RNA metabolism in tracheal epithelium: alteration in hamsters deficient in vitamin A

The electrophoretic pattern of RNA molecules that are synthesized in vitro in tracheal epithelium from hamsters deficient in vitamin A differs from that of RNA synthesized in normal, pair-fed control hamsters. There is less RNA of low electrophoretic mobility in the epithelial cells deficient in vitamin A. This alteration is reversed after the deficient animals have been treated with vitamin A.     

表皮蛋白基因TcCP14.6和TcLCPA3A参与介导赤拟谷盗对磷化氢的抗性形成

【目的】 表皮蛋白是昆虫表皮重要的结构物质,大量研究已经证实表皮蛋白基因参与介导昆虫抗药性形成。以赤拟谷盗（Tribolium castaneum）为研究对象,解析表皮蛋白基因TcCP14.6（cuticle protein CP14.6）和TcLCPA3A（larval cuticle protein A3A）在昆虫磷化氢抗性形成过程中的作用。【方法】 采用联合国粮农组织（FAO）推荐的磷化氢熏蒸方法对采自5个省份赤拟谷盗的磷化氢抗性水平进行测定。基于赤拟谷盗基因组数据获得TcCP14.6和TcLCPA3A的cDNA序列,利用在线生物信息学分析软件预测其编码的氨基酸序列、信号肽和保守结构域。分别提取赤拟谷盗不同组织（头、胸、腹的表皮、翅、足、肠道、马氏管和脂肪体）、不同磷化氢抗性水平以及磷化氢胁迫后试虫的总RNA。以TcRPS和TcRPL为内参基因,运用RT-qPCR技术分析TcCP14.6和TcLCPA3A在赤拟谷盗不同组织、不同磷化氢抗性水平和药剂胁迫下的表达模式。最后,通过RNA干扰技术结合生物测定方法分析TcCP14.6和TcLCPA3A与赤拟谷盗磷化氢抗性的关系。【结果】 生物测定结果表明,江苏（JS,RR=1.7）和云南（YN,RR=3.0）种群对磷化氢保持敏感,湖南种群（HN,RR=20.2）表现为中等抗性,四川（SC,RR=395.4）和广东（GD, RR=862.7）种群表现为极高抗。序列分析结果表明TcCP14.6和TcLCPA3A蛋白均包含信号肽和保守的几丁质结合域。RT-qPCR结果显示,TcCP14.6和TcLCPA3A均在赤拟谷盗表皮组织中高表达,而在内部器官（脂肪体、肠道、马氏管）中的表达量相对较低。此外,TcCP14.6表达量随磷化氢抗性水平的增加呈上调趋势,而TcLCPA3A表达量则呈下降趋势;赤拟谷盗经磷化氢熏蒸处理6 h,TcCP14.6和TcLCPA3A的表达量分别呈现上调和下调趋势。注射dsRNA分别干扰抗性（GD）和敏感（YN）种群两个基因的表达后再用LC₃₀的磷化氢浓度处理试虫。与对照相比,TcCP14.6基因沉默后赤拟谷盗的死亡率显著升高,而TcLCPA3A基因沉默后试虫死亡率显著下降。【结论】 表皮蛋白基因TcCP14.6和TcLCPA3A参与介导赤拟谷盗对磷化氢的抗性。     

Purine resistant mutants of Drosophila are adenine phosphoribosyltransferase deficient

A deficiency for adenine phosphoribosyltransferase activity is the primary biochemical defect in mutants of Drosophila selected for resistance to purine-induced lethality.     

Inhibition of vasopressin action by atrial natriuretic factor

Atrial natriuretic factor results in diuresis in animals and humans, perhaps because atrial natriuretic factor increases renal blood flow. The possibility that this diuresis is due to direct inhibition of renal tubular epithelial water transport was examined in rabbit collecting tubules perfused in vitro. Atriopeptin III inhibition of the hydraulic conductivity response to the hormone arginine vasopressin but not to either 3'5'-cyclic adenosine monophosphate or forskolin was found. These results suggest that atriopeptin III acts proximal to cyclic adenosine monophosphate formation to directly affect vasopressin-stimulated water transport in the mammalian nephron. They also suggest a potential role for inhibition by atrial natriuretic factor of the renal response to arginine vasopressin as a contributor to a diuretic state.     

Physiological role of silent receptors of atrial natriuretic factor

A ring-deleted analog of atrial natriuretic factor--des[Gln18, Ser19, Gly20, Leu21, Gly22] ANF4-23-NH2 (C-ANF4-23)--binds with high affinity to approximately 99% of ANF receptors in the isolated perfused rat kidney. In this preparation, C-ANF4-23 is devoid of detectable renal effects and does not antagonize any of the known renal hemodynamic and natriuretic actions of biologically active ANF1-28. In contrast, both C-ANF4-23 and ANF1-28 increase sodium excretion and decrease blood pressure in intact anesthetized rats. This apparent contradiction is resolved by the finding that the ring-deleted analog markedly increases plasma levels of endogenous immunoreactive ANF in the rat. The results show that the majority of the renal receptors of ANF are biologically silent. This new class of receptors may serve as specific peripheral storage-clearance binding sites, acting as a hormonal buffer system to modulate plasma levels of ANF.     

Cardiac rate regulated by nutritional factor in young rats

Milk fed by stomach tube to 2-week-old rats separated from their mothers without feeding for 16 hours transiently but fully reversed the decrease in cardiac rate which had occurred during separation. This effect was rapid in onset and was related to dosage; it was not dependent upon gastric distention, but did depend upon beta-adrenergic transmission.     

Biosynthesis and secretion of proatrial natriuretic factor by cultured rat cardiocytes

Rat atrial natriuretic factor (ANF) is translated as a 152-amino acid precursor preproANF. PreproANF is converted to the 126-amino acid proANF, the storage form of ANF in the atria. ANF isolated from the blood is approximately 25 amino acids long. It is demonstrated here that rat cardiocytes in culture store and secrete proANF. Incubation of proANF with serum produced a smaller ANF peptide. PreproANF seems to be processed to proANF in the atria, and proANF appears to be released into the blood, where it is converted by a protease to a smaller peptide.     

Nucleotide sequences of the human and mouse atrial natriuretic factor genes

Mouse and human atrial natriuretic factor (ANF) genes have been cloned and their nucleotide sequences determined. Each ANF gene consists of three coding blocks separated by two intervening sequences. The 5' flanking sequences and those encoding proANF are highly conserved between the two species, while the intervening sequences and 3' untranslated regions are not. The conserved sequences 5' of the gene may play an important role in the regulation of ANF gene expression.     

Coexistence of guanylate cyclase and atrial natriuretic factor receptor in a 180-kD protein

Atrial natriuretic factor (ANF) is a peptide hormone that is released from atria and regulates a number of physiological processes, including steroidogenesis in adrenal cortex and testes. The parallel stimulation of membrane guanylate cyclase and corticosterone production in isolated fasciculata cells of rat adrenal cortex has supported the hypothesis of a mediatory role for cyclic guanosine monophosphate (cyclic GMP) in signal transduction. A novel particulate guanylate cyclase tightly coupled with ANF receptor was purified approximately 273,000-fold by two-step affinity chromatography. The enzyme had a molecular size of 180 kilodaltons and was acidic in nature with a pI of 4.7. Its specific activity was 1800 nanomoles of cyclic GMP formed per minute per milligram of protein. The purified enzyme bound ANF with a specific binding activity of 4.01 nanomoles per milligram of protein, a value that is close to the theoretical binding activity of 5.55 nanomoles per milligram of protein for 1 mole of the ligand binding 1 mole of the receptor protein. These results indicate that the guanylate cyclase-coupled ANF receptor exists in a 180-kilodalton protein of rat adrenocortical carcinoma and represent a step toward the elucidation of the basic mechanism of cyclic GMP-mediated transmembrane signal transduction in response to a hormone.     

The structure of rat preproatrial natriuretic factor as defined by a complementary DNA clone

The structure of rat preproatrial natriuretic factor ( preproANF ) was determined by nucleotide sequence analysis of an ANF complementary DNA clone. PreproANF is composed of a hydrophobic leader segment (20 amino acids), a precursor containing one glycosylation site (106 amino acids), and ANF (24 amino acids). Atrial natriuretic factor is located at the carboxyl terminus of the precursor molecule. The human, mouse, and rat genomes each contain a single ANF gene which is highly conserved.     

A mutation of the circadian system in golden hamsters

A mutation has been found that dramatically shortens the period of the circadian locomotor rhythm of golden hamsters. The pattern of inheritance of this mutation suggests that it occurred at a single, autosomal locus (tau). Wild-type animals have rhythms with free-running periods averaging about 24 hours; animals heterozygous for the mutation have periods of about 22 hours, whereas homozygous animals have rhythms with periods close to 20 hours. Animals that carry the mutant alleles exhibit abnormal entrainment to 24-hour light:dark cycles or are unable to entrain.     

Melatonin induction of gonadal quiescence in pinealectomized Syrian hamsters

Pinealectomized Syrian hamsters were injected thrice daily with 25 micrograms of melatonin per injection. The injections were administered at 3-hour intervals either during the day or during the night of a photoperiodic cycle of 14 hours of light and 10 hours of darkness. After 6 weeks of treatment with melatonin during the night, both pinealectomized and intact hamsters had reduced testis weight, and pinealectomized hamsters showed decreased levels of serum gonadotropins. Injection of melatonin during the day for 7 weeks either once (75 micrograms) a day or thrice (25 micrograms per injection) daily caused a reduction in testis weight in pinealectomized hamsters. Both pinealectomized and intact females injected with melatonin thrice daily during the day became anovulatory by week 7 of treatment. These results are similar to those observed when hamsters are exposed to a short photoperiod, suggesting that melatonin may be acting as a hormone in mediating the effects of photoperiod on the reproductive system of the Syrian hamster.     

Substrate-induced conjugation of bilirubin in genetically deficient newborn rats

Bilirubin appears to induce its own conjugation with glucuronide. Bilibrubin uridine diphosphate-glucuronyltransferase activity is relatively high at birth in heterozygous offspring of permanently jaundiced female rats. The postnatal development of the transferase is accelerated in hyperbilirubinemic heterozygotes.     

Melatonin: its inhibition of pineal antigonadotrophic activity in male hamsters

Exposure of male hamsters to short daily photoperiods (1 hour of light and 23 hours of darkness daily for 9 weeks led to total involution of the testes and accessory sex organs (seminal vesicles and coagulating glands). Pituitary levels of immunoreactive prolaction also decreased by about 60 percent after dark exposure. The inhibitory effects of darkness on the reproductive organs were prevented either by pinealectomy or by the subcutaneous implantation of a melatonin-beeswax pellet into the animals each week. Both pinealectomy and melatonin treatment also returned pituitary levels of prolactin toward normal. The results suggest that melatonin is not the pineal antigonadotrophic factor in the male golden hamster.     

低磷土壤下玉米须根数的混合遗传分析

运用主基因一多基因模型分离分析法对低磷土壤条件下玉米082×掖107组合的须根数的P1、P2、F1、F2和F2∶3五世代联合遗传分析,结果表明:玉米须根数遗传符合一对加性主基因 加性显性多基因模型(D-2)。玉米须根数是由1对独立主基因控制的加性遗传,主基因遗传率为19.71%,但是微效多基因的遗传力大于主基因的遗传力,多基因控制的玉米须根数遗传力为75.06%,可见,玉米082×掖107组合须根数的遗传主要由微效基因控制。表明,以基因重组或聚合为基础的杂交育种方法仍然是改良玉米须根数的基本方法。     

Pulmonary hemorrhage in hamsters after exposure to proteolytic enzymes of Bacillus subtilis

Single exposures of Syrian hamsters by aerosol inhalation or intratracheal instillation to proteolytic enzymes of Bacillus subtilis produced massive pulmonary hemorrhage within the first week. Of 46 animals exposed, eight died as a result of extensive hemorrhage. The remainder made uneventful recovery with no apparent residual pulmonary disease 6 weeks after exposure.     

Human papovavirus (JC): induction of brain tumors in hamsters

Eighty-three percent of hamsters inoculated at birth with JC virus, a human papovavirus isolated from brain tissue of a case of progressive multifocal leukoencephalopathy, developed malignant gliomas within 6 months. Three brain tumors have been serially transplanted as subcutaneous tumors. JC virus was isolated from five of seven tumors tested. Cells from four tumors were cultivated in vitro. These cells contained an intranuclear antigen with the characteristics of a T antigen, and this antigen was antigenically related to SV40 T antigen. Although virus was not recovered from extracts of serially cultured tumor cells, JC virus was rescued when one tumor cell line was fused with permissive cells.     

Virus-induced hydrocephalus: development of aqueductal stenosis in hamsters after mumps infection

Hydrocephalus developed as a sequela of mumps virus infections of suckling hamsters. The initial infection after intracerebral inoculation was limited largely to ependymal cells lining the ventricles. This infection was clinically inapparent but later resulted in a noninflammatory stenosis or occlusion of the aqueduct of Sylvius.     

Progress in Study of Cardiac Muscle Tissue Engineering

各种类型的心脏疾病一直是困扰人类的一个难题,目前临床上采用的各种治疗方法虽然能够缓解心脏病的症状,但均无法根治。心肌组织工程的研究有望使这一难题获得解决。心肌组织工程研究主要包括种子细胞获取、支架材料研制以及工程化心肌组织构建等方面内容。在此,从心肌组织工程研究的基本途径、工程化心肌组织的特点、移植存在的问题及可能的解决办法等几方面,对近年来心肌组织工程的研究作一概述。     

Induction of an enzyme in genetically deficient rats after grafting of normal liver

Tissue from normal rat livers was grafted onto the livers of rats that were genetically deficient in bilirubin uridine diphosphate glucuronyltransferase activity. Twelve weeks after the grafting operation, the liver of the recipient rats had bilirubin uridine diphosphate glucuronyltransferase activity.