The adventitia, endothelium and atherosclerosis

Despite many theories, the initiating circumstances for the development of atherosclerosis remain obscure. The development of animal models of atherosclerosis was based upon the different theories of the origins of atherosclerosis which suggested that it originates at the intimal surface of the vessel. A more recent model of atherosclerosis involves perivascular manipulation of the vessel by positioning of a hollow silastic collar around the artery. In this model, several of the features seen in early human atherosclerosis are generated within a period of 7 days. It is hypothesized that arterial wall hypoxia following occlusion of the vasa vasorum may be the initial lesion of atherosclerosis, and hence that in some cases atherosclerosis is a disease of the outer layers of the arterial wall.

A cross-sectional study of platelet volume in healthy normotensive women with bilateral uterine artery notches

High uterine artery resistance characterized by bilateral notches seen on Doppler ultrasound in the second half of pregnancy is associated with an increased risk of adverse outcome related to pre-eclampsia and intrauterine growth retardation. We sought to establish whether there was a difference in platelet volume in healthy, normotensive women with high-resistance uterine artery Doppler findings compared to those with normal uterine artery Doppler findings. Forty-seven women were allocated prospectively into 'bilateral notch' and 'no notch' groups at color Doppler imaging of the uterine arteries carried out at a mean of 26 weeks' gestation. The difference in platelet volume between the two groups and the relationship of adverse outcome with raised platelet volume and high-resistance uterine artery Doppler findings was investigated. Twenty-three women had no evidence of uterine artery notches and 24 had bilateral uterine artery notches. Platelet volume in the women with bilateral notches was greater than in those with no notches (8.28 fl vs. 7.46 fl; p = 0.01). However, unlike high-resistance uterine artery Doppler findings, increased platelet volume was not associated with adverse outcome. Uterine artery Doppler flow abnormalities have not previously been studied in combination with hematological or biochemical markers. Our findings show, for the first time, that women with bilateral uterine artery notches have an increased platelet volume compared to those with normal uterine artery Doppler findings many weeks before clinical signs of pre-eclampsia or fetal growth retardation are evident. Women with abnormal uterine artery flow at this gestation may have other cardiovascular and hematological differences compared to those with normal flow.

Gene transfer into the carotid artery using an adventitial collar: comparison of the effectiveness of the plasmid-liposome complexes, retroviruses, pseudotyped retroviruses, and adenoviruses

We studied the efficiency of plasmid/liposome complexes, Moloney murine leukemia virus-derived (MMLV) retroviruses, pseudotyped vesicular stomatitis virus protein-G (VSV-G)-containing retroviruses, and adenoviruses in delivering genes into the rabbit carotid artery using a silastic collar applied to the adventitia. This method was used for gene transfer because (a) it provides a gene delivery reservoir; (b) no intraluminal manipulations are performed; (c) installation of the collar induces arterial smooth muscle cell (SMC) proliferation and enhances retroviral gene transfer efficiency where target cell proliferation is required. The transfer of the beta-galactosidase (lacZ) marker gene to the adventitia and media occurred with all gene transfer systems. Adenoviruses also transferred the beta-galactosidase gene to some endothelial cells. After 5 days, adenoviral vectors produced the highest gene transfer efficiency with up to 10%+/-6% of cells showing beta-galactosidase activity. Pseudotyped VSV-G retroviruses were also effective in achieving gene transfer in 0.05%+/-0.03% of cells in the adventitia and media. Plasmid/liposome complexes and MMLV retroviruses infected 0.05%+/-0.03% and <0.01%+/-0.01% of cells, respectively. It is concluded that replication-deficient adenoviruses, VSV-G pseudotyped retroviruses, and plasmid/liposome complexes can be used for gene transfer to the arterial wall using the collar method. Because the endothelium remains anatomically present throughout the experiments, the model may be useful for the gene transfer studies involving diffusible or secreted gene products that primarily act on the endothelium. Effects on medial SMC and even endothelium can be achieved from the adventitial side, suggesting an alternative route for the delivery of therapeutically useful genes into the arterial wall.

Amy as a reporter gene for promoter activity in Nocardia lactamdurans: comparison of promoters of the cephamycin cluster

Promoter probe vectors containing the pA origin of replication and the Streptomyces griseus promoterless amy gene (encoding alpha-amylase) as reporter have been constructed to study transcription initiation regions in Nocardia lactamdurans. In some of the promoter probe vectors the phage fd terminator has been introduced to avoid readthrough expression from upstream sequences. By using these vectors, four different transcription initiation regions of the cephamycin gene cluster have been studied in N. lactamdurans. The bla gene encoding a beta-lactamase has a relatively strong promoter. Two other separate promoters corresponding to the lat and cefD genes (encoding, respectively, lysine-6-aminotransferase and isopenicillin N-epimerase) showed weak transcription initiation ability. These two promoters are arranged in a bidirectional transcription initiation region located in the center of the cephamycin gene cluster. The cmcH gene (encoding 3-hydroxymethylcephem carbamoyltransferase) upstream region did not contain a functional promoter, suggesting that cmcH is transcribed as a part of a polycistronic mRNA. The native amy promoter is used very efficiently in N. lactamdurans, resulting in secretion of high levels of extracellular alpha-amylase.

A model for the design and evaluation of algorithms for closed-loop cardiovascular therapy

Developing a clinically useful closed-loop drug delivery system can be extremely time consuming and costly. One approach to reducing the time and cost associated with developing closed-loop systems is to reduce the number of animal experiments and perform an extensive set of simulation studies. Through simulations, a closed-loop controller's performance can be evaluated over a complete spectrum of the patient population, including boundary conditions. Simulation studies are repeatable, offering significant advantages in comparing modifications in control algorithms. Finally, simulation studies can be performed in a fraction of the time required for animal studies, at a fraction of the cost. We have developed a simulator, that included a nonlinear pulsatile-flow cardiovascular model, a physiological regulatory mechanism, and the pharmacology of four frequently titrated cardiovascular drugs. This simulator has already been used in the design and evaluation of two closed-loop algorithms-a self-tuning regulator (STR) and a multiple model adaptive controller (MMAC)-for blood pressure control during and after cardiac surgery.

Compartmental shifts of calcium and magnesium as a result of swimming and swimming training in rats

To describe accurately the mineral changes (Ca and Mg) provoked by swimming, the aims of this study were to analyze those tissues that, with regard to their mineral content, can better classify individuals performing both swimming until exhaustion and swimming as training and to know the shifts of these minerals between different tissues after a single session of swimming until exhaustion and after training. Wistar rats were distributed into 12 groups, six male and six female (N = 10): 1) control rest group (CR); 2) trained rest group (TR); 3) control exercise group (CE); 4) trained exercise group (TE); 5) control recovery group (CER) and 6) trained recovery group (TER). The most informative tissues of Ca and Mg compartmental shifts during exercise have been determined. Discriminant analysis selected heart Ca, muscle Ca and bone Ca, bone Mg, erythrocyte Mg, and serum Mg as the most significant variables. The animals were classified by means of two canonical axes: the first one relates to training situation and sex, and the second one shows the special characteristics of trained male rats. Another independent discriminant analysis applied to male and female groups separately showed that the first canonical axis (control/trained) is basically defined by heart Ca, bone Ca, and erythrocyte Mg (male), and by heart Ca, bone Ca, and bone Mg (female), while the second axis, related to the exercise situations, is defined by the serum Mg levels in both sexes. We think that discriminant analysis is a statistical method capable of explaining physiological processes and classifying individuals performing exercises of different length. It suggests that the homeostasis of Ca and Mg is somewhat different for males and females. Serum magnesium must be considered to distinguish exercise situations. The analysis of these tissues could inform us about the mineral status of the rats and then we could correct possible deficiencies in our research. In this work we have only found different mineral redistributions among tissues. The trained animals have a better mineral recovery capacity than the untrained ones. Training has a different physiological repercussion in male and female rats on the basis of their respective maximal swimming times after training and their mineral behavior.

Megakaryocyte ploidy and platelet changes in human diabetes and atherosclerosis

Altered platelet morphology and function have been reported in patients with diabetes. They are likely to be associated with the pathological processes and increased risk of vascular disease seen in these patients. Mean platelet volume (MPV), platelet count, and megakaryocyte (MK) ploidy (DNA content) were measured in (1) nondiabetics with normal coronary arteries, (2) nondiabetics with coronary artery atherosclerosis, (3) diabetics without evidence of vascular complications, and (4) diabetics with vascular disease. The platelet count (+/- SD) was increased in all groups but only significantly in the diabetics with vascular disease (236 +/- 65 versus 250 +/- 54 versus 257 +/- 64 versus 295 +/- 90 [P < or = .05] x 10(9)/L, for groups, I, II, II, and IV, respectively). The MPV was significantly increased in patients with atherosclerosis (7.0 +/- 0.4 versus 8.0 +/- 1.2 [P < or = .05] versus 7.2 +/- 0.9 versus 8.1 +/- 0.9 [P < or = .05] IL). Geometric mean MK ploidy was significantly increased in all groups compared with controls (16 +/- 1.5 versus 18.7 +/- 1.8 [P < or = .05] versus 19.8 +/- 1.6 [P < or = .05] versus 20.1 +/- 2.7 [P < or = .05]). Furthermore, some patients with vascular disease and/or diabetes had a modal ploidy shift from 16 (the normal mammalian modal ploidy) to 32, with a concomitant reduction of MKs in the 8 and 16 ploidy classes. This shift was seen particularly in the diabetics with vascular disease (P = .007). Interleukin-6 (IL-6) levels were measured and were elevated in patients with atherosclerosis; the highest levels were found in the diabetic patients (0.7 +/- 0.9 versus 5.3 +/- 5.5 [P < or = .05] versus 2.5 +/- 2.8 versus 6.7 +/- 5.5 [P < or = .05] ng/L). In the diabetic patients with atherosclerosis, fibrinogen levels were also increased (2.85 +/- 0.76 versus 3.34 +/- 1.32 versus 2.43 +/- 1.50 versus 5.59 +/- 1.72 [P < or = .05] g/L). Furthermore, IL-6 levels correlated with MK ploidy (r = .45, P = .009) and fibrinogen levels (r = .5, P = .0001). This study demonstrates that patients with vascular disease, particularly diabetics, have an altered MK ploidy distribution, showing a shift toward higher ploidy in association with an increased platelet mass (count x volume). Changes in platelets in diabetes probably reflect MK changes, which themselves are a response to systemic change.

Length of the follicular phase, time of insemination, coital rate and the sex of offspring

The penetrability of cervical mucus improves over the follicular phase. When the length of the follicular phase varies due to variation in the timing of the luteinizing hormone surge, mucus penetrability will also improve as the phase lengthens. As selection for Y spermatozoa decreases with improvements in mucus penetrability, sex ratios at conception should decline in longer follicular phases. Sex ratios should also decline as the time of insemination approaches ovulation unless hormonally-induced improvements in penetrability are reduced by the debris left by earlier inseminations.

Inducible nitric oxide synthase gene transcription and protein activity in the rat heart during endotoxaemia

Septicaemia leads to an impairment of myocardial contractility in animals and humans. Cytokines released during endotoxaemia are capable of increasing inducible nitric oxide synthase (iNOS) expression in vitro in myocytes, endothelial cells and macrophages. The aim of this study was to assess whether iNOS gene transcription occurs in the myocyte in vivo. Rats were injected with intraperitoneal endotoxin. Myocardial sections obtained 4, 6 and 8 hours after infection were hybridised with oligonucleotides complementary to iNOS cDNA. Myocardial homogenates were used to measure NOS enzyme activity and to detect iNOS mRNA. Uninfected control animals did not demonstrate myocardial iNOS expression. Myocardium from endotoxaemic animals contained iNOS mRNA and high calcium-independent NOS enzyme activity. In situ hybridisation did not localise iNOS to myocytes but to cells located between myocytes. Endotoxaemia leads to iNOS gene transcription and calcium-independent NOS enzyme activity in the rat myocardium. In situ hybridisation demonstrates that iNOS is not transcribed by the myocyte in vivo.

Megakaryocytes and platelets in vascular disease

Platelets are anucleate cells with no DNA. They are derived from their precursor, the megakaryocyte (MK), whose differentiation is characterized by nuclear polyploidization through a process called endomitosis. Changes in the MK-platelet-haemostasis axis may precede acute thrombotic events. Changes in MK ploidy distribution may be associated with the production of large platelets. Mean platelet volume (MPV) is an important biological variable as it is a determinant of platelet reactivity. Large platelets are denser and more active haemostatically. MPV is increased in patients after myocardial infarction (MI) and is a predictor of a further ischaemic event and death when measured after MI. It has been suggested that changes not only in platelets but also in the parental MK are associated with chronic and acute vascular events. The regulation of megakaryocytopoiesis depends on several haematopoietic factors such as thrombopoietin. An understanding of the signalling system that controls platelet number and size might give insight into a role of platelet production in thrombogenesis and atherogenesis.

New type of hexameric ornithine carbamoyltransferase with arginase activity in the cephamycin producers Streptomyces clavuligerus and Nocardia lactamdurans

The ornithine carbamoyltransferases (OTCases) from the beta-lactam-producing actinomycetes Streptomyces clavuligerus and Nocardia lactamdurans have been purified to near-homogeneity by delta-N-phosphonoacetylornithine-Sepharose 4B affinity chromatography. The S. clavuligerus and N. lactamdurans OTCases monomers had a molecular mass of 37 kDa. The native OTCases of S. clavuligerus, N. lactamdurans and Streptomyces coelicolor had molecular masses of 248, 251 and 247 kDa respectively, which correspond to a hexameric structure. The apparent K(m) values for ornithine and carbamoylphosphate of the S. clavuligerus enzyme were respectively 2.3 and 6.0 mM at pH 8.0. The enzyme showed a reverse activity on citrulline and used lysine and putrescine as substrates. The hexameric complex showed coupled arginase-OTCase activities and was able to convert arginine into citrulline in a carbamoylphosphate-dependent manner. The requirement for carbamoylphosphate might prevent the arginase-OTCase complex from carrying out a futile cycle of arginine biosynthesis and degradation.

Integration of narrow-host-range vectors from Escherichia coli into the genomes of amino acid-producing corynebacteria after intergeneric conjugation

Conjugative transfer of mobilizable derivatives of the Escherichia coli narrow-host-range plasmids pBR322, pBR325, pACYC177, and pACYC184 from E. coli to species of the gram-positive genera Corynebacterium and Brevibacterium resulted in the integration of the plasmids into the genomes of the recipient bacteria. Transconjugants appeared at low frequencies and reproducibly with a delay of 2 to 3 days compared with matings with replicative vectors. Southern analysis of corynebacterial transconjugants and nucleotide sequences from insertion sites revealed that integration occurs at different locations and that different parts of the vector are involved in the process. Integration is not dependent on indigenous insertion sequence elements but results from recombination between very short homologous DNA segments (8 to 12 bp) present in the vector and in the host DNA. In the majority of the cases (90%), integration led to cointegrate formation, and in some cases, deletions or rearrangements occurred during the recombination event. Insertions were found to be quite stable even in the absence of selective pressure.

Expression of nitric oxide synthase in ulcerative colitis

Nitric oxide (NO) is generated from L-arginine by a family of enzymes called the NO synthases. Previous investigators have proposed that the expression of this inducible enzyme (iNOS) may account for the characteristic vasodilatation, oedema and impairment of get motility seen in active ulcerative colitis. Using a specific antibody to iNOS, we have investigated the distribution of this enzyme in colonic tissue from patients with histologically proven ulcerative colitis. Eight patients with ulcerative colitis expressed calcium-independent citrulline activity (9.96 +/- 2.34 pmol citrulline mg-1 protein min-1) and showed immunoreactivity to the iNOS antibody within the inflammatory infiltrate of the lamina propria, and also within the cytoplasm of the epithelial cells lining the colon. Five age-matched controls showed no calcium-independent citrulline activity (0.2 +/- 0.08 pmol citrulline mg-1 protein min-1) and no immunoreaction to the antibody. We conclude that this enzyme is present in colonic tissue including the epithelium from patients with active colitis. Inhibition of this enzyme may provide a novel therapeutic option for patients with active ulcerative colitis.

The effects of S-nitrosoglutathione on platelet activation, hypertension, and uterine and fetal Doppler in severe preeclampsia

OBJECTIVE

To determine the effects of the platelet-specific nitric oxide donor S-nitrosoglutathione on women with severe preeclampsia.

METHODS

Ten women with severe preeclampsia or preeclampsia with severe fetal compromise at 21-33 weeks' gestation each received a 60-90-minute intravenous infusion of 50-250 micrograms/minute of S-nitrosoglutathione. Each was hypertensive, despite conventional oral antihypertensive therapy in eight. Maternal blood pressure, heart rate, platelet activation, uterine artery, and fetal Doppler indices were measured during the infusion.

RESULTS

A dose-dependent reduction in mean arterial pressure from 125 mmHg (95% confidence interval [CI] 117-133) to 103.5 (95% CI 97-111) (P < .005) and an increase in pulse rate from 73.7 beats per minute (95% CI 64.3-84.5) to 89.1 (95% CI 81.2-97.8) (P < .02) was observed during the infusion. Mean uterine artery resistance index fell from 0.76 (95% CI 0.73-0.81) to 0.70 (95% CI 0.65-0.75) (P < .009). Platelet activation measured by P-selectin expression was reduced from 3.02% (95% CI 2.09-4.36) to 1.22% (95% CI 0.94-1.58) (P < .01). Fetal Doppler indices (umbilical artery, middle cerebral artery, and thoracic aorta) showed no significant changes during the infusion.

CONCLUSION

S-nitrosoglutathione infusion reduced material mean arterial pressure, platelet activation, and uterine artery resistance without further compromising fetal Doppler indices. This study suggests that platelet-specific nitric oxide donors may prove beneficial in the management of severe preeclampsia.

MEF2B is a potent transactivator expressed in early myogenic lineages

There are four members of the myocyte enhancer binding factor 2 (MEF2) family of transcription factors, MEF2A, -B, -C, and -D, that have homology within an amino-terminal MADS box and an adjacent MEF2 domain that together mediate dimerization and DNA binding. MEF2A, -C, and -D have previously been shown to bind an A/T-rich DNA sequence in the control regions of numerous muscle-specific genes, whereas MEF2B was reported to be unable to bind this sequence unless the carboxyl terminus was deleted. To further define the functions of MEF2B, we analyzed its DNA binding and transcriptional activities. In contrast to previous studies, our results show that MEF2B binds the same DNA sequence as other members of the MEF2 family and acts as a strong transactivator through that sequence. Transcriptional activation by MEF2B is dependent on the carboxyl terminus, which contains two conserved sequence motifs found in all vertebrate MEF2 factors. During mouse embryogenesis, MEF2B transcripts are expressed in the developing cardiac and skeletal muscle lineages in a temporospatial pattern distinct from but overlapping with those of the other Mef2 genes. The mouse Mef2b gene maps to chromosome 8 and is unlinked to other Mef2 genes; its intron-exon organization is similar to that of the other vertebrate Mef2 genes and the single Drosophila Mef2 gene, consistent with the notion that these different Mef2 genes evolved from a common ancestral gene.

Mutational analysis of the DNA binding, dimerization, and transcriptional activation domains of MEF2C

There are four members of the myocyte enhancer factor 2 (MEF2) family of transcription factors in vertebrates, MEF2A, -B, -C, and -D, which have homology within a MADS box at their amino termini and an adjacent motif known as the MEF2 domain. These factors activate muscle gene expression by binding as homo- and heterodimers to an A/T-rich DNA sequence in the control regions of muscle-specific genes. To understand the mechanisms of muscle gene activation of MEF2 factors, we generated a series of deletion and site-directed mutants of MEF2C. These mutants demonstrated that the MADS and MEF2 domains mediate DNA binding and dimerization, whereas the carboxyl terminus is required for transcriptional activation. Amino acids that are essential for MEF2 site-dependent transcription but which do not affect DNA binding were also identified in the MEF2 domain. This type of positive-control mutant demonstrates that the transcription activation domain of MEF2C, although separate from the MEF2 domain, is dependent on this domain for transcriptional activation through the MEF2 site. MEF2 mutants that are defective for DNA binding act as dominant negative mutants and can inhibit activation of MEF2-dependent genes by wild-type MEF2C.

Autonomously replicating plasmids carrying the AMA1 region in Penicillium chrysogenum

Plasmid vectors containing the AMA1 sequence transformed with high efficiency and replicated autonomously in Penicillium chrysogenum. The efficiency of transformation of P. chrysogenum was related to the length of the AMA1 fragment used for constructing the different autonomously replicating plasmids. One of the two palindromic inverted repeats of AMA1 (the 2.2-kb SalI-HindIII fragment) is sufficient to confer autonomous replication and a high transformation efficiency. Deletion of the 0.6-kb central fragment located between the inverted repeats did not affect either the ability of the plasmids to replicate autonomously or the efficiency of transformation, but did alter the mitotic stability and the plasmid copy number. Deletion of any fragment of the 2.2-kb repeat caused the loss of the ability to replicate autonomously and reduced the transformation efficiency. Most of the transformants retained the original plasmid configuration, as multimers and without reorganization, after several rounds of autonomous replication. The AMA1 region works as an origin of replication in P. chrysogenum and A. nidulans but not apparently in Acremonium chrysogenum.

Platelets and Megakaryocytes in Vascular Disease

Platelets are involved in both atherosclerosis and its complications including coronary artery thrombosis. They are derived from their precursor, the mega-karyocyte (MK), a unique cell in mammalians as it can double its DNA content without intervening mitoses. There is growing evidence that changes in the megakaryocyte - platelet - haemostasis axis precede acute thrombotic events, therefore suggesting a preexisting prethrombotic state prior to thrombosis. In this context, interest has focused on changes in megakaryocyte DNA content and its relationship to platelet reactivity. An increase in MK ploidy may be associated with the production of large platelets. Large platelets are denser and are more reactive haemostatically. Mean platelet volume (MPV) is increased in patients immediately after myocardial infarction (Ml) and is a predictor of a further ischaemic event when measured after Ml.

One of the haematopoietic factors that regulate megakaryocytopoiesis has recently been characterized as the c-mpl ligand. This finding, and an understand-ing of the signalling system that controls not only platelet number but also size, might give insight into a role for platelet production in thrombogenesis and athe-rogenesis.

Platelet activation in acute myocardial infarction and unstable angina is inhibited by nitric oxide donors

Platelet activation and thrombus formation within the coronary artery are major factors in acute myocardial infarction (AMI) and unstable angina (UA), and continuing platelet activation is associated with an adverse prognosis. We assessed platelet activation by using flow cytometry to measure platelet surface expression of P-selectin and glycoprotein IIb/IIIa in 20 patients with AMI and 20 with UA, all of whom were treated with aspirin. Platelet studies were repeated after the infusion of a nitric oxide donor (glyceryl trinitrate or S-nitrosoglutathione) that produced a fall in mean arterial pressure of no more than 10 mm Hg. P-selectin was expressed on 2.5% (range, 1.4% to 6.3%) of platelets from AMI and 2.3% (range, 1.6% to 3.3%) from UA subjects compared with 1.0% (range, 0.6% to 1.9%) of platelets from 20 control volunteers without angina (P < .001). Glycoprotein IIb/IIIa expression was 101.6 +/- 2.7 arbitrary units of relative fluorescence in AMI and 100.2 +/- 3.3 in UA compared with 87.8 +/- 2.5 in control subjects (P < .01). In both AMI and UA, S-nitrosoglutathione reduced P-selectin (P < .001) and glycoprotein IIb/IIIa (P < .05) expression, as did glyceryl trinitrate (P < .02 and P < .01, respectively). In 3 of 20 patients receiving glyceryl trinitrate the lowest dose was not tolerated due to headache or hypotension. These findings show that platelet activation persists in AMI and UA despite aspirin treatment and that this can be inhibited by using glyceryl trinitrate or S-nitrosoglutathione. S-nitrosoglutathione is better tolerated at the doses required.

Inhibition of protein kinase C suppresses megakaryocytic differentiation and stimulates erythroid differentiation in HEL cells

The bisindolylmaleimide, GF109203X (2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)-maleimide ), a highly selective inhibitor of protein kinase C (PKC), was used to test the role of this enzyme in phorbol ester-induced megakaryocytic differentiation of HEL cells. Treatment of these cells with 10 nmol/L phorbol 12-myristate 13-acetate (PMA) for 3 days caused a complete inhibition of proliferation and a threefold increase in the surface expression of glycoprotein (GP) IIIa, a marker of megakaryocytic differentiation that forms part of the fibrinogen receptor complex, GPIIb/IIIa. A similar effect was observed with phorbol 12,13-dibutyrate, but not with the biologically inactive derivative PMA-4-O-methyl ether. The PMA-induced increase in GPIIIa expression was completely inhibited by GF109203X in a dose-dependent manner (IC50 = 0.5 mumol/L), with a maximal effect at 2.5 to 5.0 mumol/L. GF109203X also blocked the inhibitory effect of PMA on cell growth and inhibited PMA-stimulated phosphorylation of the 47-kD PKC substrate, pleckstrin. Incubation of HEL cells with 25 mumol/L hemin for 3 days caused a fourfold to fivefold increase in expression of the erythroid differentiation marker, glycophorin A. In contrast to the inhibitory effect of GF109203X on GPIIIa expression, hemin induction of glycophorin A was enhanced by this compound. Furthermore, GF109203X alone caused a dose-dependent increase in glycophorin A expression, and induced hemoglobinization. Consistent with these changes, Northern blot analysis revealed that GF109203X treatment reduced the steady-state level of GPIIb mRNA and increased those for glycophorin A and gamma-globin. These results suggest that PKC may act as a developmental switch controlling erythroid/megakaryocytic differentiation.

Cooperative activation of muscle gene expression by MEF2 and myogenic bHLH proteins

Members of the myocyte enhancer factor-2 (MEF2) family of MADS domain transcription factors cannot induce myogenesis in transfected fibroblasts, but when coexpressed with the myogenic basic-helix-loop-helix (bHLH) proteins MyoD or myogenin they dramatically increase the extent of myogenic conversion above that seen with either myogenic bHLH factor alone. This cooperativity required direct interactions between the DNA-binding domains of MEF2 and the myogenic bHLH factors, but only one of the factors needed a transactivation domain, and only one of the factors needed to be bound to DNA. These interactions allow either factor to activate transcription through the other's binding site and reveal a novel mechanism for indirect activation of gene expression via protein-protein interactions between the DNA-binding domains of heterologous classes of transcription factors.

The expression of mRNA for fibrinogen in megakaryocytes isolated from patients with T-cell lymphoma

The expression of fibrinogen mRNA was studied by in situ hybridization in freshly isolated megakaryocytes in 14 newly-diagnosed patients: seven with non-Hodgkin's lymphoma (NHL), three with immune thrombocytopenic purpura (ITP) and four haematologically normal patients prior to coronary artery bypass surgery. Fibrinogen mRNA in megakaryocytes was not detected in ITP, B-cell lymphomas or in healthy donors. However, it was present in all patients with the high-grade T-cell lymphomas, both with and without thrombocytopenia.

Myocardial calcium-independent nitric oxide synthase activity is present in dilated cardiomyopathy, myocarditis, and postpartum cardiomyopathy but not in ischaemic or valvar heart disease

OBJECTIVE

To determine the activity of the calcium-dependent constitutive (cNOS) and calcium-independent inducible nitric oxide (iNOS) synthases in heart tissue from patients with different cardiac diseases.

PATIENTS AND DESIGN

Endomyocardial biopsy specimens were obtained from patients with dilated hearts (by echocardiography and ventriculography) and normal coronary arteries (by selective angiography). Recognised clinical, radiological, and histopathological criteria were used to diagnose non-inflammatory dilated cardiomyopathy (DCM) (n = 6), inflammatory cardiomyopathy (ICM) (n = 5), and peripartum cardiomyopathy (PPCM) (n = 3). Comparative groups were chosen with similarly dilated hearts caused by ischaemic (n = 5) or valvar disease (n = 4), and, in addition, non-dilated hearts with ischaemic (n = 5) and valvar (n = 3) disease. Venous blood was taken at the time of myocardial biopsy for assay of plasma tumour necrosis factor alpha (TNF alpha).

RESULTS

Myocardial tissue from patients with DCM, ICM, and PPCM showed considerable iNOS activity (16.8 (2.7) pmol citrulline/mg protein/min) with little or no cNOS activity (1.3 (0.9) pmol citrulline/mg protein/min). In contrast, myocardial tissue from patients with both dilated and non-dilated hearts of ischaemic or valvar aetiology showed cNOS and little, if any, iNOS activity (dilated--cNOS 11.7 (2.4) and iNOS 0.8 (0.6) pmol citrulline/mg protein/min; non-dilated--cNOS 12.1 (1.8) and iNOS 1.4 (0.8) pmol citrulline/mg protein/min). Plasma TNF alpha was detectable only in patients with inflammatory DCM.

CONCLUSIONS

These results support the hypothesis the generation of nitric oxide by iNOS accounts for some of the dilatation and impaired contractility associated with inflammatory and non-inflammatory dilated cardiomyopathy and peripartum cardiomyopathy.

Hormonal and behavioral determinants of the secondary sex ratio

The timing of insemination relative to ovulation and the frequency of insemination appear prominently in analyses of variations in human secondary sex ratios. Explanations invoking these variables are shown to be inadequate. A new synthetic model of sex determination is proposed in which the sex of offspring is powerfully determined by the state of the cervical mucus. The cervical state is then shown to be a function of hormonal factors endogenous to the female in interaction with the effects of previous inseminations.

Cigarette smoking sensitizes and desensitizes impedance-measured ADP-induced platelet aggregation in whole blood

The effect of smoking on platelet aggregation appears to produce conflicting results, with some studies indicating an enhancement and others a decrease of aggregation. This epidemiological study of 120 male smokers, a subset of the Caerphilly Heart Disease Study, examined the relationship of two dimensions of smoking (time proximity of last cigarette before venepuncture and serum nicotine concentration) with threshold dose of adenosine diphosphate (ADP) necessary to induce platelet aggregation in whole blood. Means (range) of ADP threshold dose and nicotine concentration were 1.66 (0.5-2.5, censored) microM and 12.2 (0-35.2) ng/ml. Men smoking within 30 min of venepuncture demonstrated lower ADP threshold doses (-0.48 microM lower [95% C.I.: -0.95, -0.02])--reflecting increased sensitivity. Men with higher nicotine concentration had higher ADP threshold doses (Regression Coefficient: +0.032 microM per ng/ml [95% C.I.: 0.003, 0.062])--reflecting decreased sensitivity. Men smoking 30 min or more before venepuncture who also had high nicotine concentration (25-30 ng/ml) demonstrated the highest ADP threshold doses compared to never smokers and to men smoking the previous day (approximately 2.20 vs 1.86 and 1.81 microM). Relations involving nicotine concentration do not necessarily reflect a pharmacological effect although the potential for a short term nicotine mediated tolerance effect cannot be dismissed. These observations support an hypothesis suggesting a temporal sequence of platelet sensitization and desensitization during smoking.

Expression of mef2 genes in the mouse central nervous system suggests a role in neuronal maturation

Members of the myocyte enhancer factor 2 (MEF2) gene family are expressed in a dynamic pattern during development of the CNS of pre- and postnatal mice. The four MEF2 genes, Mef2A, -B, -C, -D, encode transcription factors belonging to the MADS (MCM1-agamous-deficiens-serum response factor) superfamily of DNA binding proteins. MEF2 factors have previously been shown to be positive regulators of gene expression in terminally differentiated muscle cells. To begin to determine the role of MEF2 factors in CNS development, we used in situ hybridization with gene-specific cRNA probes to define the expression patterns of each of the four Mef2 mRNAs in the developing and mature mouse CNS. Mef2C mRNA was first detected in a ventral portion of the telencephalon at 11.5 d postcoitum (p.c.). By 13.5 d p.c., each of the four Mef2 genes were expressed in overlapping yet distinct patterns in regions of the frontal cortex, midbrain, thalamus, hippocampus, and hindbrain. Temporal and spatial patterns of embryonic Mef2 gene expression appeared to follow gradients of neuron maturation and suggested that the onset of Mef2 gene expression coincides with withdrawal from the cell cycle and initiation of neuronal differentiation. This correlation is particularly striking for Purkinje cells in the cerebellum. Since the molecular mechanisms that regulate neuron differentiation are unknown, we propose that the MEF2 factors are likely to play an important role in this process.

Systemic effects of S-nitroso-glutathione in the human following intravenous infusion

Nitric oxide (NO) is a potent vasodilator and inhibitor of platelet aggregation. At present the clinical use of NO donors as inhibitors of platelet activation is limited by their concomitant hypotensive effect. The new NO donor S-nitroso-glutathione (GSNO) has a significant antiplatelet effect at doses that cause only a small decrease in blood pressure in rats. We have examined the antiplatelet and vasodilator properties of this nitrosothiol following systemic intravenous infusion in the human. GSNO was administered intravenously to 10 normal females of reproductive age noting changes in blood pressure, pulse and reported side effects. Ex vivo platelet aggregation to ADP was then performed in a platelet-ionized calcium lumiaggregometer on blood samples taken both before and after the infusions. Side effects such as headache or palpitations occurred only in two subjects at the highest infusion rate of 250 micrograms min-1. Blood pressure and pulse did not vary significantly during the study. Ex vivo platelet aggregation in response to ADP was significantly reduced by the infusion. These results suggest that GSNO is a more potent inhibitor of platelet activation than it is a vasodilator and therefore potentially represents a more clinically useful NO donor than has so far been available where an anti-thrombotic effect is required.

Basic fibroblast growth factor upregulates the expression of vascular endothelial growth factor in vascular smooth muscle cells. Synergistic interaction with hypoxia

BACKGROUND

Vascular endothelial growth factor (VEGF) is a hypoxia-inducible direct angiogenic factor. Upregulation of VEGF is thought to mediate many of the angiogenic effects of growth factors that are not direct endothelial cell mitogens. Like VEGF, basic fibroblast growth factor (bFGF) is considered to induce angiogenesis by a direct effect on endothelial cells. This study investigated the possibility that bFGF may also act indirectly by regulating VEGF expression in vascular smooth muscle cells (VSMCs).

METHODS AND RESULTS

Incubation of confluent and quiescent cultures of rabbit VSMCs with bFGF caused a time- and concentration-dependent increase in steady-state levels of VEGF mRNA, as analyzed by Northern blot hybridization. Exposure of VSMCs to a threshold hypoxic stimulus (2.5% O2) caused a modest increase in VEGF mRNA levels. However, the combination of 2.5% O2 with bFGF had a marked synergistic effect. This effect was specific for VEGF as hypoxia did not enhance bFGF-induced expression of the proto-oncogene c-myc. Synergistic upregulation of VEGF mRNA expression also was observed between hypoxia and TGF-beta 1.

CONCLUSIONS

These results suggest that bFGF may promote angiogenesis both by a direct effect on endothelial cells and also indirectly by the upregulation of VEGF in VSMCs. The synergy demonstrated between hypoxia and either bFGF or TGF-beta 1 suggests that multiple diverse stimuli may interact via the upregulation of VEGF expression in VSMCs to amplify the angiogenic response.

The paired-like homeo box gene MHox is required for early events of skeletogenesis in multiple lineages

Formation of cartilage and bone involves sequential processes in which undifferentiated mesenchyme aggregates into primordial condensations that subsequently grow and differentiate, eventually forming the adult skeleton. Although much has been learned about the structural molecules that compose cartilage and bone, little is known about the nuclear factors that regulate chondrogenesis and osteogenesis. MHox is a homeo box-containing gene that is expressed in the mesenchyme of facial, limb, and vertebral skeletal precursors during mouse embryogenesis. MHox expression has been shown to require epithelial-derived signals, suggesting that MHox may regulate the epithelial-mesenchymal interactions required for skeletal organogenesis. To determine the functions of MHox, we generated a loss-of-function mutation in the MHox gene. Mice homozygous for a mutant MHox allele die soon after birth and exhibit defects of skeletogenesis, involving the loss or malformation of craniofacial, limb, and vertebral skeletal structures. The affected skeletal elements are derived from the cranial neural crest, as well as somitic and lateral mesoderm. Analysis of the mutant phenotype during ontogeny demonstrated a defect in the formation and growth of chondrogenic and osteogenic precursors. These findings provide evidence that MHox regulates the formation of preskeletal condensations from undifferentiated mesenchyme.

Cloning and characterization of an alpha-amylase gene from Streptomyces sp WL6

An alpha-amylase gene from Streptomyces sp WL6 was cloned on a 3.1kb DNA fragment, which was completely sequenced. The 3088 nucleotide sequence obtained contains three putative coding regions in the same orientation. The one corresponding to the structural region of the alpha-amylase gene has a deduced amino acid sequence of 459 residues, showing up to 71% identity to other alpha-amylases. An incomplete ORF was identified upstream the alpha-amylase gene, and the deduced product presents some homology to proteins involved in catabolic regulation.

Response of digital arteries to endothelium dependent and independent vasodilators in patients with Raynaud's phenomenon

The cause of the digital artery spasm seen in Raynaud's phenomenon (RP) is unclear. A dysfunction of endothelium-dependent vasodilation might contribute to the development of this spasm. We studied the digital artery responses to endothelium-dependent and independent vasodilators in eight Raynaud's phenomenon patients and eight sex-matched controls. A sequential series of infusions alternating with physiological saline were administered at a rate of 1 mL min-1 via the radial artery. The infusions contained acetylcholine chloride (ACh) 110 nm mL-1 and 550 nm mL-1, L-arginine 50 mumol mL-1, prostacyclin (PGI2) 2.5 ng mL-1 and glyceryl trinitrate (GTN) 4.5 nm mL-1. Digital artery diameter (DAD) and cutaneous temperature were measured. DAD was measured using a high frequency A-mode ultrasound scanner. There was no significant difference in mean brachial artery pressure, digital cutaneous temperature and DAD between the two groups at the start of the study. Comparing responses in the groups, there was a significantly greater increase in DAD and cutaneous temperature to Ach (endothelium-dependent vasodilator) at both concentrations in controls. A significantly greater increase in DAD was obtained in response to GTN (endothelium-independent vasodilator) in the RP subjects. There was no significant difference in response to L-arginine and PGI2 between the groups. These results suggest that a dysfunction of endothelium-dependent vasodilation is present in RP patients.

The mouse MRF4 promoter is trans-activated directly and indirectly by muscle-specific transcription factors

MRF4 is a member of the basic helix-loop-helix (bHLH) family of muscle-specific transcription factors, which also includes MyoD, myogenin, and myf5. The myocyte enhancer binding factor 2 (MEF2) proteins also serve as important muscle-specific transcription factors. In addition to activating the expression of many muscle-specific structural genes, various members of these two classes of proteins activate their own expression and the expression of each other in a complex transcriptional network that results in the establishment and maintenance of the muscle phenotype. To begin to determine how the expression of MRF4 is regulated by other muscle-specific transcription factors, we have isolated a region of the MRF4 gene that confers muscle-specific expression and have analyzed this promoter region for cis-acting elements involved in trans-activation by the myogenic bHLH and MEF2 transcription factors. Here, we show that in 10T1/2 fibroblasts the MRF4 promoter is trans-activated by myogenin, MyoD, myf5, and by the MEF2 factors, but that MRF4 does not activate expression of its own promoter. Myogenin activated the MRF4 promoter directly by an E box-dependent mechanism, while MEF2 factors activated the promoter through an indirect pathway. The E box-dependent regulation of the MRF4 promoter is in contrast to the regulation of the myogenin and MyoD promoters and may represent a mechanism for the differential expression of these factors during myogenesis.

The influence of the adventitia on the presence of smooth muscle cells and macrophages in the arterial intima

OBJECTIVE

To test the hypothesis that atherosclerosis may be initiated by hypoperfusion or thrombotic occlusion of the adventitial vasa vasonum.

DESIGN

In a new model of atherogenesis, an early atherosclerotic lesion may be initiated by removal of the adventitia from the carotid artery of the New Zealand White rabbit, wherein lie the vasa vasorum.

SETTING

Animal laboratory, University Department of Surgery and Medicine.

CHIEF OUTCOME MEASURES

Immunocytochemistry was undertaken to demonstrate the presence of smooth muscle cells and macrophages within the intimal lesions. Smooth muscle cells were labelled with a monoclonal antibody designated HHF35 and macrophages were labelled with a rabbit specific, macrophage specific antibody, RAM11. CHIEF RESULTS: In rabbits fed a normal diet, at day 14, the intimal lesion was composed exclusively of smooth muscle cells. By day 28, such lesions had regressed. In rabbits fed a high cholesterol diet, at day 14, the intimal lesion was composed of a mixture of macrophages and smooth muscle cells. By day 42, the pattern of cellular distribution was such that macrophages (present as foam cells) were predominant. In the presence of persistent hypercholesterolaemia these lesions did not regress.

CONCLUSIONS

This new model can produce two different cellular responses that may mimic the intimal lesions seen with re-stenosis after angioplasty or in hypercholesterolaemic man and as such, might be useful in separating out these two different pathophysiologies.

Hypoxia and platelet-derived growth factor-BB synergistically upregulate the expression of vascular endothelial growth factor in vascular smooth muscle cells

Vascular endothelial growth factor (VEGF) mRNA expression was analysed in rabbit vascular smooth muscle cells following exposure to hypoxia and platelet-derived growth factor-BB (PDGF-BB). Hypoxia potently upregulated VEGF mRNA steady-state levels in a time- and concentration-dependent manner reaching a maximum level (approximately 30-fold increase) after 12-24 h at 0% 0(2). In contrast, PDGF-BB caused a modest increase in VEGF expression. However, the combination of PDGF-BB and a threshold hypoxic stimulus (2.5% O2 for 4 h) had a marked synergistic effect. Synergy between hypoxia and PDGF-BB was selective for VEGF expression as hypoxia had no effect on the PDGF-induced upregulation of the proto-oncogene c-myc. These results raise the possibility that hypoxia and PDGF-BB may act in concert to induce VEGF expression in the arterial wall during the development of atherosclerosis.

Inhibition of platelet activity by S-nitrosoglutathione during coronary angioplasty

Platelet activation is associated with acute vessel occlusion and chronic restenosis after percutaneous transluminal coronary angioplasty (PTCA). Organic nitrates, which act by releasing the vasodilator and anti-platelet agent nitric oxide (NO), have a predominantly vasodilator action and cause hypotension at doses required to inhibit platelet activation. S-nitrosoglutathione (GSNO) is an NO donor with a preferential action on platelets. We investigated platelet activation in patients undergoing PTCA and the effect of GSNO. Blood was sampled from the coronary sinus to measure platelet surface expression of P-selectin and glycoprotein IIb/IIIa as indices of platelet activation. In 7 control patients, PTCA caused a rise in platelet surface expression of P-selectin and glycoprotein IIb/IIIa, which was maximal 5 minutes after PTCA, indicating increased platelet activation despite treatment with aspirin, glyceryl trinitrate, and heparin. 6 patients received an intracoronary infusion of GSNO, starting 10 min before PTCA. GSNO significantly inhibited the PTCA-induced increase in platelet surface expression of P-selectin and glycoprotein IIb/IIIa without altering blood pressure. These findings show that platelets are activated following PTCA and that GSNO can prevent this activation.

Application of pattern recognition and image classification techniques to determine continuous cardiac output from the arterial pressure waveform

The shape of the arterial pressure waveform is a non-linear function of stroke volume, heart rate and many other cardiovascular parameters. Previous attempts have been made to exploit this relationship and derive cardiac output (CO) from the arterial pressure waveform. These classical "pulse-contour" methods utilized simplifying linear assumptions, as a result they failed to adequately estimate CO over a sufficiently wide range of hemodynamic conditions. We have applied pattern recognition and image processing techniques to the problem of deriving CO from the arterial pressure waveform, thereby eliminating the need for simplifying assumptions. Computer simulations were used to develop the basic pattern recognition algorithms and compare their performance with that of published classical "pulse-contour" methods. Animal models were subsequently used to demonstrate proof of the concept. For over 200,000 individual heart beats, covering a wide range of hemodynamic conditions, the mean error, in calculated CO compared to ultrasonic flow probe determined CO, was 2.8% with a standard deviation of 9.8%.

Nitric oxide generation. A predictive parameter of acute allograft rejection

The L-arginine:nitric oxide (NO) biosynthetic pathway has been proposed as an important mediator in host defense mechanisms and may therefore play a role in the acute allograft response. We have studied NO generation in liver allograft rejection and determined its value in immunological monitoring. Stable end products of this pathway have been determined serially in 50 primary liver recipients and compared with 2 known mediators and markers of acute allograft rejection (IL-2R positive lymphocytes and circulating TNF alpha). Plasma concentrations of acid-labile nitrosocompounds (NOx), which increased during acute allograft rejection (P < 0.0001), correlated with rejection severity and were reduced after administration of supplemental high dose glucocorticoids. Concentrations were significantly lower in nonrejection graft complications but were elevated during episodes of sepsis. Correlations between plasma NOx levels and circulating TNF-alpha (r = 0.451, P < 0.001) and IL-2R-positive lymphocytes in peripheral blood (r = 0.781, P < 0.001) were demonstrated. In a logistic analysis of these variables, plasma NOx was the most predictive parameter of an episode of acute cellular rejection. Nitric oxide generation in FK506-treated patients was lower compared with patients receiving a CsA-based immunosuppression regimen and was associated with a reduced frequency of acute rejection in the FK506 group. These data are consistent with a role for NO in the cellular alloantigen immune response and indicate that monitoring of plasma levels of NOx may be useful in the detection of acute allograft rejection.

Megakaryocyte DNA content is increased in patients with coronary artery atherosclerosis

OBJECTIVE

Increased megakaryocyte size and megakaryocyte ploidy have been observed in man following myocardial infarction and sudden cardiac death. The aim of this study was to compare megakaryocyte ploidy in patients with and without coronary artery atherosclerosis.

METHODS

Sternal megakaryocytes were obtained immediately prior to cardiac surgery in 26 patients with significant coronary artery atherosclerosis requiring surgical bypass grafting and in 14 age matched control patients requiring cardiac valve replacement or repair with minimal or no coronary atherosclerosis on arteriography. Megakaryocytes were identified using a monoclonal antibody to the CD41 (GPIIb/IIIa) surface antigen and ploidy was studied using flow cytometry.

RESULTS

Megakaryocyte modal ploidy was significantly higher in the coronary atherosclerosis patients (modal ploidy 8N, n = 0 subjects; 16N, n = 16; 32N, n = 10) as compared with the control group (modal ploidy 8N, n = 5 subjects; 16N, n = 7; 32N, n = 2), p = 0.008. Ploidy correlated with the degree of coronary atherosclerosis defined as the number of atherosclerotic vessels observed on angiography (r = 0.51, p < 0.001, 95% confidence limits 0.25 to 0.70) and the serum total cholesterol concentration (r = 0.50, p = 0.006, 95% confidence limits 0.18 to 0.72). Bleeding time was not different [315(semiquartile range 45) s v 315(75) s] between the two groups in spite of the fact that 20 of 26 coronary atherosclerosis patients were taking aspirin versus one of 14 valve patients.

CONCLUSIONS

Megakaryocyte ploidy is increased in human coronary atherosclerosis and correlates with serum lipids. Hypercholesterolaemia may induce increases in megakaryocyte ploidy, and hence the production of hyperfunctional platelets, which will contribute to atherogenesis.

Endogenous mediators and thrombophilia

Platelet function is a balance between factors determined at thrombopoiesis and prothrombotic and antithrombotic mediators from the vascular wall. Nitric oxide is a crucial vasodilator and inhibitor of platelet activation synthesized constitutively by the vascular endothelium. In some pathological states this synthesis may be impaired leading to a prothrombotic state. In other situations, synthesis may be increased by a second inducible enzyme. Nitric oxide synergizes with other antithrombotic vasodilators such as prostacyclin and is opposed by prothrombotic vasoconstrictor mediators such as thromboxane. Platelets are anucleate and their reactivity is partly determined at thrombopoiesis by their progenitor cell, the megakaryocyte. In thrombotic states, such as myocardial infarction, larger, more reactive platelets from larger megakaryocytes are observed.