Animal pharmacokinetics and interspecies scaling of Ro 25-6833 and related (lactamylvinyl)cephalosporins

From a series of six (lactamylvinyl)cephalosporins, candidates for clinical evaluation were selected on the basis of their kinetic profile in animals and predicted pharmacokinetics in man. Exploratory pharmacokinetic studies with Ro 25-6833 and five related cephalosporins were performed following intravenous administration to rats, dogs, and cynomolgus monkeys. All compounds were characterized by a high protein binding in rat, monkey, and human plasma (unbound fraction < or = 5%), whereas in dog plasma, protein binding was markedly lower. Accordingly, for most compounds, clearance was highest in dogs, and lowest in monkeys. Comparison of the renal clearance of unbound drug with creatinine clearance suggests a renal elimination of Ro 25-6833 by glomerular filtration in both rats and dogs (urinary excretion in monkey was not determined due to drug instability in monkey urine). All other compounds showed different renal excretion mechanisms in rats and dogs, thus making the validity of allometric scaling questionable. Unbound clearances in man were predicted by allometric scaling (Ro 25-6833 only) and by a correlation analysis of cephalosporin pharmacokinetics in monkey and man. Limitations of both methods are discussed. When Ro 25-6833 was later studied in man, the predicted pharmacokinetic data in man from both approaches were found to be in good agreement with the observed values.

Comparison of antiplatelet effects of aspirin, ticlopidine, or their combination after stent implantation

BACKGROUND

This study was performed to analyze the influence of either aspirin, ticlopidine, or their combination on platelet activation and aggregation parameters after stent implantation.

METHODS AND RESULTS

Sixty-one patients with successful implantation of a single Palmaz-Schatz stent in a native coronary artery were randomly assigned to either group A (aspirin 300 mg/d+ticlopidine 2X250 mg/d), group B (ticlopidine 2X250 mg/d), or group C (aspirin 300 mg/d). Platelet activation was evaluated on days 1, 7, and 14 by flow cytometry measurement of expression of CD62p (p-selectin) and the binding of fibrinogen to the platelet surface glycoprotein IIb/IIIa receptor. Platelet aggregation was induced by addition of ADP or collagen. Differences between treatment groups were compared by ANOVA. Between days 1 and 14, we observed a significant decrease in collagen-induced platelet aggregation in group A (62.2+/-2.5% versus 36.9+/-3.1%), whereas an increase was seen in group B (58.3+/-2.5% versus 67.7+/-3.2%) and no change was seen in group C (P<.0001). The ADP-induced aggregation declined significantly in group A (74.7+/-1.4% versus 55.3+/-2.6%), whereas a delayed reduction was seen in group B (72.0+/-3.0% versus 52.6+/-4.2%) and no change was seen in group C (P=.0017). The CD62p expression declined significantly in groups A (68.2+/-2.7% versus 41.3+/-2.7%) and B (64.8+/-2.9% versus 39.3+/-3.5%) but not in group C (P<.0001). Moreover, the fibrinogen binding decreased significantly in group A (61.0+/-4.3% versus 36.3+/-4.2%) and with delay in group B (58.3+/-2.2% versus 39.4+/-3.0%), whereas no alterations were seen in group C (P=.012).

CONCLUSIONS

Our results demonstrate synergistic and accelerated platelet inhibitory effects of ticlopidine plus aspirin in patients after stent implantation compared with a monotherapy with either ticlopidine or aspirin alone.

The 5-HT transporter gene-linked polymorphic region (5-HTTLPR) in evolutionary perspective: alternative biallelic variation in rhesus monkeys. Rapid communication

By conferring allele-specific transcriptional activity on the 5-HT transporter gene promoter in humans, the 5-HT transporter gene-linked polymorphic region (5-HTTLPR) influences a constellation of personality traits related to anxiety and increases the risk for neurodevelopmental, neurodegenerative, and psychiatric disorders. Here we have analyzed the presence and variability of the 5-HTTLPR in several species of primates including humans, and other mammals. PCR, Southern blot, and sequence analyses of the 5-HT transporter gene's 5'-flanking region in different mammalian species confirmed the presence of the 5-HTTLPR in platyrrhini and catarrhini (hominoids, cercopithecoids) but not in prosimian primates and other mammals. Since the 5-HTTLPR is unique to humans and simian primates, a progenitor 5-HTTLPR sequence may have been introduced into the genome some 40 Mio, years ago. In humans the majority of alleles are composed of either 14 or 16 repeat elements, while alleles with 18 or 20 repeat elements are rare. In contrast, great apes including orang-utan, gorilla, and chimpanzee display a high prevalence of alleles with 18 and 20 repeat elements. In hominoids all alleles originate from variation at a single locus (polymorphic locus 1). In the 5-HTTLPR of rhesus monkeys (rh5-HTTLPR) we found an alternative locus for length variation (polymorphic locus 2) generated by a 21 bp insertion/deletion event. The existence of a distinct biallelic variation of the 5-HTTLPR in rhesus monkeys but similar allele and genotype frequencies in this species and humans supports the notion that there may be a relationship between functional 5-HT transporter expression, anxiety-related traits, and the complexity of socialization in human and non-human primate populations.

Carboxyl-truncated STAT5beta is generated by a nucleus-associated serine protease in early hematopoietic progenitors

Hematopoiesis is tightly controlled by a family of cytokines that signal through a related set of receptors. The pleiotropic and overlapping response of a cell to different cytokines is reflected in the number and complex pattern of activated signal transducers. Of special interest is STAT5, which is stimulated by a large and diverse set of cytokines. In addition to the two highly homologous proteins, STAT5A and STAT5B, encoded by duplicated genes, expression and activation of a dominant-negative, carboxyl-truncated form has also been described in early hematopoietic progenitors. We show here that a protease expressed in early hematopoietic cells cleaves the alpha forms of STAT5A/5B (p96/p94) to generate carboxyl-truncated beta forms (p80/p77). Inhibition studies assigned this protease to the serine class of endopeptidases. Cell fractionation experiments showed that the protease is associated with the nucleus in a constitutively activated form and does not require an activated STAT5 substrate. The ability of a protease to modulate the specificity of an activated transcription factor is unprecedented and underlines the importance of proteases in regulation of cell functions.

Arterio-venous carboxyhemoglobin difference suggests carbon monoxide production by human lungs

Carbon monoxide is hypothesized to be produced by the enzyme heme oxygenase predominantly in liver and spleen, bound to hemoglobin, and excreted by the lungs. Thus, venous carboxyhemoglobin is expected to be higher or equal to arterial carboxyhemoglobin. Unspecific inflammatory stimuli have been shown to induce heme oxygenase in lung tissue possibly leading to pulmonary carbon monoxide production. Arterial and central venous carboxyhemoglobin levels were measured in critically ill patients on the third day of ICU stay (n = 59) as well as in otherwise healthy humans prior to orthopedic surgery (n = 29). Arterial and central venous carboxyhemoglobin were higher in ICU patients than in healthy humans, respectively. In both groups, arterial carboxyhemoglobin was significantly higher than central venous carboxyhemoglobin. The arteriovenous carboxyhemoglobin differences were similar in both groups. The data suggest (a) increased CO-generation in critical illness and (b) pulmonary CO-production in healthy and critically ill humans.

Introduction

First-generation diode lasers produced stimulated emission from thick active regions consisting of a single semiconductor material. However, not long after epitaxial growth techniques advanced to the point of allowing thin heterostructure layers to be deposited with a high degree of control and precision, the quantum well laser was born. It soon became apparent that besides providing a valuable vehicle for studying fundamental quantum physics and optics in a solid state environment, quantum well diode lasers were also capable of dramatic performance improvements over their bulk counterparts. The lowering of threshold current densities was especially impressive.

High-temperature HgTe/CdTe multiple-quantum-well lasers

While most previous studies of Hg-based mid-IR lasers have focused on either bulk Hg(1-x)Cd(x)Te alloys or thick (> 100 A) Hg(1-x)Cd(x)Te quantum wells with relatively large x, we show that much thinner (20-30 A) HgTe binary wells may be engineered to suppress both Auger recombination and intervalence free carrier absorption. On the basis of detailed numerical simulations, we predict 4.3 m cw emission at temperatures up to 220 K for optical pumping and 105 K for diode operation. In pulsed mode, we expect maximum lasing temperatures more than 100 K higher than any prior Hg-based mid-IR result.

Transesophageal ultrasonographic imaging in rat hearts: visualization of aortic valve vegetations in non-bacterial thrombotic endocarditis

The aim of this study was to test the feasibility of transesophageal ultrasonography in rats by using an intravascular ultrasound system for visualization of vegetations at the aortic valve in the animal model of experimental endocarditis. After anesthesia and preparation of the right carotid artery, a polyethylene catheter was advanced across the aortic valve into the left ventricle in 91 rats. For transesophageal ultrasonography an intravascular ultrasound catheter (3.5 French; 30 MHz) linked to an imaging system was introduced into the esophagus. Sonographic investigations were performed every 24 hours until death. The presence, size, and echogenicity of vegetations were evaluated. Presence and size were compared to autopsy findings. No complications occurred as a result of the sonographic investigation. Left-sided valvular structures were imaged regularly. For detection of vegetations, sensitivity and specificity were 93% and 88%, respectively. Comparing the measurements of the vegetation size the following regression equation was obtained: y = 0.74x + 0.04 (r = 0.89; standard error of estimate = 0.02 cm). Inter- and intraobserver variabilities for sonographic measurements were 8.3% and 6.2%, respectively. Transesophageal ultrasonography permits reliable detection and repetitive accurate quantification of vegetations in the rat model of endocarditis. The technique enhances longitudinal studies of the dynamic process of the growth of vegetations under defined microbial conditions.

[Prevention of catheter-related infections, The official American guidelines--from the Centers for Disease Control]

The official German guidelines for prevention of intravascular-device-associated infections were published by the Bundes-gesundheitsamt, now called the Robert-Koch-Institut, 12 years ago. The recently published official "Guidelines for Prevention of Intravascular-Device Associated Infections" of the Centers for Disease Control and Prevention (CDC) are categorized according to scientific evidence. The American guidelines are very detailed and differ in some aspects from the official German guidelines. The purpose of the present paper is to inform the German-speaking anaesthesiologist about the official CDC guidelines and to provide an update on the prevention of intravascular-device-associated infections.

In vitro examination of the coronary artery wall after balloon angioplasty using intracoronary ultrasound

After autopsy 12 human coronary arteries were investigated by intracoronary ultrasound in order to measure the vessel wall dimensions and to detect damage on the vessel wall architecture after balloon angioplasty. Histology revealed artherosclerosis in 11/12 arteries. A total of 41 representative coronary segments were selected for further off-line ultrasound and histological analysis. Intracoronary ultrasound and histological measurements of the vessel wall thickness after balloon dilatation demonstrated a good correlation between the maximum thickness of the intima (histology 0.62 mm vs. intracoronary ultrasound 0.65 mm, r = 0.87) and the intima-media complex (0.80 mm vs. 0.83 mm, r = 0.87), in contrast to a weak one between the minimum thickness (r = 0.46 and r = 0.37). A total of 21 cases of damage occurred during angioplasty; intracoronary ultrasound detected 17. Further analysis showed that it imaged 10 of 11 cases of damage involving more than 30 degrees of the vessel circumference and 7 of 10 cases of damage involving less than 30 degrees of the vessel circumference. After balloon angioplasty of diseased coronary arteries, intracoronary ultrasound is therefore reliable in measuring the maximum wall thickness and in imaging damage involving more than 30 degrees of the vessel wall circumference.

Host cis-mediated extinction of a retrovirus permissive for expression in embryonal stem cells during differentiation

The use of retroviral vectors for gene transfer into animals has been severely hampered by the lack of provirus transcription in the early embryo and embryonic stem (ES) cells. This primary block in provirus expression is maintained in differentiated cells by a cis-acting mechanism that is not well characterized. Retroviral vectors based on the murine embryonal stem cell virus (MESV), which overcome the transcriptional block in ES cells, were constructed to investigate this secondary mechanism. These vectors transferred G418 resistance to ES cells with the same efficiency as to fibroblasts, but overall transcript levels were greatly reduced. A mosaic but stable expression pattern was observed when single cells from G418-resistant clones were replated in G418 or assayed for expression of LacZ or interleukin-3. The expression levels in independent clones were variable and correlated inversely with methylation. However, a second, more pronounced, block to transcription was found upon differentiation induction. Differentiation of the infected ES cells to cells permissive for retroviral expression resulted in repression and complete extinction of provirus expression. Extinction was not accompanied by increased levels of methylation. Provirus expression is thus regulated by two independent cis-acting mechanisms: (i) partial repression in the undifferentiated state, accompanied by increased methylation but compatible with long-term, low expression of retroviral genes, and (ii) total repression and extinction during early stages of differentiation, apparently independent of changes in methylation. These results indicate a time window early during the transition from an undifferentiated to a differentiated stage in which provirus expression is silenced. The mechanisms are presently unknown, but elucidation of these events will have an important impact on vector development for targeting stem cells and for gene therapy.

The perception of risk messages regarding electromagnetic fields: extending the extended parallel process model to an unknown risk

The Extended Parallel Process Model (EPPM) was developed as a model to assist in the development of effective risk communication messages, specifically messages that elicit adaptive behavioral responses. It has shown to be effective in several settings invoking clearly delineated dangers (e.g., safety belt usage, condom usage).Unfortunately, communicating risk messages is not always so straightforward. One increasing concern in the risk communication field is the controversy over electromagnetic fields (EMFs) and the uncertain hazards they present to individuals. The purpose of this study is to test the EPPM with this unknown risk and to explore which type of risk message may motivate adaptive behavioral responses. In accordance with the EPPM model, 251 participants received either a low- or high-threat risk message and a list of control measures they could use to reduce their exposure to EMFs. Results suggest that the EPPM model can be extended to an unknown risk.

Comparison of the haemodynamic effects of nitric oxide synthase inhibition and nitric oxide scavenging in endotoxaemic sheep

OBJECTIVE

The present study compared the effects of nitric oxide (NO) synthase inhibition and NO scavenging with haemoglobin in endotoxaemic sheep.

DESIGN

12 sheep were instrumented for chronic study. Six sheep received LG-nitro-arginine-methylester (L-NAME, 2.5 mg/kg bolus followed by a continuous infusion of 0.5 mg/kg per h), the other 6 sheep received pyridoxalated haemoglobin polyoxyethylene conjugate (PHP, 100 mg/kg bolus followed by a continuous infusion of 20 mg/kg per h).

MEASUREMENTS AND RESULTS

Haemodynamic and oxygenation parameters were measured in healthy sheep, after infusion of Salmonella typhosa endotoxin (10 ng/kg per min) for 24 h and after infusion of L-NAME or PHP. The infusion of endotoxin resulted in a hypotensive, hyperdynamic circulation. Infusion of L-NAME increased mean arterial pressure (MAP) from 76.1 +/- 4.2 mmHg to normal values of 95.8 +/- 5.7 mmHg (p < 0.05). PHP increased MAP from 73.0 +/- 3.0 to 88.6 +/- 4.7 mmHg (p < 0.05). This increase in MAP was associated in the L-NAME group with a more prominent drop in cardiac index (from 10.2 +/- 0.4 to 7.0 +/- 0.51.min-1.m-2; p < 0.05) than in the PHP group (from 10.7 +/- 0.2 to 9.3 +/- 0.61.min-1.m-2). During the first 90 min of infusion, cardiac index remained lower in the L-NAME group than in the PHP group. The increase in pulmonary vascular resistance was also higher in the L-NAME group.

CONCLUSION

These results suggest, that at the doses used in the experiment, NO scavenging with PHP has smaller effects on cardiac index and pulmonary vascular resistance than NO synthase inhibition with L-NAME. Therefore, the concept of NO scavenging in hyperdynamic sepsis should be further evaluated.

Work organization and atherosclerosis: findings from the ARIC study. Atherosclerosis Risk in Communities

INTRODUCTION

The aim of this investigation was to examine the extent to which work organization (i.e., occupational stress) is associated with subclinical carotid atherosclerosis.

METHODS

For that purpose we used a cross-sectional study of four U.S. community samples conducted between 1987 and 1989. Participants in the study were 10,801 adults aged 45 to 64 years. Subclinical carotid atherosclerosis was assessed by measuring the intima-media thickness (IMT) of the carotid artery wall using B-mode ultrasound. Occupational stress was defined using six indicators: substantive complexity of work, physical demands, job insecurity, skill discretion, decision authority, and physical exertion. Information from U.S. national surveys on occupational stress indicators was linked to the study participants' occupation.

RESULTS

We observed negative associations of complexity of work and skill discretion with mean IMT of the carotid artery wall among the four race-gender groups. In addition, physical demands was positively associated with mean IMT among blacks and job insecurity was positively associated with IMT among white women and black men. After adjustment for well-established risk factors, the magnitude of these associations was substantially reduced.

CONCLUSIONS

Taken in combination with results from recent European studies, our findings suggest that work organization plays a role in the etiology of atherosclerosis.

Atomic resolution (0.94 A) structure of Clostridium acidurici ferredoxin. Detailed geometry of [4Fe-4S] clusters in a protein

The crystal structure of the 2[4Fe-4S] ferredoxin from Clostridium acidurici has been solved using X-ray diffraction data extending to atomic resolution, 0.94 A, recorded at 100 K. The model was refined with anisotropic representation of atomic displacement parameters for all non-hydrogen atoms and with hydrogens riding on their parent atoms. Stereochemical restraints were applied to the protein chain but not to the iron-sulfur clusters. The final R factor is 10.03 % for all data. Inversion of the final least-squares matrix allowed direct estimation of the errors of individual parameters. The estimated errors in positions for protein main chain atoms are below 0.02 A and about 0.003 A for the heavier [4Fe-4S] cluster atoms. Significant differences between the stereochemistry of the two clusters and distortion of both of them from ideal Td tetrahedral symmetry can be defined in detail at this level of accuracy. Regions of alternative conformations include not only protein side chains but also two regions of the main chain. One such region is the loop of residues 25-29, which was highly disordered in the room temperature structure.

Transduction of antibiotic resistance markers among Actinobacillus actinomycetemcomitans strains by temperate bacteriophages Aa phi 23

Actinobacillus actinomycetemcomitans (Aa) strain ST1 carries the tetracycline (Tc) resistance transposon Tn916 and the Aa phi ST1 prophage, which is closely related to temperate bacteriophage Aa phi 23. High titre phage preparations were obtained from this strain by mitomycin C induction and were used to transduce the TcR determinant to the TcS recipient strains ZIB1001 and ZIB1015 (MIC 2 micrograms Tc/ml). TcR transductants (MIC > or = 32 micrograms Tc/ml) were detected at frequencies of 3 x 10(-6) to 5 x 10(-8) per pfu. All TcR transductants examined contained the entire Tn916 inserted at several different locations within the Aa genome. They appear to have resulted from generalized transduction. In addition both bacteriophages, Aa phi 23 and Aa phi ST1, were capable of transducing the chloramphenicol (Cm) resistance marker of plasmid pKT210 (transduction frequencies of 2 x 10(-5) to 3 x 10(-7) per pfu) to the recipient strain ZIB1001 (MIC 8 micrograms Cm/ml). Eleven CmR ZIB1001 transductants (MIC > or = 100 micrograms Cm/ml) studied carried a plasmid indistinguishable from pKT210 by restriction analyses. In view of the high prevalence of this phage family, and the increasing use of tetracycline in periodontitis therapy, these findings may have clinical importance.