美国中小企业生存环境的八大要素

中外经济发展的实践表明，中小企业的大量存在是经济发展的内在要求和必然结果，是经济体系中形成合理的价格体系、维护市场竞争活力、确保经济运行稳定、保障充分就业的前提和条件。自20世纪70年代英国博尔顿报告以来，为中小企业尽可能地营造一个良好的生存环境，已经成为世界各国重要的政策取向，美国走在世界前列。我国中小企业的发展走过了很长一段弯路，究其原因在于没有建设好促进其生存的环境。本文分析了美国中小企业生存环境的要点，对于我国制定和调整中小企业政策、促进其健康发展具有借鉴意义。     

Cholinergic and adrenergic innervation of the penis artery of the bull: transmitter concentrations and synaptic vesicles.

The penile artery of the bull contained significant amounts of acetylcholine, noradrenaline and dopamine, and its axon profiles contained either numerous small granular or agranular vesicles, as well as some large granular vesicles. In the dorsal metatarsal artery, only noradrenaline and dopamine were detectable, and the axon profiles observed contained numerous small granular vesicles. In the penile artery, the axons with small agranular vesicles, probably cholinergic axons, were in close contact with axons containing small granular vesicles. It is suggested that, in the penile artery of the bull, one of the functions of the cholinergic nerves is suppression of excitatory adrenergic neurotransmission.     

我国中小企业板上市公司资本结构与企业价值关系研究

企业资本结构理论关于企业价值与资本结构的论述是以成熟资本市场为前提,而能在公开资本市场上融资的一般为大型企业：我国于2004年开辟了中小企业板块,使得部分中小企业可以在资本市场上融资,资本结构理论是否适用于这类企业,本文以中小企业板上市公司为对象对中小企业资本结构与企业价值关系进行实证研究.     

Neurons with dual axons in the substantia gelatinosa (SG) of the adult cat lumbosacral spinal cord

Summary A small percentage of SG neurons possessing two separate and complete axons were observed in the lumbosacral spinal cord of the adult cat. Since they are found in small numbers and are structurally similar to single axon SG cells, dual axon cells may represent a developmental aberrancy rather than a functionally distinct cell type.This research was supported by U.S.P.H.S. grant No.NS-16642-01.     

The role of jumps in the agricultural futures market on forecasting stock market volatility: New evidence

In this study, we explore the effect of cojumps within the agricultural futures market, and cojumps between the agricultural futures market and the stock market, on stock volatility forecasting. Also, we take into account large and small components of cojumps. We have several noteworthy findings. First, large jumps may lead to more substantial fluctuations and are more powerful than small jumps. The effect of cojumps and their decompositions on future volatility are mixed. Second, a model including large and small cojumps between the agricultural futures market and the stock market can achieve a higher forecasting accuracy, implying that large and small cojumps contain more useful predictive information than cojumps themselves. Third, our conclusions are robust based on various robustness tests such as the realized kernel, expanding forecasts, different forecasting windows, different jump tests, and different threshold values.     

Different types of synaptic vesicles in axons of the retractor penis muscle of the bull.

Three types of axon profiles were observed in the smooth muscle of the retractor penis and the penile artery of the bull: 1. profiles containing small granular vesicles, presumably representing adrenergic axons; 2. profiles containing small agranular vesicles, presumably representing cholinergic axons; 3. profiles containing numerous large and small granular vesicles. The third type of profile was not found in the vas deferens or the metatarsal artery. It is therefore possible that this type of profile represents the non-adrenergic, non-cholinergic inhibitory nerves, the presence of which has previously been pharmacologically indicated in these tissues.     

Differentiation of the endodermal epithelium associated with the splanchnic mesoderm]

Allantoic epithelium and epithelium from different levels of the digestive tube of the guail embryo were grafted into chick embryo splanchnopleure so that these epitheliums would come into contact with the mesoderm of the developing host digestive tube at a variety of levels. Under these conditions, the allantoic epithelium develops into an epithelium corresponding to the level of the digestive tube at which it was grafted. By contrast, the presumptive fate of epithelium from the small intestine is not modified by the mesenchyme with which it becomes associated. Mesenchyme from the small intestine, on the other hand, always dictates the type of differentiation in epithelial grafts from other levels of the digestive tube.     

Chronobiological studies on the blood-brain barrier

Summary Horseradish peroxidase (HRP) is a useful tracer for a study of the transportation of exogenous materials across vascular walls. After i.v. administration of HRP, reaction products of HRP can be recognized in the granular perithelial cells of small cerebral blood vessels at particular times of day. It suggests that there is a time-dependent fluctuation in the permeability of small cerebral blood vessels.This paper is dedicated to the late Professor Dr H. v. Mayersbach in Hannover.This study was supported in part by a grant in aid for Scientific Research from the Ministry of Education of Japan (No. 448085).     

Evidence that the establishment of pregnancy requires activation of lipoxygenase and phospholipase-A2

The present work investigates the possibility that lipoxygenase products are involved in the biochemical mechanisms of blastocyst implantation by utilizing nordihydroguaiaretic acid (NDGA) and caffeic acid (CA), inhibitors of lipoxygenase enzymes, and quinacrine (QU), an inhibitor of phospholipase-A2. It has been shown previously that inhibition of cyclooxygenase results in blockade of implantation. The inhibitors were dissolved in a standard medium and 5 microliter of the solutions were micro-injected into the uterine horns of day-4 pregnant mice. The contralateral horns acted as controls and received only vehicle. A sham-operated group provided normal controls. In 14 NDGA-treated mice, the control horns contained 40 implantations while the treated horns contained only 6 small implantations and 8 resorbing sites. These control horns were comparable to the sham controls. In 14 CA-treated mice, treated horns contained 17 small implantations plus 4 resorptions, whereas the control horns contained 26 small implantations and 4 resorptions. Twelve QU-treated mice exhibited 7 small implantations and 4 resorptions in the treated horns, plus 24 small sites and no resorptions in the control horns. Fourteen sham-operated mice had 95 implantation sites and no resorptions in their 28 horns. The results provide evidence for the involvement of the lipoxygenase enzymes and phospholipase-A2 in the initial implantation process and in the subsequent development of early pregnancy.     

Cholinergic and adrenergic innervation of the penis artery of the bull: Transmitter concentrations and synaptic vesicles

Summary The penile artery of the bull contained significant amounts of acetylcholine, noradrenaline and dopamine, and its axon profiles contained either numerous small granular or agranular vesicles, as well as some large granular vesicles. In the dorsal metatarsal artery, only noradrenaline and dopamine were detectable, and the axon profiles observed contained numerous small granular vesicles. In the penile artery, the axons with small agranular vesicles, probably cholinergic axons, were in close contact with axons containing small granular vesicles. It is suggested that, in the penile artery of the bull, one of the functions of the cholinergic nerves is suppression of excitatory adrenergic neurotransmission.This study has been supported by grants from the Sigrid Jusélius Foundation (to O.E.), from the Medical Research Council of the Academy of Finland (to E.K.) and from the Magnus Bergvall Memorial Fund (to N.O.S.). Excellent technical assistance by Mrs Paula Hasenson and Miss Seija Ovaskainen is gratefully acknowledged.     

Relation of the character of capacitance vessel responses in spleen and small intestine elicited by electrical stimulation of the sympathetic fibres to the level of oxygen exchange in the organs

Summary There is a correlation between character and magnitude of capacitance vessel responses and venous blood oxygen saturation under electrical stimulation of sympathetic fibres in the spleen and small intestine.     

A rapid method for the verification of drug injection into the cerebral ventricular system of the rat

Summary A precise method for the injection of drugs into the cerebroventricular system of small animals used for experimentation is described. This method, based on the intraventricular pressure record, gives absolute certainty for the injection of a drug into a previously selected site and thus avoids the subsequent histological studies.     

中小科技企业在香港创业板上市需特别重视的几个问题

中小科技企业由于自身的一些特点，如创建初期的风险较高、自身的资产规模较小、经营体制不健全、盈利能力差等，加上现阶段我国又缺乏必要的信用担保体系等的限制，使得其获得国有商业银行贷款的可能性不大。在这种情况下，众多中小科技企业寄希望于直接融资这一渠道上。本文试对中小科技企业在香港创业板市场上市筹备中的难点问题进行深入分析，希望有助于更多的科技企业成功上市。     

Surface morphology of the subfornical organ: effects of low and high sodium chloride diet

Ependymal cells found in the subfornical organ of the rat were counted. Cells covered by small microvilli, small protrusions and smooth cells were frequently found. Also present were cells with long or short cilia, cels with large protrusions and supraependymal cells. High and low sodium diets reduced the number of cells with large protrusions. Microvilli-covered cells increased after a low sodium diet.     

Influence of the enteric surface coat on the unidirectional flux of acetamide across the wall of rat small intestine

In vivo treatment of the jejunal mucosa with glycosidic enzymes seems to remove the enteric surface coat of the enterocyte. As a consequence, the mucosa-to-serosa unidirectional flux of acetamide increases remarkably. The glycocalyx probably represents a barrier to the diffusion of small hydrosoluble solutes.     

Influence of dietary lactose on the development of lactase activity in the digestive tract of the pig]

Lactase activity has been measured in the pancreas, the small and large intestine of 79 pigs varying in age from 6-7 months. The endogenous enzyme level fluctuated along the small intestine but the activity did not vary according to the level of lactose fed in the diet either just after weaning or from 25 to 100 kg of live weight. Measurements performed in the content of the intestine showed that lactose could be digested by the enzymes of the microflora mostly active in the ileum, the caecum and the large intestine.     

Karyotypes of shrews of the generaCryptotis andBlarina (mammalia: Soricidae)

Summary Cryptotis parva has a diploid number of 52 and a fundamental number of 50. Blarina brevicauda in Nebraska and Pennsylvania has a diploid number of 49 or 50 and a fundamental number of 48. Blarina carolinensis in Nebraska and Kansas has a diploid number of 52 and a fundamental number of 62. The X-chromosome in all 3 species is a large metacentric chromosome. The Y-chromosome is a small acrocentric in Blarina, whereas in Cryptotis it is a small subtelocentric.Funds for field work were provided by the American Philosophical Society from the Johnson Fund. We thank Dr Robert J. Baker, Texas Tech University, for use of his karyological equipment and laboratory facilities.     

Evidence that the establishment of pregnancy requires activation of lipoxygenase and phospholipase-A2

Summary The present work investigates the possibility that lipoxygenase products are involved in the biochemical mechanisms of blastocyst implantation by utilizing nordihydroguaiaretic acid (NDGA) and caffeic acid (CA), inhibitors of lipoxygenase enzymes, and quinacrine (QU), an inhibitor of phospholipase-A₂. It has been shown previously that inhibition of cyclooxygenase results in blockade of implantation. The inhibitors were dissolved in a standard medium and 5 l of the solutions were micro-injected into the uterine horns of day-4 pregnant mice. The contralateral horns acted as controls and received only vehicle. A sham-operated group provided normal controls. In 14 NDGA-treated mice, the control horns contained 40 implantations while the treated horns contained only 6 small implantations and 8 resorbing sites. These control horns were comparable to the sham controls. In 14 CA-treated mice, treated horns contained 17 small implantations plus 4 resorptions, whereas the control horns contained 26 small implantations and 4 resorptions. Twelve QU-treated mice exhibited 7 small implantations and 4 resorptions in the treated horns, plus 24 small sites and no resorptions in the control horns. Fourteen sham-operated mice had 95 implantation sites and no resorptions in their 28 horns. The results provide evidence for the involvement of the lipoxygenase enzymes and phospholipase-A₂ in the initial implantation process and in the subsequent development of early pregnancy.     

Mitotic activity in the glandular epithelium of the rat small intestine after electrothermocoagulation of the tubero-infundibular region of the hypothalamus and simultaneous resection of the pineal gland]

Radio-frequency lesions of the tubero-infundibular region of the hypothalamus and simultaneous pinealectomy are performed in rats. The double operation is followed by a significant increase of mitotic rate in the small intestine glandular epithelium. This increase is higher than the addition of the effects that are caused by each operation.     

Molecular genetics of the peptidyl transferase center and the unusual Var1 protein in yeast mitochondrial ribosomes

Mitochondria posses their own ribosomes responsible for the synthesis of a small number of proteins encoded by the mitochondrial genome. In yeast,Saccharomyces cerevisiae, the two ribosomal RNAs and a single ribosomal protein, Varl, are products of mitochondrial genes, and the remaining approximately 80 ribosomal proteins are encoded in the nucleus. The mitochondrial translation system is dispensable in yeast, providing an excellent experimental model for the molecular genetic analysis of the fundamental properties of ribosomes in general as well as adaptations required for the specialized role of ribosomes in mitochondria. Recent studies of the peptidyl transferase center, one of the most highly conserved functional centers of the ribosome, and the Varl protein, an unusual yet essential protein in the small ribosomal subunit, have provided new insight into conserved and divergent features of the mitochondrial ribosome.