皖南、赣北奥陶纪笔石立体标本形成环境的初步研究*

皖南、赣东北和赣西北地区奥陶纪笔石地层发育良好,笔石化石丰富。宁国组和胡乐组均为笔石相地层,但笔石的保存特点并不相同。立体保存的黄铁矿化笔石标本主要见于宁国组,而胡乐组的笔石几乎均为薄膜标本。在比较宁国组和胡乐组在岩性、颜色、化石、矿物和元素等方面的特点后发现,两者有较明显的差异。这表明宁国组和胡乐组形成时的环境是不同的,前者为弱还原环境,后者为较强的还原环境,而在研究区内影响笔石体立体保存的主要因素为还原环境和较高的铁含量。在还原环境下,铁可呈Fe~(2+)存在,笔石体内含有硫,死亡后经降解作用可生成H_2S;H_2S和Fe~(2+)结合可使笔石体黄铁矿化,从而使笔石体硬化而呈立体保存下来。宁国组的铁含量明显高于胡乐组,这似可以解释宁国组产有较多笔石立体标本的原因。     

慢性缺氧对肺动脉内皮依赖性和非内皮依赖性舒张反应的影响

本实验用生物测定法观察了模拟海拔5000m高度连续缺氧20d对大鼠肺动脉内皮依赖性和非内皮依赖性舒张反应的影响。结果显示慢性缺氧明显抑制了肺内和肺外动脉对乙酰胆碱、ATP、硝普钠和异丙肾上腺素舒张反应的敏感性和反应性。在浓度为10~(-6)mol/L时,缺氧组大鼠肺内动脉对乙酰胆碱、硝普钠和异丙肾上腺素的舒张反应分别只有对照组大鼠的61.3％、75.9％和61.7％,对浓度为1.8×10~(-5)mol/L的ATP的舒张反应只有对照组大鼠的64.9％。研究表明,ATP和乙酰胆碱主要是通过内皮舒张因子使肺动脉产生内皮依赖性舒张反应,硝普钠和异丙肾上腺素分别通过直接激活血管平滑肌细胞鸟苷酸环化酶和β受体使血管产生非内皮依赖性舒张反应。缺氧同时抑制了肺动脉内皮依赖性和非内皮依赖性舒张反应,提示慢性缺氧可能抑制了正常肺内舒血管活性物质的生理作用。     

Age-dependent aluminum accumulation in the human aorta and cerebral artery

The purpose of this study was to determine the extent of aluminum (Al) accumulation in the human aorta and cerebral arteries. The Al contents in the aortae and in the cerebral arteries from 23 human subjects was determined by inductively coupled plasma atomic emission spectrophotometry (ICP-AES). The subjects' age range was 45–99-yr-old; 15 of the subjects were males and 8 were females. Al was detected in twelve aortae and in six cerebral arteries, when the entire specimen was analyzed. Two specimens where Al was found in the cerebral arteries contained no Al in the aorta. No relationship to the subject's sex was found. When related to age, two groups were established. Group L (45–75 yr old) and group H (>75 yr old), which exhibited aortal Al concentrations of 33.3 and 72.7%, respectively. When the aortic wall was dissected into the tunica intima, media, and adventitia, Al was found mainly in the tunica media. In the aorta, significant relationships were found between Al and phosphorus (P) levels (r=0.801,p<0.01) and between Al and calcium (Ca) (r=0.661,p<0.05). We have concluded that Al accumulation is age-dependent and that it occurs both in the aorta and in the cerebral artery. In the aorta, accumulation occurs mainly in the tunica media. Both P and Ca appear to enhance aortal Al accumulation.     

The bronchial tree,lobular division,and blood vessels of the lung of the silvered lutong (Presbytis cristata)

The lungs of three silvered lutongs (Presbytis cristata) were examined. The right and left lungs have the dorsal, lateral, ventral, and medial bronchiole systems, which arise from the corresponding sides of both bronchi, respectively. Bronchioles in the dorsal and lateral bronchiole systems are well developed, whereas those in the ventral and medial bronchiole systems are poorly developed and lack some portions. According to the fundamental structure of bronchial ramifications of the mammalian lung (Nakakuki, 1975, 1980), the right lung consists of the upper, middle, lower, and accessory lobes, whereas the left lung consists of a bilobed middle lobe and a lower lobe, in which the right upper lobe is extremely well developed. The right pulmonary artery runs across the ventral side of the right upper lobe bronchiole, and then across the dorsal side of the right middle lobe bronchiole. Initially it runs along the lateral side of the right bronchus and then gradually comes to run along the dorsal side. During its course, it gives off branches which run mainly along the dorsal or lateral side of the bronchiole. The left pulmonary artery runs across the dorsal side of the left middle lobe bronchiole, and then follows the same course as that in the right lower lobe. The pulmonary veins run medially or ventrally to the bronchioles, and finally enter the left atrium as four or five large veins.     

Effects of posture, hypotension and locally applied vasoconstriction on the middle ear microcirculation in anaesthetized humans

Studies by laser-Doppler flowmetry of middle ear microcirculation changes induced by physical and chemical stimuli in the animal have only recently been made. This prospective study, performed in humans, was designed to compare the effects of a postural manoeuvre (headup tilt 30°), hypotension and locally applied vasoconstriction on middle ear blood flow during anaesthesia. Circulatory changes provoked by a headup tilt of 30°, and successive intravenous boluses of potent vasodilators, were compared with circulatory changes provoked by locally applied adrenaline, in ten healthy patients in good physical states undergoing middle ear surgical repair. Heart rate and direct arterial pressure were continuously recorded via a radial artery cannula. Middle ear blood flow was continuously recorded via a laser-Doppler probe placed on the promontorium cavi tympani. Metabolic parameters (partial pressure of O₂ and CO₂ in arterial blood, pH, arterial lactate concentrations) and arterial concentrations of propofol were measured just before and just after the experiment. Headup tilt did not modify heart rate, mean arterial pressure or middle ear blood flow. Vasodilators (nicardipine, nitroprusside, nitroglycerin) provoked a fall in arterial pressure (P<0.0001,P<0.0001,P<0.019, respectively), but did not induce any significant variations in heart rate; variations occurred in middle ear blood flow (P>0.05, not significant) which were different according to patients and agents. Locally applied adrenaline provoked a fall in the middle ear blood flow (P<0.0012), with no effect on heart rate and arterial pressure. There were no significant changes in metabolic values, or propofol serum concentrations. The behaviour of the middle ear blood flow submitted to hypotension, posture, or to vasoconstriction could be related to counteracting regulatory responses and/or to direct vascular effects.     

Properties of the ATP-sensitive K+ current activated by levcromakalim in isolated pulmonary arterial myocytes

Tension and patch clamp recording techniques were used to investigate the relaxation of rabbit pulmonary artery and the properties of the K⁺ current activated by levcromakalim in isolated myocytes. Under whole-cell voltage clamp, holding at –60 mV in symmetrical 139 mm K⁺, levcromakalim (10 m) induced a noisy inward current of –116 ± 19 pA (n = 13) which developed over 1 to 2 min. This current could be blocked by either glibenclamide (10 m) or phencyclidine (5–50 M) and was unaffected when extracellular Ca²⁺ was removed. Both these drugs inhibited the levcromakalim-induced relaxation of muscle strips precontracted with 20 mm [K⁺] _o . Application of voltage ramps in symmetrical 139 mm K⁺ confirmed that the levcromakalim-induced current was carried by K⁺ ions and was weakly voltage dependent over the potential range from –100 to +40 mV.The unitary current amplitude and density of the channels underlying the levcromakalim-activated whole-cell K⁺ current was estimated from the noise in the current record. We estimate that levcromakalim caused activation of around 300 channels per cell, with a single channel current of 1.1 pA, corresponding to a slope conductance of about 19 pS. Furthermore, cells dialyzed with an ATP-free pipette solution developed a large noisy inward current at –60 mV, which could subsequently be blocked by flash photolysis of caged ATP. Analysis of the noise associated with this current indicated that the single channel amplitude underlying the ATP-blocked current was 1.4 pA, a value similar to that estimated for the levcromakalim-induced current. We conclude that the conductance of this ATP-sensitive channel is likely to be small under physiological conditions and that it is present at low density.We thank SmithKline & Beecham for the gift of levcromakalim, ICI Pharmaceuticals for the gift of charybdotoxin and Prof. D. Colquhoun for the noise analysis programs. We also thank Mr. R. Davey for technical assistance with tension experiments. This work was supported by the British Heart Foundation and the Wellcome Trust. L.H.C. is a Wellcome Research Fellow and P.L. is an intermediate fellow of the BHF.     

Identification of Endothelin Receptor Subtype (ETB) in Human Cerebral Cortex Using Subtype-Selective Ligands

Abstract: Specific endothelin (ET) binding sites were characterized in membranes prepared from human cerebral cortices using binding assay and cross-linking analysis. The presence of immunoreactive (IR) ET-1 was studied by radioimmunoassay. Saturation binding experiments revealed that the K _D and B _max for ¹²⁵I-ET-1 and ¹²⁵l-ET-3 to membranes from gray matter were 25 ± 6 pM and 115 ± 15 fmol/mg of protein and 24 ± 5 p M and 108 ± 13 fmol/mg of protein, respectively. Similar results were obtained for white matter. In the presence of 10 n M sarafotoxin-6c, which is selective for ET_B receptors, ¹²⁵I-ET-1 and ¹²⁵l-ET-3 binding was totally abolished. However, in the presence of 1 μ M BQ123, which is selective for ET_Areceptors, both bindings were not affected. These results suggest that the human cerebral cortex contains only ET_Breceptors. Cross-linking of ¹²⁵I-ET-1 and ¹²⁵l-ET-3 to membranes with disuccinimidyl suberate resulted in the labeling of two bands of 48 and 31 kDa. Concentrations of IR-ET-1 in the gray and white matter were 7.0 ± 3.2 and 2.5 ± 1.7 fmol/g wet weight, respectively. The demonstration of high-affinity ET_B receptors and the presence of IRET-1 suggest that the peptide may act as a neurotransmitter or neuromodulator in the human cerebral cortex.     

DISCOVERY OF TWO MID-TERTIARY MAMMALIAN FAUNAS FROM HAIYUAN, NINGXIA, CHINA

Inl988-199otheRegionalGeologicalSurveyTeamoftheGeologicalBureauofNingxia(RGSN)foundsomefossilmammalsinthelowerpartoftheHo11g1iugouFormationandtheupperpartoftheOligocene.Inl992ajointteamoflnstituteofVertebratePaleontologyandPaleoanthropo1ogy,AcademiaSinica(IVPP),andtheRGSNwenttoHaiyuailCountyandcollectedmorefossilmamma1sfromtheYuanjia-wowoareausi11gascreen-washingmethodThemammalfaunafromthelowerpartoftheHongliugouFormationiscomposedofAprotodonsp.,Indricotheriidaeindet.,Rhinoceroti…     

Middle-ear development

Laser interferometry was used to measure umbo velocity in the developing BALB/c mouse middle ear at 133 pure-tone frequencies between 2.0 kHz and 40.0 kHz, all at a constant 100 dB sound pressure level. Umbo velocities increased with age across the entire frequency range, and reached adult-like levels by about 19 days between 2.0 and 22.0 kHz. Velocities at 28.0 and 34.0 kHz took 27 and 52 days respectively to reach adult-like levels.A simple middle-ear model utilizing compliance, resistance, and inertia elements matched the general trends of our velocity results and provided an indication of the anatomical basis for the growth in umbo velocity. The model suggested that velocity development at the lowest frequencies may be attributed to increases in tympanic membrane compliance. The model also indicated that both the frictional resistance of the middle ear and the inertia of the tympanic membrane and ossicles decreased during the growth period.At frequencies below 20.0 kHz, age-related increases in umbo velocity coincided with improvements in Nj₁ thresholds recorded from the round window and evoked potential thresholds obtained from the cochlear nucleus. These results indicated that the functional development of the middle-ear plays a major role in the development of hearing in the mouse.Portions of this work were presented at the Fifteenth Meeting of the Association for Research in Otolaryngology     

Middle paleozoic waulsortian-type mud mounds in Southern Fergana (Southern Tien-Shan,commonwealth of independent states): The shallow-water atoll model

Summary Several Waulsortian-type mud mounds nearly 500 m thick and about 5 km long occur in the Middle Paleozoic carbonate section of the Aktur nappe in the mountains on the right bank of Isfara river. These buildups form a well developed barrier system that stretches along the South Ferganian carbonate platform margin and divides the carbonate complex into a fore-reef and a back-reef part. The time of the mounds' most active growth was from the Late Silurian (Ludlow) to the Middle Devonian (Eifel). Three main facies types can be recognized in the mud mounds: 1. micritic core facies, 2. sparitic flank facies and 3. loferitic capping facies. The central massive or crudely bedded part of the mounds consists of white or light grey clotted micrite. Macrofossils are rare. The sparitic flank facies in contrast consists of coarse and densely packed crinoidal wackestone-floatstones with some brachiopod shell debris. Solitary rugose corals, tabulate corals, stromato-poroids and fragments of mollusks are also abundant. The tops of the mounds are usually covered with loferitic pelmicrites or oolitic grainstone caps. Stromatactis-like structures are very rare and poorly developed in the South Ferganian mud mounds. However, almostin all such mounds horizons of calcitic breccias can be found. In order to explain all the features found in the Fergana mounds an ‘atoll-like’ model has been proposed which starts the evolution of the mud mounds with a small nucleus bioherm. The main stage of the evolution corresponds to an atoll-like structure developing on the surface of shallow water platforms. White clotted micrite of the mound core facies is interpreted as a accumulation of fine-grained sediment in an inner lagoon flanked by crinoidal bar deposits. The mound flank facies represents the atoll rim deposits from where the carbonate mud is derived. The capping loferitic facies is considered as tidal flat deposit that developed on top of the buildups during the last stage of its evolution. The knoll shape of the mounds is explained by the retreat of the atoll flanking crinoidal bars back into the inner lagoon during the rise in sea level. Stromatactis-like structures of small cavities filled with sparry calcite owe their existence to burrowing organisms. Calcitic breccias are interpreted as paleokarst collapse breccias. They indicate that the tops of the mud mound became subaerially exposed. Other evidence for a subaerial exposure can be seen in the occurrence of Variscian ‘black and white’ limestone gravel on the tops of some mud mounds. According toWard et al. (1970) these sediments were produced above the sea level at the edge of hypersaline lakes situated on islands.