Wheezing during the first year of life in infants from low-income population: a descriptive study

BACKGROUND

Recurrent wheezing (RW) plays an important role in the morbidity and mortality of children during the first year of life in developing regions and its actual incidence in those areas is virtually unknown.

METHODS AND RESULTS

This study describes the occurrence of wheezing during the first year of life in a birth cohort of 188 infants followed monthly and living in a poor urban area in Santiago de Chile. This study showed that 80.3 % of the infants in the cohort had one or more wheezing episode during the first year of life, 43.1 % had RW (3 or more wheezing episodes), 44.1 % had their first wheezing within the first three months of life and 13.3 % had pneumonia (PN). Having one or more episode of wheezing in the first three months of life was the main risk factor for suffering from RW during the first year and RW was a significant risk factor for having PN.

CONCLUSIONS

This study found a high prevalence of RW in infants from a low-income population during the first year of life with the disease starting very early in their lives, progressing with more frequent episodes and being significantly associated to PN, particularly in the first 6 months of life.

[Neuropathies due to vasculitis in infancy]

INTRODUCTION

Vasculitis are characterised by the inflammatory infiltrate, chiefly of mononuclear cells, in the walls of the blood vessels, which can lead to occlusion with necrosis and the subsequent infarction of the affected tissue.

AIMS

The Objective of this study was to determine the clinical, anatomicopathological and neurophysiological aspects of vasculitic neuropathies in infancy.

PATIENTS AND METHODS

Each patient was submitted to the following tests: a complete hemogram, systemic lupus erythematosus cells (LE cells), lupus anticoagulant, antinuclear antibodies, neutrophil anticytoplasmic antibodies, venereal disease research laboratory test (VDRL), erythrocyte sedimentation rate, liver transaminases, serological testing for hepatitis C, B and A, cytochemical study of the cerebrospinal fluid, study of motor and sensory conduction, electromyography and nuclear magnetic resonance, when required; a biopsy of the sural nerve was performed, which was replaced by a necropsy if the patient died.

RESULTS

15 patients from a total of 25 who were studied had vasculitic neuropathies; the most usual presentation was multiple mononeuropathy; aetiologies found included microscopic polyangiitis, systemic lupus erythematosus, JRA, overlap syndrome and several undetermined vasculitis. Of the patients who were submitted to a biopsy, 75% showed signs of vasculitis, which affected the small and medium sized vessels in 62.5% of patients.

CONCLUSIONS

The presence of neuropathy in association with symptoms and signs of systemic involvement suggested the possibility of a neuropathy in the course of a vasculitis. The examination of biopsy specimens of the sural nerve is useful for the diagnosis and classification of the aetiology of vasculitis. Response to treatment with immunosuppressant drugs was good, both in the case of the neuropathy and of the underlying disease.

Genotipo y expresión fenotípica de la hemocromatosis hereditaria en España

INTRODUCTION

The prevalence of C282Y homozygosity in patients with hereditary hemochromatosis (HH) has been reported to be markedly lower in the Mediterranean Basin than in northern Europe. In Spain, the available data are contradictory and limited to small series in specific regions. The objective of this study is to determine the prevalence of the 2 main HFE gene mutations in a large series of unrelated Spanish patients with HH from different geographical origins.

PATIENTS AND METHOD

The criteria for HH diagnosis were: repeat serum transferrin saturation index (> 45% plus C282Y homozygosity and/or hepatic iron index (> 1.9 of dry liver weight in non-cirrhotic patients or (> 4.1 in patients with liver cirrhosis. Cases in related individuals were excluded. Demographic data, clinical expression, iron parameters and HFE gene mutations (C282Y and H63D) were assessed in 222 patients.

RESULTS

A total of 83.3% of patients were C282Y homozygous and 5% were compound heterozygous (C282Y/H63D). No significant differences in phenotypic expression or in the frequency of C282Y homozygosity were observed between patients born in the North and South of Spain.

CONCLUSION

The genotypic and phenotypic expression of HH in Spain is very similar to that reported in Northern Europe. Thus, the genetic heterogeneity described in some Southern European regions cannot be considered a common feature to all countries of the Mediterranean Basin.

[Recurring ischemic cerebral infarction caused by primary thrombocytosis in infancy]

INTRODUCTION

Ischemic cerebrovascular disease includes a set of entities that are produced by disorders in components of the blood, the blood flow, the walls of blood vessels or the heart, and can be anatomical, functional or even mixed.

CASE REPORT

We describe the case of an 18-month-old male patient with compensated celiac disease, with repeated ischemic strokes in different territories, including the right posterior cerebral artery and middle cerebral artery, in the course of a hypercoagulable state due to essential thrombocytosis. Computerised axial tomography scans, brain angioresonance, a complete blood chemistry analysis and bone marrow biopsy were all performed and confirmed the previous diagnosis. Exchange transfusion, antiplatelet drugs and a platelet production inhibitor (anagrelide) were begun as therapy. At present, the patient is 2 years old and still has a slight direct hemiparesis, which is complete and predominantly faciobrachial, with no alterations to language.

CONCLUSIONS

Cerebral infarctions in infancy are infrequent, and their presentation obliges the attending clinician to seek causes that are not usual. In our patient the hypocoagulability came about due to essential thrombosis, which is rare in infancy. The cause behind the infarction determines the chances of its recurring. Acetylsalicylic acid did not prove to be effective for this purpose. We suggest using carbamazepine for the treatment of kinesigenic dystonias.

Outbreak of TEM-24-producing Enterobacter aerogenes in a Spanish hospital

Organisms encoding multidrug resistance genes are becoming increasingly prevalent. During a 2-month period (December, 2000, to January, 2001), 83 consecutive isolates of Enterobacter spp. were collected in our microbiology department. Antibiotic susceptibility was determined using the Vitek II automatic system. We selected strains with decreased susceptibility to extended-spectrum cephalosporins. The double-disk potentiation test was positive in 10 of these strains, indicating the presence of extended-spectrum beta-lactamases (ESBLs). Polymerase chain reaction (PCR), isoelectric focusing (IEF), and sequencing identified TEM 24 beta-lactamase in the 10 selected E. aerogenes. Random amplification of polymorphic DNA (RAPD-PCR) revealed the same clonal origin for all the strains tested and strongly suggest an outbreak of multidrug-resistant E. aerogenes. To follow up the trends in ESBLs-producing Enterobacter infections in the hospital over time, we repeated the study 1 year later (December, 2001, to February, 2002). Only three ESBLs-producing Enterobacter were found. All of them corresponded to the previously characterized clone.

[Can sural nerve biopsy be used to orientate the treatment of chronic inflammatory demyelinating polyneuropathy?]

INTRODUCTION

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired neuropathy characterized by demyelination of the peripheral nerves and roots. The course of the illness is progressively chronic or of relapses and remissions. Biopsy of the sural nerve is not essential for diagnosis. It is therefore not necessary to carry it out on all occasions, but probably permits a more rational approach to treatment.

OBJECTIVE

To show whether biopsy of the sural nerve is useful for orientation of the treatment required in cases of CIDP.

PATIENTS AND METHODS

We studied a total of 16 patients admitted to hospital with a diagnosis of CIDP. They had neurophysiological studies, sural nerve biopsy and other studies to rule out other diagnoses. The patients were assigned to the therapeutic protocols recommended. During 8 years of follow up we compared the response to treatment with intacglobin/plamapheresis, steroids and cytostatic drugs.

RESULTS

It was highly significant (p< 0.001) that the patients with axon lesions on sural nerve biopsy did not respond to treatment with intac globin/plasmapheresis or steroids but did respond to cyclophosphamide, without any serious adverse effects being seen.

CONCLUSIONS

Axonal histopathological lesions of CIDP at the onset of the disease may require cytostatic treatment since they do not usually improve on standard treatment. Sural biopsy is usually invaluable in such cases.

Diverse BF recombinants have spread widely since the introduction of HIV-1 into South America

OBJECTIVE

To describe the genetic diversity of HIV-1 in South America by full genome sequencing and analysis.

METHODS

Purified peripheral blood mononuclear cell DNA from HIV-infected individuals in Argentina, Uruguay and Bolivia was used to amplify full HIV-1 genomes. These were sequenced using the ABI 3100 automated sequencer and phylogenetically analysed.

RESULTS

Twenty-one HIV-1 strains from three South American countries, 17 of which were pre-screened by envelope heteroduplex mobility assay (HMA), were studied. Ten out of 10 HMA subtype F and four out of seven HMA subtype B strains were actually BF recombinants upon full genome analysis. Two BF recombinants from Argentina and two from Uruguay had the same structure, representing a new circulating recombinant form termed CRF12_BF(ARMA159). Twelve other BF recombinants had structures related to CRF12 but with additional segments of subtype B; each was unique. BF recombinants were temporally and geographically widespread, found as early as 1986-1987 in vertically infected Argentinian children and in Argentina, Uruguay, and Bolivia.

T-type Ca(2+) channels mediate neurotransmitter release in retinal bipolar cells

Transmitter release in neurons is thought to be mediated exclusively by high-voltage-activated (HVA) Ca(2+) channels. However, we now report that, in retinal bipolar cells, low-voltage-activated (LVA) Ca(2+) channels also mediate neurotransmitter release. Bipolar cells are specialized neurons that release neurotransmitter in response to graded depolarizations. Here we show that these cells express T-type Ca(2+) channel subunits and functional LVA Ca(2+) currents sensitive to mibefradil. Activation of these currents results in Ca(2+) influx into presynaptic terminals and exocytosis, which we detected as a capacitance increase in isolated terminals and the appearance of reciprocal currents in retinal slices. The involvement of T-type Ca(2+) channels in bipolar cell transmitter release may contribute to retinal information processing.

Impairment of H+-K+-ATPase-dependent proton transport and inhibition of gastric acid secretion by ethanol

Ethanol (1-20% vol/vol) caused a dose-dependent reduction in the basal rate of acid formation in isolated rabbit gastric glands with a calculated EC(50) value of 4.5 +/- 0.2%. Ethanol also reduced ATP levels in isolated gastric glands and in cultured parietal cells (EC(50): 8.8 +/- 0.4% and 8.5 +/- 0.2%, respectively) and decreased both basal and forskolin-stimulated cAMP levels. In studies carried out in gastric gland microsomes, ethanol inhibited the hydrolytic activity of H+-K+-ATPase(EC(50): 8.5 +/- 0.6%), increased passive proton permeability (EC(50): 7.9%), and reduced H+-K+-ATPase-dependent proton transport (EC(50): 3%). Our results show that the inhibition of gastric acid secretion observed at low concentrations of ethanol (< or =5%) is mainly caused by the specific impairment of H+-K+-ATPase-dependent proton transport across cell membranes rather than inhibition of the hydrolytic activity of H+-K+-ATPase, reduction in the cellular content of ATP, or increase in the passive permeability of membranes to protons, although these changes, in combination, must be relevant at concentrations of ethanol > or =7%.

A 5-HT(7) receptor-mediated depolarization in the anterodorsal thalamus. I. Pharmacological characterization

Little is currently known regarding the electrophysiological response elicited by 5-hydroxytryptamine-7 (5-HT(7)) receptor stimulation in the brain. Previous anatomical studies have shown that the anterior thalamus expresses a high density of 5-HT7 receptors. Therefore, we used whole-cell recording techniques in the in vitro brain slices to examine the effects of serotonin on neurons of the anterodorsal nucleus of the thalamus (ADn). Bath application of 5-HT induces a large membrane depolarization and inward current in neurons of the ADn. Since these cells expressed 5-HT7 receptor mRNA, as determined by single-cell reverse transcriptase-polymerase chain reaction, we pharmacologically characterized the 5-HT receptor mediating this response. We found that the 5-HT1 and 5-HT7 agonists 5-carboxamidotryptamine (5-CT) and 5-methoxytryptamine mimicked the response to 5-HT, whereas the 5-HT2 agonist 2,5-dimethoxy-4-iodoamphetamine did not. Consistent with the involvement of a 5-HT7 receptor, 5-CT was approximately 18 times more potent than 5-HT. Furthermore, administration of the 5-HT(1A) and 5-HT7 agonist 8-hydroxydipropylaminotetralin mimicked and antagonized the effect of serotonin, suggesting it acted as a partial agonist. To determine if either the 5-HT1 or 5-HT7 receptor mediated the 5-HT-induced inward current, we used antagonists. We found that the 5-HT7 ligands ritanserin, methylsergide, LSD, and mesulergine could inhibit the 5-HT-induced inward current, whereas the 5-HT1 antagonist cyanopindolol had no effect. The pA(2) value determined for mesulergine closely approximated that expected for a 5-HT7 receptor. Finally, we found that bath application of the selective antagonist SB-269770 blocks the 5-HT-induced inward current. These results identify the receptor mediating the serotonin-induced membrane depolarization in the ADn as the 5-HT7 subtype.

A 5-HT(7) receptor-mediated depolarization in the anterodorsal thalamus. II. Involvement of the hyperpolarization-activated current I(h)

Previous studies have shown that 5-hydroxytryptamine (5-HT) can modulate the hyperpolarization-activated nonselective cation current (I(h)) to elicit a membrane depolarization in neurons. However, the receptor subtype involved in this response remains controversial. In the accompanying study, we have identified a 5-HT7 receptor-mediated depolarization in the anterodorsal nucleus of the thalamus (ADn). In the present study, we have examined the possible role of I(h) in mediating this 5-HT7 receptor-mediated depolarization. We used the blind tight-seal patch clamp technique to examine the ability of 5-HT to modulate I(h) in the ADn. We found that 5-HT induced a shift in the voltage dependence of I(h) to more depolarized potentials. The pharmacology of the receptor mediating this effect was consistent with that of a 5-HT7 receptor. Since the 5-HT7 receptor is coupled positively to adenylate cyclase, we examined the cAMP dependence of the 5-HT-induced modulation of I(h). Intracellular addition of cAMP mimicked and occluded the 5-HT response. Conversely, in the presence of the protein kinase inhibitors H-8 and staurosporine, ADn neurons still expressed a 5-HT-induced shift in the voltage dependence of I(h). These results suggest that 5-HT regulates I(h) in the ADn through a cAMP-dependent but protein kinase A (PKA)-independent mechanism. To determine the contribution of I(h) to the 5-HT7 receptor-mediated depolarization, we used the selective I(h) blocker ZD7288. This compound greatly reduced the depolarizing response elicited by activation of 5-HT7 receptors. We conclude that 5-HT7 receptors depolarize ADn neurons primarily by increasing I(h) through a cAMP-dependent, PKA-independent mechanism.

Nucleoplasmin binds to nuclear pore filaments and accumulates in specific regions of the nucleolar cortex

Nucleoplasmin is a karyophilic protein that is involved in nucleosome formation and decondensation of chromatin, although other precise functions and modes of action of this molecule are still poorly understood. In the present paper we describe a novel nucleocytoplasmic transport assay that has enabled us to study the nuclear distribution of nucleoplasmin following its transport into the nucleus. Single Xenopus laevis oocyte nuclei were isolated and incubated with Xenopus egg extract containing colloidal gold-conjugated nucleoplasmin. After a period of incubation, each individual nucleus was processed for electron microscopy. The nuclear accumulation of nucleoplasmin was dependent upon the karyophilic properties of the protein, since BSA-conjugated gold particles did not enter the nuclear interior under the same experimental conditions. Once inside the nucleus, nucleoplasmin was detected in tracks emanating from the nuclear pores and reaching the nucleolus. Additionally, we found a striking accumulation of nucleoplasmin in specific areas of the nucleolar cortex. These perinucleolar regions were surrounded by areas of electron density similar to that of the fibrillar centers. Our results indicate that nucleoplasmin may play an important role in the transcription of ribosomal precursors. Moreover, this nucleocytoplasmic transport assay will enable the determination of the precise intranuclear localization of other karyophilic proteins.

Molecular characterization of human immunodeficiency virus type 1-infected individuals from bolivia reveals the presence of two distinct genetic subtypes B and F

Thirty HIV-1-positive samples from Bolivia were genetically characterized on the basis of HMA and DNA sequencing, revealing the presence of B and F subtypes, in accordance with the molecular epidemiology pattern already described for other South American countries such as Brazil and Argentina. The interpatient divergence of subtype B Bolivian specimens was on average 14.2% (4.3-19.8%) at the nucleotide level, whereas the two unlinked subtype F samples (BO23 and BO29) were only 8.2% divergent, suggesting a more recent introduction of this subtype in the country. In our study group, which represents 13% of the HIV/AIDS cases already described in Bolivia as of May 1996, the transmission occurred more frequently through heterosexual exposures (46.7%), followed by homosexual (23.3%), bisexual (10%), intravenous drug use (3.3%), and vertical (3.3%); in one case the potential exposure category could not be defined (3.3%). No association could be established between exposure categories, gender, or clinical classification and subtype distribution in the Bolivian HIV/AIDS patients.

Multicenter retrospective study of response to interferon in chronic hepatitis B

AIM

The only agent known to have a lasting beneficial effect in chronic hepatitis B is interferon alpha, which achieves long-term remission in 25-40% of the patients. The goals of treatment are to induce clearance of HBV DNA from serum, to return serum aminotransferases to normal, and to improve histological findings in the liver. The most important factors predictive of response to treatment are high serum aminotranferases levels, low serum HBV DNA concentrations, and active histologic changes on liver biopsy. The aim of this study was to assess the response to interferon alpha in patients with chronic hepatitis B and to analyze the factors predictive of response.

METHODS

We conducted a multicenter retrospective study to investigate the effect of interferon treatment in 132 patients with chronic hepatitis B in overall terms and based on HBeAg, and factors predictive of response.

RESULTS

A overall sustained response was noted in 59 of 132 interferon-treated patients (45%) and 61 patients were nonresponders (46%). 12 patients relapsed (9%). None of the patients had negative HBsAg. No difference was observed in the response rate between the two treatment groups (HBeAg-positive and HBeAg-negative patients). Overall, high initial levels of serum AST and ALT predicted a good response. Age and liver biopsy findings were factors predictive of response in HBeAg-positive and HBeAg-negative patients respectively. Sex, epidemiological factors, treatment and type of virus did not correlate with the response to interferon.

CONCLUSIONS

A sustained response to interferon alpha was observed in 45% of the patients with chronic hepatitis B. HBeAg seroconversion was found in up to 50% of HBeAg-positive patients. None of the patients had negative HBsAg. Overall, the response rate was higher in patients with high pretreatment serum aminotransferase levels. Age was the predictive factor in HBeAg-positive patients, and histological features were predictive in the HBeAg-negative group. However, further studies in a larger patient population are necessary to obtain well-substantiated conclusions.

Real-time analysis of preprotachykinin promoter activity in single cortical neurons

Technological limitations have hindered the study of gene elements regulating transcription within CNS neurons. In the present stuides, rat cortical brain slices endogenously expressing the preprotachykinin (PPT) gene were transfected with gene constructs encompassing green fluorescent protein (GFP) under the control of the PPT promoter. These slices were maintained in organotypic culture so that the fluorescence intensity within individual living cells could be quantified using laser scanning confocal microscopy before and after application of stimulatory agents. Combined treatment with forskolin and elevated potassium significantly increased expression of both endogenous PPT mRNA and the PPT promoter-GFP construct. The ability to follow fluorescence changes within single neurons in real time offers a powerful "within-subject" experimental approach for analysis of neural gene promoters.

RNase II removes the oligo(A) tails that destabilize the rpsO mRNA of Escherichia coli

Polyadenylation controls mRNA stability in procaryotes, eucaryotes, and organelles. In bacteria, oligo(A) tails synthesized by poly(A) polymerase I are the targets of the 3'-to-5' exoribonucleases: polynucleotide phosphorylase and RNase II. Here we show that RNase II very efficiently removes the oligo(A) tails that can be used as binding sites by PNPase to start degradation of the rpsO mRNA. Both enzymes are impeded by the secondary structure of the transcription terminator at the 3' end of the mRNA. RNase II mostly generates tailless transcripts harboring 2 unpaired nt downstream of the transcription terminator hairpin, whereas PNPase releases molecules that exhibit a single-stranded stretch of 5-7 nt terminated by a tail of 3-5 As. The rpsO mRNAs whose oligo(A) tails have been removed by RNase II are more stable than oligoadenylated molecules that occur in strains deficient for RNase II. Moreover, the rpsO mRNA is stabilized when RNase II is overproduced. This modulation of mRNA stability by RNase II is only observed when poly(A) polymerase I is active. These in vivo data demonstrate that RNase II protects mRNAs ending by stable terminal hairpins, such as primary transcripts, from degradation by poly(A)-dependent ribonucleases.

Calcium-independent afterdepolarization regulated by serotonin in anterior thalamus

Previous studies have identified an afterdepolarization (ADP) in thalamocortical neurons that is mediated by an upregulation of the hyperpolarization-activated current I(h). This ADP has been suggested to play a key role in the generation of spindle oscillations. In the lateral geniculate nucleus, upregulation of I(h) has been shown to be signaled by a rise in intracellular calcium leading to the activation of adenylate cyclase and formation of cAMP. However, it is unclear how generalizable this mechanism is to other thalamic nuclei. We have used whole cell recording to examine the electrophysiological properties of neurons of the anterodorsal thalamic nucleus, a nucleus thought not to undergo spindle oscillations. We now report that cells in this nucleus also display an ADP mediated by I(h). Surprisingly, the ADP and the underlying upregulation of I(h) persisted even after buffering intracellular calcium and blocking calcium influx. These results indicate that, in neurons of the anterodorsal thalamic nucleus, an I(h)-mediated ADP can occur through a mechanism that does not involve a rise in intracellular calcium. We next examined the possibility that this calcium-independent ADP might be modulated by serotonin. Serotonin produced a robust enhancement in the amplitude of the ADP even after strong buffering of intracellular calcium and blockade of calcium channels. These results indicate that neurons of the anterodorsal thalamic nucleus display a calcium-independent, I(h)-mediated ADP and that this ADP is a target for regulation by serotonin. These findings identify a novel mechanism by which serotonin can regulate neuronal excitability.

Cloning and characterization of cDNA encoding cardosin A, an RGD-containing plant aspartic proteinase

Cardosin A is an abundant aspartic proteinase from pistils of Cynara cardunculus L. whose milk-clotting activity has been exploited for the manufacture of cheese. Here we report the cloning and characterization of cardosin A cDNA. The deduced amino acid sequence contains the conserved features of plant aspartic proteinases, including the plant-specific insertion (PSI), and revealed the presence of an Arg-Gly-Asp (RGD) motif, which is known to function in cell surface receptor binding by extracellular proteins. Cardosin A mRNA was detected predominantly in young flower buds but not in mature or senescent pistils, suggesting that its expression is likely to be developmentally regulated. Procardosin A, the single chain precursor, was found associated with microsomal membranes of flower buds, whereas the active two-chain enzyme generated upon removal of PSI is soluble. This result implies a role for PSI in promoting the association of plant aspartic proteinase precursors to cell membranes. To get further insights about cardosin A, the functional relevance of the RGD motif was also investigated. A 100-kDa protein that interacts specifically with the RGD sequence was isolated from octyl glucoside pollen extracts by affinity chromatography on cardosin A-Sepharose. This result suggests that the 100-kDa protein is a cardosin A receptor and indicates that the interaction between these two proteins is apparently mediated through RGD recognition. It is possible therefore that cardosin A may have a role in adhesion-mediated proteolytic mechanisms involved in pollen recognition and growth.

Characteristic distribution of HTLV type I and HTLV type II carriers among native ethnic groups in South America

To confirm the geographic and ethnic segregation of HTLV-I and HTLV-II carriers in native populations in South America, we have conducted a seroepidemiological study of native populations in South America, including HTLV-I carriers distributed among seven ethnic groups in the Andes highlands of Colombia, Peru, Bolivia, Argentina, and Chile, and two ethnic groups on Chiloe Island and Easter Island; and HTLV-II carriers distributed among seven ethnic groups of the lowlands along the Atlantic coast of Colombia, Orinoco, Amazon, and Patagonia, and one ethnic group on Chiloe Island. The incidence rate of HTLV-I and HTLV-II carriers varied among the ethnic groups, ranging from 0.8 to 6.8% for HTLV-I seropositivity and from 1.4 to 57.9% for HTLV-II seropositivity. A new HTLV-I focus was found among the Peruvian Aymara (1.6%), the Bolivian Aymara (5.3%) and Quechua (4.5%), the Argentine Puna (2.3%), and the Chilean Atacama (4.1%), while on HTLV-II focus was found among the Brazilian Kayapo (57.9%), the Paraguayan Chaco (16.4%), and the Chilean Alacalf (34.8%) and Yahgan (9.1%). The distribution of HTLV-I/II foci showed a geographic clustering of HTLV-I foci in the Andes highlands and of HTLV-II foci in the lowlands of South America. It was thus suggested that South American natives might be divided into two major ethnic groups by HTLV-I and HTLV-II carrier state.

Muscarinic receptors regulate two different calcium-dependent non-selective cation currents in rat prefrontal cortex

Pyramidal neurons of layer V in rat prefrontal cortex display a prominent fast afterdepolarization (fADP) and a muscarinic-induced slow afterdepolarization (sADP). We have shown previously that both of these ADPs are produced by the activation of calcium-dependent non-selective cation currents. In the present report we examine whether they represent two distinct currents. In most pyramidal neurons recorded with caesium gluconate-based intracellular solution, a calcium spike is followed by a fast decaying inward aftercurrent (IfADP). The decay of IfADP is monoexponential with a time constant (t) of approximately 35 ms. Administration of carbachol (10-30 microm) increases the time constant of this decay by approximately 80% and induces the appearance of a much slower inward aftercurrent (IsADP). IfADP recorded in control conditions and in the presence of carbachol increases linearly with membrane hyperpolarization. In contrast, the carbachol-induced IsADP decreases with membrane hyperpolarization. When the sodium driving force across the cell membrane was reduced, IfADP was found to reverse at around -40 mV whereas IsADP remain inward over the same voltage range tested. Finally, bath administration of flufenamic acid (100 microm-1 mm) selectively blocks the carbachol-induced IsADP without a significant effect on the amplitude of IfADP. These differences in the electrical and pharmacological properties of IfADP and IsADP suggest that they were mediated by two distinct non-selective cation currents.

Regulation of membrane excitability in the central nervous system by serotonin receptor subtypes

Serotonin exerts multiple electrophysiological effects on neurons of the central nervous system. It is now known that this diversity reflects at least in part the existence of multiple serotonin receptor subtypes. An example of this occurs in the CA1 region of the hippocampus where as many as ten different serotonin receptor subtypes appear to be expressed. Recent electrophysiological studies have been able to assign specific functional roles to at least 5 of these receptors. These receptors are differentially expressed in the two different cell types present in this region, pyramidal cells and GABAergic interneurons, and mediate different effects on membrane excitability. This distribution is consistent with the different functional roles played by these cells in hippocampus. Thus the differential expression of serotonin receptor subtypes in the CA1 region allows serotonin to modify the function of hippocampal neuronal networks in a manner that is both selective and precise.

The nuclear basket of the nuclear pore complex is part of a higher-order filamentous network that is related to chromatin

We have achieved well-preserved nuclear basket structures in amphibian nuclear envelope spreads dried by the critical point method after tannic acid fixation, and we have compared these images with those obtained from conventional sections of amphibian oocyte nuclei. In cross sections, bundles of filaments from adjacent nuclear pore complexes were interconnected at regular distances, building up a higher-order network. Sometimes these bundles were observed to extend inward to amplified nucleoli located near the nuclear envelope. Furthermore, immunoelectron analysis indicated that DNA and histones were localized at these intranuclear filaments, suggesting a close relationship between chromatin and nuclear pore complexes. A model is proposed by which the intranuclear filaments associated with adjacent nuclear pore complexes create a regular higher-order network, which extends into the nucleus.

Molecular characterization of human and rat RGS 9L, a novel splice variant enriched in dopamine target regions, and chromosomal localization of the RGS 9 gene

A novel splice variant of RGS 9 was isolated from a rat hypothalamus, human retina, and a human kidney (Wilm's) tumor. This variant, termed RGS 9L, differs from the retinal form (termed RGS 9S) identified previously in that it contains a 211- (rat) or 205- (human) amino acid proline-rich domain on the carboxyl terminus. The pattern of RGS 9 mRNA splicing was tissue specific, with striatum, hypothalamus- and nucleus accumbens expressing RGS 9L, whereas retina and pineal expressed RGS 9S almost exclusively. This pattern of mRNA splicing seemed to be highly conserved between human and rodents, suggesting cell-specific differences in the function of these variants. Transient expression of RGS 9L augmented basal and beta-adrenergic receptor-stimulated adenylyl cyclase activity while suppressing dopamine D2 receptor-mediated inhibition. Furthermore, RGS 9L expression greatly accelerated the decay of dopamine D2 receptor-induced GIRK current. These results indicate RGS 9L inhibits heterotrimeric Gi function in vivo, probably by acting as a GTPase-activating protein. The human RGS 9 gene was localized to chromosome 17 q23-24 by radiation hybrid and fluorescent in situ hybridization analyses. The RGS 9 gene is within a previously defined locus for retinitis pigmentosa (RP 17), a disease that has been linked to genes in the rhodopsin/transducin/cGMP signaling pathway.