[Investigation of potency to produce interleukin-2 of the peripheral blood T lymphocytes in patients with hemorrhagic stroke]

For further understanding the changes in immune function of the patients with hemorrhagic stroke, we investigated the activity of interleukin-2 (IL-2) in the peripheral blood T lymphocytes from 32 patients. The results showed that the levels of IL-2 in the patients were lower than those of the healthy controls, but no significant difference was observed between the cerebral hemorrhage group and subarachnoid hemorrhage group. It suggests the cellular immune function of patients at the acute period is low. We consider that IL-2 might be of use as a kind of therapeutic measure to modulate patients' immune function and treat the diseases.

[Role of pulmonary arterial angiotensin converting enzyme in development of hypoxic pulmonary hypertension]

OBJECTIVE

To study the effect of local pulmonary arterial renin-angiotensin system on hypoxic pulmonary hypertension(PAH).

METHOD

Normobaric hypoxic PAH animal model was adopted. Systolic pulmonary arterial pressure(PAPs), pulmonary arterial angiotensin converting enzyme(ACE) activity, collagen content(HP) were measured and ultrastructure of pulmonary smooth muscle cells (SMC) and was observed.

RESULTS

During hypoxia, PAPs, pulmonary ACE activity, HP increased significantly and SMC changed into secretive phenotype. Treatment with cilazapril, an ACE inhibitor, decreased ACE activity along with reversal of PAPs. HP and SMC phenotype.

CONCLUSIONS

Pulmonary ACE participated in the modulation of changes of SMC phenotype and collagen metabolism during hypoxic PAH.

Structural Model of the Orthorhombic Non-Fibonacci Approximant in the Al12Fe2Cr Alloy

Al5.103(Fe, Cr), orthorhombic, Imm2, a = 12.34, b = 12.41, c = 30.71 Å, V = 4701 Å3, atoms/cell = 305 (average), D x \simeq 3.4 g cm−3. A structural model of the non-Fibonacci approximant O-AIFeCr with composition Al5.103(Fe, Cr) found in an Al12Fe2Cr alloy has been derived from its high-resolution electron microscopy images and the structure of the hexagonal \mu-Al4Mn [Shoemaker, Keszler & Shoemaker (1989). Acta Cryst. B45, 13–20], being isostructural to \mu-Al4Cr. Among the 14 unique positions of transition metal (TM) atoms, 13 are icosahedrally coordinated: five of these icosahedra interpenetrate into each other, forming icosahedral chains along [010], and the remaining eight icosahedra with their twofold axis parallel to this axis. This structural model describes a (010) layer structure with a sequence P^{m}FP(P^{m}FP)_I, where a flat layer F (a mirror plane) is sandwiched between two puckered P and P m layers, and (P^{m}FP)I is related to P^{m}FP through a body-centred translation. The interatomic distances are 2.51–2.74 Å for TM—TM, 2.38–2.99 for TM—Al and 2.41–3.18 Å, for Al—Al. Simulated images and electron diffraction patterns calculated based on this structural model are comparable with the experimentally observed results.

[Alterations of substance P-immune reaction positive neurons of cerebral tissues in epileptic rats]

Employing the immunocytochemical analysis, we observed the alterations of Substance P-Immune Reaction (SP-IR) positive neurons of the cerebral cortex, hippocampus and amygdala in rats suffering from epilepsy induced by Penicillin (PEN). The result showed that the number of neurons of epileptic group was higher than that of the control group and no significant change in the rumber of neurons was observed in the group in which PEN was given after injection of Nimodine. It indicates that SP and Ca2+ participate in the process of epileptogenesis.

Rapid induction of B-cell lymphomas in mice carrying a human IgH/c-mycYAC

Activation of the c-myc proto-oncogene by one of the immunoglobulin (Ig) loci after chromosomal translocation is a consistent feature of Burkitt's lymphoma. Different subtypes of this tumor vary in the molecular architecture of the translocation region. In most cases there are no known regulatory elements of the Ig locus neighboring the oncogene and this considerably obscures the mechanism of its deregulation. In order to assess possible oncogene activation signals, we produced an experimental translocation region by insertion of a c-myc gene about 50 kb from the IgH intron enhancer in a yeast artificial chromosome (YAC) containing a 220 kb region of the human Ig heavy chain (IgH) locus. Single copy integration of this YAC into the genome of mouse embryonic stem (ES) cells was achieved by spheroplast fusion. Chimeric mice derived from these ES cells developed monoclonal B-cell lymphomas expressing surface IgM by 8-16 weeks of age. The IgH/c-myc translocus showed different V(h)DJ(H) rearrangement in almost all tumors without any alterations of the distance between c-myc and the IgH intron enhancer. This mouse model can be used for the in vivo analysis of c-myc deregulation and the tumor formation capacity of the IgH locus in aberrant rearrangements.

Induction of c-myc transcription by the v-Abl tyrosine kinase requires Ras, Raf1, and cyclin-dependent kinases

v-Abl is an oncogenic form of the c-Abl nonreceptor tyrosine kinase. v-Abl induces transcription of c-myc, and c-Myc function is a necessary but not sufficient component of the v-Abl transformation program. Previously we showed that the E2F site in the c-myc promoter is a v-Abl response element and that v-Abl appears to induce c-myc by initiating a phosphorylation cascade that ultimately activates E2F-binding proteins. In this work we have investigated the signaling pathway between the v-Abl tyrosine kinase and activated E2F proteins. We show that the Ras GTPase and Raf1 serine/threonine kinase are required in this pathway. However, in contrast to other aspects of v-Abl signaling, induction of c-myc transcription is independent of the Rac GTPase. Our results also establish a requirement for activated cyclin-dependent kinases (cdks), as v-Abl-dependent induction of c-myc transcription is blocked by cdk inhibitor p21 and induction of c-myc is accompanied by activation of cdk2 and cdk4. Finally, we show that v-Abl-dependent induction of c-myc is accompanied by hyperphosphorylation of pRb, p107, and p130. On the basis of these data, we propose a model for the signaling path from v-Abl to c-myc.

Anti-tumor promoting activity of canventol and its synthetic analogs through inhibition of protein isoprenylation

Canventol, a synthetic compound, is a new inhibitor of tumor promotion on mouse skin by okadaic acid. We previously reported that canventol acts by inhibiting both protein isoprenylation and tumor necrosis factor-alpha (TNF-alpha) release. In this study we examined the potencies of 10 newly synthesized canventol analogs through their effect on mevalonate metabolism, and then examined 3 representative analogs for inhibition of protein isoprenylation. Since canventol in vitro did not directly inhibit farnesyl protein transferase or geranylgeranyl protein transferase-I, the effects of canventol and its synthetic analogs on the fate of [3H]mevalonate in cells were studied. Canventol at 500 microM changed the ratio of newly synthesized sterols (cholesterol and lathosterol) to ubiquinones from 0.7 to 8.2 in NIH/3T3 cells which had previously been labeled with [3H]mevalonate, suggesting that the altered pattern of mevalonate metabolism is associated with inhibition of protein isoprenylation in the cells. We named this ratio the inhibition of protein isoprenylation index (IPI index). The 10 analogs showed a wide range of IPI indices. Two analogs, S3 and S9 had effects similar to, or stronger than, canventol. Three analogs, C44, C46 and C47, with lower IPI indices, inhibited tumor promotion on mouse skin slightly less than canventol itself did. This study shows that inhibition of protein isoprenylation in the cells, indicated by an increase in the IPI index, is a new biomarker for estimating inhibition of tumor promotion.

Dominant expression of a 1.3 Mb human Ig kappa locus replacing mouse light chain production

Expression studies of multigene families, such as the immunoglobulin (Ig) loci, are difficult because of their large size and the necessity to introduce germline configured regions into an animal. Antibody diversity from Ig gene miniloci is limited by the number of variable (V) region genes and the need for distal regulatory elements to control expression. Here, we show germline transfer into mice of a 1300 kb human Ig kappa light chain locus on a yeast artificial chromosome that resulted in early DNA rearrangement and highly efficient human light chain expression. The human locus was assembled from a 300 kb authentic region using contig extension by addition of cosmid multimers to supplement the variable gene cluster. This resulted in the addition of about 100 V region genes in germline configuration from different families. In transgenic animals with Ig kappa disruption, this large human kappa locus replaced the endogenous locus, and subsequent down-regulation of Ig lambda light chain contribution led to a dominant expression of the rearranged human genes. Contrary to expectation, rather than providing a solely selective advantage for ensuring repertoire formation controlled by the sheer number of introduced genes, the lambda/kappa ratio in serum appears to be the result of competition for early surface Ig expression maintained in the developing B cell.-Zou, X., Xian, J., Davies, N. P., Popov, A. V., Brüggemann, M. Dominant expression of a 1.3 Mb human Ig kappa locus replacing mouse light chain production.

[The significance of circulating endothelial cell in hypoxic injury of pulmonary vascular endothelial cell]

OBJECTIVE

To observe the changes of vascular endothelial cell (VEC) in hypoxic rats and to check the damage of VEC in vivo, an experiment for observing circulating endothelial cells was conducted.

METHOD

Thirty male Wistar rats were classified into 5 groups in random, exposted to 10% O2 and 1% FeCl3 intraveniously. After 0, 1, 2, 3, 4 weeks, PaO2, circulating endothelial cells (CEC) were measured and the lung specimens, the pulmonary artery were examined by transmission electron micrography (TEM) and scanning electron micrography (SEM).

RESULTS

Lung specimens and pulmonary artery under TEM and SEM: swollen appeared to VEC after 1 week. As time prolonged, VEC appeared splitting, broken and peeled off. The amount of CEC increased as the time proceeding, the longer the time, the higher the number of the CEC. Obvious hypoxemia developed in the tested animals as the time prolonged.

CONCLUSIONS

All above results indicated: the time of anoxia proceeding, the structure of lung and pulmonary artery VEC were damaged obviously. The increase of CEC matched with the changes of ultrastructure of lung VEC. CEC specifically reflected the damage of VEC. Non-invasive measurement of CEC is valuble in evaluation of hypoxic injury of pulmonary VEC.

v-Abl activates c-myc transcription through the E2F site

The v-abl oncogene of Abelson murine leukemia virus encodes a deregulated form of the cellular nonreceptor tyrosine kinase. v-Abl activates c-myc transcription, and c-Myc is an essential downstream component in the v-Abl transformation program. To explore the mechanism by which v-Abl activates c-myc transcription, a cotransfection assay was developed. We show that transactivation of a c-myc promoter by v-Abl requires the SH1 (tyrosine kinase) and SH2 domains of v-Abl; the C-terminal domains are not required for transactivation. The assay also identified the E2F site in the c-myc promoter as a v-Abl-responsive element. In addition, multimerized E2F sites were shown to be sufficient to confer v-Abl-dependent activation on a minimal promoter. This is the first identification of a v-Abl response element for transcriptional activation. v-Abl tyrosine kinase-dependent changes in proteins binding the c-myc E2F site were also demonstrated, including induction of a complex containing DP1, p107, cyclin A, and cdk2. Identification of v-Abl-dependent changes in E2F-binding proteins provides an important link between v-Abl, transcription, cell cycle regulation, and control of cellular growth.

C/EBP proteins activate transcription from the human immunodeficiency virus type 1 long terminal repeat in macrophages/monocytes

Three binding sites for C/EBP proteins are found in the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) (V. M. Tesmer, A. Rajadhyaksha, J. Babin, and M. Bina, Proc. Natl. Acad. Sci. USA 90:7298-7302, 1993). We have determined the functional role of C/EBP proteins and C/EBP sites in regulating transcription from the HIV-1 LTR in monocytes/macrophages. Inhibition of endogenous C/EBP proteins, using either an excess of C/EBP binding sites or a trans-dominant negative inhibitor, demonstrated that C/EBP proteins are required for basal and activated levels of HIV-1 LTR transcription in the promonocytic cell line U937. Northern (RNA) blots and binding assays showed that NF-IL6 is the only known C/EBP family member which is increased when U937 cells are activated. Mutational analyses of the HIV-1 LTR showed that one C/EBP site is required for normal LTR transcription both before and after cellular activation and that the two 3' C/EBP sites are functionally equivalent. However, transcription from crippled HIV-1 LTRs lacking C/EBP sites can still be induced following activation of U937 cells. Several models are suggested for how elevated NF-IL6 may participate in an autostimulatory loop involving HIV infection, macrophage activation, cytokine expression, and HIV replication.

Subtle differences in antibody responses and hypermutation of lambda light chains in mice with a disrupted chi constant region

Analysis of lambda light chain use in normal mice is made difficult by the dominant chi light chain repertoire. We produced mice rendered deficient in chi light chain expression by gene targeting and focused on questions concerned with the generation of lambda light chain diversity. Whilst these mice compensate the chi deficiency with increased lambda liters, and their Ig level is therefore not significantly reduced, they show major differences in immunization titers, germinal center (GC) development and somatic hypermutation. After immunization, using antigens that elicit a restricted IgL response in normal mice, we obtained in the chi-/- mice elevated primary antibody titers but a subsequent lack in titer increase after repeated antigen challenge. Analysis of the Peyer's patches (PP) revealed a dramatically reduced cell content with rather small but highly active GC. Flow cytometric analysis showed different cell populations in the PP with enriched peanut agglutinin (PNA)hi/CD45R(B220)+ B cells, implying that the apparent compensation for the lack of lambda light chain expression involves the GC microenvironment in cell selection, the initiation of hypermutation and high affinity expansion. The three V lambda genes, V1, V2 and Vx, are mutated in the GC B cells, but show no junctional diversity. In contrast, a reduced rate of V lambda hypermutation is found in the hybridoma antibodies, which appears to reflect a selection bias rather than structural constraints. However, mechanisms of somatic mutation and specificity selection can operate with equal efficiency on the few V lambda genes.

The determination of strong mutagen MX [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] in drinking water in China

The strong mutagen, [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] (MX) was found to occur in chlorinated drinking water in China. Some tap water samples from Jiangsu province, which contained MX of 3-60ng/L, were analyzed. Quantitation is based on gas chromatography-mass spectrometry, using peak area of selective ion monitoring of the methyl derivative of MX.

[Postoperative management of crisis of myasthenia gravis: analysis of 20 patients]

From June 1983 to March 1992, 95 patients with of myasthenia gravis were treated with thyrmoma-thymectomy. Among them 90 patients were taken midsternotomy, and others standard lateral thoracotomy. All the patients had postoperative crisis of myathenia except one who had a cholinergic crisis. 12 patients (60%) belonged to type III and IV According to the Osserman's classification. The pathological findings showed that 17 patients had combined thyrmoma. The management for crisis was satisfactory with a success rate of 95%. The mortality rate was 5% (1/20) in early postoperative stage and 35% (7/20) in later stage, respectively. 12 patients survived for 2.5 to 10 years. Tracheotomy, mechanical ventilation adjustment, control of infection of the respiratory tract, and nourishment supports are the key measures for successful postoperative therapy and decrease of mortality.

Ab-interno sclerostomy using a goniodiathermy instrument

We describe the use of a new instrument designed to create a simultaneous goniopuncture with diathermy using an ab-interno technique. The goniodiathermy ab-interno procedure was first performed on three eyes of three cynomolgus monkeys. Intraocular pressure (IOP) assessment and histologic examination were performed over a 10-day period. A functioning filtration bleb with a patent sclerostomy was achieved in all of the experimental eyes. A pilot study involving four eyes of four glaucoma patients also was performed. Of these four, successful long-term functioning filtration areas with adequate lowering of IOP were achieved in only two. The remaining two required further surgical intervention. Although combining goniopuncture and diathermy into a one-step ab-interno procedure proved successful in the primates studied, the preliminary use of this new instrument as a method of creating a filter in humans raises questions regarding its clinical usefulness.

Heteronuclear nuclear magnetic resonance studies of cobalt corrinoids. 15. The structure of glutathionylcobalamin: a 1H and 13C two-dimensional nuclear magnetic resonance study at 600 MHz

Glutathionylcobalamin (GSCbl), the complex formed between glutathione (GSH, gamma-glutamylcysteinylglycine) and aquacobalamin (H2OCbl), has been implicated as an intermediate in the pathway for the formation of the cobalamin coenzymes. In chemical model studies, GSCbl has been shown to be a substrate for methylcobalamin formation in the presence of S-adenosylmethionine and a thiol reductant. Although GSCbl was first described in 1964, the structure of this compound, particularly the site of GSH coordination, has been unknown. GSCbl was prepared by reacting GSH (5-fold molar excess) with H2OCbl in 0.1 M sodium phosphate (pH 6.5) and was purified by gel-permeation chromatography on a Bio-Gel P2 polyacrylamide column. By use of a combination of homonuclear [homonuclear J-correlated spectroscopy (COSY), homonuclear Hartmann-Hahn spectroscopy (HOHAHA), and absorption-mode nuclear Overhauser effect spectroscopy (NOESY)] and inverse detected heteronuclear [1H-detected heteronuclear multiple-quantum coherence (HMQC) and 1H-detected multiple-bond heteronuclear multiple-quantum coherence (HMBC) spectroscopies] two-dimensional NMR methods at 600 MHz, the complete 1H and 13C NMR spectra of GSCbl have now been assigned. Comparison of the 1H and 13C NMR chemical shifts of the GS moiety of GSCbl to those of free GSH and GS- shows that by far the largest differences occur at the cysteine alpha and beta positions. This result strongly suggests that GSH is coordinated to the cobalt atom in GSCbl via the cysteine sulfur atom.

Canventol inhibits tumor promotion in CD-1 mouse skin through inhibition of tumor necrosis factor alpha release and of protein isoprenylation

A synthetic compound named canventol, 2-isopropyl-4-isopropylidencyclohex-2-ene-1-ol, inhibited tumor promotion of okadaic acid on mouse skin initiated with 7,12-dimethylbenz(a)anthracene in two-stage carcinogenesis experiments more strongly than sarcophytol A, isolated from a soft coral, although canventol has a simpler structure than sarcophytol A. Their mechanisms of action were studied based on our recent evidence that tumor necrosis factor alpha release induced by okadaic acid is an essential mechanism of tumor promotion. Canventol inhibited mouse tumor necrosis factor alpha release from BALB/3T3 cells less strongly than sarcophytol A, indicating that canventol has additional activity. Canventol inhibited isoprenylation of proteins with various molecular weights, such as M(r) 22,000, 17,000, and 13,000, whereas sarcophytol A did not show significant inhibition. Thus, a potent anticarcinogenic activity of canventol is mediated through the inhibitory bifunctions of tumor necrosis factor alpha release and of protein isoprenylation. Since canventol is less toxic to cells than sarcophytol A, these bifunctions are useful markers for screening for new cancer chemopreventive agents.

Effects of papaverine pilocarpine and epinephrine on fistulized rabbit conjunctiva

Pretreatment with pilocarpine hydrochloride has been demonstrated to increase the number of myofibroblasts in fistulized conjunctiva in rabbits. To determine if this observation is related to changes in the conjunctival vasculature that may be linked to pilocarpine, we evaluated the effects of a vasodilator and a vasoconstrictor in comparison with pilocarpine hydrochloride. Twenty Dutch-belted rabbits, with five rabbits per group, were treated in a masked fashion in both eyes with topical solutions of 4% pilocarpine hydrochloride, 0.3% papaverine, a combination of 4% pilocarpine and 2% epinephrine, or artificial tears for 3 months. Four of five rabbits in each group underwent thermal sclerostomies in both eyes; the fifth rabbit in each group served as a nonsurgical control. The mean number of myofibroblasts per high-power field was greater in the surgical eyes treated with pilocarpine (6.35 $pM 0.48) or papaverine (9.22 $pM 0.44) than in the eyes treated with both epinephrine and pilocarpine (4.80 $pM 0.70) or artificial tears (5.20 $pM 0.40). These results suggest that the vasoactive properties of topical agents can increase or limit the number of myofibroblasts following filtration surgery.

Volatile N-nitrosamines in salted fish samples from high- and low-risk areas for NPC in China

Four carcinogenic volatile nitrosamines (N-dimethylnitrosamine, NDMA; N-diethylnitrosamine, NDEA; N-nitrosopyrroline, NPYR; and N-nirosopiperilidine, NPIP) were screened in twenty specimens of salted fish collected from areas in China with different nasopharyngeal carcinoma (NPC) mortality rates. The highest NDMA, NDEA and total N-nitrosamine contents (322.92, 50.27 and 373.19 micrograms/kg, respectively) were found in the samples from Sihui, one of the areas with highest NPC mortality. The lowest contents (12.64, 7.65 and 20.29 micrograms/kg, respectively) were seen in the samples from Shanghai, the area with the lowest mortality from NPC in the study. These results confirm that there are appreciable levels of nitrosamines in the salted fishes consumed by residents in high-risk areas of NPC in China.

[Central neural mechanism underlying pressor response to excitation of locus coeruleus in rats]

Experiments were done on urethane anesthetized, tubocurarine immobilized and artificially ventilated rats and the following results were observed: (1) Injection of sodium L-glutamate (Glu) into locus coeruleus (LC) could evoke a pressor response, but heart rate was not significantly affected; while depressor and bradycardia effects were observed when injecting into closely adjacent areas. (2) The LC-pressor response decreased after a brain transection caudal to nucleus paraventricularis was made but remained unchanged if the transection was rostral to the nucleus; The LC-pressor response could also be attenuated by preinjection of phentolamine propranolol or atropine respectively into the rostral ventrolateral medulla (RVL). The above results suggest that LC-pressor response is not only mediated by RVL, but also by nucleus paraventricularis.

Multiecho, spin-echo sequence to eliminate unwanted echoes

Two types of artifacts--a mirror-reversed image about the phase-encode direction and a wave-like intensity variation across the image--may appear when using a conventional multiecho spin-echo sequence. We describe and demonstrate a new method, which eliminates such artifacts, using only one excitation per phase-encoding step and without the need for spoiler gradients.

MR angiography without subtraction

A new NMR method for producing angiograms with strong suppression of the static spin signal and without the need for subtraction is described and demonstrated. A velocity-selective pulse sequence was implemented whereby the magnetization of all stationary spins is driven to the -z axis and is not detected, while maximizing the signal intensity of the moving spins. A theory of the method is presented and gives good agreement with experimental results obtained on a flow phantom. It is shown theoretically and experimentally that high-quality velocity-independent angiograms of the head and neck can be obtained with strong suppression of static spin signal when TR approximately T1. The method can be extended to produce three-dimensional angiograms.

[Comparative study of cerebral infarction treated with acupuncture at 6 acupoints of yang meridian and calan]

This article reports the curative effects of acupuncture on 6 acupoints of Yang meridian in treating 32 cases of cerebral infarction in comparison with another 31 cases treated with calan tablets 55 out of 63 patients have been diagnosed as cerebral infarction by computer tomography. Diagnosis of 8 cases relied on history, symptoms, signs together with cerebrospinal fluid examination. Patients were divided randomly into two treatment groups: acupuncture group and calan tablet group. Therapeutic method: (1) For acupuncture group, main acupoints consisted of Jianyu (L.I. 15), Quchi (I. I. 11), Hegu (L. I.4) in the upper extremity and Huantiao (G. B. 30), Yanglingquan (G. B. 34), Guangming (G. B. 37) in the lower extremity. According to the syndrome differentiation, Taichong (Liv. 3), Fengchi (G. B. 20), Tianshu (St. 25), Fenglong (St. 40), Zusanli (St. 36), Sanyinjiao (Sp. 6), Taixi (K. 3) were added. The lifting and thrusting was manipulated. The needles were retained for 30 minutes after the patient felt local sourness, distension and heaviness. Acupuncture was carried out every day for 6 weeks. (2) For calan tablet group, calan tablet 5 mg was administered 3 times a day for the same treatment session as the former group.

RESULT

The total effective rates were 93. 75% and 83.87% respectively. The therapeutic effect in the acupuncture group was much better than that in the calan tablet group (P less than 0.05). The majority of hemorheological indices of patients in two groups were obviously higher than those of the normal in the same age group.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of praeruptorin C and E isolated from 'Qian-Hu' on swine coronary artery and guinea-pig atria

Praeruptorin C and E isolated from Peucedanum praeruptorum Dunn. decreased the maximum contractile effect of Ca2+ in potassium-depolarized swine coronary strips and shifted the concentration-response curve to the right in a non-parallel manner. The calcium antagonistic activity of praeruptorin C and E expressed as pD'2 value was 5.7 and 5.2, respectively. Nifedipine, with a pD'2 value of 6.88, was used as a known calcium antagonistic drug to compare the potency of the drugs studied. The relaxation induced by praeruptorin C was concentration-dependent and the IC50 value was 79 microM. Praeruptorin C also reduced the maximum contractile response and shifted the concentration-response curve for calcium to the right in a non-parallel manner in potassium-depolarized guinea-pig left atria (pD'2 = 5.52) but its potency was much less than that of nifedipine (pD'2 = 7.19). The results suggest that praeruptorin C and E relaxed swine coronary artery and decreased contractility in guinea-pig left atria. These effects are similar in many respects to those displayed by drugs that have calcium entry blocking activity.