Cerebrovascular serotonergic receptors mediating vasoconstriction: further evidence for the existence of 5-HT2 receptors in rat and 5-HT1-like receptors in guinea-pig basilar arteries

Pharmacological experiments were carried out on isolated basilar arteries (BA) from the brain vasculature of guinea-pig and rat in order to characterize post-junctional serotonergic receptors mediating contraction by the use of selective agonists and antagonists. The sensitivity to 5-HT was higher, but the intrinsic activity lower, in guinea-pig compared to rat vessels. The contractile potency of the 5-HT1 agonists, 5-carboxamidotryptamine (5-CT), was three times higher than 5-HT in guinea-pig but 16 times lower in rat BA. In arteries from both species the 5-HT1A agonist, 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), only caused weak contraction. In rat BA, where the serotonergic contractile receptors are ketanserin-sensitive, mesulergine inhibited the contraction in doses high enough to block 5-HT2 receptors, and also propranolol slightly inhibited the contraction, probably due to its binding to these receptors. Methiothepin, a potent antagonist of the 5-HT1-like receptors, affected the contraction in a non-competitive manner. The antagonist profile was different in guinea-pig BA: propranolol was ineffective, mesulergine caused a slight, non-surmountable inhibition, whereas methiothepin acted as a true, competitive antagonist. The data support previous suggestions that the serotonergic contraction in rat BA is mediated by 5-HT2 receptors, whereas the present data show that 5-HT1-like receptors predominate in guinea-pig BA.

Enhancement of herpes simplex virus type 2 (HSV-2) DNA synthesis in infected cells that constitutively express the BglII-N region of the HSV-2 genome

The BglII-N fragment of the herpes simplex virus type-2 (HSV-2) genome encodes one of two known transforming regions of this DNA virus. In this study, we report the derivation of HeLa S3 cells (2DC4) that stably express the HSV-2 BglII-N region, including the small subunit of HSV-2 ribonucleotide reductase (RR). Superinfection of the 2DC4 cells with wild-type HSV-2 resulted in the efficient induction of HSV-2-encoded ICP10, DNA polymerase, and thymidine kinase. The amount of HSV-2 DNA synthesis in 8-hr HSV-2-infected 2DC4 cells was enhanced 2.6 +/- 0.6-fold relative to infected control cells. Furthermore, the replication kinetics of HSV-2 DNA in 2DC4 cells were accelerated relative to HeLa S3 cells; HSV-2 DNA synthesis was detectable as early as 3 hr postinfection in 2DC4 cells as compared to 6 hr postinfection in HeLa S3 cells. These results suggest that the BglII-N region of HSV-2 encodes function(s) that activate the viral DNA synthesis apparatus and that this activation could relate to the transforming ability of this DNA region.

Asymmetric somatosensory activation with right- vs left-hand stimulation: a positron emission tomographic study

Metabolic activation of the right and left somatosensory cortices (SSC) in response to an active sensorimotor task (palpation and sorting of mah jongg tiles) was studied in 16 right-handed normal volunteers using positron emission tomography (PET) and a double-injection [18F]fluorodeoxyglucose strategy. In 8 subjects with right-hand stimulation, cerebral metabolic rate for glucose (CMRglc) in the contralateral SSC increased by 16.7 +/- 5.1% (mean +/- S.D.); the increase in the ipsilateral SSC was 4.8 +/- 3.2%. In contrast, in the 8 subjects with left-hand stimulation, the contralateral increase was 12.0 +/- 2.9% and the ipsilateral increase was 5.9 +/- 1.5%. Thus, contralateral SSC activation was significantly higher with stimulation of the right hand, while the ipsilateral/contralateral symmetry of activation was greater when the left hand was stimulated.

Periplasmic secretion of human growth hormone by Escherichia coli

The gene coding for human growth hormone (hGH) was fused to the coding sequence for the signal peptide of a secreted Escherichia coli protein. STII heat-stable enterotoxin. This hybrid gene was expressed in E. coli. The signal peptide is properly processed and hGH is secreted in to the periplasmic space. In E. coli, some of the material made is proteolytically clipped or deamidated. The effect of culture conditions on the expression and secretion of hGH was studied and several important parameters were identified, including culture temperature and duration, cultivation pH, K+ levels, plasmid structure, and nutrient supplements. Alteration of culture conditions significantly improves the recovery yield and product quality of human growth hormone.

Effect of a 5-lipoxygenase (5-LO)/cyclooxygenase (CO) inhibitor, WY-47, 288, on cutaneous models of inflammation

WY-47,288 (2-[(1-naphthalenyloxy)methyl]quinoline) demonstrated topical antiinflammatory activity in several animal models of skin inflammation. Application of WY-47,288 to mouse ear surfaces inhibited arachidonic acid (ED50 = 0.3 mg/ear) and tetradecanoylphorbol acetate (TPA)-induced inflammation (40% at 1 mg/ear). Administration of WY-47,288 (1 mg/ear) at 30 min and 5 h after TPA reduced ear edema and epidermal proliferation by 50%. WY-47,288 also inhibited oxazolone-induced contact hypersensitivity in mouse ears (ED50 = 0.4 mg/ear) and UVB-induced guinea pig skin erythema (ED50 approximately 0.25 mg/spot). These antiinflammatory effects may be due to inhibition of 5-lipoxygenase (5-LO) and cyclooxygenase (CO) since the synthesis of 5-LO and CO products by rat neutrophils and mouse macrophages was dose-dependently reduced by WY-47,288. By contrast, WY-47,288 demonstrated no appreciable inhibition of 12-LO (rabbit platelet), 15-LO (soybean) or phospholipase A2 (human platelet). Furthermore, no systemic adverse effects were observed after topical, parenteral or oral administration of WY-47,288, suggesting that WY-47,288 is a safe topical 5-LO/CO inhibitor for treating skin inflammation.

Binding of heparin to human antithrombin III activates selective chemical modification at lysine 236. Lys-107, Lys-125, and Lys-136 are situated within the heparin-binding site of antithrombin III

A new water-soluble color reagent, 4-N,N-dimethylaminoazobenzene-4'-isothiocyano-2'-sulfonic acid (S-DABITC), was used to identify lysine residues of antithrombin III which participate in the binding of heparin. Antithrombin, modified with S-DABITC in the presence and absence of low molecular weight heparin (Mr 5000) was reduced, carboxymethylated, and digested with trypsin. The digest was analyzed by high-performance liquid chromatography and monitored at 465 nm. In the absence of heparin, four major colored peptides (T1, T2, T3, and T4) were identified. When antithrombin was preincubated with heparin (2-fold by weight), followed by S-DABITC modification, the recovery of peptide T4 remained unchanged, but the recoveries of T1, T2, and T3 were reduced by 93, 86, and 98%, respectively. In addition, a new colored peptide, TA, appeared. Amino acid sequencing of peptides T1, T2, T3, and TA localized S-DABITC modification sites as Lys-136, Lys-125, Lys-107, and Lys-236, respectively. Thus, binding of heparin to human antithrombin diminished S-DABITC modification at Lys-107, Lys-125, and Lys-136, but at the same time enhanced S-DABITC modification at Lys-236. This phenomenon was further characterized by varying the molar ratio of heparin/antithrombin (from 0.04 to 20). The shielding of Lys-125 and Lys-136 was inversely proportional to the activation of Lys-236. At a heparin/antithrombin molar ratio of 1, the extent of shielding of Lys-125 and Lys-136 and the unmasking of Lys-236 were 25-33%. This shielding-unmasking effect correlated with enhanced antithrombin inhibition of thrombin. We conclude that Lys-107, Lys-125, and Lys-136 are situated within the heparin-binding site of human antithrombin and that binding of heparin to antithrombin causes a conformational change of antithrombin that leads to the exposure of Lys-236 for S-DABITC modification.

Predominant left hemisphere metabolic dysfunction in dementia

Thirty-one patients with probable Alzheimer's disease and 11 patients with memory disorders, attributable to multiple cerebral infarctions, were studied using 18-F-fluorodeoxyglucose-positron emission tomography scans. Asymmetry in cerebral glucose metabolism within these diagnostic groups was assessed by comparison with the metabolic rates obtained in age-equivalent healthy control subjects. A significantly greater number of individuals in both patient groups exhibited predominant left rather than right hemisphere hypometabolism. In addition, for patients with Alzheimer's disease, the degree of asymmetry was not related to either the severity or duration of dementia. These findings could be explained by greater susceptibility of the left hemisphere to degenerative or ischemic brain disease, by a specific sampling effect, or most likely, by greater metabolic deficits resulting from left rather than right hemisphere impairment.

Two behavioral states studied in a single PET/FDG procedure: error analysis

In a previous publication the theory, procedure, and results of a method were described for making two sequential measurements of cerebral metabolic rate for glucose (CMRglc), within a 2-hr period, using [18F]fluorodeoxyglucose. The error that is specific to this technique was estimated using computer simulations. CMRglc for the second state was sensitive to errors in (a) the values of the rate constants, (b) alignment of PET slices between the two scans, and (c) subtraction of one PET image from another. The root mean square of the average error from each error source was 6.4%, which gives the theoretical reliability of this method. The measured reproducibility, taken from our previous publication, was 4.2-6.2%, which is in good agreement with the present result. This method contributes a small additional error above that expected for two independent scans. However, independent scans done on different days are likely to be subject to larger physiological variations in CMRglc than would occur using this method.

Isolation and NH2-terminal amino acid sequences of rat serum carrier proteins for insulin-like growth factors

Three N-glycosylated carrier proteins (CP) for insulin-like growth factors (apparent molecular weights 30-32, 42 and 45 kDa) were isolated from adult rat serum. They share the same amino terminus (up to amino acid 31) and are constituents of the growth hormone-dependent native 150-200 kDa IGF carrier complex. Residues 12-31 display 60 and 50% sequence homology, respectively, to residues 2-21 of fetal rat and to residues 4-22 of a human amniotic fluid IGF carrier protein. No homology exists with the type I or II IGF receptors. Adult rat serum also contains a fourth IGF CP (24 kDa) whose 9 NH2-terminal amino acids are identical to those of the fetal form. Our findings suggest that the three N-glycosylated components originate from the same IGF carrier protein (adult form) and that the 24 kDa protein is a separate (fetal) species.

Sensitivity of cerebral glucose metabolism to age, gender, brain volume, brain atrophy, and cerebrovascular risk factors

In 76 normal volunteers studied by positron emission tomography, with [18F]fluorodeoxyglucose, CMRglu was significantly lower in the elderly as compared with young subjects and significantly higher in females relative to males. However, in 58 of these subjects who also had magnetic resonance imaging scans, age and gender were found to be unrelated to CMRglu, when the effects of brain volume and brain atrophy on CMRglu were partialed out using covariate analyses. Individually, brain volume was found to have a significant effect on CMRglu, explaining approximately 17% of the variability in CMRglu measures and brain atrophy explaining approximately 8% of the variance in CMRglu. Together these two measures accounted for approximately 21% of the variance. Cerebrovascular risk factors in normal subjects were not found to affect mean CMRglu or the variability of CMRglu measures. In this study almost 80% of the variance in CMRglu could not be explained by any of the factors that had been considered. This implies a lack of sensitivity of absolute values of global CMRglu to the mild effects of brain dysfunction. Although some of the unexplained variance is probably methodological in origin, physiological factors that are difficult to quantify, such as the state of arousal, are likely to be contributory as well.

Cerebral metabolic effects of a verbal fluency test: a PET scan study

Sixteen normal volunteers were studied with [F-18] fluorodeoxyglucose and positron emission tomography scans during behavioral activation with a verbal fluency test, and 35 age-matched controls were studied with resting-state scans. There was an overall increase of the cerebral glucose metabolic rate of 23.3% during verbal fluency activation, compared to the resting state, with the greatest activation in bilateral temporal and frontal lobes. A negative correlation between test performance scores and indices of metabolism was found in frontal, temporal, and parietal regions. Damage to the left frontal lobe maximally affects scores on verbal fluency tests, but performing the test activates a network of regions, of which the left frontal lobe is only one. Proficient performance in verbal fluency seems to require less metabolic activation than poor performance, perhaps because of the efficiency of cognitive strategies employed.

A complete quantitative N-terminal analysis method

A complete quantitative N-terminal analysis (QNA) technique based on the application of dimethylaminoazobenzene isothiocyanate is described. The method allows recovery of all free N-terminal amino acids, including Asn, Gln, Trp, Ser, and Thr in quantitative yield. N-Termini of polypeptides as little as 5 pmol can be reliably and reproducibly determined by this method. This QNA method is useful in many aspects of protein structure analysis. (a) QNA is useful in assessing the purity, identity, and quantity of a polypeptide preparation. It has also been applied in our lab as a routine guarding step to prevent impure or ill-characterized samples from occupying the space of the gas-phase sequenator. (b) QNA of a trypsinized protein generates a miniaturized amino acid composition which is useful both in characterizing the identity of a protein and in comparing the homology of structurally related proteins. (c) QNA can be used to follow the pathway and preferential cleavage sites of limited proteolysis. (d) QNA is useful in characterizing selectively modified Lys and Arg residues. The details of this QNA method and the results of its applications are presented here.

Preparation and characterization of proteolyzed forms of human alpha-thrombin

The kinetics of the tryptic digestion of human alpha-thrombin were studied. Based on the results of these studies a procedure for the preparation of highly purified, active human beta-thrombin was developed. This beta-thrombin contained less than 5% of other thrombin forms, was active towards tripeptidyl paranitroanilide substrates, but had lost more than 99% of its fibrinogen cleaving activity. Protein-chemical characterization of beta-thrombin showed that it had been cleaved at a single site (Arg73-Asn74) in the beta-chain, in contrast to human beta-thrombin obtained by autolysis, which is cleaved at both Arg-62 and Arg-73.

Amino acids of the Torpedo marmorata acetylcholine receptor alpha subunit labeled by a photoaffinity ligand for the acetylcholine binding site

The acetylcholine-binding sites on the native, membrane-bound acetylcholine receptor from Torpedo marmorata were covalently labeled with the photoaffinity reagent [3H]-p-(dimethylamino)-benzenediazonium fluoroborate (DDF) in the presence of phencyclidine by employing an energy-transfer photolysis procedure. The alpha-chains isolated from receptor-rich membranes photolabeled in the absence or presence of carbamoylcholine were cleaved with CNBr and the radiolabeled fragments purified by high-performance liquid chromatography. Amino acid and/or sequence analysis demonstrated that the alpha-chain residues Trp-149, Tyr-190, Cys-192, and Cys-193 and an unidentified residue(s) in the segment alpha 31-105 were all labeled by the photoaffinity reagent in an agonist-protectable manner. The labeled amino acids are located within three distinct regions of the large amino-terminal hydrophilic domain of the alpha-subunit primary structure and plausibly lie in proximity to one another at the level of the acetylcholine-binding sites in the native receptor. These findings are in accord with models proposed for the transmembrane topology of the alpha-chain that assign the amino-terminal segment alpha 1-210 to the synaptic cleft. Furthermore, the results suggest that the four identified [3H]DDF-labeled residues, which are conserved in muscle and neuronal alpha-chains but not in the other subunits, may be directly involved in agonist binding.

Increases in both cerebral glucose utilization and blood flow during execution of a somatosensory task

To investigate local metabolic and hemodynamic interrelationships during functional activation of the brain, paired studies of local cerebral glucose utilization (lCMRGlc) and blood flow (lCBF) were carried out in 10 normal subjects (9 right-handed, 1 ambidextrous) at rest and during a unilateral discriminative somatosensory/motor task--palpation and sorting of mah-jongg tiles by engraved design. The extent of activation was assessed on the basis of percentage difference images following normalization to compensate for global shifts. The somatosensory stimulus elevated lCMRGlc by 16.9 +/- 3.5% (mean +/- standard deviation) and lCBF by 26.5 +/- 5.1% in the contralateral sensorimotor cortical focus; smaller increments were noted in the homologous ipsilateral site. The increments of lCMRGlc and lCBF correlated poorly with one another in individual subjects. Stimulation of the right hand resulted in significantly higher contralateral lCMRGlc activation (19.6%) than did stimulation of the left hand (14.1%) (p less than 0.005), whereas the lCBF response was independent of the hand stimulated. Our results indicate that both glycolytic metabolism and blood flow increase locally with the execution of an active sensorimotor task and suggest that both measures may serve as reliable markers of functional activation of the normal brain.

Evidence for coexistence of serotonin and noradrenaline in sympathetic nerves supplying brain vessels of guinea pig

Nerve fibers containing 5-hydroxytryptamine (5-HT) were demonstrated immunohistochemically in the wall of pial vessels associated with the circle of Willis in the guinea pig. The fibers formed a network structure which was more dense in the rostral part of the arterial circle and its branches than in the caudal part. The 5-HT immunoreactive fibers disappeared in all arteries studied after bilateral superior cervical ganglionectomy, and unilateral ganglionectomy eliminated the 5-HT immunoreactivity in the ipsilateral part of the middle cerebral, posterior cerebral and superior cerebellar arteries. Decentralization of the superior cervical ganglion had no effect on the perivascular nerve plexus. Subsequent staining with dopamine-beta-hydroxylase (DBH) antiserum following elution of the first antibody revealed that 5-HT was present in the noradrenergic nerve fibers. Small intensive fluorescent cells with positive immunoreaction for 5-HT and DBH, respectively, were located in clusters within the ganglion, which showed no immunohistochemical evidence for the presence of serotonergic neurons. It is concluded that 5-HT is probably not synthesized in truly serotonergic fibers but rather taken up and stored together with noradrenaline in cerebrovascular sympathetic nerves originating in the superior cervical ganglia.

Differential vasomotor action of noradrenaline, serotonin, and histamine in isolated basilar artery from rat and guinea-pig

Vasomotor effects of the amines, serotonin (5-hydroxytryptamine; 5-HT), noradrenaline (NA) and histamine, were studied in isolated basilar arteries (BA) of the rat and guinea-pig in vitro. 5-HT produced marked contraction in rat BA, about 70% of that induced by high (124 mM) K+ solution. This response was inhibited by the specific 5-HT2 receptor antagonist, ketanserin, with a pA2 value of 9.35. In the guinea-pig, 5-HT caused only moderate contraction amounting to 30% of that produced by K+. Ketanserin at concentrations up to 10(-6) M showed a comparatively small, non-surmountable inhibition of the contraction. EC50 values for 5-HT in the guinea-pig and rat were 5.65 x 10(-8) M and 3.70 x 10(-7) M, respectively. NA had no effect on rat BA, but moderately contracted guinea-pig BA. The contraction was not altered by yohimbine but was inhibited by prazosin. Histamine contracted guinea-pig BA with a maximum that was 110% of the K+-induced contraction. It was not changed by the H2 antagonist, cimetidine. The H1 antagonist, pyrilamine, caused competitive inhibition with a pA2 of 9.20 at a slope of 0.94. In preconstricted rat BA, histamine induced vasodilatation in a concentration-dependent manner. The H1 agonist, pyridylethylamine (PEA), and the H2 agonist, impromidine, dilated less effectively than histamine. The vasodilatation induced by histamine was inhibited by the H2 antagonist, cimetidine, and to a smaller extent by the H1-receptor antagonist, pyrilamine. Removal of the endothelium abolished the vasodilator effect of PEA but not that of impromidine. In vessels with intact endothelium, the vasodilatation caused by histamine was slightly reversed by pyrilamine, which did not affect the dilatation in endothelium denuded vessels. Cimetidine markedly reversed this vasodilator effect in both intact and endothelium denuded preparations; in the latter the counteraction was almost complete. In precontracted guinea-pig vessels, histamine failed to induce dilatation even in the presence of the H1 antagonist, pyrilamine. Thus, 5-HT-induced contraction is mediated by 5-HT2 receptors in the rat and probably by 5-HT1 receptors in the guinea pig. NA failed to contract rat BA but contracted guinea-pig BA through alpha 1 receptors. Histamine was a potent dilator agent in rat BA through a combination of both H1 and H2 receptors. The dilatation mediated by the H1 receptors, but not that mediated by H2 receptors, was endothelium-dependent. Histamine caused strong vasoconstriction in the guinea-pig BA through H1 receptors.

The heparin binding site of human antithrombin III. Selective chemical modification at Lys114, Lys125, and Lys287 impairs its heparin cofactor activity

Heparin binds to human antithrombin III and accelerates its inhibitory activity in the blood coagulation system. Previous reports (Rosenberg, R. D., and Damus, P. S. (1973) J. Biol. Chem. 248, 6490-6505; Pecon, J. M., and Blackburn, M. N. (1984) J. Biol. Chem. 259, 935-938) have shown that selective chemical modification of a limited number of lysine residues in antithrombin III causes drastic loss of its heparin cofactor activity. We have performed chemical modification of antithrombin III with trinitrobenzene sulfonic acid in order to determine the location of these lysine residues. When antithrombin III was treated with 100 M excess of trinitrobenzene sulfonic acid for 10 min, about 3.2 mol of amino group per mol of antithrombin III were modified. The heparin cofactor activity dropped to about 25%, whereas the progressive inhibitory activity (in the absence of heparin) remained essentially intact (about 95%). The modified amino groups were identified to be Lys114 (75%), Lys125 (94%), and Lys287 (96%). These results were obtained by comparing and analyzing the cyanogen bromide fragments derived from native antithrombin III and the 10-min modified antithrombin III. When antithrombin III was pretreated with heparin, followed by trinitrobenzene sulfonic acid modification, the extent of modification at Lys114 and Lys125 decreased from 75% and 94% to 20% and 40%, respectively, whereas the modification at Lys287 remained nearly quantitative (greater than 95%). Based on these results, we conclude that Lys114 and Lys125 are essential for the heparin cofactor activity of human antithrombin III.

Nerves containing serotonin, its interaction with noradrenaline, and characterization of serotonin receptors in cerebral arteries of monkey

1 Immunohistochemistry was applied to study the presence of 5-hydroxytryptamine (5-HT) and dopamine-beta-hydroxylase (DBH) in cerebrovascular nerves of monkeys, and serotonergic receptors were characterized in the vessels by in vitro pharmacology. 2 A well-developed plexus of 5-HT immunoreactive fibres was found to supply the pial arteries at the base of the brain. The network closely resembled the distribution of neural DBH, used as an index for noradrenergic nerves. 3 5-HT contracted the basilar artery (BA) and middle cerebral artery (MCA) with equal potency and intrinsic activity. The effect was not antagonized by phentolamine or propranolol. 4 The 5-HT2 receptor antagonist, ketanserin, inhibited the response to 5-HT in a competitive manner in both vessels, with pA2 values obtained from Schild plots of 9.15 in BA and 9.40 in MCA. 5 Electrical field stimulation elicited a neurogenic contraction that was completely blocked by 3 X 10(-7) M tetrodotoxin, 3 X 10(-6) M guanethidine, and 10(-6) M phentolamine. The response was also antagonized by ketanserin, but only in concentrations higher than those inhibiting the response to 5-HT. 6 In accordance with the findings during nerve stimulation, noradrenaline (NA) contracted the pial arteries, particularly MCA where the intrinsic activity closely resembled the value obtained with 5-HT. Ketanserin antagonized the response, but less efficiently than that induced by 5-HT. 7 5-HT had no effect on the (noradrenergic) neurogenic contraction obtained during electrical stimulation. Nor did 5-HT affect the contraction induced by exogenous NA. 8 It is concluded that 5-HT and NA may be co-localized in perivascular nerves of the monkey brain. 5-HT contracts pial arteries through postjunctional 5-HT2 receptors, but does not seem to interfere prejunctionally with the noradrenergic nerves or with exogenous NA.

Chemical modification of the carboxyl groups of protein substrates enhances their thrombin susceptibility

Native or denatured protein substrates which are hardly digested by thrombin can become much more efficiently cleaved by the enzyme after chemical modification of their carboxyl groups. Five antibody kappa-chains were used to demonstrate this effect. The selective cleavage sites were determined by quantitative N-terminal analysis and N-terminal sequencing. All five kappa-chains share the same cleavage sites at Arg-Thr (residues 108-109), Arg-Glu (residues 142-143, Glu side chain modified with glycine amide), Lys-Ser (residues 207-208) and Arg-Gly (residues 211-212). One of the major cleavage sites (Arg-Thr) is located at the joint of the variable/constant region. The amino acids adjacent to these cleavage sites underline the proposed structural requirements for a potential thrombin substrate [(1985) Eur. J. Biochem. 151, 217-224]. This approach can facilitate the application of thrombin in generating large polypeptide fragments of proteins.

Probing the heparin-binding domain of human antithrombin III with V8 protease

From structural analysis on genetically abnormal and chemically modified human antithrombin III [Koide, T., Odani, S., Takahashi, K., Ono, T. and Sakuragawa, N. (1984) Proc. Natl Acad. Sci. USA 81, 289-293; Chang, J.-Y. and Tran, T. H., (1986) J. Biol. Chem. 261, 1174-1176; Blackburn, M. N., Smith, R. L., Carson, J. and Sibley, C. C. (1984) J. Biol. Chem. 259, 939-941], the heparin-binding site of antithrombin III has been suggested to be in the region of Pro-41, Arg-47 and Trp-49. In this study the heparin-binding site was probed by preferential cleavage of V8 protease on heparin-treated and non-treated native antithrombin III. The study has been based on the presumption that the heparin-binding site of antithrombin III is situated at exposed surface domain and may be preferentially attacked during limited proteolytic digestion. Partially digested antithrombin III samples were monitored by quantitative amino-terminal analysis and amino acid sequencing to identify the preferential cleavage sites. 1-h-digested antithrombin III was separated on HPLC and peptide fragments were isolated and characterized both qualitatively and quantitatively. The results reveal that Glu-Gly (residues 34-35), Glu-Ala (residues 42-43) and Glu-Leu (residues 50-51) are three preferential cleavage sites for V8 protease and their cleavage, especially the Glu-Ala and the Glu-Leu sites, was drastically inhibited when antithrombin III was preincubated with heparin. Both high-affinity and low-affinity antithrombin-III-binding heparins were shown to inhibit the V8 protease digestion of native antithrombin III, but the high-affinity sample exhibited a higher inhibition activity than the low-affinity heparin. These findings (a) imply that the segment containing residues 34-51 is among the most exposed region of native antithrombin III and (b) support the previous conclusions that this region may play a pivotal role in the heparin binding.

Involvement of specific receptors and calcium mechanisms in serotonergic contractile response of isolated cerebral and peripheral arteries from rats

Studies were performed on isolated cerebral and peripheral arterial segments from the rat to define contractile receptors for 5-hydroxytryptamine (5-HT) and to elucidate the responses to calcium channel blockers in relation to their effects on potassium-induced contractions. 5-HT induced strong contraction of the middle cerebral artery, arteries forming the circle of Willis, basilar artery and tail artery in the mentioned order of relative potency and with an intrinsic activity in the brain vessels approximately 70% of that caused by 124 mM potassium in the buffer solution. Ketanserin inhibited the contraction both in the basilar and tail arteries competitively, with pA2 = 9.35 and 9.09, respectively, suggesting mediation by 5-HT2 receptors. The inhibition by cyproheptadine and methysergide (of the response in the basilar artery) was noncompetitive. High potassium in the buffer solution contracted the basilar and tail arteries biphasically, including prazosin-sensitive alpha-adrenoceptor activation in the latter. Cyproheptadine, nimodipine, verapamil and diltiazem inhibited the 5-HT-induced contraction in the mentioned order of potency. Verapamil was more potent than diltiazem, also in the tail artery, but nimodipine inhibited the contraction only by 35%. Also the (tonic) contraction induced by high potassium concentration was attenuated, with the same relative potency as in the presence of 5-HT except for cyproheptadine, which was less efficient than nimodipine. The transient potassium-induced contraction was inhibited less effectively by the calcium antagonists. The IC50 values were characteristically lower in the basilar than in the tail artery, irrespective of whether the contraction had been produced by 5-HT or high potassium.(ABSTRACT TRUNCATED AT 250 WORDS)

Human task-specific somatosensory activation

We used positron emission tomography to study normal patterns of local cortical metabolic activation induced by somatosensory stimuli. Palpation and sorting of mah-jongg tiles by textured design increased local glucose metabolic rate (lCMRgl), by 18% on average, in contralateral somatosensory cortex. A graphesthesia task gave a similar result. In contrast, vigorous vibrotactile stimulation of fingers, face, or knee did not produce a consistent focus of activation. Our results indicate that lCMRgl activation is best achieved by somatosensory tasks requiring an active perceptual effort.

Behavioral activation and the variability of cerebral glucose metabolic measurements

Variability in cerebral glucose metabolism was examined between and within subjects when paired studies were performed in the resting state or in a behaviorally activated state. Both normal and demented subjects were studied twice each, from 1 to 6 weeks apart, under near-identical conditions, using positron emission tomography (PET) and [18F]fluorodeoxyglucose. Resting state studies were repeated in nine normal and four demented subjects. A picture-viewing test, used for activation during PET, was used repeatedly in seven normal and five demented subjects. Within-subject variability, as assessed by the percent difference in metabolic rates in paired studies, was reduced by 60-70% for activation state compared to resting state studies in normals. It is concluded that PET studies of brain metabolism, which are designed to study the active brain, should indeed be performed in functionally activated states, as in addition to demonstrating metabolism during a defined functional state, activation studies show reduced variability of cerebral metabolic measures.

Two behavioral states studied in a single PET/FDG procedure: theory, method, and preliminary results

We have developed a method that allows two sets of regional cerebral metabolic rates of glucose (rCMRglc) to be obtained in a single extended procedure using positron emission tomography (PET) and [18F]fluorodeoxyglucose (FDG). This is an adaptation of the deoxyglucose method, with the addition of a second injection of FDG immediately after completion of the first scan, then followed 30 min later by a second scan. A model has been developed to allow for correction of measured tracer concentration in the second scan by subtracting the predicted remnant from the first scan. The possible applications of this method in studying behavior-metabolism relationships are demonstrated. The preliminary results show 6%-12% changes in rCMRglc values for appropriate brain regions when the behavioral state is altered, but show 0%-5% change in rCMRglc values when the behavioral state is unchanged. The method can contribute significantly to the understanding of behavior-metabolism relationships by allowing the noninvasive study of two behavioral states in a single PET procedure.

Identification in the human central nervous system, pituitary, and thyroid of a novel calcitonin gene-related peptide, and partial amino acid sequence in the spinal cord

Two human genes encoding precursors for two calcitonin gene-related peptides (CGRP) I (or alpha) and II (or beta) have been identified (Steenbergh, P. H., Höppener, J. W. M., Zandberg, J., Lips, C. J. M., and Jansz, H. S. (1985) FEBS Lett. 183, 403-407). The amino acid sequence of CGRP-I was obtained in medullary thyroid carcinoma extracts (Morris, H. R., Panico, M., Etienne, T., Tippins, J., Girgis, S. I., and MacIntyre, I. (1984) Nature 308, 746-748), but not in normal human tissues. The human CGRP-II peptide remained to be discovered. Here we have determined in the human spinal cord the amino acid composition and the partial amino acid sequence of the DNA-predicted CGRP-I and -II. The data indicate for the first time the existence of a second CGRP different from the known CGRP-I. CGRP-II has been identified in the central nervous system, pituitary, thyroid, and in medullary thyroid carcinoma as a major CGRP form together with CGRP-I.

Identification of calmodulin activity in purified retroviruses

Several viruses have been shown to require calcium for their function, and to bind calcium at specific sites. However, the nature of the calcium binding molecule on viruses has not been established. One possibility is the ubiquitous calcium-binding protein calmodulin. Our studies were designed to determine whether feline leukemia virus contained calmodulin. Accordingly, we tested purified feline leukemia virus for the presence of calmodulin-like activity. The virus, like authentic calmodulin, activated cyclic AMP phosphodiesterase. The ability of the virus to activate the enzyme was blocked in the presence of the known calmodulin inhibitors trifluoperazine and W-7. This indirect evidence for the presence of calmodulin was confirmed by radioimmunoassay. Several other retroviruses were also tested using radioimmunoassay and found to contain calmodulin. Our results indicate that the calcium binding site in retroviruses may be calmodulin.

Identical N-terminal peptide sequences of asymmetric forms and of low-salt-soluble and detergent-soluble amphiphilic dimers of Torpedo acetylcholinesterase. Comparison with bovine acetylcholinesterase

We have determined partial N-terminal sequences of acetylcholinesterase (AChE) catalytic subunits from Torpedo marmorata electric organs and from bovine caudate nucleus. We obtain identical sequences (23 amino acids) for the soluble ('low-salt-soluble' or LSS fraction) and particulate ('detergent-soluble', or DS fraction) amphiphilic dimers (G2 form) and for the asymmetric, collagen-tailed forms ('high-salt-soluble', or HSS fraction, A12 + A8 forms). There are two amino acid differences, at position 3 (Asp/His) and 20 (Ile/Val), with the sequences obtained for T. californica by MacPhee-Quigley et al. [(1985) J. Biol. Chem. 260, 12185-12189] for the soluble G2 form and the lytic G4 form which is derived from asymmetric AChE. The bovine sequence (12 amino acids) presents an identity of 4 amino acids (Glu-Leu-Leu-Val) with that of Torpedo, at positions 5-8 (Torpedo) and 7-10 (bovine). There is also a clear homology with the sequence of human butyrylcholinesterase [(1986) Lockridge et al. J. Biol. Chem., in press] indicating that these enzymes probably derive from a common ancestor.

The structures and proteolytic specificities of autolysed human thrombin

Three Arg/Lys-Xaa bonds in the B-chain of human alpha-thrombin were found to be the major autolytic sites. Under the conditions of 1 mg of alpha-thrombin/ml in 50 mM-ammonium bicarbonate solution at 25 degrees C, the 50% cleavage times of Lys-Gly (residues 154-155), Arg-Tyr (residues 70-71) and Arg-Asn (residues 73-74) were 32 h, 72 h and 96 h respectively. Fragments generated from these three major autolytic sites were purified and analysed. In addition, minor and random autolytic cleavages occurred simultaneously that eventually led to the complete breakdown of the enzyme. These results reveal several novel aspects about the process of autolysis and the structure of autolysed human thrombin. It identifies a major autolytic site at Arg-Tyr (residues 70-71) that has not been previously reported. It demonstrates that beta-thrombin is not an obligatory intermediate during the process of conversion of alpha-thrombin into gamma-thrombin. There exists a new form of autolysed thrombin, designated as beta'-thrombin (with cleavage at Lys-Gly only), which also serves as the intermediate in the conversion of alpha-thrombin into gamma-thrombin. It shows that autolysis of human alpha-thrombin does not proceed in an absolutely clear-cut manner. Numerous minor cleavages, which amount to approx. 20% of the three major autolytic sites, occur simultaneously. It is the first time that several autolytic sites of human alpha-thrombin have been quantitatively analysed, and that it has been shown that formation of beta-, beta'- and gamma-thrombins can be quantitatively followed by the h.p.l.c. method. Furthermore, the data demonstrate that alpha-thrombin and the autolysed thrombin (mixture of beta-, beta'- and gamma-thrombins) have comparable proteolytic activity and specificity towards various sizes of non-fibrinogen polypeptide substrates with relative molecular masses ranging from 3000 to 25,000.

[Smoking and mortality in lung cancer]

From 1978 to 1980, a retrospective epidemiologic survey on mortality of lung cancer was undertaken in Taiyuan, an industrial city of Shanxi Province. The average crude mortality was 14.35/100,000, the third place in death of the malignancies. In the male the mortality was 20.46 ranking the second. In the female, it was 7.26, the fourth. It was increased markedly in the man over 35 years old and in the woman over 40. The death rate was higher in the urban districts than in the suburbs of the city. This difference was statistically significant (P less than 0.05). In the urban districts, suburbs of this city and its countryside, both the incidence and mortality showed significant differences in smoking and non-smoking groups (P less than 0.01). This result indicates that smoking is related to lung cancer. The mortality of malignant tumors was 176.69/100,000 in the smoking group, whereas in the non-smoking group, it remained at the level of 46.65/100,000. It should be further studied that how smoking exerts influence on the other malignancies. The relative risks (RR) of lung cancer to smoking were 3.07 in the male and 2.60 in the female with a total RR of 3.52. The data mentioned above suggest that cigarette smoking plays an important role in the cause of lung cancer. Hence, to advocate abstinence of smoking is of vital importance, especially in the industrial districts.

Novel 1,3-bis(aryloxy)propanes as leukotriene D4 antagonists

The synthesis and structure-activity relationships of a number of 1,3-bis(aryloxy)propanes, which are in vivo antagonists of LTD4 in the guinea pig, are described. One of these compounds, 4 (Wy-44,329), was not only approximately equipotent with the standard 1 (FPL 55712) in the LTC4 (ID50 = 0.17 and 0.23 mg/kg iv, respectively) and LTD4 (ID50 = 0.11 and 0.15 mg/kg iv, respectively) challenge models but also possessed greater potency in the ovalbumin challenge model (ID50 = 0.47 mg/kg and 4.1 mg/kg iv, respectively) and a longer duration of action. This compound was a competitive LTD4 antagonist on guinea pig ileum (pA2 = 9.4) and possessed mediator release (rat PCA, ID50 = 0.26 mg/kg iv) and 5-lipoxygenase (IC50 = 32 microM vs. 5-HETE) inhibitory activities.

Structure of the high-affinity binding site for noncompetitive blockers of the acetylcholine receptor: serine-262 of the delta subunit is labeled by [3H]chlorpromazine

The membrane-bound acetylcholine receptor from Torpedo marmorata was photolabeled by the noncompetitive channel blocker [3H]chlorpromazine under equilibrium conditions in the presence of agonist. Incorporation of radioactivity into all subunits occurred and was reduced by addition of phencyclidine, a specific ligand for the high-affinity site for noncompetitive blockers. The delta subunit was purified and digested with trypsin, and the resulting fragments were fractionated by reversed-phase HPLC. The labeled peptide could not be purified to homogeneity because of its marked hydrophobic character, but a combination of differential CNBr subcleavage and cosequencing of partially purified fragments enabled us to identify Ser-262 as being labeled by [3H]chlorpromazine. The labeling of this particular residue was prevented by phencyclidine and thus took place at the level of, or in proximity to, the high-affinity site for noncompetitive blockers. Ser-262 is located in a hydrophobic and potentially transmembrane segment termed MII.

Antithrombin III Basel. Identification of a Pro-Leu substitution in a hereditary abnormal antithrombin with impaired heparin cofactor activity

Antithrombin III Basel is a hereditary abnormal antithrombin with normal progressive inhibition activity (normal reactive site) and reduced heparin cofactor activity (impaired heparin binding site). Structures of antithrombin III Basel and normal antithrombin III isolated from the same patient were compared by peptide mapping using the dimethylaminoazobenzene isothiocyanate precolumn derivatization technique. Of the approximately 50 tryptic peptides of normal and abnormal antithrombin III, one peptide comprising residues 40-46 had a different retention time in reversed-phase high performance liquid chromatography. The amino acid sequence of the peptide from antithrombin III Basel had a single substitution of Pro (normal) by Leu (abnormal) at position 41. This substitution is close to an Arg (residue 47) and a Trp (residue 49) which have previously been shown to be critical for heparin binding by antithrombin III. Although additional amino acid substitutions in antithrombin III Basel cannot be ruled out, this Pro-Leu replacement could cause a conformational change by increasing both the helical structure and the hydrophobicity around residue 41. These data suggest that: (i) the heparin binding site of antithrombin III encompasses the region containing residues 41, 47, and 49; and (ii) the impaired heparin cofactor activity of antithrombin III Basel is likely due to a conformational change of the heparin binding site induced by the Pro-Leu substitution at position 41.

Thrombin specificity. Selective cleavage of antibody light chains at the joints of variable with joining regions and joining with constant regions

Selective cleavage of polypeptides by alpha-thrombin can be reasonably predicted [Chang, J.Y. (1985) Eur. J. Biochem. 151,217-224]. This knowledge was applied to the selective cleavage of antibody light chains with the aim of producing intact fragments of both variable region and constant region. (a) Mouse kappa light chains 10K26 and 10K44 from anti-(azobenzene arsonate) antibodies contain 20 Arg/Lys-Xaa bonds. Only two of them, one ProArg-Thr bond located at the joint of the variable region with the joining peptide and one ValLys-Ser bond located near the carboxyl-terminal end of the constant region, were selectively cleaved by alpha-thrombin. The ProArg-Thr bond has a 50% cleavage time of about 10 min under the designated conditions, whereas the ValLys-Ser has a 50% cleavage time approx. 9-10 h. A single selective cleavage at the joining position of the variable region and joining peptide can be achieved by short-time thrombin digestion. Fragments containing intact variable region (1-96) and intact joining peptide-constant region (97-214) obtained from both denatured and native light chains of 10K26 can be separated by gel filtration. (b) lambda light chains from both human and mouse all begin with the GlnProLys-(Ala/Ser) structure (positions 108-111) at their constant regions. This ProLys-Ala/Ser bond is also susceptible to specific thrombin cleavage. Four human lambda chain (KERN, NEI, NEW, VOR) and one mouse lambda chain (RPC20) were shown to be selectively cleaved by thrombin at these ProLys-Ala/Ser bonds. For human lambda chains, the 50% cleavage time at this ProLys-Ala bond was approx. 3-4 h under the designated conditions. Six additional thrombin specific cleavages were also detected within the variable regions of NEI, VOR and RPC-20. (c) Heparin inhibits thrombin cleavage of Arg/Lys-Xaa bonds located near the center of the antibody light chain, but slightly activates thrombin cleavage of those located near the amino or carboxyl-terminal ends of the protein. The significance of these findings is threefold. (a) It demonstrates that selective cleavage of large polypeptides by alpha-thrombin can also be reasonably predicted. (b) It provides a useful method for light chain fragmentation which can greatly facilitate amino acid sequencing of antibodies. (c) It serves to generate fragments containing intact variable regions and constant regions from antibody light chains of human and mouse. Such fragments may be useful for chemical semisynthesis of a human-mouse light chain chimeras.

Thrombin specificity. Requirement for apolar amino acids adjacent to the thrombin cleavage site of polypeptide substrate

alpha-Thrombin cleavage of 30 polypeptide hormones and their derivatives were analysed by quantitative amino-terminal analysis. The polypeptides included secretin, vasoactive intestinal polypeptide, cholecystokinin fragment, dynorphin A, somatostatins, gastrin-releasing peptide, calcitonins and human parathyroid hormone fragment. Most of them were selected mainly on the ground that they contain sequence structures homologous to the well known tripeptide substrates of alpha-thrombin. All selected polypeptides have one single major cleavage site and both Arg-Xaa and Lys-Xaa bonds were found to be selectively cleaved by alpha-thrombin. Under fixed conditions (1 nmol polypeptide/0.5 NIH unit alpha-thrombin in 20 microliters of 50 mM ammonium bicarbonate at 25 degrees C), the time required for 50% cleavage ranges from less than 1 min to longer than 24 h. Heparin invariably enhanced thrombin cleavage on all polypeptide analysed. The optimum cleavage site for alpha-thrombin has the structures of (a) P4-P3-Pro-Arg-P1'-P2', where P3 and P4 are hydrophobic amino acid and P1', P2' are nonacidic amino acids and (b) P2-Arg-P1', where P2 or P1' are Gly. The requirement for hydrophobic P3 and P4 was further demonstrated by the drastic decrease of thrombin cleavage rates in both gastrin-releasing peptide and calcitonins after chemical removal of hydrophobic P3 and P4 residues. The requirement for nonacidic P1' and P2' residues was demonstrated by the drastic increase of thrombin cleavage rates in both calcitonin and parathyroid hormone fragments, after specific chemical modification of acidic P1' and P2' residues. These findings confirm the importance of hydrophobic P2-P4 residues for thrombin specificity and provide new evidence to indicate that apolar P1' and P2' residues are also crucial for thrombin specificity. It is concluded that specific cleavage of polypeptides by alpha-thrombin can be reasonably predicted and that chemical modification can be a useful tool in enhancing thrombin cleavage.

Chromogenic labeling of monosaccharides using 4'-N,N-dimethylamino-4-aminoazobenzene

Twenty-three monosaccharides, e.g., D- or L-pentoses, D- or L-hexoses, heptose, 2- or 6-deoxyhexoses, 2-deoxy-2-aminohexoses, hexuronic acids, and N-acetylmuramic acid, were coupled to the azo dye 4'-N,N-dimethylamino-4-aminoazobenzene by reductive amination using sodium cyanoborohydride as reducing agent and in the presence of pentaerythritol. The structure of the colored glycamines was established by mass spectrometry. The average yield of the reaction was more than 80%. The sugar derivatives were separated either by silica-gel thin-layer chromatography or by high-performance liquid chromatography. Spectrophotometric quantitation was performed in the visible range at the picomole level. The method was applied to the determination of the sugar composition of the glycosphingolipid globotetraosyl ceramide and the human milk oligosaccharide lacto-N-fucopentaose I.

Proteolytic conversion of [Met]enkephalin-Arg6-Gly7-Leu8 by brain synaptic membranes. Characterization of formed peptides and mechanism of proteolysis

The degradation of the enkephalin-containing octapeptide Tyr-Gly-Gly-Phe-Met-Arg-Gly-Leu (YGGFMRGL) was systematically investigated by incubating the peptide with synaptic membranes from rat striatum or with purified peptidases. The degradation products were derivatized with 4-dimethylamino-azobenzene-4'-isothiocyanate and then analyzed by high pressure liquid chromatography and by amino-terminal analysis. The incubation of YGGFMRGL with synaptic membranes yielded YGG, YGGF, YGGFM, and MR in a manner that was linear with respect to time. The corresponding carboxyl-terminal fragments FMRGL, MRGL, and RGL could not be detected, which suggests that the degradation of YGGFMRGL by synaptic membranes occurs by carboxypeptidase activity. The incubation of YGGFMRGL with different purified peptidases produced cleavage patterns unique from that seen with synaptic membranes. Enkephalinase recognized only the Gly-Phe bond to produce YGG and FMRGL. Thermolysin recognized the Gly-Phe bond and the Phe-Met bond to yield YGG, YGGF, FMRGL, and MRGL. Angiotensin-converting enzyme (ACE) produced primarily YGGF, MR, and lesser amounts of YGGFMR and YG. The formation of YGG, YGGF, and YGGFM by synaptic membranes could be stimulated 3-fold by the addition of 30 mM NaCl and inhibited by MK-422, an ACE inhibitor, with an IC50 of 3 nM. These data suggest that ACE, a dipeptidyl carboxypeptidase, is the primary enzyme involved in the degradation of YGGFMRGL in brain. ACE apparently works in concert with another carboxypeptidase in brain to yield YGGFM and YGG since the carboxyl-terminal peptides RGL and FMRGL could not be detected.

Elastase-cathepsin G inhibitors eglin b and eglin c differ by a single Tyr----His substitution. A micro-method for the identification of amino-acid substitution

The structures of eglin b and eglin c, both potent inhibitors of human neutral granulocytic proteinase elastase and cathepsin G, were compared by micro amino-acid analysis and peptide mapping techniques. Eglin b and eglin c differ by one amino-acid substitution in the middle of the polypeptide chain. Tyrosine residue at position 35 of eglin c was substituted by histidine in eglin b. This amino-acid substitution requires one base exchange (U----C) at the DNA level and apparently does not affect the reactive site of eglins. Though without disulfide linkages, eglins are very rigid molecules and can be effectively digested by trypsin only after rigorous acid incubation.

Murine V kappa 25 and V kappa 27 amino-acid sequences of C57B1/6 origin: monoclonal antibodies 17S29.1 and 22S25.1 specific for the group A-streptococcal polysaccharide

Antibodies 17S29.1 and 22S25.1 are monoclonal, hybridoma-derived gamma 3 kappa murine immunoglobulins with specificity for N-acetyl-glucosamine beta 1----3-linked to the L-rhamnose backbone structure, the immunodeterminant of the streptococcal Group A polysaccharide. The VL 17S29.1 amino-acid sequence is the third complete one reported from an antibody with this specificity, the second fully determined V kappa 25 structure and the first complete V kappa sequence of C57B1/6 origin derived from a carbohydrate-specific antibody. VL22S25.1 is a member of the V kappa 27 isotype of murine immunoglobulin VL regions. V kappa 17S29.1 and the determined part of the V kappa 22S25.1 sequence are compared to the previously described V kappa regions of streptococcal Group A polysaccharide-specific antibodies and to 12 selected partial and complete V kappa regions of antibodies with other specificities, predominantly to carbohydrate antigens. Both V kappa 17S29.1 and V kappa 22S25.1 increase the variability of known murine V kappa regions. They are the most homologous to the other V kappa regions derived from antibodies with streptococcal Group A polysaccharide specificity and share with them the amino-acid residue Arg74, so far characteristic for V kappa regions from antibodies with this specificity. The analysis of groups of independently expressed, highly homologous V kappa regions, namely V kappa 17S29.1 and V kappa 2S1.3 as one and V kappa 7S34.1 and V kappa 22S25.1 as a second group, offers the possibility of estimating the minimal number of V kappa germline genes involved in the immune response to the structurally defined streptococcal Group A polysaccharide antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

Murine V kappa 21A isotype sequence: monoclonal antibody 50S10.1 specific for the group A streptococcal polysaccharide

Antibody 50S10.1 is a hybridoma-derived gamma 3 kappa antibody of BAB-14 mouse strain origin, with specificity for N-acetylglucosamine beta 1----3 linked to L-rhamnose, the immunodeterminant of the streptococcal Group A polysaccharide. The VL50S10.1 amino acid sequence is the fourth complete one reported with this specificity and the first fully determined V kappa 21A structure. Furthermore it is the first V kappa 21A isotype sequence derived from an antibody with known antigen specificity. The V kappa region of this and the previously described monoclonal anti-streptococcal Group A polysaccharide antibodies 7S34.1, 2S1.3 and 17S29.1 are compared, showing that in monoclonal antibody 50S10.1 a V kappa germline gene is expressed which is unrelated to those previously shown to be expressed in antibodies of this specificity. V kappa 50S10.1 increases the variability of known murine V kappa regions and confirms stretches of V kappa 21A sequences previously established.

The complete amino-acid sequence of anglerfish somatostatin-28 II. A new octacosapeptide containing the (Tyr7, Gly10) derivative of somatostatin-14 I

A new somatostatin-28 has been isolated from the Teleostean fish (Lophius piscatorius) Brockmann organs. Determination of its aminoacid sequence indicates that it corresponds to an octacosapeptide containing in its C-terminal end the Tyr-7 Gly-10 derivative of somatostatin-14 I. This structure is in agreement with the one predicted by Hobart et al. (Nature (1980) 288, 137-141) from a cDNA nucleotide sequence. It demonstrates that, since the corresponding somatostatin-14 II cannot be detected in this organ, S-28 II is a terminal product of prosomatostatin II processing in anglerfish pancreatic islets.

Strategy for the measurement of regional cerebral blood flow using short-lived tracers and emission tomography

This report describes a strategy for measurement of regional CBF that rigorously accounts for differing tracer partition coefficients and recirculation, and is convenient for use with positron emission tomography. Based on the Kety model, the measured tissue concentration can be expressed in terms of the arterial concentration, the rate constant K, and the blood flow f. The local partition coefficient may be computed as p = f/K. In our approach, maps of K and f are computed from two transverse section reconstructions. The reconstructions are based on weighted sums of projection data measured frequently during the observation period. Theoretical studies of noise propagation in the estimates of K and f were carried out as a function of tomographic count rate, total measurement time, and tracer half-life for varying input functions. These calculations predict that statistical errors in f of between 5 and 10% at a resolution of 1 cm full width at half maximum can be obtained with existing tomographs following i.v. injection. To compare theory and experiment, a series of flow studies were carried out in phantoms using a positron tomograph. These measurements demonstrate close agreement between computed flow and noise estimates and those measured in a controlled situation. This close agreement between theory and experiment as well as the low statistical errors observed suggest that this approach may be a useful tool in clinical investigation.

Microisolation of DABITC-derivatized protein by gel electrophoresis: application to the purification of antibody heavy and light chains

Proteins and polypeptides are derivatized with dimethylaminoazobenzene isothiocyanate (DABITC) before their separation on sodium dodecyl sulfate-polyacrylamide gels. DABITC-derivatized proteins are detected visually in the picomole range without further staining and destaining procedures. The recovered colored protein can also be used for direct sequence determinations. This method was applied to purify heavy and light chains of murine hybridoma-derived antibodies. Starting with ammonium sulfate-precipitated protein mixture, this method allows, in a one-step procedure, the isolation of pure light and heavy chains suitable for automatic sequencing.

The functional domain of hirudin, a thrombin-specific inhibitor

Hirudin is a thrombin-specific inhibitor of Mr 8000 (65 amino acid residues). Native hirudin contains 3 disulfide linkages within the first 39 amino-terminal residues, and a highly acidic C-terminal segment which is freely accessible to enzyme digestion by both endo- and exo-peptidases. Removal of the acidic C-terminal amino acids of native hirudin by both chemical and enzymatic methods resulted in a concomitant loss of hirudin inhibition activity. It is concluded that this acidic C-terminal segment of hirudin is essential for hirudin-thrombin interaction. The implication of the hirudin-thrombin interaction for the enzymatic specificity of thrombin is also discussed.

A new isotype sequence (V kappa 27) of the variable region of kappa-light chains from a mouse hybridoma-derived anti-(streptococcal group A polysaccharide) antibody containing an additional cysteine residue. Application of the dimethylaminoazobenzene isothiocyanate technique for the isolation of peptides

The first complete sequence of the variable region of a kappa-light chain (V kappa) from a mouse anti-(streptococcal group A polysaccharide) antibody (immunoglobulin 7S34.1) is reported. Immunoglobulin 7S34.1 was isolated from the ascitic fluid of hybridoma 7S34.1 previously cloned in vitro. A newly developed technique for the isolation of peptides by using pre-column formation of peptide derivatives with dimethylaminoazobenzene isothiocyanate also served to complete the sequence. The sequence of the variable region of the kappa-light chain of immunoglobulin 7S34.1 defines a new mouse V kappa isotype (V kappa 27) and is the first mouse immunoglobulin light-chain variable region to be shown to have an extra cysteine residue at position 48.