this behavior; and the precocious centromere separation was highly exaggerated, affecting all chromosomes in such metaphases. Apparently, as the sister centromeres continued to pull apart, they carried the chromatids with them, except for the telomere regions, giving a ring-like configuration. Eventually, the sister chromatids became completely separated. Whether this bizarre phenomenon was induced by the polyphenols contained in this green tea extract GTE-TP91 is not known, but this phenomenon, upon further investigation, may throw some light on chromosomal proteins, centromere behavior, telomere behavior and related questions.

Chromosomal aberrations induced by 12C6+ heavy ion irradiation in spermatogonia and spermatocytes of mice

The testes of Kun-Ming strain mice were radiated with different doses of 12C6+ ion or 60Co gamma-ray. Chromosomal aberrations induced in spermatogonia and spermatocytes were analyzed by the air-drying method. The relative biological effectiveness (RBE) of 12C6+ ion was calculated with respect to 60Co gamma-ray for the induction of chromosomal aberrations. The 12C6+ ion and 60Co gamma-ray dose-response relationships for chromosomal aberrations were plotted by linear quadratic models. The results showed that there was an increase in frequency of chromosomal aberrations in all the treated groups compared to controls. The RBE values were 1.67 for aberrations of spermatogonia and 1.66 for aberrations of spermatocytes for a dose of 2.0 Gy. Moreover, a different distribution of the various types of aberrations has been found for 12C6+ ion and 60Co gamma-ray irradiations. The dose-response relationships for 12C6+ ion and 60Co gamma-ray exhibited negative curvature in both spermatogonia and spermatocytes groups: the frequencies of aberrations increased sharply at low doses and exhibited less sharp increases for higher doses, which may be related to an interaction between the chromosomal damage and a block in cell cycle. Our results may provide useful information for the assessment of genetic risks of humans exposed to heavy ions.