Prognostic significance of blood pressure and heart rate variabilities: the Ohasama study

To investigate the association between cardiovascular mortality and short-term variabilities in blood pressure and heart rate, we performed a long-term prospective study of ambulatory blood pressure monitoring in Ohasama, Japan, starting in 1987. We obtained ambulatory blood pressure and heart rate in 1542 subjects >/=40 years of age. Blood pressure and heart rate variabilities were estimated as a standard deviation measured every 30 minutes by ambulatory monitoring. There were 67 cardiovascular deaths during the follow-up period (mean=8.5 years). The Cox proportional hazards model, adjusted for possible confounding factors, demonstrated a significant increase in cardiovascular mortality, with an increase in daytime systolic ambulatory blood pressure variability. A similar trend was observed in daytime diastolic and nighttime ambulatory blood pressures. Cardiovascular mortality rate increased linearly, with a decrease in daytime heart rate variability. Subjects in whom the daytime systolic ambulatory blood pressure variability was larger than third quintile and the daytime heart rate variability was lower than the mean-SD were at extremely high risk of cardiovascular mortality. The blood pressure and heart rate variabilities obtained every 30 minutes by ambulatory blood pressure monitoring were independent predictors for cardiovascular mortality in the general population.

Site-specific phosphorylation of synapsin I by mitogen-activated protein kinase and Cdk5 and its effects on physiological functions

Posttranslational modifications of synapsin I, a major phosphoprotein in synaptic terminals, were studied by mass spectrometry. In addition to a well known phosphorylation site by calmodulin-dependent protein kinase II (CaM kinase II), a hitherto unrecognized site (Ser553) was found phosphorylated in vivo. The phosphorylation site is immediately followed by a proline, suggesting that the protein is an in vivo substrate of so-called proline-directed protein kinase(s). To identify the kinase involved, three proline-directed protein kinases expressed highly in the brain, i.e. mitogen-activated protein (MAP) kinase, Cdk5-p23, and glycogen synthase kinase 3beta, were tested for the in vitro phosphorylation of synapsin I. Only MAP kinase and Cdk5-p23 phosphorylated synapsin I stoichiometrically. The phosphorylation sites were determined to be Ser551 and Ser553 with Cdk5-p23, and Ser62, Ser67, and Ser551 with MAP kinase. Upon phosphorylation with MAP kinase, synapsin I showed reduced F-actin bundling activity, while no significant effect on the interaction was observed with the protein phosphorylated with Cdk5-p23. These results raise the possibility that the so-called proline-directed protein kinases together with CaM kinase II and cAMP-dependent protein kinase play an important role in the regulation of synapsin I function.

A novel feature of the multistep phosphorelay in Escherichia coli: a revised model of the RcsC --> YojN --> RcsB signalling pathway implicated in capsular synthesis and swarming behaviour

In this study, we re-investigated the previously characterized RcsC (sensor His-kinase) --> RcsB (response regulator) phosphorelay system that is involved in the regulation of capsular polysaccharide synthesis in Escherichia coli. The previously proposed model hypothesized the occurrence of a direct phosphotransfer from RcsC to RcsB in response to an unknown external stimulus. As judged from the current general view as to the His --> Asp phosphorelay, this RcsC --> RcsB framework is somewhat puzzling, because RcsC appears to contain both a His-kinase domain and a receiver domain, but not a histidine (His)-containing phosphotransmitter domain (e.g. HPt domain). We thus suspected that an as yet unknown mechanism might be underlying in this particular His --> Asp phosphorelay system. Here, we provide several lines of in vivo and in vitro evidence that a novel and unique His-containing phosphotransmitter (named YojN) is essential for this signalling system. A revised model is proposed in which the multistep RcsC --> YojN --> RcsB phosphorelay is implicated. It was also demonstrated that this complex signalling system is somehow involved in the modulation of a characteristic behaviour of E. coli cells during colony formation on the surface of agar plates, namely swarming.

Differential roles for two gelatinolytic enzymes of the matrix metalloproteinase family in the remodelling cornea

We have documented changes in collagenolytic/gelatinolytic enzymes of the matrix metalloproteinase family (MMP) in remodelling rabbit cornea. MMP-2 (65 kDa gelatinase) in the proenzyme form is synthesized by the cells of the normal corneal stroma. After keratectomy the level of MMP-2 is increased in the stroma and enzyme appears in both pro- and activated forms. In addition, corneal cells synthesize MMP-9 (92 kDa gelatinase) in the proenzyme form after keratectomy; expression occurs in both the epithelial as well as stromal corneal layers. Changes in expression of both enzymes are precisely localized to the repairing portion of cornea, but demonstrate important differences in timing that correlate with the timing of specific events of matrix remodelling. Our data suggest that each of the gelatinases plays a different role in tissue remodelling after injury. We hypothesize that MMP-2 performs a surveillance function in normal cornea, catalyzing degradation of collagen molecules that occasionally become damaged. After wounding, this enzyme appears to participate in the prolonged process of collagen remodelling in the corneal stroma that eventually results in functional regeneration of the tissue. MMP-9 expression does not correlate with stromal remodelling, but we suggest that the enzyme might play a part in controlling resynthesis of the epithelial basement membrane.

An expression system of rat calmodulin using T7 phage promoter in Escherichia coli

An efficient expression system of rat calmodulin in Escherichia coli is presented. To express rat calmodulin cDNA, we employed a pET expression vector which contains the T7 phage promoter and terminator. After transformation of E. coli BL21(DE3) strain which carries T7 phage RNA polymerase inducible with isopropyl-beta-D-thiogalactopyranoside, induction of the expression, and chromatography of soluble proteins on a phenyl-Sepharose column, about 250 mg of recombinant rat calmodulin was obtained from 1 liter of E. coli culture. The recombinant calmodulin lacked the N-terminal methionine, and posttranslational modifications such as Nalpha-acetylation and methylation. This system facilitates the large amount preparation of calmodulin and the mutant proteins required for the structural analysis by NMR spectrometry and/or X-ray crystallography.

Prognosis of isolated systolic and isolated diastolic hypertension as assessed by self-measurement of blood pressure at home: the Ohasama study

BACKGROUND

Although the clinical significance of systolic-diastolic hypertension and isolated systolic hypertension has been established, the significance of isolated diastolic hypertension has not been fully investigated.

OBJECTIVE

To clarify the prognostic significance of isolated systolic and isolated diastolic hypertension as assessed by self-measurement of blood pressure (BP) at home (home BP measurements), which has a better reproducibility and prognostic value than casual BP measurements in the general population.

SUBJECTS AND METHODS

We obtained home BP measurements for 1913 subjects aged 40 years or older, then followed up their survival status (mean, 8.6 years). We classified the subjects into the following 4 groups according to their home BP levels: systolic-diastolic hypertension, isolated systolic hypertension, isolated diastolic hypertension, and normotension. The prognostic significance of each type of hypertension for the risk of cardiovascular mortality risk was investigated using a Cox proportional hazards regression model adjusted for possible confounding factors.

RESULTS

The risk for isolated systolic hypertension and systolic-diastolic hypertension were significantly higher than the relative hazard for normotension, while isolated diastolic hypertension was associated with no significant increase in risk. Home pulse pressure measurement was also independently associated with an increase in the risk of cardiovascular mortality.

CONCLUSIONS

Isolated diastolic hypertension, as assessed by home BP measurements, carried a low risk of cardiovascular mortality, similar to that found in subjects with normotension, suggesting that the prognosis of hypertension would be improved by treatment focused on systolic rather than on diastolic home BP measurements. To our knowledge, this study is the first to demonstrate the clinical significance of pulse pressure as assessed by home BP measurement. Arch Intern Med. 2000;160:3301-3306.

Endothelin-1 gene variant associates with blood pressure in obese Japanese subjects: the Ohasama Study

A recent report based on the results of 2 epidemiological studies, the Etude Cas-Temoin de l'Infarctus Myocarde (ECTIM) and the Glasgow Heart Scan Study, revealed that a G/T polymorphism with an amino acid substitution (Lys-->Asn) at codon 198 in exon 5 of the endothelin-1 gene (ET-1) is associated with blood pressure in overweight people. They suggested that G/T polymorphism of ET-1 strongly interacted with body mass index (BMI) in the determination of BP levels. To examine interaction among G/T polymorphism of ET-1, BMI, and BP, we performed an association study in a general Japanese population. Subjects (n=1250) were recruited from Ohasama, a cohort in a rural community of northern Japan. DNA was extracted from buffy coat of participants, and G/T polymorphism of ET-1 was determined by the TaqMan probe polymerase chain reaction method, a powerful tool for semiautomatic genotype determination of a large number of samples. Frequency of T (Asn 198) allele in Japanese (27%) was slightly but significantly higher than in whites (24%). Baseline characteristics (age, BMI, systolic and diastolic BP, and antihypertensive treatment) of all subjects were not significantly different according to the genotype of G/T polymorphism. However, in obese subjects (> or =25 kg/m(2)) diastolic BPs were significantly associated with G/T polymorphism of ET-1. After adjustment for confounding factors, significant association remained; for overweight subjects, diastolic BP level in those with T allele (GT + TT) was 1.8 mm Hg (P=0.04) higher than in those with GG genotype. That similar results were obtained from subjects of different races suggests that the Lys198Asn polymorphism of ET-1 is involved in determination of BP levels in obese subjects.

Characteristics of blood pressure measured at home in the morning and in the evening: the Ohasama study

OBJECTIVE

To determine the qualitative and quantitative differences of blood pressure measured at home (home measurement) in the morning versus the evening.

METHODS

Of 3744 participants, aged 20 years or older in the Ohasama population, more than 14 home measurements in the morning and in the evening, respectively, were obtained in each of 1207 individuals (881 untreated, 56.1 +/- 11.4 years and 326 treated, 66.0 +/- 9.2 years). A casual/screening measurement was also obtained in these individuals.

RESULTS

The home measurements in the morning were significantly higher than those in the evening. The bivariate linear regression analysis demonstrated that the difference between diastolic home measurement in the morning and that in the evening increased with an increase in diastolic home measurements. The multiple step-wise linear regression analysis, however, demonstrated that male sex, the use of antihypertensive medication, and SD of home measurements in individuals (blood pressure variability), but not level of home measurements, were positively associated with the difference between home measurement in the morning and that in the evening. The SD of home measurement in the evening in individuals was significantly larger than that in the morning, and the SD in treated individuals was significantly larger than that in untreated individuals. The correlations between casual and home measurements were moderate in untreated individuals (r = 0.509-0.567) but poor in treated subjects (r= 0.223-0.384). The correlations between home systolic measurements in the morning and in the evening were very close in both treated and untreated subjects (r = 0.814-0.902). The correlations between the SD of home measurements in the morning and in the evening were moderate in both treated and untreated individuals (r = 0.585-0.657).

CONCLUSIONS

Qualitative and quantitative differences in home blood pressure measurement, due to the differential time of measurement, should be taken into consideration in clinical use of home blood pressure measurements.

Usefulness of home blood pressure measurements in assessing the effect of treatment in a single-blind placebo-controlled open trial

OBJECTIVES

Reproducibility of home blood pressure measurements (HBP), and the placebo effect on HBP, were examined to establish the number of subjects required in order to observe a significant antihypertensive effect of a drug for a comparative study between placebo and active treatment.

METHODS

Reproducibility of HBP (n = 172 for systolic blood pressure and n = 137 for diastolic blood pressure) and the placebo effect on HBP (n = 35 for systolic and n = 42 for diastolic blood pressure) were examined using a semi-automatic electronic device on untreated hypertensive subjects during 21 consecutive days of measurements. From these two studies, the number of subjects required in order to observe a significant antihypertensive drug effect was assessed. In both studies, measurements from the first 3 days were excluded from the analysis.

RESULTS

Reproducibility, defined as the difference between the initial 5 day average (days 4-8) and the last 5 day average (days 17-21) was -1.9 +/- 7.0/-1.4 +/- 4.8 mmHg (mean +/- SD), indicating high reproducibility with a minimal regression to the mean effect. A placebo was administered after the 8 day run-in period. The difference between the initial 5 day average (days 4-8) and the last 5 day average (days 17-21) was compared. The mean difference was 1.1 +/- 6.2/0.2 +/- 5.7 mmHg, suggesting that there was a minimal, if any, placebo effect. As determined by the power calculations, based on the standard deviations of the tests for reproducibility and the placebo effect, nine of 13 subjects are required to show that a 9/5 mmHg decrease in systolic HBP/diastolic HBP (50% of estimated effective decrease in systolic HBP/diastolic HBP according to the guidelines for clinical trials in Japan) is statistically significant

CONCLUSIONS

The results suggest that the HBP measurement is highly reproducible and that there is a minimal, if any, placebo effect. These characteristics of HBP contribute to minimizing the number of subjects necessary for assessment of antihypertensive drug effects in comparative studies between an active treatment and placebo.

Stromal fibroblasts synthesize collagenase and stromelysin during long-term tissue remodeling

The process of connective tissue remodeling is an important mechanism contributing to tissue morphogenesis in development and homeostasis. Although it has long been known that remodeling tissues actively mediate collagenolysis, little is understood about the molecular mechanisms controlling this cell-regulated process. In this study, we examined the biosynthesis of collagenase and the related metalloproteinase, stromelysin, during remodeling of repair tissue deposited after mechanical injury to the rabbit cornea. Neither enzyme was synthesized by uninjured corneas; however, synthesis and secretion was detectable within one day after injury. Collagenase accumulated in its latent form while stromelysin appeared to be partially activated. Enzymes were synthesized by cells having a fibroblast phenotype. These cells were found within the stroma. New synthesis was correlated with accumulation of enzyme-specific mRNA. Highest levels of enzyme synthesis were observed in the repair tissue. However, stromal cells outside of the repairing area also synthesized both enzymes. The level of synthesis decreased in a gradient radiating from the repair tissue. Total synthetic levels in a given area of cornea were dependent on both the number of cells expressing enzyme and the rate of enzyme synthesis. Synthesis of collagenase was detected in repair tissue as long as nine months after injury. Our findings provide direct support for the hypothesis that new collagenase synthesis by cells in repair tissue is the first step in collagen degradation during long-term tissue remodeling.

Tuning of the porin expression under anaerobic growth conditions by his-to-Asp cross-phosphorelay through both the EnvZ-osmosensor and ArcB-anaerosensor in Escherichia coli

BACKGROUND

Widespread bacterial signal transduction circuits are generally referred to as 'two-component systems' or 'histidine (His)-to-aspartate (Asp) phosphorelays.' In Escherichia coli, as many as 30 distinct His-to-Asp phosphorelay signalling pathways operate in response to a wide variety of environmental stimuli, such as medium osmolarity and anaerobiosis. In this regard, it is of interest whether or not some of them together constitute a network of signalling pathways through a physiologically relevant mechanism (often referred to as 'cross-regulation'). We have addressed this issue, with special reference to the osmo-responsive EnvZ and anaero-responsive ArcB phosphorelay signalling pathways in E. coli.

RESULTS

Under standard aerobic growth conditions, it is well known that the osmoregulatory profile of the outer membrane porins (OmpC and OmpF) is mainly regulated by the EnvZ-OmpR phosphorelay system in response to medium osmolarity. In this study, it was found that, under anaerobic growth conditions, E. coli cells exhibit a markedly altered expression profile of OmpC and OmpF This profile was significantly different from that observed for the cells grown aerobically. Results from extensive genetic studies showed that, under such anaerobic growth conditions, the arcB gene encoding the anaero-sensory His-kinase appears to be an auxiliary genetic determinant that regulates the expression profile of porins. We then provided several lines of in vivo and in vitro evidence, which taken together, supported the following conclusions.

CONCLUSIONS

Under anaerobic growth conditions, porin expression is tuned not only by the authentic osmo-resposive EnvZ sensor, but also by the anaero-responsive ArcB sensor, in an OmpR-dependent manner. It is suggested that such ArcB-mediated cross-regulation plays a physiological role by integrating anaerobic respiratory signals into the porin regulation in E. coli anaerobiosis. The proposed model is a clear example of the interplay of two distinct His-to-Asp phosphorelay signalling pathways.

Remodeling of neutrophil phospholipids with 15(S)-hydroxyeicosatetraenoic acid inhibits leukotriene B4-induced neutrophil migration across endothelium

5-Lipoxygenase products, such as leukotrienes, are important stimuli for leukocyte-mediated tissue injury in acute inflammation. 15-Hydroxyeicosatetraenoic acid (15-HETE) is an eicosanoid generated by a variety of cell types via the actions of 15-lipoxygenases and, in addition, cyclooxygenases and epoxygenases. 15-HETE levels are frequently elevated at sites of inflammation, and extracellular 15(S)-HETE is esterified rapidly into neutrophil (PMN) phospholipids in vitro to levels that are comparable with arachidonic acid. We present evidence that remodeling of PMN phospholipids with 15(S)-HETE stereoselectively inhibits PMN migration across endothelium in response to leukotriene B4 (LTB4) and other chemoattractants. Esterified 15(S)-HETE causes a striking reduction in the affinity of LTB4 cell-surface receptors for their ligand and inhibition of LTB4-triggered stimulus-response coupling. As a result of these actions, esterified 15(S)-HETE attenuates the cytoskeletal rearrangements and CD11/CD18-mediated adhesive events that subserve directed locomotion of PMN across endothelium. These observations indicate that products of the 5-lipoxygenase and 15-lipoxygenase pathways can exert counterbalancing influences on PMN trafficking across endothelium. They suggest that 15(S)-HETE may be a potent endogenous inhibitor of PMN-endothelial interactions in vivo and serve to limit or reverse acute inflammation.

Regulational effect of ghrelin on growth hormone secretion from perifused rat anterior pituitary cells

Ghrelin, a novel growth hormone (GH)-releasing peptide, was recently isolated from the rat stomach as an endogenous ligand to growth hormone secretagogue receptor (GHS-R). Ghrelin specifically stimulates the release of GH from the rat anterior pituitary gland, but the regulational effect of ghrelin on GH secretion has not yet been clarified. We used a perifusion system to examine the single effect and combined effects of ghrelin with growth hormone-releasing hormone (GHRH) and somatostatin on GH secretion from rat anterior pituitary cells. The increase in GH concentration due to ghrelin stimulation showed a transitory peak that was almost the same as that previously reported for GHS, but apparently distinct from that of GHRH. Ghrelin (10(-10) M to 10(-8) M) stimulated GH secretion from the rat anterior pituitary cells in a dose-dependent manner. Serial ghrelin stimulation of the dispersed cells at 1-h intervals decreased the GH response, but the response recovered with stimulation at 3-h intervals, indicating that ghrelin strongly desensitized cells. Costimulation with ghrelin and GHRH elicited neither a synergistic nor an additive GH response from the rat pituitary cells. Furthermore, pretreatment to anterior pituitary cells with somatostatin strongly abolished ghrelin- and/or GHRH-stimulated GH secretion. In this study, we demonstrated that ghrelin caused weaker GH secretion than that caused by GHRH, and we also showed that costimulation with GHRH had no additive or synergistic effect on GH secretion, suggesting that ghrelin indirectly affects coordinated GH release from pituitary gland, as found in vivo.

An Escherichia coli protein that exhibits phosphohistidine phosphatase activity towards the HPt domain of the ArcB sensor involved in the multistep His-Asp phosphorelay

The Escherichia coli sensory kinase, ArcB, possesses a histidine-containing phosphotransfer (HPt) domain, which is implicated in the His-Asp multistep phosphorelay. We searched for a presumed phosphohistidine phosphatase, if present, which affects the function of the HPt domain through its dephosphorylation activity. Using in vivo screening, we first identified a gene that appeared to interfere with the His-Asp phosphorelay between the HPt domain and the receiver domain of OmpR, provided that the gene product was expressed through a multicopy plasmid. The cloned gene (named sixA) was found to encode a protein consisting of 161 amino acids, which has a noticeable sequence motif, an arginine-histidine-glycine (RHG) signature, at its N-terminus. Such an RHG signature, which presumably functions as a nucleophilic phosphoacceptor, was previously found in a set of divergent enzymes, including eukaryotic fructose-2,6-bisphosphatase, E. coli periplasmic phosphatase and E. coli glucose-1-phosphate phosphatase, and ubiquitous phosphoglycerate mutase. Otherwise, the entire amino acid sequences of none of these enzymes resembles that of SixA. It was demonstrated in vitro that the purified SixA protein exhibited the ability to release the phosphoryl group from the HPt domain of ArcB, but the mutant protein lacking the crucial histidine residue in the RHG signature did not. Evidence was also provided that a deletion mutation of sixA on the chromosome affected the in vivo phosphotransfer signalling. These results support the view that SixA is capable of functioning as a phosphohistidine phosphatase that may be implicated in the His-Asp phosphorelay through regulating the phosphorylation state of the HPt domain.

Neuroprotective effect of riluzole in MPTP-treated mice

The neuroprotective effects of riluzole, a Na(+) channel blocker with antiglutamatergic activity, and MK-801, a blocker of N-methyl-D-aspartate (NMDA) receptors, were compared in the model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced depletion of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels in mice. The mice were injected intraperitoneally (i.p.) with four administrations of MPTP (10 mg/kg) at 1 h intervals and then the brains were analyzed 1, 3 and 7 days after the treatment. Dopamine and DOPAC levels were significantly decreased in the striatum from 1 day after MPTP treatment. A severe depletion in dopamine and DOPAC levels was found in the striatum 3 and 7 days after MPTP treatment. Riluzole antagonized the MPTP-induced decrease in dopamine, DOPAC and HVA levels in the striatum. On the other hand, MK-801 prevented the MPTP-induced decrease in DOPAC levels, but not in dopamine levels in the striatum. An immunohistochemical study indicated that riluzole can protect against MPTP-induced neuronal damage in the substantia nigra. These results suggest that riluzole is effective against MPTP-induced neurodegeneration of the nigrostriatal dopaminergic neuronal pathway.

Biochemical and immunohistological changes in the brain of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mouse

We investigated neurochemically and neuropathologically the utility of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice as a model of Parkinson's disease. The changes in dopamine D1 and D2 receptors and dopamine uptake sites were determined by quantitative autoradiography using [3H]SCH23390, [3H]raclopride and [3H]mazindol, respectively. Dopamine and 3,4-dihydroxyphenyl acetic acid (DOPAC) contents in the striatum were measured by high-performance liquid chromatography. The distribution of nigral neurons and reactive astrocytes was determined by immunohistochemical staining with antibody against tyrosine hydroxylase (TH) and glial fibrillary acidic protein (GFAP). The mice received four intraperitoneal injections of MPTP (10 mg/kg) at 1-h intervals and then the brains were analyzed at 3 and 7 days after the treatments. No significant change in dopamine D1 receptors was observed in the striatum and substantia nigra after acute treatment with MPTP. Dopamine D2 receptors were reduced significantly in the substantia nigra only 7 days after the MPTP treatment, whereas striatum showed no significant change in the binding throughout the experiments. In contrast, dopamine uptake sites were reduced markedly in the striatum and substantia nigra 3 and 7 days after the MPTP treatment. Dopamine and DOPAC content were also reduced in the striatum 3 and 7 days after the MPTP treatment. An immunohistochemical study indicated a loss of the number of TH-positive neurons in the substantia nigra 7 days after the MPTP treatment. In contrast, numerous GFAP-positive astrocytes were evident in the striatum 7 days after the MPTP treatment. These results provide valuable information for the pathogenesis of acute stage of Parkinson's disease.

Effect of dietary alpha-linolenate/linoleate balance on mean survival time, incidence of stroke and blood pressure of spontaneously hypertensive rats

Following the suckling period, stroke-prone spontaneously hypertensive rats (SHR-SP) were fed semi-purified diets supplemented either with safflower seed oil (rich in linoleic acid) or with perilla seed oil (rich in alpha-linolenic acid). The mean survival time of male SHR-SP fed the perilla diet was longer than that fed the safflower diet by 17% (p less than 0.001) while the difference was 15% in female SHR-SP (p less than 0.05). The mean survival times of female SHR-SP were more than 40% longer than those of male SHR-SP in both dietary groups. Post-mortem examinations of brains revealed apoplexy-related symptoms as the major cause of the death in both dietary groups. The systolic blood pressure was lower by ca. 10% (21 mmHg) in the perilla group than in both the safflower group and conventional diet group. The eicosapentaenoate (20:5 n-3)/arachidonate (20:4 n-6) ratio of platelet phospholipids in spontaneously hypertensive rat (SHR), a measure of platelet aggregability, was much higher in the perilla group than in the safflower group. Thus, increasing the dietary alpha-linolenate/linoleate ratio resulted in an increased mean survival time of SHR-SP rats, possibly by lowering blood pressure and platelet aggregability.

Identification of the calmodulin-binding domain of neuron-specific protein kinase C substrate protein CAP-22/NAP-22. Direct involvement of protein myristoylation in calmodulin-target protein interaction

Various proteins in the signal transduction pathways as well as those of viral origin have been shown to be myristoylated. Although the modification is often essential for the proper functioning of the modified protein, the mechanism by which the modification exerts its effects is still largely unknown. Brain-specific protein kinase C substrate, CAP-23/NAP-22, which is involved in the synaptogenesis and neuronal plasticity, binds calmodulin, but the protein lacks any canonical calmodulin-binding domain. In the present report, we show that CAP-23/NAP-22 isolated from rat brain is myristoylated and that the modification is directly involved in its interaction with calmodulin. Myristoylated and non-myristoylated recombinant proteins were produced in Escherichia coli, and their calmodulin-binding properties were examined. Only the former bound to calmodulin. Synthetic peptides based on the N-terminal sequence showed similar binding properties to calmodulin, only when they were myristoylated. The calmodulin-binding site narrowed down to the myristoyl moiety together with a nine-amino acid N-terminal basic domain. Phosphorylation of a single serine residue in the N-terminal domain (Ser5) by protein kinase C abolished the binding. Furthermore, phosphorylation of CAP-23/NAP-22 by protein kinase C was also found myristoylation-dependent, suggesting the importance of myristoylation in protein-protein interactions.

Circular dichroism and 1H NMR studies on the structures of peptides derived from the calmodulin-binding domains of inducible and endothelial nitric-oxide synthase in solution and in complex with calmodulin. Nascent alpha-helical structures are stabilized by calmodulin both in the presence and absence of Ca2+

There exist two types of nitric-oxide synthase (NOS); constitutive isozymes that are activated by binding calmodulin in response to elevated Ca2+ and an inducible isozyme that binds calmodulin regardless of Ca2+. To study the structural basis of the difference in Ca2+ sensitivity, we have designed synthetic peptides of minimal lengths derived from the calmodulin-binding domain of endothelial NOS (eNOS) and that of macrophage NOS (iNOS). A peptide, KRREIPLKVLVKAVLFACMLMRK, derived from human iNOS sequence, retained the ability to bind to calmodulin both in the presence and absence of Ca2+, while a peptide derived from human eNOS sequence, RKKTFKEVANAVKISASLMG, bound to calmodulin only in the presence of Ca2+. Circular dichroism and two-dimensional 1H nuclear magnetic resonance studies suggested that both peptides assume nascent alpha-helical structures in aqueous solution. When mixed with calmodulin, both peptides showed circular dichroism spectra characteristic for alpha-helix. In contrast to other target proteins, the addition of iNOS peptide to calmodulin did not affect the Ca2+ binding of calmodulin appreciably. The peptide derived from the calmodulin-binding domain of iNOS, therefore, binds in alpha-helical structures both to Ca2+-calmodulin and apo-calmodulin, which is unique among various target proteins of calmodulin.

Dichotomic action of glucocorticoids on growth hormone secretion

The mechanism of apparently discrepant actions of glucocorticoids (GC) on GH secretion, in vivo suppression and in vitro potentiation, was studied in rats. Dexamethasone (Dex), at the concentration of 50 nmol/l, potentiated basal and GHRH-stimulated GH release from monolayer culture of normal rat pituitary cells in 48 h. On the other hand, in vivo administration of Dex, 165 micrograms daily for 3 days, consistently suppressed serum GH levels in female rats. In these rats, the hypothalamic content of immunoreactive (IR) SRIH was significantly increased, whereas that of IR-GHRH was significantly decreased in comparison with the untreated rats. Bioassayable GH-releasing activity was also lower in Dex-treated rats. These findings indicate that the suppressing effect of GC on GH release in vivo is, at least partially, due to the increase in hypothalamic SRIH release and probably also to the decrease in GHRH release, and these effects surpass the potentiating effect of GC on GH release at the pituitary level, resulting in a net inhibitory effect in vivo.