[An observation on the pacemaker current I(f) in sheep cardiac Purkinje fibers under ischemia-mimic condition]

Effects of "ischemia" and adrenergic agonists on pacemaker current I(f) were observed in sheep cardiac Purkinje fibers. After perfusion with ischemia-mimic solution for 15, 30 and 60 min, the amplitude of I(f) current were decreased at all membrane potential levels between Ec-60 mV to -120 mV (n = 7, P < 0.05), activation time and half activation time to a steady state value of I(f) current were prolonged (n = 7, P < 0.05), activation curve of I(f) shifted to a more hyperpolarized position. Isoproterenol 1 x 10(-6) mol/L increased amplitude of I(f) current (n = 10, P < 0.05), shortened the activation time and half activation time (n = 10, P > 0.05), and shifted the activation curve to a more depolarized position; but isoproterenol of 1 x 10(-6) mol/L could not completely reverse the inhibitory effects of "ischemia" on I(f) current. In the presence of 5 x 10(-7) mol/L propranolol the effects of phenylephrine 5 x 10(-5) mol/L on I(f) current was variable; but aggravated the inhibitory effects of I(f) current due to "ischemia". The above results indicate that normal pacemaker activity of ventricular Purkinje fibers does not increase but rather decrease during myocardial ischemia-mimic condition, an observation suggesting that acute ischemic ventricular arrhythmia may not be due to abnormal strengthening of normal ventricular pacemaker activity.

[The refinement of retinotectal projection on tectal whole mount during the regeneration of the goldfish optic nerve labeled with DiI anterogradely]

The refinement of retinotectal projection during the regeneration of the goldfish optic nerve was studied with microinjection of the lipophilic dye DiI (1,1-dioctadecyl-3,-3,-3',-3',-tetramethylindo-carbocyanine perchlorate) into the dorsal retina to label a few of retinal ganglion cells, which could be transported anterogradely to their terminal arbors on the tectum. The regenerated optic nerve fibers on the tectal whole mount were examined at various time intervals (from 7 to 365 days) following an optic nerve crush. At the early regeneration stage (2 to 8 weeks postcrush), the regenerated optic fibers travelled in abnormal paths through both appropriate ventral and inappropriate dorsal hemitecta, but the majority of the fibers (about 60% to 70%) were found in the appropriate ventral hemitectum. At the late regeneration stage (2 months afterward postcrush), after refinement of regenerated optic fibers, the retinotectal projection was reestablished preciously as in the normal fish. Present study shows that the refinement of the retinotectal projection manifests in three major changes: 1) The disappearance of the regenerated optic fibers at the inappropriate tectal positions; 2) The disappearance of the side branches on the optic fiber shaft; 3) The formation of overlapping terminal arbors by the optic fibers that arrived at the retinotopic target. These results suggest that there may be two kinds of factors in the tectum: One is a common guiding factor which distributes over all the tectum and guides the regenerated optic fibers growing into the tectum at early regeneration; another is a position-specific neurotrophic factor which guides the regenerated optic fibers arriving at the retinotopic target at late regeneration.

Antiferromagnetic Ordering and Paramagnetic Behavior of Ferromagnetic Cu 6 and Cu 18 Clusters in BaCuO 2+ x

Magnetization and neutron diffraction measurements on polycrystalline BaCuO2+x revealed a combination of magnetic behaviors. The Cu(6) ring clusters and Cu(18) sphere clusters in this compound had ferromagnetic ground states with large spins 3 and 9, respectively. The Cu(6) rings ordered antiferromagnetically below the Néel temperature T(N) = 15 +/- 0.5 kelvin, whereas the Cu(18) spheres remained paramagnetic down to 2 kelvin. The ordered moment below T(N) was 0.89(5) Bohr magnetons per Cu in the Cu(6) rings, demonstrating that quantum fluctuation effects are small in these atomic clusters. The Cu(18) clusters are predicted to exhibit ferromagnetic intercluster order below about 1 kelvin.

ESR dating of tooth enamel: comparison with U-series, FT and TL dating at the Peking man site

Deer tooth samples from Zhoukoudian, the Peking Man Cave, were studied. Non-linear fitting is used to determine AD, from which ESR ages were calculated by both the disequilibria model (DU) and linear uptake model (LU). Comparison of ESR ages with those from U-series, FT and TL methods show that the enamel of deer teeth is a suitable material for ESR dating.

Evolutionary analysis of Pinus densata Masters, a putative Tertiary hybrid : 1. Allozyme variation

Allozyme differentiation at 13 loci was studied in populations of Pinus tabulaeformis, P. densata, and P. yunnanensis from China. It was previously suggested that P. densata represents a Tertiary hybrid between P. tabulaeformis and P. yunnanensis. The observed levels of allozyme variation within and among the investigated species were comparable to those of other conifers. P. tabulaeformis differed markedly from P. yunnanensis with respect to allozyme frequencies, while P. densata was intermediate between the two putative parents. There was evidence of homozygote excess in embryos from all investigated species, as compared to Hardy-Weinberg expectations. The observed allozyme composition of P. densata conformed to earlier morphological and molecular evidence indicating hybrid origin of this taxon. It was proposed that fusion of gene pools from P. tabulaeformis and P. yunnanensis has led to adaptive evolution of a new species, P. densata.

[Secretion of human embryonic atrial specific granules (SG) in culture]

Atrial muscle cells from three cases of 4-month human embryonic (by uterotomy) were studied through for electronic microscopy and the evidences obtained were as follows: 1. Mechanical stimulation and noradrenaline (20ng/ml) induced SG secretion. 2. 654-2 (10 micrograms/ml), COQ10 (2.5 micrograms/ml), Se(10(-7) M) and verapamil (1 microgram/ml) did not depress SG secretion by noradrenaline.

Surgical treatment of congenital choledochal cyst

20 cases of congenital choledochal cyst were operated by modified Lilly's method from 1980 to November 1985 in our Hospital. There were 4 males and 16 females. Their ages ranged from 50 days to 15 years with a mean of 5.1 years. All patients had preoperative ultrasonographic examination, barium meal radiography of the gastrointestinal tract or percutaneous transhepatic cholangiography. All had choledochal cystectomy with retention of the outer layer of the posterior wall of the cyst. We modified Lilly's method by injecting normal saline between the outer and inner layer of the choledochal cyst so that the outer layer could be isolated. Reconstruction of the biliary tract was then performed. 2 patients had choledochoduodenostomy and 18 patients had hepaticojejunostomy (1 end to end and 17 end to side). 19 patients had also had cholecystectomy. The post-operative course of the operation was found to be smooth and safe. Patients were followed up for a period from 6 months to 7 years. 3 patients had cirrhosis of liver, 2 of whom died within 8 months. The mortality rate in our series was 10%. The operative treatment and the problems of biliary reconstruction are discussed.

Study on the constituents of Desmodium styracifolium

Two triterpenoid saponins (1 and 2) were isolated from Desmodii Herba [the dried whole plants of Desmodium styracifolium (Osbeck) Merr. (Leguminosae)] and their chemical structures were characterized as soyasaponin I and a new saponin, 3-O-[alpha-L-rhamnopyranosyl-(1----2)-beta-D-galactopyranosyl- (1----2)-beta-D-glucuronopyranosyl]soyasapogenol E, respectively, by chemical and spectroscopic means.

Detection of ABR thresholds with a statistical synchrony measure

Using the method of Fridman and his colleagues, a statistical test of auditory brainstem responses (ABR) for detecting auditory thresholds is presented. The synchrony measure (SM) which represents the degree of reproducibility for group averages was used to calculate the selected Fourier components of the group averages from phase variance. The sensitivity of the test was demonstrated on 35 normal ABRs with 60 and 45 dB SL stimulus intensity and in the absence of stimulus from the ipsilateral recordings. The SM of all cases of normal ABRs at 60 and 45 dB SL exceeded those in the absence of stimulation. The same procedure was applied to 16 ears with cochlear hearing loss with (4 ears) and without (10 ears) recruitment and 2 ears with relatively normal hearing threshold (less than 30 dB HL). Seven out of 10 ears without recruitment had the SM value at 60 dB SL stimulus intensity significantly lower than those of normal ABRs.

Two Gamma-Ray Sources and Ancient Guest Stars

On the basis of the fact that the youngest neutron stars such as the Crab pulsar and the Vela pulsar emit strong gamma-ray radiation, it is suggested that a few gamma-ray sources may be identified with young compact sources formed in the events of guest stars. Two such sources, 2CG 353+16 and 2CG 054+01, are identified with guest stars observed in the 14th century B.C. and A.D. 1230, respectively.

Determination of clozapine and its metabolites in serum and urine by reversed phase HPLC

A rapid, specific and sensitive method using reversed phase HPLC for the simultaneous determination of clozapine and its two metabolites in serum and urine has been developed. The mobile phase was a mixture of 67% (v/v) methanol in water containing 0.4% tetramethylethylenediamine and 0.32% acetic acid (pH 5.5). The influence of methanol content, the pH of the mobile phase and the effect of adding alkylammonium ions as peak tailing reducer in the mobile phase have been investigated. The solvent for extracting clozapine from serum and urine was ether. 50 microliters of 0.25 M H2SO4 solution was used to redissolve the dry residue to eliminate the endogenous compounds which could otherwise be eluted together with clozapine from the HPLC column. The analysis of a single sample was accomplished within half an hour. The identities of the chromatographic peaks of clozapine and its N-demethyl metabolite collected from the patient urine sample were confirmed by mass spectrometry. The method is sufficiently sensitive (5 ng/ml) and reproducible (CV 2.9%-6.7%) for clinical and pharmacokinetic studies, and preliminary results in these respects are presented.