Existence of both fast and slow channel activity during the early stages of ventricular fibrillation

Although sodium channels have been reported to be inactive after 5-10 minutes of ventricular fibrillation (VF), their state during early VF is unknown. In 12 open-chest dogs, a floating glass microelectrode was used to record intracellular action potentials from the right ventricle during pacing and during electrically induced VF. Before any drug was administered, an initial episode of VF was continuously recorded for at least 20 seconds followed by defibrillation. Recordings were made during VF episodes after superfusion for 15 minutes around the microelectrode site by low (2.8 x 10(-5) M) and high (10(-4) M) concentrations of tetrodotoxin (TTX) in five dogs, or by low (4 microM) and high (100 microM) concentrations of verapamil in another four dogs. In three dogs, VF was induced without drugs three times to determine if the effects observed in the previous dogs were caused by the drugs or by successive episodes of VF. Ten consecutive action potentials were analyzed at the onset and after 5, 10, 15, and 20 seconds of VF. Action potential amplitude and duration during paced rhythm or VF were not changed by the local perfusion of either TTX or verapamil. In the TTX group, the maximum upstroke rate of depolarization of an action potential (Vmax) during paced rhythm was 104 +/- 14 V/sec for control cycles before any drug was given, 86 +/- 15 V/sec for the low TTX concentration, and 55 +/- 14 V/sec for the high TTX concentration (p less than 0.05 versus other two). Vmax decreased from 55 +/- 32 V/sec at the beginning of VF to 37 +/- 27 V/sec after 20 seconds of VF for predrug VF, from 39 +/- 20 V/sec to 18 +/- 11 V/sec for low-dose TTX VF, and from 18 +/- 13 V/sec to 12 +/- 7 V/sec for high-dose TTX VF (p less than 0.05 among the three groups). In the dogs receiving verapamil, VF was still inducible with Vmax not significantly different from predrug VF at the onset and after 5 or 20 seconds of VF but with Vmax smaller (p less than 0.05) for verapamil than for predrug VF after 10 or 15 seconds of VF. In three dogs, Vmax was not significantly different during three successive episodes of VF when no drug was given between the episodes.(ABSTRACT TRUNCATED AT 400 WORDS)

Molecular cloning and characterization of a novel rat activin receptor

We report the isolation of a full-length rat cDNA for a new activin receptor. The deduced amino acid sequence of this receptor shows 67 percent overall identity with that of a previously identified mouse activin receptor. As predicted for the mouse activin receptor, the amino acid sequence of the rat receptor is consistent with a polypeptide containing an extracellular ligand binding domain, a hydrophobic transmembrane domain, and a serine/threonine kinase intracellular domain. In an expression assay, this new receptor was found to bind I125 radiolabeled activin.

The relationship between the changes in plasma atrial natriuretic peptide and renin angiotensin contents and hemodynamics in pulmonary hypertensive rats

Pulmonary artery pressure (PAP) increased significantly in rats after hypobaric hypoxic exposure for 15 days (CH15) (P less than 0.001) and was maintained at the same level after prolonged hypoxic exposure for 40 days (CH40). There were no significant changes in carotid systolic and diastolic blood pressure in CH15 and CH40 rats. The contractility of the right and left ventricles of CH15 and CH40 rats showed no difference as compared with the control group. Plasma atrial natriuretic peptide (ANP) content in CH40 rats was obviously increased (P less than 0.001), while angiotensin II (AII) dropped markedly (P less than 0.05). Plasma renin activity was increased in both hypoxic groups (P less than 0.05 respectively). These results indicate that during chronic hypoxia, plasma ANP and the renin-angiotensin system (RAS) play an important role in the modulation of pulmonary as well as systemic hemodynamics. They may work cooperatively to limit the development of pulmonary hypertension and to maintain systemic blood pressure within the normal range.

[Mechanism of the photosensitive effects of methylene blue in the inhibition of DNA synthesis in cancer cells]

In the present study, we found that various concentrations of methylene blue (38, 3.8, 0.38, 0.038, 0.0038 mumol/L) significantly inhibited DNA synthesis in ascites hepatoma (AH) cells. The inhibition increased with the concentration of methylene blue as well as with irradiation time. Photosensitization of methylene blue was not due to 1O2, OH., or O2.-, but was closely related to H2O2. The mechanism of inhibition of DNA synthesis may be attributed to the damage of DNA replication template.

[Preliminary study on the relation between serum growth hormone and 1,25-dihydroxyvitamin D3 in acromegalic patients]

Eight acromegalic patients were treated with SMS 201-995 for 12 months. At the 3rd, 6th and 12th month from the beginning of treatment, blood samples of these patients were taken for determination of growth hormone (GH), 1,25-(OH)2D3, SMC, calcium and phosphorus. The serum levels of GH decreased significantly at the 3rd, 6th and 12th months compared with the basal levels before treatment (P less than 0.01, P less than 0.05 and P less than 0.05 respectively). The concentrations of serum 1,25-(OH)2D3 and SMC also decreased significantly. Mean serum GH, 1,25-(OH)2D3 and SMC levels were reduced from 34.8 +/- 10.7 to 15.5 +/- 5.9 ng/ml (P less than 0.05), 76.2 +/- 2.7 to 45.9 +/- 8.3 pg/ml (P less than 0.05) and 8.5 +/- 1.2 to 4.4 +/- 1.0 U (P less than 0.05) respectively at the 12th month after treatment. Serum phosphorus levels reduced from 4.7 +/- 0.4 to 4.1 +/- 0.2 mg% (P less than 0.05) at the 6th month after treatment, but there was no change in the serum levels of total calcium. The treatment with SMS 201-995 directly evoked a reduction of serum GH in acromegalic patients and at the same time, the levels of serum SMC and 1,25-(OH)2D3 were decreased. The results suggest that GH may stimulate indirectly the production of 1,25-(OH)2D3 through the mediation of SMC.

[Study of enamel caries-lesion produced by artificial plaque]

The authors used the cariogenic bacteria isolated from human dental plaque to produce an artificial plaque which can produce carious lesion in vitro. Lesions on human enamel slabs produced by artificial plaque and single bacterium were observed under polarized light microscope and scanning electron microscope. The results showed that the characters of artificial carious lesions are very similar to natural enamel caries. It is very difficult to differentiate them under the microscopes. Compared with the lesions produced by single strain, the destructive fashion observed in lesions produced by artificial plaque is more similar to the changes produced by natural dental plaque.

[Analysis of follow-up data in 83 cases of primary liver cancer]

Eighty-three patients with primary liver cancer (PLC) having survived over 5 years were investigated. 50.6% (42/83) of them were in Stage I and 49.4% (41/83) were in Stage II. Resection was performed in 94.0% (78/83), and hepatic artery ligation and/or cannulation was done in 6.0% (5/83). By the end of March 1990, 66.3% (55/83), were cancer-free, 4.8% (4/83) were living with the cancer, 20.5% (17/83) died from recurrence or metastasis of cancer, 7.2% (6/83) died from liver failure, and 1.2% (1/83) lost followup. 29 cases survived over 10 years after resection of PLC. A comparison with 811 patients having less than 5 years during the same period demonstrates that early discovery, lower gamma glutamyl transpeptidase (gamma-GT) and alanine aminotransferase (ALT), tumor less than or equal to 5 cm, single nodule, well-encapsulated tumor, radical resection, and alpha fetoprotein (AFP) normalization after resection may contribute to prolonged survival. It is concluded that early detection and early radical resection are essential to improve the therapeutic effects.

[Diagnosis, treatment and prognosis of single-nodular minute hepatocellular carcinoma]

This article presents 14 patients of single-nodular minute hepatocellular carcinoma (HCC less than or equal to 2 cm) with coexisting cirrhosis. Of these nine patients were discovered by alpha-fetoprotein (AFP) mass screening or health check-up; and five by follow-up observations of chronic liver disease. All the 14 patients received radical resection with no operative mortality. The 1-5 year survival rates after resection were 100% (14/14), 100% (12/12), 100% (11/11), 100% (9/9), and 100% (7/7), respectively. This study demonstrates that the key point of further improvement in the detection of minute HCC lies in the establishment of diagnosis at a relatively low AFP level (less than 200 ng/ml). Realtime ultrasonography is the diagnostic modality of first choice in screening and monitoring. Surgery is strongly indicated for minute HCC with compensated liver function; Limited resection is the main type of resection for minute HCC with liver cirrhosis. The present data also indicate that HCC is not always multicentric in origin, even in patients with liver cirrhosis Intrahepatic spreading rather than multicentric origin may play a more important role in the multinodular pattern of HCC.

[Electron microscopic observation of the effects of Rhodiola kirilowii (Regel.) Maxim. in preventing damage of the rat viscera by a hypoxic high altitude environment]

This paper has shown that the pathologic damages done to rat's viscera due to hypoxic environment of altitude can be reduced significantly by oral administrations of Shengmaiyin, Danshen-Chuanxiong mixture and Rhodiola kirilowii. Shengmaiyin that maintains interior substances in the plate layer bodies proves more effective than Danshen-Chuanxiong mixture, while the latter excels in preventing capillary contraction, thus improving blood circulation. Rhodiola kirilowii has the effects of both Shengmaiyin and Danshen-Chuanxiong mixtures.

[Hemodynamic effects of nifedipine on pulmonary hypertension secondary to congenital heart disease with shunts]

Ten patients (pts) with pulmonary hypertension (PAH) secondary to congenital heart diseases (CHD) with left to right and bidirectional shunts were studied by right heart catheterization. After getting the control hemodynamic data, pts were given nifedipine (NIF) capsule 10-20 mg sublingually and their pulmonary artery pressure (PAP), systemic blood pressure (SBP), heart rate (HR) were monitored for 60 minutes and the hemodynamic data were redetermined. The results showed that the PAP as well as SBP was decreased and the quantity index of left to right shunt (L-R QI) was also reduced by NIF in L-R shunt group (3/10). In bidirectional shunts group (7/10), 4/7 cases showed total pulmonary artery resistance index (TPRI), pulmonary artery resistance index (PARI) were decreased by 29% (P less than 0.01) and 30% (P less than 0.05) respectively without seriously increased R-L shunts. The other 3/7 pts' TPRI, PARI were increased while systemic vascular resistance index (SVRI) was lowered by 41% (P less than 0.05). The quantity index of pulmonary blood flow (Qlp) was decreased by 30 (P less than 0.05) quantity index of right to left shunt R-L QI was increased sharply by 138% (P less than 0.05) while L-R QI decreased by 76% (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

[Matched investigation of risk factors in coronary heart patients with gallstones]

Seventy-five cases of coronary heart disease with gallstones and another 75 cases without gallstones as controls were studied. The positive rates of previous cholecystitis and chronic intestinal diseases, and familial history of gallstone in the first group were obviously higher than those in the control group (P less than 0.05 & 0.11). The odd ratio (OR) was 4.22, 9.00 and 6.00, respectively. There was no difference in high serous lipid level, obesity, high cholesterol and fat intake (P greater than 0.05) neither group took clofirrate. It demonstrated that susceptible factors for coronary heart disease patients to develop gallstones are probably the same as in general population. The imbalance of lipoid metabolism had no direct associate with gallstones. The synergistic action of the imbalance of lipid metabolism and administration of some kinds of medicine might be a susceptible factor for coronary heart disease patients to develop gallstones.

Isolation and nucleotide sequence determination of a gene encoding a heat-stable enterotoxin of Escherichia coli

An enterotoxin-producing strain of E. coli has been isolated from an infant patient in Shanghai Children Hospital and the gene of its heat-stable enterotoxin has been cloned and sequenced. The pre-pro-STI was composed of 72 amino acid residues corresponding to the encoding of 216 base pairs. There was only one nucleotide difference in the pro-part between this STI gene and the STIb gene reported in the literature. A guanosine base in our STI gene was substituted for a cytosine base in STIb gene resulting in a replacement of proline by alanine. Hence, the STI genes from different human sources are highly conserved though mutagenesis still occurs.

Site-specific degradation of Streptomyces lividans DNA during electrophoresis in buffers contaminated with ferrous iron

Streptomyces lividans DNA contains a modification which makes it susceptible to double-strand cleavage during electrophoresis in buffers contaminated with ferrous iron (which may be present in some batches of EDTA). The cleavage of the DNA is site-specific and the average fragment size resulting from limit digestion of total S. lividans DNA is about 6kb. DNA from Streptomyces coelicolor A3(2) and several other Streptomyces strains, and from E. coli, is not cleaved under the same conditions. A S. lividans mutant has been isolated which lacks the DNA modification. We suspect that many reports of "poor" preparations of S. lividans plasmids may be due to the above effect.