The murine gene, Traube, is essential for the growth of preimplantation embryos

Little is known about the genetic control of preimplantation development. We have isolated, characterized, and mutated a previously undescribed mouse gene, Traube (Trb), essential for preimplantation development. Similar protein coding sequences are found in rats, humans, and yeast. The TRB protein contained two amino-terminal acidic domains, a leucine zipper, and three putative nuclear localization signals. The Trb gene was expressed at low levels ubiquitously early in development and became restricted to the liver and the central nervous system from E11.5 onward. Myc-tagged TRB protein was localized to the nucleus, and in a large proportion of the cells to the nucleoli. The Trb mutant embryos halted in development at the compacted morula stage at E2.5. At E3.5 they started to decompact and a day later they disintegrated and died. The observed defect was cell autonomous, as mutant cells failed to participate in the formation of chimeric embryos. The Trb mutant embryos showed a 50% reduction of the total cell number. The mutant embryos exhibited a paucity of ribosomes, polyribosomes, and rough endoplasmic reticulum. This paucity of ribosomes together with the localization of TRB to the nucleoli, the site of ribosome synthesis, suggests that TRB is involved in the synthesis of ribosomes.

Relationship of serum leptin levels with body composition and sex steroid and insulin levels in men and women

Whether the higher serum leptin levels in women are due to gender differences in fat mass or to other factors such as sex steroids remains unclear. In addition to sex steroids, serum insulin levels also appear to be related to leptin levels, although whether this effect is independent of the effects of body composition is unclear. The purpose of this study was to identify the major determinants of circulating serum leptin levels. We studied a large, population-based cohort of 345 men (23 to 90 years), 137 premenopausal women (21 to 54 years), and 212 postmenopausal women (34 to 94 years), including 47 women on hormone replacement therapy (HRT). Serum leptin levels were related to body composition as assessed by dual-energy x-ray absorptiometry (DEXA) and to circulating sex steroid and insulin levels. Serum leptin levels remained significantly higher in women versus men even after adjustment for fat mass, and leptin levels were significantly correlated with fat mass independently of age. By univariate analyses, logarithmically transformed serum leptin levels correlated positively with bioavailable estrogen ([E] estradiol plus estrone) in postmenopausal women not on HRT, and negatively with total and bioavailable testosterone (T) levels in men. Serum insulin levels were directly related to leptin levels regardless of gender and age. By multivariate analyses, fat mass, lean mass, and insulin levels were the strongest predictors of leptin levels in all groups. In addition, bioavailable E entered the model in the postmenopausal women not on HRT. These studies indicate that the fat mass, lean mass, and insulin level are the major determinants of the serum leptin level in adults. Moreover, after adjusting for these variables, bioavailable E also explains a significant proportion of the variance in leptin levels among postmenopausal women not on HRT.

A role for adenosine in modulating cardio-respiratory responses: a mini-review

Evidence is provided that purine nucleotides play a major role in modulating cardio-respiratory control through actions at specific sites in the central nervous system (CNS). The accumulation of adenosine in the extracellular space of the nucleus tractus solitarius (NTS) on hypothalamic defence area stimulation is described, and is shown to result from the extracellular breakdown of neurally released adenosine triphosphate (ATP). The actions of adenosine in modulating synaptic actions in the NTS are discussed in relation to the potential presynaptic action of adenosine in modulating transmitter release. Actions of adenosine and ATP at other sites in the medulla concerned with cardio-respiratory control are discussed. The inter-relationships between ATP and adenosine are mentioned.

Regulation of estrogen receptor mRNA by 2,3,7,8-tetrachlorodibenzo-p-dioxin as measured by competitive RT-PCR

Environmental contaminants, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), cause alterations in gene expression. In this study, we measured the regulation of estrogen receptor (ER) mRNA in female CD-1 mice by competitive RT-PCR. Previous work suggests that ER protein levels are affected by TCDD, but how this is regulated is uncertain. These studies found no significant changes in ER mRNA levels, but the methods used (Northern blot analysis and RNase protection assays) lack sensitivity for measuring the low levels of RNA transcript, such as ER mRNA. The method described here offers an excellent alternative for quantifying the changes in mRNA levels. Internal competitors were created with gene-specific primers for ER and beta-actin by PCR reactions at low annealing temperatures. For each sample, the mRNA levels of ER and beta-actin were determined. Using competitive RT-PCR, the relative changes in ER mRNA from TCDD-treated and control animals were determined after normalization with the levels of beta-actin mRNA. The ER mRNA from female CD-1 mice treated with TCDD (single dose 5 micrograms/kg, i.p., 4 days) was found to be significantly suppressed as compared with the vehicle control in all tissues examined. TCDD decreased ER mRNA in the liver (30.1%) as expected. However, the greatest effect was in the reproductive tissues, with a 64.2% reduction in ER mRNA in the ovary. This is the first demonstration that TCDD causes tissue-specific downregulation of ER mRNA. These effects may contribute to the tissue-specific toxicity of TCDD.

Failure-free survival following brachytherapy alone or external beam irradiation alone for T1-2 prostate tumors in 2222 patients: results from a single practice

PURPOSE

To evaluate failure-free survival (FFS) for brachytherapy (BT) alone compared to external beam radiotherapy (EBRT) alone for Stage T1-2 Nx-No Mo patients over the same time period by a single community-based practice in the prostate-specific antigen (PSA) era.

MATERIALS AND METHODS

The database of Arizona Oncology Services (a multiphysician radiation oncology practice in the Phoenix metropolitan area) was reviewed for patients meeting the following criteria: (1) T1 or T2 Nx-No Mo prostate cancer; (2) no prior or concurrent therapy including hormones; (3) treatment period 12/88-12/95; and (4) treatment with either EBRT alone or BT alone ((125)I or (103)Pd). This yielded 1527 EBRT and 695 BT patients; no patients meeting the above criteria were excluded from analysis. Median follow-up for EBRT patients was 41.3 months and, for BT patients, 51.3 months. Patients were not randomized to either therapy but rather received EBRT or BT based upon patient, treating, and/or referring physician preference. PSA failure was defined according to the ASTRO consensus guidelines. The median patient age was 74 years for both groups.

RESULTS

Failure-free survival at 5 years for EBRT and BT are 69% and 71%, respectively (p = 0.91). For T stage, no significant difference in FFS at 5 years is observed between EBRT and BT for either T1 (78% vs. 83%, p = 0.47) or T2 (67% vs. 67%, p = 0.89) tumors. Analysis by Gleason score shows superior outcomes for Gleason 8-10 lesions treated with EBRT vs. BT (5-year FFS 52% vs. 28%, p = 0.04); outcomes for lower grade lesions (Gleason 4-6) when analyzed by Gleason score alone do not significantly differ according to treatment received. Patients with initial PSA values of 10-20 ng/dL have an improved FFS with EBRT vs. BT at 5 years (70% vs. 53%, p = 0.001); outcomes for patients with initial PSA ranges of 0-4 ng/dL, of > 4-10 ng/dL, and > 20 ng/dL did not differ significantly by treatment received. FFS was also determined for presenting Gleason score/PSA combinations; all Gleason combinations in the initial PSA range >10-20 ng/dL had superior outcomes with EBRT compared to BT, and this reached statistical significance for Gleason scores of 2-4 (72% vs. 58%, p = 0.026), Gleason 7 (67% vs. 28%, p = 0.002), and Gleason 8-10 (63% vs. 23%, p = 0.05).

CONCLUSION

In our patient population, either EBRT or BT appear equally efficacious for patients with T1/T2 disease with Gleason scores </= 6 or PSA </= 10 ng/dL. Patients with presenting Gleason scores of 8-10 or PSA > 10 ng/dL (but </= 20 ng/dL) appear to fare significantly worse with BT alone compared to EBRT alone. Neither EBRT nor BT alone was particularly effective for patients with a presenting PSA > 20 ng/dL, as would be anticipated from the significant risks of occult distant metastasis in this group. To our knowledge, this is the first report comparing the outcome of EBRT and BT treatment in patients treated concurrently by a single group, and these results, achieved in a community-based practice, compare favorably to data from academic centers regarding external beam, brachytherapy, or surgical outcomes and should be generalizable to the community at large.

Corrugator supercilii muscle resection and migraine headaches

This study was conducted to determine whether there is an association between the removal of the corrugator supercilii muscle and the elimination or significant improvement of migraine headaches. Questionnaires were sent to 314 consecutive patients who had undergone corrugator supercilii muscle resection during endoscopic, transpalpebral, or open forehead rejuvenation procedures. The patients were queried as to whether they had a history of migraine headaches and, if so, whether the headaches significantly improved or disappeared after surgery. If the answer was affirmative, then the patients were further questioned about the duration of the improvement or cessation of the headaches and the relationship to the timing of the surgery. After an initial evaluation of the completed questionnaires, a telephone interview was conducted to confirm the initial answers and to obtain further information necessary to ensure that the patients had a proper diagnosis based on the International Headache Society criteria for migraine headaches. The charts of the patients who had migraine headaches were studied to ascertain and classify the type of surgery they had undergone. Patient demographics were reviewed, and the results were statistically analyzed. Of the 314 patients, 265 (84.4 percent) either responded to the questionnaire, were interviewed, or both responded to the questionnaire and were interviewed. Of this group, 16 patients were excluded because of the provision of insufficient information to meet the International Headache Society criteria, the presence of organic problems, and other exclusions mandated by study design. Thirty-nine (15.7 percent) of the remaining 249 patients had migraine headaches that fulfilled the Society criteria. Thirty-one of the 39 (79.5 percent) with preoperative migraine noted elimination or improvement in migraine headaches immediately after surgery (p < 0.0001; McNemar), and the benefits lasted over a mean follow-up period of 47 months. When the respondents with a positive history of migraine headaches were further divided, 16 patients (p < 0.0001; McNemar) noticed improvement over a mean follow-up period of 47 months, and 15 (p < 0.0001; McNemar) experienced total elimination of their migraine headaches over a mean follow-up period of 46.5 months. When divided by migraine headache type, 29 patients (74 percent) had nonaura migraine headaches. Of these patients, the headaches disappeared in 11 patients, improved in 13 patients, and did not change in five patients (p < 0.0001). Ten patients experienced aura-type headaches, which disappeared or improved in seven of the patients and did not change in three of the patients (p < 0.0001). This study proves for the first time that there is indeed a strong correlation between the removal of the corrugator supercilii muscle and the elimination or significant improvement of migraine headaches.

Sensing arterial CO(2) levels: a role for medullary P2X receptors

ATP has been shown to act as an excitatory neurotransmitter in the central nervous system. In this review, evidence is presented to indicate that when ATP is micro-injected into the ventrolateral medulla (VLM) of the rat, changes in respiratory activity are elicited. These effects, and accompanying changes in heart rate and blood pressure are mediated by P2X purinoreceptors. Immunocytochemistry indicates a prevalence of P2X(2) and P2X(6) purinoreceptors in this region of the medulla. The P2 purinoceptor antagonists, suramin and PPADS blunt the respiratory responses to changes in arterial CO(2) levels when micro-injected into the VLM. This effect is shown electrophysiologically to be mediated by purinoreceptors located primarily on respiratory neurones of the VLM including the Bötzinger complex. As the effects of agonist activation of P2X(2) purinoceptors expressed in HEK293 cells and Xenopus oocytes are potentiated by lowering pH, these data imply that the central respiratory response to CO(2) depends in part on the pH sensitivity of purinoreceptors located on inspiratory neurones. The implications for respiratory activity and control are discussed.

Coexpression of rat P2X2 and P2X6 subunits in Xenopus oocytes

Transcripts for P2X(2) and P2X(6) subunits are present in rat CNS and frequently colocalize in the same brainstem nuclei. When rat P2X(2) (rP2X(2)) and rat P2X(6) (rP2X(6)) receptors were expressed individually in Xenopus oocytes and studied under voltage-clamp conditions, only homomeric rP2X(2) receptors were fully functional and gave rise to large inward currents (2-3 microA) to extracellular ATP. Coexpression of rP2X(2) and rP2X(6) subunits in Xenopus oocytes resulted in a heteromeric rP2X(2/6) receptor, which showed a significantly different phenotype from the wild-type rP2X(2) receptor. Differences included reduction in agonist potencies and, in some cases (e.g., Ap(4)A), significant loss of agonist activity. ATP-evoked inward currents were biphasic at the heteromeric rP2X(2/6) receptor, particularly when Zn(2+) ions were present or extracellular pH was lowered. The pH range was narrower for H(+) enhancement of ATP responses at the heteromeric rP2X(2/6) receptor. Also, H(+) ions inhibited ATP responses at low pH levels (<pH 6.3). The pH-dependent blocking activity of suramin was changed at this heteromeric receptor, although the potentiating effect of Zn(2+) on ATP responses was unchanged. Thus, the rP2X(2/6) receptor is a functionally modified P2X(2)-like receptor with a distinct pattern of pH modulation of ATP activation and suramin blockade. Although homomeric P2X(6) receptors function poorly, the P2X(6) subunit can contribute to functional heteromeric P2X channels and may influence the phenotype of native P2X receptors in those cells in which it is expressed.

Querkopf, a MYST family histone acetyltransferase, is required for normal cerebral cortex development

In order to find, and mutate, novel genes required for regulation of neurogenesis in the cerebral cortex, we performed a genetic screen in mice. As the result of this screen, we created a new mouse mutant, querkopf. The querkopf mutation is due to an insertion into a MYST family histone acetyltransferase gene. Mice homozygous for the querkopf mutation have craniofacial abnormalities, fail to thrive in the postnatal period and have defects in central nervous system development. The defects in central nervous system development are particularly prominent in the cerebral cortex, which is disproportionally smaller than in wild-type mice. A large reduction in the size of the cortical plate was already apparent during embryogenesis. Homozygous mice show a lack of large pyramidal cells in layer V of the cortex, which is reflected in a reduction in the number of Otx1-positive neurons in this layer during postnatal development. Homozygous mice also show a reduction in the number of GAD67-positive interneurons throughout the cortex. Our results suggest that Querkopf is an essential component of a genetic cascade regulating cell differentiation in the cortex, probably acting in a multiprotein complex regulating chromatin structure during transcription.

Phylogenetic relationship and antifouling activity of bacterial epiphytes from the marine alga Ulva lactuca

It is widely accepted that bacterial epiphytes can inhibit the colonization of surfaces by common fouling organisms. However, little information is available regarding the diversity and properties of these antifouling bacteria. This study assessed the antifouling traits of five epiphytes of the common green alga, Ulva lactuca. All isolates were capable of preventing the settlement of invertebrate larvae and germination of algal spores. Three of the isolates also inhibited the growth of a variety of bacteria and fungi. Their phylogenetic positions were determined by 16S ribosomal subunit DNA sequencing. All isolates showed a close affiliation with the genus Pseudoalteromonas and, in particular, with the species P. tunicata. Strains of this bacterial species also display a variety of antifouling activities, suggesting that antifouling ability may be an important trait for members of this genus to be highly successful colonizers of animate surfaces and for such species to protect their host against fouling.

Uncx4.1 is required for the formation of the pedicles and proximal ribs and acts upstream of Pax9

The expression of the homeobox gene Uncx4.1 in the somite is restricted to the caudal half of the newly formed somite and sclerotome. Here we show that mice with a targeted mutation of the Uncx4.1 gene exhibit defects in the axial skeleton and ribs. In the absence of Uncx4.1, pedicles of the neural arches and proximal ribs are not formed. In addition, dorsal root ganglia are disorganized. Histological and marker analysis revealed that Uncx4.1 is not necessary for somite segmentation. It is required to maintain the condensation of the caudal half-sclerotome, from which the missing skeletal elements are derived. The loss of proximal ribs in Pax1/Pax9 double mutants and the data presented here argue for a role of Uncx4.1 upstream of Pax9 in the caudolateral sclerotome. Our results further indicate that Uncx4.1 may be involved in the differential cell adhesion properties of the somite.

Effects of long-term microgravity exposure on cancellous and cortical weight-bearing bones of cosmonauts

BACKGROUND

Microgravity has been thought to induce osteoporosis because of reduced weight-bearing. However, up to now, few data have been available about its precise nature and timecourse.

METHODS

We measured bone mineral density (BMD) at the distal radius and tibia in 15 cosmonauts of the Russian MIR space station who sojourned in space either 1 (n=two), 2 (two), or 6 months (11). After recovery periods of similar duration to the space missions, BMD was measured for the 2-month and 6-month crews.

FINDINGS

Neither cancellous nor cortical bone of the radius was significantly changed at any of the timepoints. On the contrary, in the weight-bearing tibial site, cancellous BMD loss was already present after the first month and deteriorated with mission duration. In tibial cortices, bone loss was noted after a 2-month flight. In the 6-month group, cortical bone loss was less pronounced than that for cancellous bone. In some individuals, tibial deterioration was great. Actual BMD did not depend on preceding cumulative periods spent in space. During recovery, tibial bone loss persisted, suggesting that the time needed to recover is longer than the mission duration.

INTERPRETATION

In space, despite physical training, bone loss is an adaptive process that can become pathological after recovery on Earth. Striking interindividual variations in bone responses seem to suggest a need for adequate crew preselection. Targeted treatment or prevention strategies would be useful, not only for space purposes, but also for the increasing number of osteoporotic patients on Earth.

Vascular actions of estrogen and Alzheimer's disease

Women are two to three times more likely to develop late-onset Alzheimer's disease (AD) than age-matched men. A large number of observational reports and a few randomized clinical trials have indicated that estrogen replacement therapy (ERT) may retard the development and severity of dementia in postmenopausal women. A chronic inflammatory reaction mediated by abnormal deposition of proteins such as amyloid-beta (A beta) is central to the pathology of AD. We investigated the effect of low doses of conjugated estrogen (Premarin) in an animal model of A beta-induced vascular disruption and inflammatory reaction. Estrogen prevented vascular deposition of A beta, endothelial and vessel wall disruption with plasma leakage, platelet and mast cell activation, and characteristic features of an inflammatory reaction: adhesion and transmigration of leukocytes. The beneficial effect was lost when estrogen treatment was discontinued. This novel protective effect of estrogen against A beta-induced vascular dysfunction may contribute to the therapeutic efficacy of estrogen in AD and coronary vascular disease.

Structural analysis of the elongation factor G protein from the low-temperature-adapted bacterium Arthrobacter globiformis SI55

The first structural analysis of elongation factor G (EF-G) from a cold-adapted bacterium is presented. EF-G is an essential protein involved in the elongation process during protein synthesis and is therefore thought to play a crucial role in the low-temperature adaptation of cold-adapted microorganisms. To define its importance, the EF-G gene (fus) from the psychrotolerant bacterium Arthrobacter globiformis SI55 was cloned and sequenced. The deduced primary structure of the elongation factor is composed of 700 amino acids with a predicted molecular mass of 77.4 kDa. A three-dimensional model of the protein was constructed based on the known crystal structures of structurally homologous proteins. Structural features that might potentially be important for activity and flexibility at low temperature were deduced by comparisons with models of the EF-G proteins from the closely related mesophiles Micrococcus luteus and Mycobacterium tuberculosis. These features include a loss in the number of salt bridges in intradomain and interdomain positions, increased solvent interactions mediated by greater charge and polarity on domain surfaces, loop insertions, loss of proline residues in loop structures, and an increase of hydrophobicity in core regions. Specific changes have also been identified in the catalytic domain (G domain) and sites of potential ribosome interaction, which may directly affect guanosine triphosphate (GTP) hydrolysis and elongation rates at low temperature.

Proposed curriculum for an "observational" international emergency medicine fellowship program

This article presents information on considerations involved in setting up and conducting fellowship training programs in emergency medicine (EM) for physicians from other countries. General goals for these programs are to assist in providing physicians from other countries with the knowledge and skills needed to further develop EM in their home countries. The authors report their opinions, based on their cumulative extensive experiences, on the necessary and optional structural elements to consider for international EM fellowship programs. Because of U.S. medical licensing restrictions, much of the proposed programs' content would be "observational" rather than involving direct "hands-on" clinical EM training. Due to the very recent initiation of these programs in the United States, there has not yet been reported any scientific evaluation of their structure or efficacy. International EM fellowship programs involving mainly observational EM experience can serve as one method to assist in EM development in other countries. Future studies should assess the impact and efficacy of these programs.

Animal model of Alzheimer-like vascular pathology and inflammatory reaction

This in vivo animal model of vascular inflammatory reaction facilitates morphologic and hemodynamic analyses of leukocyte-endothelial interaction and can be monitored by video microscopy and electron microscopy. The model has served as a rapid means to explore the deleterious vascular actions and inflammatory response to the cytokines tumor necrosis factor, interleukin-1 and amyloid-beta, as well as the protective effects of superoxide dismutase, estrogen, and cytokine antagonists.

Low temperature regulated DEAD-box RNA helicase from the Antarctic archaeon, Methanococcoides burtonii

DEAD-box RNA helicases, by unwinding duplex RNA in bacteria and eukaryotes, are involved in essential cellular processes, including translation initiation and ribosome biogenesis, and have recently been implicated in enabling bacteria to survive cold-shock and grow at low temperature. Despite these critical physiological roles, they have not been characterized in archaea. Due to their presumed importance in removing cold-stabilised secondary structures in mRNA, we have characterised a putative DEAD-box RNA helicase gene (deaD) from the Antarctic methanogen, Methanococcoides burtonii. The encoded protein, DeaD is predicted to contain a core element involved in ATP hydrolysis and RNA-binding, and an unusual C-terminal domain that contains seven perfect, trideca-peptide, direct repeats that may be involved in RNA binding. Alignment and phylogenetic analyses were performed on the core regions of the M. burtonii and other DEAD-box RNA helicases. These revealed a loose but consistent clustering of archaeal and bacterial sequences and enabled the generation of a prokaryotic-specific consensus sequence. The consensus highlights the importance of residues other than the eight motifs that are often associated with DEAD-box RNA helicases, as well as de-emphasising the importance of the "A" residue within the "DEAD" motif. Cells growing at 4 degrees C contained abundant levels of deaD mRNA, however no mRNA was detected in cells growing at 23 degrees C (the optimal temperature for growth). The transcription initiation site was mapped downstream from an archaeal box-A element (TATA box), which preceded a long (113 nucleotides) 5'-untranslated region (5'-UTR). Within the 5'-UTR was an 11 bp sequence that closely matches (nine out of 11) cold-box elements that are present in the 5'-UTRs of cold-shock induced genes from bacteria. To determine if the archaeal 5'-UTR performs an analagous function to the bacterial 5'-UTRs, the archaeal deaD 5'-UTR was transcribed in E. coli under the control of the cspA promoter and transcriptional terminator. It has previously been reported that overexpression of the cspA 5'-UTR leads to an extended cold-shock response due to the 5'-UTR titrating cellular levels of a cold-shock repressor protein(s). In our hands, the cold-shock protein profiles resulting from overexpression of Escherichia coli cspA and M. burtonii deaD 5'-UTRs were similar, however they did not differ from those for the overexpression of a control plasmid lacking a 5'-UTR. In association with other recent data from E. coli, our results indicate that the role of the 5'-UTR in gene regulation is presently unclear. Irrespective of the mechanisms, it is striking that highly similar 5'-UTRs with cold-box elements are present in cold induced genes from E. coli, Anabaena and M. burtonii. This is the first study examining low temperature regulation in archaea and provides initial evidence that gene expression from a cold adapted archaeon involves a bacterial-like transcriptional regulatory mechanism. In addition, it provides the foundation for further studies into the function and regulation of DEAD-box RNA helicases in archaea, and in particular, their roles in low temperature adaptation.

Localization and action of adenosine A2a receptors in regions of the brainstem important in cardiovascular control

In vitro autoradiography and central microinjections of a P1 adenosine A2a receptor antagonist have been employed to investigate a possible role for centrally located adenosine A2a receptors in modulation of the baroreceptor reflex. In vitro autoradiography using [125I]4-(2-[7-amino-2-[2-furyl][3,2,4]triazolol[2,3-a][1,3,5]tr iazin-5-yl-amino]ethyl)phenol ([125I]ZM241385), the high-affinity adenosine A2a receptor antagonist, revealed a heterogeneous distribution of adenosine A2a binding sites within the lower brainstem of the rat. Image analysis showed high levels of binding in rostral regions of both the nucleus tractus solitarius and the ventrolateral medulla. Intermediate levels of binding were observed in the commissural nucleus tractus solitarius and the dorsal vagal motor nucleus, with low levels of binding in caudal regions of the nucleus tractus solitarius and the ventrolateral medulla, and the hypoglossal nucleus. Unilateral microinjections of unlabelled ZM241385 into the nucleus tractus solitarius had no effect on baseline levels of arterial pressure, heart rate and phrenic nerve activity recorded in anaesthetized, artificially ventilated rats. However, microinjections of ZM241385 reduced the bradycardia evoked by stimulation of the ipsilateral aortic nerve. In contrast, ZM241385 had no effect on the depressor response or the reduction in phrenic nerve activity evoked by aortic nerve stimulation. Our results indicate that adenosine A2a binding sites are located in a number of brainstem regions involved in autonomic function, consistent with the idea that adenosine acts as a neuromodulator of a variety of cardiorespiratory reflexes. Specifically, the data support the hypothesis that adenosine A2a receptors located within the nucleus tractus solitarius are activated during baroreceptor stimulation and have an important modulatory role in the pattern of cardiovascular changes associated with this reflex.

Monoamine oxidase-B inhibitors in the treatment of Alzheimer's disease

The monoamine oxidase-B (MAO-B) inhibitor L-deprenyl (Selegiline) is effective in treating Parkinson's disease and possibly Alzheimer's disease, with a concomitant extension of life span. It has been suggested that the therapeutic efficacy of L-deprenyl may involve actions other than the inhibition of the enzyme MAO-B. This article reviews some novel actions of L-deprenyl and suggests that stimulation of nitric oxide (NO) production could be central to the action of the drug. L-Deprenyl induced rapid increases in NO production in brain tissue and cerebral blood vessels. In vitro or in vivo application of L-deprenyl produced vasodilatation. The drug also protected the vascular endothelium from the toxic effects of amyloid-beta peptide. Because NO modulates activities including cerebral blood flow and memory, and reduced NO production has been observed in AD brain, stimulation of NO production by L-deprenyl could contribute to the enhancement of cognitive function in AD. MAO-B inhibitors are unique in that they exert protective effects on both vascular and neuronal tissue and thus warrant further consideration in the treatment of vascular and neurodegenerative diseases associated with aging.

Winged helix transcription factor Foxb1 is essential for access of mammillothalamic axons to the thalamus

Our aim was to study the mechanisms of brain histogenesis. As a model, we have used the role of winged helix transcription factor gene Foxb1 in the emergence of a very specific morphological trait of the diencephalon, the mammillary axonal complex. Foxb1 is expressed in a large hypothalamic neuronal group (the mammillary body), which gives origin to a major axonal bundle with branches to thalamus, tectum and tegmentum. We have generated mice carrying a targeted mutation of Foxb1 plus the tau-lacZ reporter. In these mutants, a subpopulation of dorsal thalamic ventricular cells “thalamic palisade” show abnormal persistence of Foxb1 transcriptional activity; the thalamic branch of the mammillary axonal complex is not able to grow past these cells and enter the thalamus. The other two branches of the mammillary axonal complex (to tectum and tegmentum) are unaffected by the mutation. Most of the neurons that originate the mammillothalamic axons suffer apoptosis after navigational failure. Analysis of chimeric brains with wild-type and Foxb1 mutant cells suggests that correct expression of Foxb1 in the thalamic palisade is sufficient to rescue the normal phenotype. Our results indicate that Foxb1 is essential for diencephalic histogenesis and that it exerts its effects by controlling access to the target by one particular axonal branch.

ATP as a mediator of mammalian central CO2 chemoreception

1. A role for P2 purinoceptors in the chemosensory response of respiratory neurones localised in the ventrolateral medulla to changes in arterial CO2 levels was investigated in the anaesthetised rat. Extracellular recordings were made from different classes of respiratory neurone and the effects of P2 receptor blockade on CO2-evoked changes in activity investigated. 2. Increasing inspired CO2 excited 85 % of inspiratory neurones in the pre-Botzinger complex. In all cases, CO2-evoked excitation was blocked by ionophoretic application of the P2 receptor antagonists suramin (0.02 M) and pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS; 100 microM), but not the adenosine receptor antagonist 8-phenyltheophylline (8-PT; 100 microM). Suramin and PPADS often reduced ongoing activity, and blocked the excitatory effects of ATP. Inspiratory neurones were also excited by the P2X receptor agonist alphabeta-methyleneATP, suggesting a specific role for P2X receptors. 3. Sixty-six per cent of pre-inspiratory neurones were also excited by CO2. This effect was reduced or abolished by prior application of P2 receptor antagonists. Although post-inspiratory and expiratory neurones were excited by increasing levels of CO2, and also by ionophoretically applied ATP, the CO2-evoked effects were unaffected by P2 receptor blockade. 4. We suggest that ATP, possibly acting via P2X purinoceptors localised within the ventral respiratory group, is involved in central chemoreception. Specifically, these distinctive CO2-P2X-mediated actions were observed only in inspiratory neurones (incrementing inspiratory neurones and pre-inspiratory neurones), which appear to have purinoceptors with pH sensitivity that can account for the actions of CO2 in modifying ventilatory activity.