The CoPhyLab comet-simulation chamber

The Comet Physics Laboratory (CoPhyLab) is an international research program to study the physical properties of cometary analog materials under simulated space conditions. The project is dedicated to studying, with the help of multiple instruments and the different expertise and background from the different partners, the physics of comets, including the processes inside cometary nuclei, the activity leading to the ejection of dust and gas, and the sub-surface and surface evolution of cometary nuclei when exposed to solar illumination. CoPhyLab will provide essential information on the formation and evolution of comets and insights into the origins of primitive Solar System bodies. To this end, we constructed a new laboratory that hosts several small-scale experiments and a large-scale comet-simulation chamber (L-Chamber). This chamber has been designed and constructed to host ice-dust samples with a diameter of up to 250 mm and a variable height between 100 and 300 mm. The cometary-analog samples will be kept at temperatures below 120 K and pressures around 10^-6 mbar to ensure cometary-like conditions. In total, 14 different scientific instruments are attached to the L-Chamber to study the temporal evolution of the physical properties of the sample under different insolation conditions. Due to the implementation of a scale inside the L-Chamber that can measure weight changes of the samples with high precision, the cooling system is mechanically decoupled from the sample holder and cooling of the samples occurs by radiation only. The constructed chamber allows us to conduct uninterrupted experiments at low temperatures and pressures up to several weeks.

Poisson approximation of intermediate empirical processes

We investigate the asymptotic behaviour of empirical processes truncated outside an interval about the (1 – s(n)/n)-quantile where s(n) → ∞ and s(n)/n → 0 as the sample size n tends to ∞. It is shown that extreme value (Poisson) processes and, alternatively, the homogeneous Poisson process may serve as approximations if certain von Mises conditions hold.

COMETARY SCIENCE. Thermal and mechanical properties of the near-surface layers of comet 67P/Churyumov-Gerasimenko

Thermal and mechanical material properties determine comet evolution and even solar system formation because comets are considered remnant volatile-rich planetesimals. Using data from the Multipurpose Sensors for Surface and Sub-Surface Science (MUPUS) instrument package gathered at the Philae landing site Abydos on comet 67P/Churyumov-Gerasimenko, we found the diurnal temperature to vary between 90 and 130 K. The surface emissivity was 0.97, and the local thermal inertia was 85 ± 35 J m(-2) K(-1)s(-1/2). The MUPUS thermal probe did not fully penetrate the near-surface layers, suggesting a local resistance of the ground to penetration of >4 megapascals, equivalent to >2 megapascal uniaxial compressive strength. A sintered near-surface microporous dust-ice layer with a porosity of 30 to 65% is consistent with the data.

The advanced glycation end-product Nɛ-(carboxymethyl)lysine level is elevated in cerebrospinal fluid of patients with amyotrophic lateral sclerosis

Oxidative stress is involved in the aetiopathogenesis of amyotrophic lateral sclerosis (ALS), a fatal degenerative disorder. To test whether oxidative stress in ALS is increased and confined to the central nervous system, we have measured the glycoxidation product N(epsilon)-(carboxymethyl)lysine (CML) in serum and cerebrospinal fluid (CSF) samples by means of a novel enzyme immunoassay. Significant increases of CSF/serum ratio of CML in ALS patients (n = 25) as compared to normal controls (n = 20, p = 0.001) and to Alzheimer disease patients (n = 9, p = 0.029) suggest intrathecal production of this glycoxidation product. Measurement of CML levels may provide a novel diagnostic tool and may supplement current monitoring strategies in interventional trials.

A unique strategy of host colony exploitation in a parasitic ant: workers of Polyrhachis lama rear their brood in neighbouring host nests

The formicine ant Polyrhachis lama is a social parasite, exploiting its ponerine host ant species Diacamma sp. In most social parasitic associations, the parasitic species are closely related to their host species group, evolving directly from independent ancestors of the host species. However, in the Polyrhachis lama- Diacamma sp. association, the associated species belong to different ant subfamilies. Based on preliminary field surveys, we had presumed that P. lama might have given up its reproductive division of labour, i.e. workers would be able to produce males as well as workers and females parthenogenetically. In this study, this hypothesis was disproved: Polyrhachis lama workers cannot be fertilized and are only able to produce males. In the host-parasite association originating from nests possessing a P. lama queen, workers penetrate surrounding Diacamma sp. nests, carrying brood for rearing within these satellite nests. In this peculiar way, a single P. lama colony is able to exploit several Diacamma sp. colonies simultaneously.

The homeodomain transcription factor Xvent-2 mediates autocatalytic regulation of BMP-4 expression in Xenopus embryos

Like other genes of the transforming growth factor-beta family, the BMP-4 gene is regulated by an autocatalytic loop. In Xenopus embryos this loop can be ectopically induced by injection of BMP-2 RNA. However, cycloheximide treatment subsequent to BMP-2 overexpression revealed that BMP signaling is not direct but requires additional factor(s). As putative mediator we have identified Xvent-2 which is activated by BMP-2/4 signaling and, in turn, activates BMP-4 transcription. Using promoter/reporter assays we have delineated Xvent-2 responsive elements within the BMP-4 gene. We further demonstrate that Xvent-2 which has recently been characterized as a transcriptional repressor can also act, context dependent, as an activator binding two copies of a 5'-CTAATT-3' motif in the second intron of the BMP-4 gene. Replacement of Xvent-2 target sites within the goosecoid (gsc) promoter by the BMP-4 enhancer converts Xvent-2 caused repression of gsc to strong activation. This switch is obviously due to adjacent nucleotides probably binding a transcriptional co-activator interacting with Xvent-2. A model is presented describing the mechanism of BMP-4 gene activation in Xenopus embryos at the early gastrula stage.

Neurofilament architecture combines structural principles of intermediate filaments with carboxy-terminal extensions increasing in size between triplet proteins

Mammalian neurofilament triplet proteins (68 K, 160 K and 200 K) have been correlated by a biochemical, immunological and protein chemical study. The 160 K and 200 K triplet proteins are intermediate filament proteins in their own right, since they reveal the alpha-helical coiled-coil rod domain analyzed in detail for the 68 K protein. Triplet proteins display two distinct arrays. Their amino-terminal region built analogously to non-neuronal intermediate filament proteins should allow a co-polymerization process via the interaction of coiled-coil domains. The extra mass of all triplet proteins is allocated to carboxy-terminally located extensions of increasing size and unique amino acid sequences. These may provide highly charged scaffolds suitable for interactions with other neuronal components. Such a domain of 68 K reveals, in sequence analysis, 47 glutamic acids within 106 residues. The epitope recognized by a monoclonal antibody reacting probably with all intermediate filament proteins has been mapped. It is located within the last 20 residues of the rods, where six distinct intermediate filament proteins point to a consensus sequence.

"Friends in need": designing and implementing a psychoeducational group for school children from drug-involved families

Despite widespread recognition of the risks that parental drug use pose to children, few resources are available to help such children. Using a developmental intervention approach, the authors designed and tested a model curriculum for use with groups of latency-aged children in schools located in communities where drug use is pervasive. In implementing this curriculum, the authors documented the need that children affected by family drug use have for workable strategies and skills for coping with aversive environments. The responsiveness of group participants to structure, predictability, and affirmation in the groups was remarkable. Measurable changes occurred in classroom behavior and feelings of self-worth. Obstacles to implementing and testing such an intervention are discussed.

Xvent-1 mediates BMP-4-induced suppression of the dorsal-lip-specific early response gene XFD-1' in Xenopus embryos

Ectopic expression of the ventralizing morphogen BMP-4 (bone morphogenetic protein-4) in the dorsal lip (Spemann organizer) of Xenopus embryos blocks transcription of dorsal-lip-specific early response genes. We investigated the molecular mechanism underlying the BMP-4-induced inhibition of the fork head gene XFD-1'. The promoter of this gene contains a BMP-triggered inhibitory element (BIE) which prevents activation of this gene at the ventral/vegetal side of the embryo in vivo. In the present study, we show that BMP-4-induced inhibition is not direct but indirect, and is mediated by Xvent homeobox proteins. Micro-injections of Xvent-1 RNA and XFD-1' promoter deletion mutants demonstrate that Xvent-1 mimics the effect of BMP-4 signalling not only by suppression of the XFD-1' gene, but also by utilizing the BIE. Suppression could be reverted using a dominant-negative Xvent-1 mutant. The repressor domain was localized to the N-terminal region of the protein. Gel-shift and footprint analyses prove that Xvent-1 binds to the BIE. Moreover, PCR-based target-site selection for the Xvent-1 homeodomain confirms distinct motifs within the BIE as preferential binding sites. Thus, biological and molecular data suggest that Xvent-1 acts as direct repressor for XFD-1' transcription and mediates BMP-4-induced inhibition.

Transcription factors and induction in Xenopus laevis embryos

Studies with amphibian embryos have contributed major insights into the molecular basis of induction processes and the formation of germ layers during vertebrate embryogenesis. Primary signals that have been identified as growth factors or growth factor-related ligands act as inducing factors on their target cells and, by a change of the genetic program, evoke a specification of the cellular differentiation pathways. While at present the signal transduction mechanisms leading from the ligands via cognate receptors to the nuclei are still poorly understood, there is growing information on transcription factors which are activated upon induction. They govern the expression of other regulatory molecules and co-ordinate the expression of cell type-specific structural genes. Meanwhile, it is generally accepted that development and cellular differentiation in all multicellular organisms depends upon a cascade of evolutionarily conserved transcription factors. Striking structural similarities within their DNA-binding domains allow many of these factors to be subdivided into different transcription factor families. Most of the basic knowledge on these factors emerged from the pioneering work done with Drosophila embryos which was greatly facilitated by the availability of numerous mutants. Despite the fact that Drosophila development until the blastoderm stage proceeds in a multinuclear syncytium and thus is significantly different from that in vertebrate organisms, the primary structures of many embryonic transcription factors have been conserved in higher organisms. This especially holds true for the various DNA binding motifs and it facilitated the isolation and characterization of vertebrate homologues to factors previously identified in lower organisms.

Antagonistic actions of activin A and BMP-2/4 control dorsal lip-specific activation of the early response gene XFD-1' in Xenopus laevis embryos

Transcription of the early response gene XFD-1' (XFKH1) in the dorsal lip (Spemann organizer) of Xenopus embryos is activated by dorsal mesoderm inducing factors. Promoter studies revealed the presence of an activin A response element (ARE) which is both necessary and sufficient for transcriptional activation of reporter genes in animal cap explants incubated with activin A. Surprisingly, this ARE is also active within vegetal explants in the absence of exogenously added inducers, but an additional inhibitory response element prevents transcription of the XFD-1' gene in the ventral/vegetal region of the embryo in vivo. This element is located upstream of the ARE, it responds to bone morphogenic proteins 2 and 4 (BMP-2/4) triggered signals and it overrides the activating properties of the ARE. Expression patterns of BMP-2 and BMP-4 in the late blastula stage embryo and, especially, their absence from the dorsal blastopore lip may thus control the spatial transcription of the XFD-1' gene. Accordingly, the temporal activation and the spatial restriction of XFD-1' gene activity to the Spemann organizer is regulated by antagonistic actions of two distinct members of the TGF-beta family (activin and BMP) which act on different promoter elements.

Five years on the wings of fork head

Since its discovery five years ago the conserved family of fork head/HNF-3-related transcription factors has gained increasing importance for the analysis of gene regulatory mechanisms during embryonic development and in differentiated cells. Different members of this family, which is defined by a conserved 110 amino acid residues encompassing DNA binding domain of winged helix structure, serve as regulatory keys in embryogenesis, in tumorigenesis or in the maintenance of differentiated cell states. The purpose of this review is to summarize the accumulating amount of data on structure, expression and function of fork head/HNF-3-related transcription factors.

Neurohormonal activation in patients with right ventricular failure from pulmonary hypertension: relation to hemodynamic variables and endothelin levels

OBJECTIVES

This study sought to determine whether neurohormonal activation occurs in isolated right heart failure.

BACKGROUND

Neurohormonal activation appears to parallel the severity of left heart failure, but little is known about its role in right heart failure.

METHODS

We evaluated neurohormonal activation and endothelin levels in 21 patients with primary pulmonary hypertension at the time of right heart catheterization.

RESULTS

Plasma norepinephrine levels correlated significantly with pulmonary artery pressure (r = 0.66, p < 0.01), cardiac index (r = -0.56, p < 0.01) and pulmonary vascular resistance (r = 0.69, p < 0.001). Atrial natriuretic peptide levels were higher in the pulmonary artery than the right atrium and femoral artery and correlated closely with pulmonary artery oxygen saturation (r = -0.73, p < 0.0001). Plasma renin levels were not elevated. Endothelin levels were increased and correlated with right atrial pressure (r = 0.74, p < 0.0001) and pulmonary artery oxygen saturation (r = -0.070, p < 0.0004).

CONCLUSIONS

Neurohormonal activation occurs in patients with isolated right ventricular failure and inherently normal left ventricles and appears to be related to the overall severity of cardiopulmonary derangements. The elevation in endothelin levels is consistent with its release in response to pulmonary hypertension.

The Drosophila fork head domain protein crocodile is required for the establishment of head structures

The fork head (fkh) domain defines the DNA-binding region of a family of transcription factors which has been implicated in regulating cell fate decisions across species lines. We have cloned and molecularly characterized the crocodile (croc) gene which encodes a new family member from Drosophila. croc is expressed in the head anlagen of the blastoderm embryo under the control of the anterior, the dorsoventral and the terminal maternal organizer systems. The croc mutant phenotype indicates that the croc wild-type gene is required to function as an early patterning gene in the anterior-most blastoderm head segment anlage and for the establishment of a specific head skeletal structure that derives from the non-adjacent intercalary segment at a later stage of embryogenesis. As an early patterning gene, croc exerts unusual properties which do not allow it to be grouped among the established segmentation genes. A single-site mutation within the croc fkh domain, which causes a replacement of the first out of four conserved amino acid residues thought to be involved in the coordinate binding of Mg2+, abolishes the DNA binding of the protein in vitro. In view of the resulting lack-of-function mutant phenotype, it appears likely that metal binding by the affected region of the fkh domain is crucial for proper folding of the DNA-binding structure.

DNA recognition site analysis of Xenopus winged helix proteins

DNA binding proteins of the winged helix family contain a conserved 110 amino acid region, the fork head/HNF-3 domain. Three members of the recently described XFD (Xenopus fork head domain related) multigene family in the frog Xenopus laevis that contain this DNA-binding domain have been studied. We determined the in vitro DNA recognition sequences by means of two independent methods: PCR supported site selection with degenerated deoxyoligonucleotides and affinity chromatography of genomic Xenopus DNA fragments. In contrast to a remarkable sequence divergence within their protein sequence of the fork head domains, all three proteins share a similar 7 bp DNA target motif. The protein-DNA interaction has been studied by means of DMS interference and hydroxyl radical footprinting. A region of 18 bp encompassing the 7 bp target motif is sufficient to confer binding and specificity. The specificity of binding could be attributed on the DNA level to residues located 5' to the 7 bp core region, and on the protein level most likely to a region within the first half of the fork head domain. The possible role of specific nucleotides within the target site in binding the protein is discussed in the context of the current crystal structure of the complex of this domain with DNA.

Comparative acute effects of adenosine and prostacyclin in primary pulmonary hypertension

Vasodilators have been a main focus of therapy for primary pulmonary hypertension. Adenosine and prostacyclin have been shown to reduce pulmonary vascular resistance acutely in these patients. In order to compare the acute hemodynamic effects of adenosine and prostacyclin, ten patients with severe primary pulmonary hypertension, unresponsive to medical therapy, were studied. After baseline hemodynamics were obtained, an adenosine infusion, 50 to 100 ng/kg/min, was begun and titrated to the maximum tolerated dose. Hemodynamics were allowed to return to baseline, and thereafter, a prostacyclin infusion was begun at 2 ng/kg/min, and titrated to the maximum tolerated dose. Overall, adenosine (200 +/- 53 ng/kg/min) produced a 33 +/- 18% (p < 0.001) fall in pulmonary vascular resistance and a 52 +/- 25% (p < 0.001) increase in cardiac output with no effect on pulmonary or systemic arterial pressures. Prostacyclin (8 +/- 4 ng/kg/min) caused a 22 +/- 18% (p < 0.01) fall in pulmonary vascular resistance and a 25 +/- 26% (p < 0.05) increase in cardiac output with a 14 +/- 6% (p < 0.001) decrease in systemic arterial pressure, but no change in pulmonary arterial pressure. The effects of adenosine and prostacyclin on pulmonary vascular resistance were similar (r = 0.70, r2 = 0.49, p = 0.02). Adenosine and prostacyclin have similar hemodynamic effects acutely in primary pulmonary hypertension. Adenosine may be useful as a test of the potential for long-term prostacyclin therapy in patients with primary pulmonary hypertension.

[Pneumothorax in laparoscopic cholecystectomy (I)]

A case of pneumothorax during laparoscopic cholecystectomy is reported. Etiology, evaluation and therapy are discussed.

The interaction of DNA with the DNA-binding domain encoded by the Drosophila gene fork head

The Drosophila gene fork head (fkh) encodes a nuclear protein which shares sequence similarity with the rat hepatocyte-enriched transcription factor family HNF3 alpha-gamma. The sequence similarity is restricted to the region that has been defined as the DNA-binding domain of these proteins, termed the fork head domain. In this study, we investigate the structural properties of the fork head domain of the prototype of this protein family encoded by fkh and its interaction with DNA. The core sequence required for DNA binding of the fork head domain consists of 114 amino acids and represents a stable and highly compact monomer of globular structure with an alpha-helix content of 37%. The fork head domain binds specifically to the DNA target sequence of HNF3 alpha-gamma and to an enhancer element that is derived from a regulatory sequence of an in vivo Drosophila target gene. The specific interaction between the DNA-binding domain of the fkh-encoded protein and its target DNA is mediated by two contact regions which are separated from each other by one turn of the DNA. Our data are consistent with a structural model which derived rom X-ray diffraction analysis of the DNA-binding domain of HNF3 gamma. Differences concerning the DNA contact sites between the DNA-binding domain of the fkh-encoded protein and the HNF3 protein family are discussed.

Timing of single lung transplantation for primary pulmonary hypertension

Single lung transplantation has been advocated as a definitive treatment for primary pulmonary hypertension. Because of reports of improved survival in some patients with vasodilators and anticoagulants, the timing of referral for single lung transplantation needs to be examined. Survival in primary pulmonary hypertension was estimated, with the use of a proportional hazards model, from data obtained from the National Institutes of Health registry on primary pulmonary hypertension. Waiting times for single lung transplantation, obtained from the United Network for Organ Sharing, were found to follow an exponential distribution. Under the assumption that waiting time and survival are independent, a model was developed to estimate the probability of surviving to single lung transplantation, depending on the waiting time for a single lung transplantation, and the delay in transplant referral. Examples were computed with hemodynamic data from the National Institutes of Health registry on primary pulmonary hypertension: waiting times of 6, 12, 18, and 24 months and delays in single lung transplantation referral of 0, 1, 2, and 3 years. For a waiting time of 6 months, the chance of surviving to single lung transplantation with a 3-year delay varies from 19% for a patient with a mean pulmonary artery pressure of 80 mm Hg to 72% for a patient with a mean pulmonary artery pressure of 41 mm Hg. For a waiting time of 24 months and a 3-year delay in single lung transplantation referral, this probability varies from 14% (mean pulmonary artery pressure 80 mm Hg) to 59% (mean pulmonary artery pressure 41 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)

Reliability of differing densities of sample grids used for the monitoring of forest condition in Europe

Concern about the possible deterioration of forest health led to the establishment in the 1980s of inventories of forest condition throughout Europe. International standardisation of the programmes was sought and a number of recommendations were made concerning sampling and assessment procedures. One of the most important rulings was that the assessment should be made on a systematic grid, the minimum density of which was 16×16 km. However, many countries adopted denser sampling grids, with 4×4 km being used in several countries and 1×1 km being used in the Netherlands. With five or more years of monitoring completed, there is a growing belief that a rapid and irreversible decline in forest health is not occurring. Consequently, some countries/regions are seeking to reduce their annual investment in forest health monitoring.The precision of national/regional estimates of forest health can be directly related to the sample size. As the sample size decreases, so also does the precision of the estimates. This is illustrated using data collected in Switzerland in 1992 and using grid densities of 4×4 km, 8×8 km, 12×12 km and 16×16 km. The value of the data is dependent on the sample size and the degree to which it is broken down (by region or species). The loss of precision associated with most subdivisions at the 8×8 km grid level remains acceptable, but a sharp deterioration in the precision occurs at the 12×12 km and 16×16 km grid levels. This has considerable implications for the interpretation of the inventories from those countries using a 16×16 km grid. In Switzerland, a reduction from the current 4×4 km grid to an 8×8 km grid (i.e. 75% reduction in sample size) would have relatively little impact on the overall results from the annual inventories of forest health.

The prevalence and significance of a patent foramen ovale in pulmonary hypertension

In order to determine the prevalence and significance of a patent foramen ovale (PFO) in pulmonary hypertension, 58 patients were studied with transesophageal echocardiography, right-sided heart catheterization, and exercise testing. In order to examine if a PFO might be associated with a better outcome, survival was estimated, based on a formula derived from the National Institutes of Health Primary Pulmonary Hypertension Registry, for the patients with primary pulmonary hypertension (PPH). A PFO was found in 26 percent (15 of 58) of all patients studied, 25 percent (10 of 40) of those with PPH, and 28 percent (5 of 18) of those with secondary pulmonary hypertension. We found no significant difference in any hemodynamic variable or exercise tolerance between the patients with and without a PFO, or for subsets of patients with primary and secondary pulmonary hypertension. We also found no significant difference in the 1-, 2-, 3-, 4-, or 5-year estimated survival, for the patients with PPH between those with and without a PFO. The prevalence of a PFO in pulmonary hypertension appears similar to the normal population. A PFO provides no detectable influence on resting hemodynamics or exercise tolerance in patients with pulmonary hypertension and is not clearly associated with patients expected to survive longer.

Effects of adenosine in combination with calcium channel blockers in patients with primary pulmonary hypertension

OBJECTIVES

The purpose of this study was to evaluate the effects of vasodilator combination therapy in patients with primary pulmonary hypertension.

BACKGROUND

Calcium channel blockers and adenosine have each been shown to be effective in reducing pulmonary artery pressure and pulmonary vascular resistance in patients with primary pulmonary hypertension. However, the effects of combining these vasodilators have not been studied.

METHODS

To test the combination, 12 patients were placed on oral nifedipine and 3 on diltiazem therapy, using a dose titrated to maximal effect (mean nifedipine dose 103 +/- 24 mg, mean diltiazem dose 300 +/- 49 mg). Patients were then given maintenance doses of the calcium channel blocker at half the cumulative loading dose at 6-h intervals. One hour after the maintenance dose of calcium blocker, all patients received an infusion of adenosine, starting with 50 micrograms/kg per min and increasing by 50 micrograms/kg per min at 2-min intervals to a maximally tolerated dose (180 +/- 63 micrograms/kg per min).

RESULTS

Ten patients responded to calcium channel blockers (defined as a > or = 20% decrease in pulmonary vascular resistance), with a 16% decrease in mean pulmonary artery pressure (p = 0.057), a 39% decrease in pulmonary vascular resistance (p = 0.002) and a 24% increase in stroke volume (p = 0.007). Five patients were nonresponders, with no significant changes in pulmonary artery pressure, pulmonary vascular resistance, cardiac index or stroke volume. In the calcium channel blocker responders, the combination of adenosine and calcium blocker reduced pulmonary vascular resistance by 49%, increased stroke volume by 33% and decreased mean pulmonary artery pressure by 14% compared with drug-free baseline values. In nonresponders, combination therapy resulted in nonsignificant changes in pulmonary artery pressure and pulmonary vascular resistance.

CONCLUSIONS

Adenosine has the ability to further decrease pulmonary artery pressure and pulmonary vascular resistance in patients with primary pulmonary hypertension who respond to calcium channel blockers. Those who fail to respond to these agents have little added effect from adenosine.

In vitro binding to the leucine tRNA gene identifies a novel yeast homeobox gene

In a search for gene products of Saccharomyces cerevisiae interacting with the internal promoter of yeast tRNA genes two genes encoding a homeodomain protein of the Drosophila Antennapedia type were isolated. One of them codes for Pho2, and the second codes for a previously unknown protein (Yox1). The corresponding gene, termed YOX1, maps to chromosome 16. The amino acid sequence of Yox1 shows a remarkable similarity within the homeobox domain to many proteins from a wide variety of sources. Fusion proteins that contain sequences encoded by these genes demonstrate that the genes encode DNA-binding proteins that are capable of binding to the DNA of the leucine tRNA gene in vitro. However, deletion of YOX1 gene activity does not give rise to a scorable mutant phenotype. This result leaves open whether Yox1 binding to the leucine tRNA gene is necessary for the in vivo regulation of the gene and its suggests that the YOX1 gene codes for a non-essential product.

The effect of high doses of calcium-channel blockers on survival in primary pulmonary hypertension

BACKGROUND

Primary pulmonary hypertension is a progressive, fatal disease of unknown cause. Vasodilator drugs have been used as a treatment, but their efficacy is uncertain.

METHODS

We treated 64 patients with primary pulmonary hypertension with high doses of calcium-channel blockers. Patients who responded to treatment (defined as those whose pulmonary-artery pressure and pulmonary vascular resistance immediately fell by more than 20 percent after challenge) were treated for up to five years. Their survival was compared with that of the patients who did not respond and with patients enrolled in the National Institutes of Health (NIH) Registry on Primary Pulmonary Hypertension. Warfarin was given to 55 percent of the patients as concurrent therapy, on the basis of a lung scan showing nonuniformity of pulmonary blood flow (47 percent of patients who responded and 57 percent of those who did not respond).

RESULTS

Seventeen patients (26 percent) responded to treatment, as indicated by a 39 percent fall in pulmonary-artery pressure and a 53 percent fall in the pulmonary-vascular-resistance index (P less than 0.001). Nifedipine (mean [+/- SD] daily dose, 172 +/- 41 mg) was given to 13 patients, and diltiazem (mean daily dose, 720 +/- 208 mg) was given to 4 patients. After five years, 94 percent of the patients who responded (16 of 17) were alive, as compared with 55 percent of the patients who did not respond (26 of 47, P = 0.003). The survival of the patients who responded was also significantly better than that of the NIH registry cohort (P = 0.002) and patients from the NIH registry who were treated at the University of Illinois (P = 0.001). The use of warfarin was associated with improved survival (P = 0.025), particularly in the patients who did not respond.

CONCLUSIONS

This study suggests that high doses of calcium-channel blockers in patients with primary pulmonary hypertension who respond with reductions in pulmonary-artery pressure and pulmonary vascular resistance may improve survival over a five-year period.

High dose titration of calcium channel blocking agents for primary pulmonary hypertension: guidelines for short-term drug testing

Forty-seven patients with primary pulmonary hypertension were evaluated with a dose titration protocol utilizing nifedipine (20 mg orally) or diltiazem (60 mg orally) given every hour until maximal effectiveness was achieved. Of the patients tested, 15 (32%) had a greater than 20% reduction in pulmonary artery pressure (mean 36.2 +/- 8%, p less than 0.01) and pulmonary vascular resistance (mean 50.2 +/- 7%, p less than 0.01) (pressure responders). Nineteen (40%) had a greater than 20% reduction in pulmonary vascular resistance (mean 25.2 +/- 12%, p less than 0.01), with less than a 20% decrease in pulmonary artery pressure (resistance responders). Ten had no significant change in pulmonary artery pressure or pulmonary vascular resistance (nonresponders), and three were unable to tolerate the calcium channel blocking agents. No hemodynamic profile allowed prediction of the type of response to these agents. No mortality or serious morbidity was associated with the drug testing. These findings indicate that calcium channel blockers, when titrated to maximally effective doses, may cause substantial reductions in pulmonary artery pressure and pulmonary vascular resistance in patients with primary pulmonary hypertension. Testing with hemodynamic monitoring is necessary to ascertain which patients will respond. Patients with primary pulmonary hypertension are able to tolerate short-term administration of high doses of calcium channel blockers.

Autoantibodies against platelet glycoprotein Ib/IX: a frequent finding in autoimmune thrombocytopenic purpura

Many autoantibodies involved in the pathogenesis of autoimmune thrombocytopenic purpura (AITP) are directed against epitopes on platelet glycoproteins (GP). These autoantibodies are a specific diagnostic characteristic of patients with AITP. In this study, the relative frequency of antibodies against GPs IIb/IIIa and Ib/IX was assessed in sera from 81 AITP patients with a glycoprotein-specific enzyme immunoassay (MAIPA assay) using monoclonal antibodies against these platelet GPs. All sera contained platelet-specific antibodies which had been detected by platelet immunofluorescence. Of the 81 antibodies tested, 58 (72%) reacted with at least one of the platelet GPs studied. Autoantibodies against GPIb/IX were as common as antibodies against the GPIIb/IIIa complex. The same ratio of specificities was observed on autologous platelets of an independent cohort of 29 patients. The epitope of three autoantibodies against GPIb/IX and of mab Gi10, a monoclonal antibody, which inhibits binding of these autoantibodies, was further characterized. Severity of thrombocytopenia was not related to the GP specificity of the autoantibody. The observation that in 23 (28%) of these sera the antigenic determinants could not be assigned to the glycoproteins under investigation suggests that platelet autoantibodies may react with other GPs or other membrane constituents, e.g. glycolipids.

Affinity chromatographic purification of a protein which binds specifically to the yeast leucine tRNA gene

A crude cell extract from yeast Saccharomyces cerevisae was fractionated by affinity chromatography using the leucine tRNA gene as the recognition site. This approach enables the rapid purification of a protein, which retained its full DNA binding capacity during the enrichment procedure. The active fraction contains two major polypeptides of 140 and 170 kDa and a minor component of 100 kDa. The 170-kDa component does not bind to the DNA. The likelihood that the DNA binding protein is one of the components of transcription factor tau is discussed.

Characterization of the Band 3 substrate site in human red cell ghosts by NDS-TEMPO, a disulfonatostilbene spin probe: the function of protons in NDS-TEMPO and substrate-anion binding in relation to anion transport

NDS-TEMPO is a specific disulfonatostilbene spin label for the Band 3 substrate site (K.F. Schnell, W. Elbe, J. Käsbauer & E. Kaufmann, Biochim. Biophys. Acta 732:266-275, 1983). The pH dependence of NDS-TEMPO binding and of chloride and sulfate binding was studied in resealed human erythrocyte ghosts. pH was varied from 6.0 to 9.0. The ESR spectra from NDS-TEMPO-labeled red cell ghosts exhibited a strong immobilization of membrane-bound NDS-TEMPO. Changes of pH had no effect upon the mobility of membrane-bound NDS-TEMPO. A mutual competition between NDS-TEMPO binding and the binding of the substrate-anions, chloride and sulfate, was observed throughout the entire pH range. The maximal number of NDS-TEMPO binding sites per cell was in the range of 9.0 X 10(5) to 1.10 X 10(6) and was found to be insusceptible to changes of pH. The NDS-TEMPO/substrate-site and the chloride/substrate-site dissociation constants amounted to 1.25 microM and to 17 mM and were independent of pH from pH 6.0 to 8.0, while the sulfate/substrate-site dissociation constant displayed a strong pH dependency with a maximum of approximately 50 mM at about pH 7.0. The NDS-TEMPO inhibition constants from the chloride and the sulfate flux experiments were 0.5 microM (0 degree C) and 1.8 microM (25 degrees C), respectively, and are in close accordance with the NDS-TEMPO/substrate-site dissociation constants. Our studies provide strong evidence for the assumption that NDS-TEMPO binds in fact to the substrate site of Band 3. They show that the strong pH dependence of the chloride and of the sulfate transport cannot result from the pH dependency of substrate-anion binding, but point to the participation of ionizable regulator sites in transport catalysis. These regulator sites seem to be positioned outside the substrate site of the Band 3 transport domain.

Comparison of short-latency trigeminal evoked potentials elicited by painful dental and gingival stimulation

Painful stimulation of tooth pulp and of the maxillary gingiva was undertaken in 16 volunteers. Short-latency evoked potentials (15-50 msec) were recorded over 800 trials in each case at F3-P3 of F4-P4, and the resultant averaged wave forms were compared. The gingival wave was distinct in all subjects and could be averaged across subjects while the dental waves were either noise or very inconsistent over subjects. Averaging of the dental wave forms across subjects yielded an uninterpretable result. It was clear that dental evoked potentials could not be recorded at the sites. These findings could be explained by either or both of two hypotheses: dental afferents are predominantly small fiber, nociceptive end organs that conduct more slowly than soft tissue afferents whereas gingival stimulation activates both large and small fiber populations; and dental representation in somatosensory cortex is different and phylogenetically more primitive than that of neighboring soft tissue. Therefore, the location of the generator sites in cortex and the orientation of the dipole may be different for dental than for gingival wave forms.

Intermediate filament forming ability of desmin derivatives lacking either the amino-terminal 67 or the carboxy-terminal 27 residues

Amino acid sequence data and results from limited proteolytic digestion have been used to define the three-domain structure of intermediate filament proteins. A centrally located highly alpha-helical domain of about 310 residues well-conserved in sequence principles and length is flanked by the highly variable sequences of the non-alpha-helical headpiece and tailpiece. A direct involvement in filament formation of one or both terminal domains was previously proposed for desmin since chymotryptic removal of head and tailpiece provided a derivative unable to form filaments. In order to evaluate directly the importance of these regions we have prepared desmin derivatives lacking either the amino-terminal 67 (T-desmin) or carboxy-terminal 27 residues (L-desmin). Whereas the latter derivative is fully polymerization-competent the fragment lacking only the basic and arginine-rich headpiece cannot form filaments on its own and remains in a protofilamentous stage. These structures of T-desmin are not incorporated into filaments when mixed with protofilaments of desmin. If, however, the two proteins are mixed in 7 M-urea subsequent dialysis provides morphologically normal filaments containing T-desmin. The results suggest that at least certain hybrid protofilaments containing less than four headpieces are accepted in the filament. The removal of the 27 carboxy-terminal residues in L-desmin, although not interfering with filament formation, leads to a change in surface since filaments show lateral aggregation at 170 mM but not at 50 mM salt. The results are discussed in relation to current models of intermediate filament structure.

Antiparallel orientation of the two double-stranded coiled-coils in the tetrameric protofilament unit of intermediate filaments

The chymotryptically excised middle domain of desmin slightly exceeds in length the structurally conserved alpha-helical middle region documented in all intermediate filament proteins by amino acid sequence data. This rod domain is a protofilament derivative with a tetrameric organization, thus indicating the presence of two double-stranded coiled-coil units. We now show by immunoelectron microscopy that Fab fragments of a desmin-specific monoclonal antibody mixed with the rod lead to dumb-bell-shaped structures. The tagging of both ends together with the length of the rod (48 nm) argues for an antiparallel orientation of the two coiled-coils without a major stagger. This information combined with the lateral 21 nm periodicity of the intermediate filament observed by us and others leads to a structural hypothesis similar to those entertained from X-ray data on wool alpha-keratins, although here an antiparallel tetrameric unit of some 60 to 66 nm is invoked, which has never been isolated. The structure that we discuss allows for the existence of both the particles, and the antibody experiment strongly supports the antiparallel orientation postulated in both approaches. The tube-like filament structure proposed for the intermediate filament agrees with recent mass per unit length measurements and allows for two minor classes of intermediate filaments with different values in this property as also found experimentally.

SDS-PAGE strongly overestimates the molecular masses of the neurofilament proteins

Direct molecular mass determination of the three porcine neurofilament proteins (H, M and L) was performed in 6 M guanidine-HCl using analytical gel filtration and sedimentation equilibrium centrifugation. The results show that SDS-PAGE strongly overestimates the values of the 'higher molecular mass' components H and M. This discrepancy stems from the carboxyterminal extensions known to have unusual amino acid composition.

Electron spin resonance studies on the inorganic-anion-transport system of the human red blood cell. Binding of a disulfonatostilbene spin label (NDS-TEMPO) and inhibition of anion transport

The disulfonatostilbene spin label, NDS-TEMPO, was synthesized (purity over 96%) and the binding of the spin label to human red-cell ghosts was studied. NDS-TEMPO is readily absorbed to the membrane surface. Both pretreatment of the ghosts with FDNB and DIDS and the presence of DNDS completely prevent the binding of NDS-TEMPO to red-cell ghosts. Chloride and sulfate competitively inhibit the binding of NDS-TEMPO. Conversely, NDS-TEMPO is a strong, competitive inhibitor of chloride and of sulfate transport. The dissociation constants of NDS-TEMPO from the ESR studies were in the range 1.0-2.0 microM (pH 7.6, 20 degrees C). The inhibition constants of NDS-TEMPO as obtained from the flux experiments were in the range 0.5-2.5 microM (pH 7.3, 25 degrees C). The close accordance of the NDS-TEMPO dissociation constants from the ESR studies with the NDS-TEMPO inhibition constants from the flux measurements indicate a specific labeling of the inorganic-anion-transport system.

Proteinchemical characterization of three structurally distinct domains along the protofilament unit of desmin 10 nm filaments

Limited chymotryptic cleavage of soluble chicken gizzard desmin protofilaments allows the characterization of three structurally distinct domains. A surface-exposed very basic amino-terminal region (the headpiece) with an amino acid sequence excluding alpha-helical organization (7.5 kd) is separated from the perhaps globular carboxy-terminal 48 residues (the tailpiece) by a distinctly different middle domain of approximately 330 residues. This 38 kd domain is very rich in alpha-helix (at least 83%), and electron microscopy reveals a thin rod with a length of 500 +/- 50 A. Amino acid sequence data also show that the rod domain is interrupted by a nonhelical portion. An alpha-helical array is able to form a coiled-coil spanning the carboxy-terminal half of the 38 kd domain. The alpha-type diffraction pattern of 10 nm filaments arises from a coiled-coil conformation displayed through most but not all of the middle domain of the protofilaments.