Ionic basis for plateau potentials in deep dorsal horn neurons of the rat spinal cord

Approximately 28% of dorsal horn neurons (DHNs) in lamina V of the rat spinal cord generate voltage-dependent plateau potentials underlying accelerating discharges and prolonged afterdischarges in response to steady current pulses or stimulation of nociceptive primary afferent fibers. Using intracellular recordings in a transverse slice preparation of the cervical spinal cord, we have analyzed the ionic mechanisms involved in the generation and maintenance of plateau potentials in lamina V DHNs. Both the accelerating discharges and afterdischarges were reversibly blocked by Mn(2+) and enhanced when Ca(2+) was substituted with Ba(2+). The underlying tetrodotoxin-resistant regenerative depolarization was sensitive to dihydropyridines, being blocked by nifedipine and enhanced by Bay K 8644. Substitution of extracellular Na(+) with N-methyl-D-glucamine or choline strongly decreased the duration of the plateau potential. Loading the neurons with the calcium chelator BAPTA did not change the initial response but clearly decreased the maximum firing frequency and the duration of the afterdischarge. A similar effect was obtained with flufenamate, a specific blocker of the calcium-activated nonspecific cation current (I(CAN)). We conclude that the plateau potential of deep DHNs is supported by both Ca(2+) influx through intermediate-threshold voltage-gated calcium channels of the L-type and by subsequent activation of a CAN current. Ca(2+) influx during the plateau is potentially of importance for pain integration and the associated sensitization in spinal cord.

Altered in vitro and in vivo flumazenil binding in human epileptogenic neocortex

In vitro and in vivo parameters of flumazenil (FMZ) binding were measured in spiking and nonspiking neocortex identified by intraoperative electrocorticography in epileptic patients who underwent cortical resection for seizure control. In vitro measures of receptor affinity (K(D)), number (Bmax) and laminar distribution for [3H]-FMZ binding in the epileptic focus (n = 38) were compared to nonspiking cortex from a subgroup of the patients (n = 12) and to tissue obtained from trauma patients (n = 5). The in vitro binding parameters were compared to in vivo [11C]-FMZ binding measured with positron emission tomography (PET) (n = 19). The Bmax was higher in the 38 spiking tissues as compared to the 12 nonspiking tissues (P = .012). Paired comparison of spiking versus nonspiking binding in the 12 patients from whom nonspiking tissue was available showed increases in both K(D) (P = .037) and Bmax (P = .0047) in spiking cortex. A positive correlation was found between K(D) and Bmax values for 38 patients (r = 0.55, P < .0001), the magnitude of the K(D) increase being twice that of the Bmax increase. In addition, there was a significant correlation between the asymmetry indices of the in vivo FMZ binding on PET and in vitro K(D) of spiking cortex (n = 19, r = 0.52, P = .02). The laminar distribution of [3H]-FMZ showed increased FMZ binding in cortical layers V-VI in spiking cortex compared to nonspiking and control cortex. The increased receptor number in spiking cortical layers V-VI may be a compensatory mechanism to decreased GABAergic input. The increased Bmax in spiking cortex was accompanied by a larger decrease in the affinity of FMZ for the receptor suggesting that decreased FMZ binding in the epileptic focus measured with PET is due to a decrease in the affinity of the tracer for the receptor.

Light quality-dependent nuclear import of the plant photoreceptors phytochrome A and B

The phytochrome (phy) family of plant photoreceptors controls various aspects of photomorphogenesis. Overexpression of rice phyA-green fluorescent protein (GFP) and tobacco phyB-GFP fusion proteins in tobacco results in functional photoreceptors. phyA-GFP and phyB-GFP are localized in the cytosol of dark-adapted plants. In our experiments, red light treatment led to nuclear translocation of phyA-GFP and phyB-GFP, albeit with different kinetics. Red light-induced nuclear import of phyB-GFP, but not that of phyA-GFP, was inhibited by far-red light. Far-red light alone only induced nuclear translocation of phyA-GFP. These observations indicate that nuclear import of phyA-GFP is controlled by a very low fluence response, whereas translocation of phyB-GFP is regulated by a low fluence response of phytochrome. Thus, light-regulated nucleocytoplasmic partitioning of phyA and phyB is a major step in phytochrome signaling.

IL1B gene polymorphisms influence the course and severity of inflammatory bowel disease

There is evidence of a disbalance in the inflammatory regulation of patients with inflammatory bowel diseases (IBD). Interleukin-1 beta plays an important role in the pro-inflammatory response. Our aim was to study the influence which IL1B gene polymorphisms may have on the severity and course of these diseases. Ninety-six patients with ulcerative colitis (UC), 98 patients with Crohn's disease (CD), and 132 ethnically matched healty individuals (HC) were typed for the polymorphic sites in the promoter region (position -511) and in exon 5 (position +3953) of the IL1B gene, using polymerase chain reaction (PCR)-based methods. In the CD group a significant association (P = 0.009) was found in this pair of genes. Homozygotes for allele 1 at position +3953 were more often present (69% vs 31%) in the subgroup of patients carrying at least one copy of allele 2 at position -511. This association was significant in patients with non-perforating disease (P = 0.002), but was not present in patients with perforating-fistulizing disease. The distribution of both allelic pairs in the non-fistulizing group proved to be significantly different from HC (P < 0.05), UC (P < 0.03), and the fistulizing group (P < 0.05). There was a similar association in non-operated patients (P = 0.024), whereas no such association was found in surgically treated patients. Among carriers of allele 2 at position -511, UC patients with more severe bleeding symptoms (P = 0.006) were less frequently found. These results suggest that IL1B gene polymorphisms participate in determining the course and severity of inflammatory bowel disease and contribute to explain the heterogeneity of these diseases.

[Analysis of the activity of neurologic intensive care units]

The authors analysed six-year activity of the intensive Care Unit of Department of Neurology, Medical University of Pécs (POTEI), and two-year activity of the Intensive Care Unit of Department of Neurology, Semmelweis University of Medicine, Budapest (SOTEI). Mortality at POTEI and SOTEI was 33.9% and 32.2%, respectively. Mean duration of stay of survivors at POTEI was 10 +/- 12.8 days, and 7 +/- 6.8 days at SOTEI; mean duration of care of the deceased patients at POTEI was 6.3 +/- 10.5 days, and 10 +/- 13.7 days at SOTEI. At POTEI 60.7%, at SOTEI 63% of the patients was admitted because of cerebrovascular insult. Mortality of patients with brain haemorrhage at POTEI and SOTEI was 53.4% and 57.7% respectively. Mortality of the ischaemic group was 40.6% (POTEI) and 35.3% (SOTEI). In the group of intracranial tumours 44.4% mortality was recorded at POTEI and 47.6% at SOTEI. At POTEI 240 patients (15.9%), while at SOTEI 94 patients (21%) were admitted to treat epileptic seizures. Among the 510 patients, who died within one month 284 patients (55.6%) were unconscious at admission. From those with coma due to severe structural lesion of the brain (brain ischaemia, bleeding, meningitis) only 15 patients survived. Among the 184 patients, who were comatose and survived, the most frequent diagnosis was suicidal attempt with hypnotics (n = 67), metabolic encephalopathy (n = 19) and epilepsy (n = 12). At SOTEI among the 144 deceased patients 102 (70.8%) were unconscious at admission. Coma at admission proved to be a strong predictor of mortality. Mortality of the ventilated patients was 83% at POTEI and of those having subclavian catheter (n = 592) was 47.1%. In the acute phase of brain ischaemia at POTEI 39%, at SOTEI 10.7% of the patients received heparin. At SOTEI the cost of medication of patients who died after two weeks of care was 65.2% higher than that of the survived patients.

[11C]Flumazenil PET in patients with epilepsy with dual pathology

PURPOSE

Coexistence of hippocampal sclerosis and a potentially epileptogenic cortical lesion is referred to as dual pathology and can be responsible for poor surgical outcome in patients with medically intractable partial epilepsy. [11C]Flumazenil (FMZ) positron emission tomography (PET) is a sensitive method for visualizing epileptogenic foci. In this study of 12 patients with dual pathology, we addressed the sensitivity of FMZ PET to detect hippocampal abnormalities and compared magnetic resonance imaging (MRI) with visual as well as quantitative FMZ PET findings.

METHODS

All patients underwent volumetric MRI, prolonged video-EEG monitoring, and glucose metabolism PET before the FMZ PET. MRI-coregistered partial volume-corrected PET images were used to measure FMZ-binding asymmetries by using asymmetry indices (AIs) in the whole hippocampus and in three (anterior, middle, and posterior) hippocampal subregions. Cortical sites of decreased FMZ binding also were evaluated by using AIs for regions with MRI-verified cortical lesions as well as for non-lesional areas with visually detected asymmetry.

RESULTS

Abnormally decreased FMZ binding could be detected by quantitative analysis in the atrophic hippocampus of all 12 patients, including three patients with discordant or inconclusive EEG findings. Decreased FMZ binding was restricted to only one subregion of the hippocampus in three patients. Areas of decreased cortical FMZ binding were obvious visually in all patients. Decreased FMZ binding was detected visually in nonlesional cortical areas in four patients. The AIs for these nonlesional regions with visual asymmetry were significantly lower than those for regions showing MRI lesions (paired t test, p = 0.0075).

CONCLUSIONS

Visual as well as quantitative analyses of FMZ-binding asymmetry are sensitive methods to detect decreased benzodiazepine-receptor binding in the hippocampus and neocortex of patients with dual pathology. MRI-defined hippocampal atrophy is always associated with decreased FMZ binding, although the latter may be localized to only one sub-region within the hippocampus. FMZ PET abnormalities can occur in areas with normal appearance on MRI, but FMZ-binding asymmetry of these regions is lower when compared with that of lesional areas. FMZ PET can be especially helpful when MRI and EEG findings of patients with intractable epilepsy are discordant.

Significant differences in the interleukin-1beta and interleukin-1 receptor antagonist gene polymorphisms in a Hungarian population with inflammatory bowel disease

BACKGROUND

There is growing evidence of the importance of genetic predisposition and the activation of the mucosal immune system in the pathogenesis of inflammatory bowel disease. Thus, genes involved in the regulation of inflammation are receiving increased attention. We have studied whether Crohn's disease (CD) or ulcerative colitis (UC) is associated with certain allelic combinations of IL1B/IL1RA gene polymorphisms in a different European population than the ones studied so far.

METHODS

Ninety-six patients with UC, 97 with CD, and 132 healthy individuals (HC) were typed for the polymorphic regions in exon 5 of the IL1B gene and in intron 2 of the IL1RA gene, using polymerase chain reaction-based methods.

RESULTS

In CD homozygotes for allele 1 in IL1B gene polymorphism were more often present (72% versus 28%; P = 0.01) in the subgroup of patients carrying at least one copy of allele 2 in IL1RA gene polymorphism. This association was not found in HC (HC versus CD; P = 0.03) or UC. However, in UC patients with pancolitis a similar trend was observed (75% versus 25%). Several genotype combinations characterized by the presence of allele 2 of the IL1RA gene polymorphism were more common in CD (P = 0.001) and UC (P = 0.049) than in HC.

CONCLUSIONS

Our data support the concept that CD and severe UC have a genetic disequilibrium in the distribution of IL1B and IL1RA gene polymorphisms. These findings together with functional studies will contribute to the understanding of the pathogenesis of the chronicity of inflammation in these diseases.

Nociceptive integration in the rat spinal cord: role of non-linear membrane properties of deep dorsal horn neurons

Deep dorsal horn neurons (DHNs) involved in nociception can relay long-lasting inputs and generate prolonged afterdischarges believed to enhance the transfer of nociceptive responses to the brain. We addressed the role of neuronal membrane properties in shaping these responses, by recording lamina V DHNs in a slice preparation of the rat cervical spinal cord. Of 256 neurons, 102 produced accelerating discharges in response to depolarizing current pulses, whereas the other neurons showed spike frequency adaptation. Two mechanisms mediated the firing acceleration: a slow inactivation of a K+ current expressed upon activation of the neuron from hyperpolarized holding potentials, and the expression of a regenerative plateau potential activating around resting membrane potential. The increase in firing frequency was much stronger when sustained by the plateau potential (71 DHNs, 28%). A few neurons produced adaptation and both types of acceleration, in different membrane potential domains, showing that the firing pattern of a deep DHN is not a rigid characteristic. Plateau potentials could be elicited by stimulation of nociceptive primary afferent fibres. The bistability associated with plateau potentials permitted afterdischarges. Because plateau potentials had slow activation kinetics and were voltage-dependent, the neurons had non-linear input-output relationships in both the amplitude and time domains. Nociceptive primary afferent stimulation elicited intense and prolonged responses in plateau-generating DHNs, while brief bursts of spikes were evoked otherwise. These results indicate that in a population of deep DHNs, intense firing and prolonged afterdischarges in response to nociceptive stimulation depend on non-linear intrinsic membrane properties.

[Endoscopic therapy of pancreas divisum]

Pancreas divisum is the most frequent congenital ductal anomaly of the pancreas: it occurs in 5-10% of the population. In the majority of patients, this congenital anomaly is of no clinical importance. In a certain subset of patients, however, pancreas divisum is clinically important as a cause of abdominal pain, acute recurrent pancreatitis or chronic obstructive pancreatitis. The authors, experience on endoscopic drainage of the minor papilla is reported. In the history of patient 1., three episodes of recurrent pancreatitis and permanent upper abdominal pain were explored. ERP revealed a pancreas divisum and a mild irregularity and dilation of the dorsal pancreatic duct. A 7 F stent (length: 6 cm) was implanted in the dorsal pancreatic duct following a papillotomy on the stenotic minor papilla. A repeated Lundh test revealed a 58% improvement in the exocrine pancreatic function. No recurrence of pancreatitis has been observed in spite of the moderate continuous abdominal pain. In patient 2., ERP demonstrated a pancreas divisum and a severely dilated dorsal pancreatic duct as causes of the previous permanent abdominal pain. An 8 F stent (length: 5 cm) was inserted through the minor papilla without endoscopic sphincterotomy. A significant improvement in exocrine pancreatic function (70%) ensued. No abdominal pain has since been observed. In conclusion, dorsal pancreatic duct stenting (mainly in cases involving a dilated pancreatic duct) seems to have a beneficial effect in patients with both recurrent acute pancreatitis or chronic obstructive pancreatitis evoked by pancreas divisum.

UV-B-induced differential transcription of psbA genes encoding the D1 protein of photosystem II in the Cyanobacterium synechocystis 6803

UV-B irradiation of intact Synechocystis sp. PCC 6803 cells results in the loss of photosystem II activity, which can be repaired via de novo synthesis of the D1 (and D2) reaction center subunits. In this study, we investigated the effect of UV-B irradiation on the transcription of the psbA2 and psbA3 genes encoding identical D1 proteins. We show that UV-B irradiation increases the level of psbA2 mRNA 2-3-fold and, more dramatically, it induces a 20-30-fold increase in the accumulation of the psbA3 mRNA even at levels of irradiation too low to produce losses of either photosystem II activity or D1 protein. The induction of psbA3 transcript accumulation is specific for UV-B light (290-330 nm). Low intensity UV-A emission (330-390 nm) and white light induce only a small, at most, 2-3-fold enhancement, whereas no effect of blue light was observed. Expression patterns of chimeric genes containing the promoter regions of the psbA2, psbA3 genes fused to the firefly luciferase (luc) reporter gene indicate that (i) transcription of psbA2/luc and psbA3/luc transgenes was elevated, similarly to that of the endogenous psbA genes, by UV-B irradiation, and that (ii) a short, 80-base pair psbA3 promoter fragment is sufficient to maintain UV-B-induced transcription of the luc reporter gene. Furthermore, our findings indicate that UV-B-induced expression of the psbA2 and psbA3 genes is a defense response against UV-B stress, which is regulated, at least, partially at the level of transcription and does not require active electron transport.

Transcription of the Arabidopsis CPD gene, encoding a steroidogenic cytochrome P450, is negatively controlled by brassinosteroids

The Arabidopsis CPD gene encodes a cytochrome P450 steroid side-chain hydroxylase (CYP90) that plays an essential role in the biosynthesis of the plant hormone brassinolide. Expression of the CPD gene is confined to cotyledons and leaf primordia in etiolated seedlings and detectable in the adaxial parenchyma of expanding leaves in light-grown plants. Transcription of the CPD gene is not affected by the plant growth factors auxin, ethylene, gibberellin, cytokinin, jasmonic acid and salicylic acid, but is specifically down-regulated by brassinolide in both dark and light. Steady-state mRNA levels of a CPD promoter-driven uidA reporter gene correlate with the expression of resident CPD gene in transgenic plants. Intermediates of the early and late C-6 oxidation pathways of brassinolide, carrying C-22 and C-23 side-chain hydroxyls, efficiently inhibit the activity of the CPD promoter. Repression of CPD transcription by brassinosteroids is sensitive to the protein synthesis inhibitor cycloheximide, indicating a requirement for de novo synthesis of a regulatory factor.

Light-induced expression of fatty acid desaturase genes

In cyanobacterial cells, fatty acid desaturation is one of the crucial steps in the acclimation processes to low-temperature conditions. The expression of all the four acyl lipid desaturase genes of Synechocystis PCC 6803 was studied as a function of temperature and separately as a function of light. We used cells grown at 25 degreesC in light-activated heterotrophic growth conditions. In these cells, the production of alpha-linolenic acid and 18:4 fatty acids was negligible and the synthesis of gamma-linolenic acid was remarkably suppressed compared with those of the cells grown photoautotrophically. The cells grown in the light in the presence of glucose showed no difference in fatty acid composition compared with cells grown photoautotrophically. The level of desC mRNA for delta9 desaturase was not affected by either the temperature or the light. It was constitutively expressed at 25 degreesC with and without illumination. The level of desB transcripts was negligible in the dark-grown cells and was enhanced about 10-fold by exposure of the cells to light. The maximum level of expression occurred within 15 min. The level of desA and desD mRNAs was higher in dark-grown cells than that of desB mRNA for omega3 desaturase. However, the induction of both desA and desD mRNAs for delta12 and delta6 desaturases, respectively, was enhanced by light about 10-fold. Rifampicin, chloramphenicol, and 3-(3, 4-dichlorophenyl)-1,1-dimethylurea completely blocked the induction of the expression of desA, desB, and desD. Consequently, we suggest the regulatory role of light via photosynthetic processes in the induction of the expression of acyl lipid desaturases.

A heat-sensitive Arabidopsis thaliana kinase substitutes for human p70s6k function in vivo

In mammalian cells, mitogen-induced phosphorylation of ribosomal protein S6 by p70s6k has been implicated in the selective translational upregulation of 5'TOP mRNAs. We demonstrate here that the homologous Arabidopsis thaliana protein, AtS6k2, ectopically expressed in human 293 cells or isolated from plant cells, phosphorylates specifically mammalian and plant S6 at 25 degrees C but not at 37 degrees C. When Arabidopsis suspension culture cells are shifted from 25 to 37 degrees C, the kinase becomes rapidly inactivated, consistent with the observation that heat shock abrogates S6 phosphorylation in plants. Treatment with potato acid phosphatase reduced the specific activity of immunoprecipitated AtS6k2 threefold, an effect which was blocked in the presence of 4-nitrophenyl phosphate. In quiescent mammalian cells, AtS6k2 is activated by serum stimulation, a response which is abolished by the fungal metabolite wortmannin but is resistant to rapamycin. Treatment of mammalian cells with rapamycin abolishes in vivo S6 phosphorylation by p70s6k; however, ectopic expression of AtS6k2 rescues the rapamycin block. Collectively, the data demonstrate that AtS6k2 is the functional plant homolog of mammalian p70s6k and identify a new signalling pathway in plants.

Inhibitory control of plateau properties in dorsal horn neurones in the turtle spinal cord in vitro

1. The role of inhibition in control of plateau-generating neurones in the dorsal horn was studied in an in vitro preparation of the spinal cord of the turtle. Ionotropic and metabotropic inhibition was found to condition the expression of plateau potentials. 2. Blockade of gamma-aminobutyric acid (GABAA) and glycine receptors by their selective antagonists bicuculline (10-50 microM) and strychnine (5-20 microM) enhanced the excitatory response to stimulation of the dorsal root and facilitated the expression of plateau potentials. 3. Bicuculline and strychnine also facilitated the generation of plateau potentials in response to depolarizing current pulses, suggesting the presence of tonic ionotropic inhibitory mechanisms in turtle spinal cord slices. 4. Activation of GABAB receptors also inhibited plateau-generating neurones. The selective agonist baclofen (5-50 microM) inhibited wind-up of the response to repeated depolarizations induced synaptically or by intracellular current pulses. 5. Baclofen reduced afferent synaptic input. This effect was not affected by bicuculline or strychnine and was blocked by the selective GABAB receptor antagonist 2-hydroxysaclofen (2-OH-saclofen, 100-400 microM). 6. Postsynaptically, baclofen inhibited plateau properties. Activation of GABAB receptors produced a hyperpolarization (7.0 +/- 0.5 mV, mean +/- S.E.M., n = 29) with an associated decrease in input resistance (22.7 +/- 3.1%, n = 24). These effects were blocked by extracellular Ba2+ (1-2 mM). 7. When the baclofen-induced hyperpolarization and shunt were compensated for by adjusting the bias current and the strength of the stimulus, baclofen still inhibited generation of plateau potentials. Wind-up and after-discharges were also inhibited by baclofen. These effects remained in the presence of tetrodotoxin (1 microM) and were antagonized by 2-OH-saclofen. 8. The inhibition of plateau properties was observed even when the baclofen-induced hyperpolarization and shunt were blocked by Ba2+ and when potassium channels were blocked by Ba2+ (3 mM), tetraethylammonium (TEA, 15 mM) and apamin (0.25-0.5 microM). The baclofen-sensitive component of the plateau potential was reduced by nifedipine (10 microM), suggesting a modulation of postsynaptic L-type Ca2+ channels. 9. We suggest that inhibitory regulation of plateau properties plays a role in somatosensory processing in the dorsal horn. The inhibitory control of wind-up and after-discharges may be particularly significant in physiological and therapeutic control of central sensitization to pain.

Transcription of Arabidopsis and wheat Cab genes in single tobacco transgenic seedlings exhibits independent rhythms in a developmentally regulated fashion

Transcription of Cab genes has been previously shown to be regulated by a circadian oscillator coupled to the red light-absorbing plant photoreceptor phytochrome in various plant species. In addition, it has recently been suggested that rhythmic expression of the Cab genes could also be affected by a phytochrome-independent circadian oscillator in a developmentally regulated fashion. This study has shown that a red light-insensitive oscillator and a phytochrome-coupled circadian clock indeed coregulate the oscillating expression of individual Cab genes at the level of transcription at an early developmental stage. The study involved analysing the expression patterns of transgenes, containing short fragments of the Arabidopsis thaliana Cab2 or the wheat Cab-1 promoter fused to the firefly luciferase reporter gene, by a video-imaging system in single, etiolated tobacco seedlings. Germination and red/far-red light treatments applied between 12 and 36 h after sowing lead to the appearance of two independent circadian rhythms. These rhythms coexist, both exhibiting period lengths close to 25 h but phased differently. However, repeated red-light treatments given 60 h or later after sowing synchronize these free-running rhythms and induce a single new circadian oscillation. These data indicate that both oscillators regulate the expression of the Cab genes studied at the level of transcription and that the cis-acting element(s) of the wheat Cab-1 and A. thaliana Cab2 genes mediating these responses are located on short, 250 bp promoter regions. Furthermore, these red-light induced rhythms are also inducible by far-red light treatments alone. Therefore, in tobacco, the phytochrome-coupled oscillator is regulated, at least partially, by the very low fluence response of phytochrome A.

Neuroborreliosis in county Baranya, Hungary

The incidence and clinical characteristics of Lyme neuroborreliosis (NB) in a region of high prevalence of tick-bite in Hungary is described. In the county Baranya 66 patients were recorded in a five-year period (1989-93). Fifty-six patients (85%) were in "early", and 10 patients (15%) in "late stage" of NB. The sex distribution was equal. The incidence of NB was 2.9-100,000/year in this region. The incidence of radiculitis/neuritis, meningitis, encephalitis and myelitis in the sample was 56.1%, 19.7%, 18.2% and 6%, respectively. The EEG and evoked potentials showed both central and peripheral neural involvement, EMG and ENG abnormalities were related to the peripheral clinical signs. Non-specific white matter lesions could be found by MRI in 5 patients with central involvement. Cerebrospinal fluid changes were not obligatory but a better indicator of inflammatory process in cases with meningitis and/or encephalitis forms (positivity 75%) than in cases with myelitis and radiculitis (positivity 49%).

Kaposi's sarcoma-associated herpesvirus/human herpesvirus-8: a new virus in human pathology

The discovery of a new human herpesvirus in Kaposi's sarcoma (KS) tissue of patients with AIDS has opened up new vistas in virology and oncology. This herpesvirus was first descriptively named KS-associated herpesvirus (KSHV), but was recently renamed human herpesvirus 8 (HHV8). KSHV/HHV8 DNA has been found in all forms of KS, suggesting that it might be involved in the pathogenesis of KS. In addition, KSHV/HHV8 can be detected in both malignant and benign lymphoproliferative disease. KSHV/HHV8 was also found in patients with angiosarcoma of the face and angiolymphoid hyperplasia with eosinophilia. Although only a limited portion of the virus has been sequenced, KSHV/HHV8 is equipped with genes that could confer oncogenic potential. The virus can now be cultured, providing the possibility for studies of viral replication and the mode of transmission. The recently developed serologic assays for antiviral antibodies suggest that infection with KSHV/HHV8 is not ubiquitous because KSHV/HHV8 seropositivity is limited to a small proportion of the population.

The ursodeoxycholic acid-p-aminobenzoic acid deconjugation test, a new tool for the diagnosis of bacterial overgrowth syndrome

OBJECTIVE

To determine the possible complementary role of the ursodeoxycholic acid-p-aminobenzoic acid (UDCA-PABA) loading test in the diagnosis of intestinal bacterial overgrowth.

DESIGN

A prospective clinical study.

PATIENTS AND METHODS

The hydrogen breath and UDCA-PABA tests were performed simultaneously in 68 patients with suspected contaminated small bowel syndrome (CSBS), and in 10 healthy control subjects. The hydrogen breath test was performed by oral loading of 25 g of lactose and/or 10 g of lactulose. The UDCA-PABA test was carried out by oral loading of 250 mg of UDCA-PABA conjugate, followed by measurement of the amount of PABA excreted in the urine. The diagnosis of bacterial overgrowth was considered to be established when either the hydrogen breath test or the UDCA-PABA test produced abnormal results.

RESULTS

Thirty-five of the 68 patients proved to have CSBS. In 13 of these 35 patients, only the enhanced urinary PABA excretion (11.7 +/- 1.42 mg vs. 3.6 +/- 0.68 mg) indicated bacterial overgrowth, 15 of the 35 patients gave only a positive hydrogen breath test, and in the remaining seven cases the results of both tests were abnormal. In eight CSBS patients, the urinary excretion of PABA was decreased significantly following 10-day tinidazole treatment (5.5 +/- 1.29 mg vs. 13.1 +/- 2.07 mg).

CONCLUSION

The UDCA-PABA test is a valuable clinical method for the detection of bacterial overgrowth, especially in cases where hydrogen production alone fails to reveal CSBS. It is also a useful procedure for evaluating the efficacy of antibacterial treatment.

[The ursodeoxycholic acid-p-aminobenzoic acid test in the diagnosis of small bowel bacterial overgrowth syndrome]

Contaminated small bowel syndrome is frequently associated with meteorism due to excessive gas formation, and diarrhoea as a result of bacterial fermentative processes, including splitting of carbohydrates or deconjugating and dehydroxylating bile salts. In addition to gas production, bacteria capable of metabolizing bile salts have been shown to release p-aminobenzoic acid (PABA) from and Ursodeoxycholic-acid-PABA substrate. Our aim was to determine the possible complementary role of the UDCA-PABA test in the diagnosis of bacterial overgrowth.

PATIENTS AND METHODS

The H2 breath and UDCA-PABA tests were performed simultaneously on 46 patients with suspected contaminated small bowel syndrome, and on 7 healthy subjects. The H2 breath test was performed by oral loading of 25 g lactose and/or 10 g lactulose. The UDCA-PABA test was carried out by determining urinary excretion of PABA after oral loading with 250 mg UDCA-PABA conjugate. The diagnosis of bacterial overgrowth was established, when either H2 breath, or UDCA-PABA test proved to be pathological.

RESULTS

Based upon the pathologic values of either the H2 breath test, or the UDCA-PABA test, 25 out of 46 patients proved to have contaminated small bowel syndrome. In 10 out of 25 patients only pathologic urinary PABA excretion (12.772 +/- 1.707 vs 4.1 +/- 0.58), indicated bacterial overgrowth, and in 9 out of the same group only positive H2 breath test (early rise of > 20 ppm of H2) indicated the same, while in 6 cases both tests proved to be pathological. In 7 CSBS patients the urinary excretion of PABA significantly decreased following a 10 day Tinidazole treatment (5.48 +/- 1.286 vs 13.068 +/- 2.068).

CONCLUSION

The UDCA-PABA test proved to be a valuable complementary method to detect bacterial overgrowth, when H2 production failed to reveal bacterial overgrowth.

Modulation of plateau properties in dorsal horn neurones in a slice preparation of the turtle spinal cord

1. Modulation of plateau properties in dorsal horn neurones was studied in a transverse slice preparation of the spinal cord of the turtle. In plateau-generating neurones high frequency stimulation of the ipsilateral dorsal root (10-20 Hz, 0.5-2 min) produced a slow depolarization (2.9 +/- 0.6 mV, mean +/- S.E.M.; n = 6) and enhanced the properties mediated by dihydropyridine-sensitive Ca2+ channels. The tetanic stimulus facilitated wind-up and after-discharges even when fast synaptic transmission was blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10-20 microM), (+/-)-2-amino-5-phosphonopentanoic acid (AP5, 100 microM), bicuculline (10-20 microM) and strychnine (5-20 microM). 2. Application of cis-(+/-)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD, 10-50 microM) produced a slow depolarization (5.9 +/- 0.5 mV, n = 21) accompanied by an increase in input resistance (28.8 +/- 5.1%, n = 12). 3. ACPD increased the excitability by facilitating the plateau properties. In the presence of tetrodotoxin (TTX, 1 microM) a lower threshold and a slower decay of the plateau potential were observed. These effects resulted in facilitation of wind-up and prolonged after-discharges. 4. All ACPD-induced effects were blocked by alpha-methyl-4-carboxyphenylglycine (MCPG, 0.5-1 mM), a selective antagonist of metabotropic glutamate receptors. The selective agonist for the type I metabotropic glutamate receptor ((RS)-3,5-dihydrophenylglycine (DHPG, 50 microM)) reproduced all the effects of ACPD. 5. Application of a supposed neuromodulator, substance P (1-2 microM) produced a transient depolarization (4 +/- 0.6 mV) lasting 4-6 min during continued application of substance P. Variable effects on the input resistance were observed, a slight increase (12 +/- 2%) being the most frequent. In 61% of the cells, substance P induced a clear increase in excitability with no detectable change in input resistance or membrane potential. 6. The effects of substance P on plateau properties were indistinguishable from those produced by ACPD. Unlike the transient depolarization, the facilitation of the plateau properties persisted in the presence of the agonist. 7. The substance P-induced facilitation of the plateau potential was blocked by GR 82334 (5-10 microM), a selective NK-1 tachykinin-receptor antagonist, and was not affected by MEN 10376 (2 microM), a selective NK-2 antagonist. 8. The facilitation of plateau properties produced by dorsal root stimulation was also reduced by antagonists of metabotropic glutamate receptors and NK-1 tachykinin receptors. 9. We propose that modulation of postsynaptic plateau properties in dorsal horn neurones by activation of type I metabotropic glutamate receptors and NK-1 tachykinin receptors is involved in processing nociceptive information.

Characterization of proteins that interact with the GTP-bound form of the regulatory GTPase Ran in Arabidopsis

Ran, a small soluble GTP-binding protein, has been shown to be essential for the nuclear translocation of proteins and it is also thought to be involved in regulating cell cycle progression in mammalian and yeast cells. Genes encoding Ran-like proteins have been isolated from different higher plant species. Overexpression of plant Ran cDNAs, similarly to their mammalian/yeast homologues, suppresses the phenotype of the pim46-1 cell cycle mutant in yeast cells. The mammalian/yeast Ran proteins have been shown to interact with a battery of Ran-binding proteins, including the guanidine nucleotide exchange factor RCC1, the GTPase-activating Ran-GAP, nucleoporins and other Ran-binding proteins (RanBPs) specific for Ran-GTP. Here, the characterization of the first Ran-binding proteins from higher plants is reported. The yeast two-hybrid system was used to isolate cDNA clones encoding proteins of approximately 28 kDa (At-RanBP1a, At-RanBP1b) that interact with the GTP-bound forms of the Ran1, Ran2 and Ran3 proteins of Arabidopsis thaliana. The deduced amino acid sequences of the At-RanBP1s display high similarity (60%) to mammalian/yeast RanBP1 proteins and contain the characteristic Ran-binding domains. Furthermore, interaction of the plant Ran and RanBP1 proteins, is shown to require the acidic C-terminal domain (-DEDDDL) of Ran proteins in addition to the presence of an intact Ran-binding domain. In whole cell extracts, the GST-RanBP1a fusion protein binds specifically to GTP-Ran and will not interact with Rab/Ypt-type small GTP-binding proteins. Finally, in good agreement with their proposed biological function, the At-Ran and the At-RanBP genes are expressed coordinately and show the highest level of expression in meristematic tissues.

A plant in vitro system for the nuclear import of proteins

This paper reports the development of an in vitro system that allows the direct assay of protein import into plant nuclei. In this assay the import of fluorescently labelled karyophilic protein substrates into nuclei isolated from evacuolated tobacco BY-2 suspension cells is monitored. It is demonstrated that import of the fluorescently labelled peptide conjugates is rapid, saturable and nuclear localization signal (NLS)-dependent. Exclusion of high molecular weight (70 kDa) dextran and substrates carrying mutated NLS sequences further underline the specificity of this system. Nuclear translocation of karyophilic import substrates in tobacco, similar to mammalian systems, is inhibited by the non-hydrolysable GTP analogue GTP-gamma-S. In contrast, protein uptake is not blocked by wheat germ agglutinin, N-ethyl-maleinimide and iodoacetic acid. Furthermore, it is shown that nuclear import of proteins is only partially inhibited by low temperature (0-4 degrees C). The in vitro nuclear import assay does not depend on exogenously added ATP or cytosolic factors. However, a block of nuclear import with GTP-gamma-S could be overcome by the addition of cytosolic extract, suggesting the dependence on cytosolic factors or proteins. These data indicate that the characteristics of nuclear protein import in plant and mammalian cells are similar, but may be, at least in some respects, also different from each other.

Modulation of regenerative membrane properties by stimulation of metabotropic glutamate receptors in rat deep dorsal horn neurons

1. Intracellular recordings were obtained from 111 dorsal horn neurons in lamina V, in an in vitro transverse spinal cord slice preparation of the cervical region from young rats. 2. Of these neurons, 28% showed voltage-dependent plateau potentials, mainly underlain by a tetrodotoxin-resistant dihydropyridine-sensitive Ca2+ current. When depolarized, neurons with plateau properties produced accelerating firing frequency, afterdischarge, and bistability. They also exhibited windup of action potentials when stimulated by repetitive intracellular injections of current. 3. Glutamate being the main excitatory transmitter released by primary afferents, we also considered the effects of specific agonists of metabotropic glutamate receptors and showed that they modulate positively (induce or enhance) plateau properties in the deep dorsal horn neurons.

Clinical anatomy: a review course for emergency medicine residents

An understanding of anatomy is essential to the practice of Emergency Medicine. A significant amount of anatomy knowledge is lost in the transition from student to clinician. This article describes the content and structure of a clinically oriented anatomy review course for senior emergency medicine residents.

Brassinosteroids rescue the deficiency of CYP90, a cytochrome P450, controlling cell elongation and de-etiolation in Arabidopsis

The cpd mutation localized by T-DNA tagging on Arabidopsis chromosome 5-14.3 inhibits cell elongation controlled by the ecdysone-like brassinosteroid hormone brassinolide. The cpd mutant displays de-etiolation and derepression of light-induced genes in the dark, as well as dwarfism, male sterility, and activation of stress-regulated genes in the light. The CPD gene encodes a cytochrome P450 (CYP90) sharing homologous domains with steroid hydroxylases. The phenotype of the cpd mutant is restored to wild type both by feeding with C23-hydroxylated brassinolide precursors and by ectopic overexpression of the CPD cDNA. Brassinosteroids also compensate for different cell elongation defects of Arabidopsis det, cop, fus, and axr2 mutants, indicating that these steroids play an essential role in the regulation of plant development.

The Tissue-Specific Expression of a Tobacco Phytochrome B Gene

We have isolated a genomic clone from Nicotiana tabacum, designated Nt-PHYB-1, encoding a type-II, "green tissue" phytochrome apoprotein. Recombinant genes, consisting of the 3319-bp promoter of the Nt-PHYB-1 gene (including the entire 5[prime] untranslated sequence but not the ATG) or its deletion derivatives and the bacterial [beta]-glucuronidase reporter gene, were constructed and transferred into tobacco. The expression patterns and levels of the endogenous Nt-PHYB-1, as well as those of the transgenes, were determined by RNase protection assays and by [beta]-glucuronidase histochemical staining. We show that (a) the PHYB-1 gene has three transcription start sites, (b) the abundance of the three PHYB-1-specific mRNAs is different, and that (c) it is not regulated by light. However, we do demonstrate that transcription of the endogenous PHYB-1 gene and that of the recombinant genes exhibit a well-defined organ and tissue specificity. This tobacco PHYB gene is relatively highly expressed in leaf, stem, and different floral organs but not in root. Deletion analysis of the Nt-PHYB-1 promoter indicates that a 382-bp region, located between -1472 and -1089, is required for high-level expression of this gene.

Anti-granulocyte immunoscintigraphy and [99mTc]hexamethylpropyleneamine-oxime-labeled leukocyte scintigraphy in inflammatory bowel disease

A prospective study was carried out on 13 patients with ulcerative colitis and 11 with Crohn's disease to compare the value of radioimmunoscintigraphy involving 99mTc-labeled antigranulocyte monoclonal antibody (BW 250/183) with that of hexamethylpropyleneamine-oxime-labeled leukocyte scintigraphy. The extent of the process (various segments of the small bowel; ascending, transverse, and descending colon; and rectosigmoideum) was determined in 115 segments by means of radioimmunoscintigraphy and leukocyte scintigraphy and compared with the results of enteroclysis and colonoscopy in 64 segments. The scintigraphic activity, calculated by summing the segment scores, was compared with clinical and laboratory parameters. During radioimmunoscintigraphy, the 24-hr fecal excretion of the antibody was measured. The two methods revealed a different extent of the process (P<0.01). The segmental sensitivity and specificity were 63% and 96% in radioimmunoscintigraphy, and 87% and 94% in leukocyte scintigraphy. Leukocyte scintigraphy proved to be superior in cases with small intestine involvement, but the methods are of similar value in cases with large bowel involvement. The scintigraphic activity determined by radioimmunoscintigraphy and the fecal excretion of monoclonal antibody correlated with seven parameters, while that determined by leukocyte scintigraphy did so with 12 variables. Both methods are of similar value for the detection of large bowel involvement, but leukocyte scintigraphy was the better method for determination of the involved segments in the small intestine. The scintigraphic activity proved a useful parameter, correlating well with the clinical and laboratory variables.

Human herpesvirus 8 in classic Kaposi sarcoma

Recent studies suggest the role of a new human herpesvirus (HHV8) in the pathogenesis of different forms of Kaposi sarcoma (KS). In the present work we investigated the presence of HHV8 sequences in KS tumour tissues from patient with classic KS. Since clear evidences point to the role of immune suppression in the development of AIDS-associated KS or patients receiving immunosuppressive therapy, immunological investigations were also performed. We could show a highly consequent association of HHV8 sequences with classic KS in the large series of patients supporting our previous findings that this virus might be in some way involved in the pathogenesis of this tumour. In addition immunological examination of the patients revealed a mild decrease in the CD4 positive cell number, a significantly reduced CD4/CD8 ratio, a diminished PHA reactivity and leukocyte migration factor production of lymphocytes. The changes observed in the present study are similar, but much less pronounced than those may be observed in HIV infection.

The light-induced reduction of the gravitropic growth-orientation of seedlings of Arabidopsis thaliana (L.) Heynh. is a photomorphogenic response mediated synergistically by the far-red-absorbing forms of phytochromes A and B

Hypocotyls of dark-grown seedlings of Arabidosis thaliana exhibit a strong negative gravitropism, which is reduced by red and also by long-wavelength, far-red light treatments. Light treatments using phytochrome A (phyA)- and phytochrome B (phyB)-deficient mutants showed that this response is controlled by phyB in a red/far-red reversible way, and by phyA in a non-reversible, very-low-fluence response. Crosses of the previously analyzed phyB-1 allele (in the ecotype Landsberg erecta background) to the ecotype Nossen wild-type (WT) background resulted in a WT-like negative gravitropism in darkness, indicating that the previously described gravitropic randomization observed with phyB-1 in the dark is likely due to a second mutation independent of that in the PHYB gene.

Transcription of tobacco phytochrome-A genes initiates at multiple start sites and requires multiple cis-acting regulatory elements

Promoter regions of the Nicotiana tabacum PHYA1 and PHYA2 genes display 89% sequence identity. Analysis of the 5' ends of both the PHYA1 and the PHYA2 transcript revealed multiple, distinct mRNA species, each differing in length and in abundance. The levels of the major PHYA1, PHYA2 transcripts were found to be auto-regulated by phytochrome. This auto-regulation was most efficient in 2-8-day old seedlings. Furthermore, we examined the expression pattern of the PHYA1-GUS reporter gene, containing a 4700 bp PHYA1 promoter fragment or its 5'-deletion derivatives, by GUS histochemistry and by RNase protection assays in transgenic tobacco plants. Our data indicate that the PHYA1 promoter contains three regions which are necessary for the maximum level and regulated expression. We show that a 264 bp promoter fragment contains a cis-regulatory element(s) responsible for expression in the root tips of transgenic seedlings. The major cis-regulatory elements required for high-level transcription and expression in other organs are located in separate regions of the PHYA1 promoter. These data indicate the contribution of multiple cis-regulatory elements for the maximum and regulated expression of tobacco genes coding for phytochrome A protein.

Cholera toxin elevates pathogen resistance and induces pathogenesis-related gene expression in tobacco

In animals, plants and fungi, cholera toxin (CTX) can activate signalling pathways dependent on heterotrimeric GTP binding proteins (G-proteins). We transformed tobacco plants with a chimeric gene encoding the A1 subunit of CTX regulated by a light-inducible wheat Cab-1 promoter. Tissues of transgenic plants expressing CTX showed greatly reduced susceptibility to the bacterial pathogen Pseudomonas tabaci, accumulated high levels of salicylic acid (SA) and constitutively expressed pathogenesis-related (PR) protein genes encoding PR-1 and the class II isoforms of PR-2 and PR-3. In contrast, the class I isoforms of PR-2 and PR-3 known to be induced in tobacco by stress, by ethylene treatment and as part of the hypersensitive response to infection, were not induced and displayed normal regulation. In good agreement with these results, microinjection experiments demonstrated that CTX or GTP-gamma-S induced the expression of a PR1-GUS reporter gene but not that of a GLB-GUS reporter gene containing the promoter region of a gene encoding the class I isoform of PR-2. Microinjection and grafting experiments strongly suggest that CTX-sensitive G-proteins are important in inducing the expression of a subset of PR genes and that these G-proteins act locally rather than systemically upstream of SA induction.

Bladder augmentation with detubularized intestinal segment

The authors report on 9 cases of bladder augmentation with detubularized intestinal segments. The capacity of the contracted bladder was increased in 4 cases; care was taken to prevent the development of an hour-glass bladder. In a young female patient a caecal-ileal segment was applied so that in case of a possible future pregnancy the mesentery should not hinder the growth of the uterus. In 4 cases hypertonic neurogenic bladders were augmented with intestinal segments, thus the further destruction of the kidneys could be avoided. In one case the reflux was hindered by a Kock valve, but stagnation developed above the valve, therefore it was eliminated and replaced by a 15 cm intestinal segment. In one case the uninhibited neurogenic bladder was augmented, the resistance of the urethra increased as a result of which the patient stayed dry between self-catheterizations. Attention is called upon the metabolic disturbances and increased risk of infection following intestinal implantations.

Characterization of membrane-bound small GTP-binding proteins from Nicotiana tabacum

We have cloned nine cDNAs encoding small GTP-binding proteins from leaf cDNA libraries of tobacco (Nicotiana tabacum). These cDNAs encode distinct proteins (22-25 kD) that display different levels of identity with members of the mammalian Rab family: Nt-Rab6 with Rab6 (83%), Nt-Rab7a-c with Rab7 (63-70%), and Nt-Rab11a-e with Rab11 (53-69%). Functionally important regions of these proteins, including the "effector binding" domain, the C-terminal Cys residues for membrane attachment, and the four regions involved in GTP-binding and hydrolysis, are highly conserved. Northern and western blot analyses show that these genes are expressed, although at slightly different levels, in all plant tissues examined. We demonstrate that the plant Rab5, Rab6, and Rab11 proteins, similar to their mammalian and yeast counterparts, are tightly bound to membranes and that they exhibit different solubilization characteristics. Furthermore, we show that the yeast GTPase-activating protein Gyp6, shown to be specifically required to control the GTP hydrolysis of the yeast Ypt6 protein, could interact with tobacco GTP-binding proteins. It increases in vitro the GTP hydrolysis rate of the wild-type Nt-Rab7 protein. In addition, it also increases, at different levels, the GTP hydrolysis rates of a Nt-Rab7m protein with a Rab6 effector domain and of two other chimaeric Nt-Rab6/Nt-Rab7 proteins. However, it does not interact with the wild-type Nt-Rab6 protein, which is most similar to the yeast Ypt6 protein.

Expression of tobacco genes for light-harvesting chlorophyll a/b binding proteins of photosystem II is controlled by two circadian oscillators in a developmentally regulated fashion

Light-induced expression of genes encoding the light-harvesting chlorophyll a/b binding proteins of photosystem II (Cab) was shown to be controlled by a circadian oscillator coupled to the red-light-absorbing plant photoreceptor phytochrome. Here we show that a red-light-insensitive oscillator is also involved in regulating the expression of the Cab genes. We provide evidence that germination leads, in a light-independent manner, to the setting and/or synchronization of endogenous oscillators and that it induces the expression of Cab genes in a circadian fashion. This circadian oscillator is not coupled to phytochrome, as it cannot be reset by red light for at least 44 h after sowing. Short red light pulses given between 12 and 44 h after sowing, however, induce new rhythms without perturbing the already free-running red-light-independent circadian oscillation. At this stage of development, the phytochrome-coupled and uncoupled circadian rhythms coexist. Both circadian rhythms are expressed and exhibit period lengths close to 24 h but are phased differently. At later stages of development (60 h or later after sowing), red light treatments synchronized these free-running rhythms and led to the appearance of a single new circadian oscillation. These data indicate that during early development the expression of single tobacco Cab genes, particularly expression of the Cab21 and Cab40 genes, is controlled in a developmentally dependent manner by two circadian oscillators.

Molecular characterization and expression of a tobacco histone H1 cDNA

We have isolated a 1104 bp tobacco cDNA clone (H1c12) which includes an 846 bp open reading frame. This encodes a polypeptide of 282 amino acid residues and represents the largest plant H1 histone identified so far. The structure of the deduced protein shows the classical tripartite organization of the H1-type linker histones. The expression of the tobacco H1 histone gene(s) corresponding to the H1c12 cDNA clone was examined during different developmental stages. We found that, at the level of steady-state mRNA, expression of gene(s) encoding this H1 histone was rapidly induced in germinating seeds. The H1 gene was expressed in all tissues examined. However, its expression was higher in tissues known to contain meristematic cells. Furthermore, in the leaves of mature plants accumulation of the H1 mRNA exhibits a very characteristic oscillation. This latter finding indicates that, at least in fully developed plants, the expression of this type of H1 histone gene(s) is modulated by a diurnal cycle.

On the ultrastructure of the spermatozoa in the Siberian hamster (Phodopus sungorus campbelli)

Spermatozoa of the Siberian hamster were examined using transmission and scanning electron microscopy. The sperm are approximately 119 microns in length and exhibit a falciform head typical of murine rodents. A rod-like structure runs almost the entire length of the subacrosomal space within the subacrosomal cytoskeleton. Scrolls of redundant nuclear membrane are consistently asymmetric on concave and convex sides of the sperm head with the convex side presenting much more elaborate whorls. Mitochondria in the middle piece number approximately 133 pairs and present either one or two distinct cross-sectional profiles. Determining the number of mitochondrial pairs is presented as a means of distinguishing among the various species or subspecies of Phodopus. Viewed in longitudinal section, the annulus also presents two different configurations; one profile is cuneiform, the other semilunar. The axonemal complex is typical of most rodent sperm flagellae. Dense fibers 1, 5 and 6 are substantially larger and fiber 9 is somewhat larger in diameter than the rest.

Phenotype of the fission yeast cell cycle regulatory mutant pim1-46 is suppressed by a tobacco cDNA encoding a small, Ran-like GTP-binding protein

Mutations in which the onset of mitosis is uncoupled from the completion of DNA replication has recently been described. Characterization of these mutants led to the identification of Pim1/Spi1 in fission yeast and RCC1/Ran proteins in mammalian cells. Their Saccharomyces cerevisae homologues, the MTR1/CNR1 proteins, appear to be involved in controlling RNA metabolism and transport. Here the isolation and partial characterization of plant cDNA clones which encode proteins homologous to the mammalian/fission yeast/budding yeast Ran/Spi/CNR proteins are reported. Higher plants appear to contain more than one gene per haploid genome which codes for Ran proteins. These genes are expressed in different plant tissues, including root tips and stems, known to contain mitotically active cells. The tobacco Ran-like proteins, like their mammalian and yeast homologues, are soluble proteins which are found in the cytoplasm and in the nucleus. In addition, it has been shown that overexpression of the tobacco Nt-Ran-A1 cDNA suppressed the phenotype of the temperature-sensitive fission yeast pim1-46 mutant. These results suggest that the plant Ran genes can be functionally equivalent to the mammalian/fission yeast/budding yeast Ran/Spi/CNR genes and that they may play a role: (i) in maintaining a coordinated cell cycle; (ii) in controlling RNA metabolism and transport in higher plants; and/or (iii) in protein import into the nucleus.

A rhythmic modulatory gating system in the stomatogastric nervous system of Homarus gammarus. III. Rhythmic control of the pyloric CPG

1. Two modulatory neurons, P and commissural pyloric (CP), known to be involved in the long-term maintenance of pyloric central pattern generator operation in the rock lobster Homarus gammarus, are members of the commissural pyloric oscillator (CPO), a higher-order oscillator influencing the pyloric network. 2. The CP neuron was endogenously oscillating in approximately 30% of the preparations in which its cell body was impaled. Rhythmic inhibitory feedback from the pyloric pacemaker anterior burster (AB) neuron stabilized the CP neuron's endogenous rhythm. 3. The organization of the CPO is described. Follower commissural neurons, the F cells, and the CP neuron receive a common excitatory postsynaptic potential from another commissural neuron, the large exciter (LE). When in oscillatory state, CP in turn excites the LE neuron. This positive feedback may maintain long episodes of CP oscillations. 4. The pyloric pacemaker neurons follow the CPO rhythm with variable coordination modes (i.e., 1:1, 1:2) and switch among these modes when their membrane potential is modified. The CPO inputs strongly constrain the pyloric period, which as a result may adopt only a few discrete values. This effect is based on mechanisms of entrainment between the CPO and the pyloric oscillator. 5. Pyloric constrictor neurons show differential sensitivity from the pyloric pacemaker neurons with respect to the CPO inputs. Consequently, their bursting period can be a shorter harmonic of the bursting period of the pyloric pacemakers neurons. 6. The CPO neurons seem to be the first example of modulatory gating neurons that also give timing cues to a rhythmic pattern generating network.

BICUCULLINE/BACLOFEN-INSENSITIVE GABA RESPONSE IN CRUSTACEAN NEURONES IN CULTURE

Neurones were dissociated from thoracic ganglia of embryonic and adult lobsters and kept in primary culture. When gamma-aminobutyric acid (GABA) was applied by pressure ejection, depolarizing or hyperpolarizing responses were produced, depending on the membrane potential. They were accompanied by an increase in membrane conductance. When they were present, action potential firing was inhibited. The pharmacological profile and ionic mechanism of GABA-evoked current were investigated under voltage-clamp with the whole-cell patch-clamp technique. The reversal potential of GABA-evoked current depended on the intracellular and extracellular Cl- concentration but not on extracellular Na+ and K+. Blockade of Ca2+ channels by Mn2+ was also without effect. The GABA-evoked current was mimicked by application of the GABAA agonists muscimol and isoguvacine with an order of potency muscimol&gt;GABA&gt;isoguvacine. cis-4-aminocrotonic acid (CACA), a folded and conformationally restricted GABA analogue, supposed to be diagnostic for the vertebrate GABAC receptor, also induced a bicuculline-resistant chloride current, although with a potency about 10 times lower than that of GABA. The GABA-evoked current was largely blocked by picrotoxin, but was insensitive to the GABAA antagonists bicuculline, bicuculline methiodide and SR 95531 at concentrations of up to 100 &micro;mol l-1. Diazepam and phenobarbital did not exert modulatory effects. The GABAB antagonist phaclophen did not affect the GABA-induced current, while the GABAB agonists baclophen and 3-aminopropylphosphonic acid (3-APA) never evoked any response. Our results suggest that lobster thoracic neurones in culture express a chloride-conducting GABA-receptor channel which conforms to neither the GABAA nor the GABAB types of vertebrates but shows a pharmacology close to that of the novel GABAC receptor described in the vertebrate retina.

A rhythmic modulatory gating system in the stomatogastric nervous system of Homarus gammarus. I. Pyloric-related neurons in the commissural ganglia

1. Operation of the pyloric neural network in the crustacean stomatogastric ganglion (STG) depends on constant firing of modulatory inputs from anterior ganglia. We have identified two bilaterally symmetrical pairs of these inputs in the commissural ganglia (COGs) of the European rock lobster Homarus gammarus. During operation of the pyloric CPG, they fired in pyloric time, out of phase with the pyloric pacemakers. 2. One of the pair was the commissural pyloric (CP) neuron and the other was homologous to the P neuron described in the spiny lobster Panulirus interruptus. We describe their morphology and location in the COG. The CP neuron projected to the STG via the superior esophageal nerve (son) and the stomatogastric nerve (stn), whereas the P neuron projected via the inferior esophageal nerve (ion) and stn. 3. To determine the total number of commissural neurons projecting to the STG, we used cobalt and Lucifer yellow backfilling from their cut axons in the stn. With the ion cut, there were between 8 to 12 labeled somata in each COG including CP cell body, whereas only 2 somata (including P) were labeled with the son cut. Among these neurons, CP and P appeared to be the only commissural neurons that fired in pyloric time and projected in the STG on the pyloric network. 4. The CP neuron produced monosynaptic excitatory postsynaptic potentials (EPSPs) on the pyloric dilator (PD), lateral pyloric (LP), and inferior cardiac (IC) neurons, whereas the P neuron produced monosynaptic EPSPs on all pyloric motoneurons but IC. The P neuron was gamma-aminobutyric acid immunoreactive, and the P-derived EPSPs in pyloric neurons were reversibly blocked by bicuculline, picrotoxin, and D-tubocurarine. 5. The CP and P neurons were electrically coupled, and modification of membrane potential in either one of them appreciably changed the firing frequency of the coupled neuron. 6. A negative-feedback loop from the pyloric anterior burster (AB) interneuron provoked simultaneous rhythmic inhibitions in the P and CP neurons. Together with the electrical coupling, the rhythmic inhibition contributed to synchronize firing of the two commissural neurons. 7. The following papers in the series of describe the modulatory and rhythmic control exerted by the P and CP neurons over the pyloric pattern generator.

A rhythmic modulatory gating system in the stomatogastric nervous system of Homarus gammarus. II. Modulatory control of the pyloric CPG

1. In the European rock lobster, Homarus gammarus, two bilaterally symmetrical pairs of commissural neurons, P and commissural pyloric (CP), evoke excitatory postsynaptic potentials in the neurons of the pyloric motor network. The present paper shows that the two commissural neurons also exert a modulatory control over the pyloric network. 2. The P and CP neurons were active during ongoing pyloric rhythms. Ongoing pyloric activity was terminated when the neurons were hyperpolarized to inhibit their firing. 3. When the pyloric network was quiescent, depolarizing either the P or CP neuron induced a robust pyloric rhythm. 4. We studied the actions of the P and CP neurons on individual pyloric neurons isolated in situ from network interactions by a photoinactivation techniques. The P neuron induced oscillatory properties in the pacemaker pyloric dilator (PD) neurons and the motor neuron, ventricular dilator (VD), whereas the CP neuron induced rhythmogenic properties in all the network neurons but VD. Together, the P-CP neurons modulated the entire pyloric network. The modulatory effects of the P-CP neurons did not outlast the duration of their discharge. 5. The P and CP neurons also controlled the firing frequency of all the pyloric neurons. They may, in addition, control phasing of the constrictor neurons discharges, but this effect was state-dependent and occurred only when the pyloric central pattern generator was functioning weakly. Their role in providing flexibility to the network operation appeared relatively limited. 6. We conclude that the P and CP neurons are good candidates for insuring long-term maintenance of pyloric network activity patterns.

A receptor with GABAC-like pharmacology in invertebrate neurones in culture

We have characterized in crustacean neurones in culture a receptor for gamma-aminobutyric acid (GABA) which conforms to the pharmacological profile of the proposed type-C GABA receptor (GABAC) found in the vertebrate retina. It is associated with a chloride-selective ion channel and is blocked by picrotoxin. It is neither inhibited by bicuculline nor activated by baclofen, while diazepam and phenobarbital are without modulatory effect. Like the GABAC-like receptor of the vertebrate retina it is activated by the folded GABA analogue cis-4-aminocrotonic acid (CACA). Desensitization is moderate allowing for a more sustained action of GABA. Single channel recordings revealed a bicuculline-resistant GABA- and CACA-activated chloride channel with a conductance about eight times higher than that described for the bicuculline-resistant GABA receptor channel from the rat retina.

Developmental, hormonal, and pathogenesis-related regulation of the tobacco class I beta-1,3-glucanase B promoter

The class I beta-1,3-glucanases are antifungal vacuolar proteins implicated in plant defense that show developmental, hormonal, and pathogenesis-related regulation. The tobacco enzymes are encoded by a small gene family with members derived from ancestors related to the present-day species Nicotiana sylvestris and N. tomentosiformis. We studied the expression in transgenic tobacco plants of a chimeric beta-glucuronidase (GUS) reporter gene fused to 1.6 kb of upstream sequence of the tobacco class I beta-1,3-glucanase B (GLB) gene, which is of N. tomentosiformis origin. Expression of the GUS reporter gene and the accumulation of class I beta-1,3-glucanase and its mRNA showed very similar patterns of regulation. In young seedlings the reporter gene was expressed in the roots. In mature tobacco plants it was preferentially expressed in lower leaves and roots and was induced in leaves by ethylene treatment and by infection with tobacco mosaic virus (TMV). Furthermore, it was down-regulated in cultured leaf discs by combinations of the hormones auxin and cytokinin. Histological studies of GUS activity showed that the GLB promoter shows highly localized expression in roots of seedlings. It is also expressed in a ring of cells around necrotic lesions induced by TMV infection, but not in cells immediately adjacent to the lesions or in the lesions themselves. The results of deletion analyses suggest that multiple positive and negative elements in the GLB promoter regulate its activity. The region from -1452 to -1193 containing two copies of the heptanucleotide AGCCGCC, which is highly conserved in plant-stress and defense-related genes, is necessary for high level expression in leaves. Additional regions important for organ-specific and regulated expression were: -568 to -402 for ethylene induction of leaves; -402 to -211 for expression in lower leaves and cultured leaf discs and for TMV induction of leaves; and -211 to -60 for expression in roots.

Muscarinic modulation of a pattern-generating network: control of neuronal properties

The aim of this article is to investigate the cellular mechanisms underlying cholinergic modulation of the pyloric network in the stomatogastric ganglion (STG) of the Cape lobster Jasus Ialandii. Bath application of the muscarinic agonists muscarine, oxotremorine, and pilocarpine on the STG activates a rhythmic pattern from a quiescent pyloric network. The mechanisms of this modulation were investigated on individual pyloric neurons isolated both from synaptic interactions within the network (by photoinactivation of most of the presynaptic neurons and pharmacological blockade of the remaining synapses) and from central inputs (by a sucrose block of the input nerve). All three muscarinic agonists activated bursting and plateau properties of all the neurons comprising the pyloric network. The activation was dose dependent, and was blocked by the muscarinic antagonists atropine, pirenzepine, and scopolamine. The oscillatory behavior triggered by the muscarinic stimulation was specific to each type of pyloric neuron. The isolated neuron AB had the shortest oscillation period and depolarizing phase. The constrictor neurons (LP, PY, IC) were the slowest oscillators, and only oscillated upon hyperpolarizing current injection. Under muscarinic modulation, the individual bursting activities of the isolated pyloric neurons were of the same type as their activities when isolated from the network but modulated by central inputs (Bal et al., 1988). The VD neuron is an exception since it was a rapid oscillator in the latter situation and became a slow oscillator when modulated by a single muscarinic agonist. To determine the relative importance of the muscarinic-dependent bursting properties of the individual pyloric neurons in the operation of the intact network, a progressive reconstruction of the synaptic circuitry was attempted. We found that under certain conditions of muscarinic modulation a new composite pacemaker could be created, composed of the electrically coupled VD, AB, and PD neurons. This can result in the generation of new pyloric patterns that were very sensitive to the membrane potential of individual network neurons. The data also confirmed that, in a rhythmic "pattern-generating network," the pacemaker role may not be definitely attributed to a given neuron but instead could be assigned to other neurons by modulation of their respective oscillatory capabilities.