下丘脑外侧区注射TRH对大鼠胃酸分泌的影响

本文采用连续收集胃腔灌流法,观察下丘脑外侧区(LHA)注射促甲状腺激素释放激素(TRH)对大鼠胃酸分泌的影响,并分析TRH在LHA促进胃酸分泌的作用机制。结果表明:(1)LHA注射TRH(1μg)明显地刺激胃酸分泌;(2)预先向LHA注射酚妥拉明(10μg)、美多心安(5μg)及胃泌素抗体1μl(1:640)并不影响TRH的泌酸作用,如预先向LHA注射阿托品(5μg)则可消除TRH的泌酸效应;(3)垂体摘除及肾上腺切除均不影响TRH的泌酸作用;(4)隔下迷走神经切断后,LHA注入TRH的泌酸效应仍然出现,但持续时间显著缩短;腹腔交感神经节摘除后,TRH仍能促进胃酸分泌,但分泌量少而平稳。以上结果提示:LHA是TRH中枢泌酸效应的有关结构之一,其中枢机制是通过胆碱能M受体中介的,腹腔交感神经节和膈下迷走神经是TRH泌酸效应的传出途径。前者引起的泌酸反应出现较早且引起泌酸高峰,但持续时间短;后者则引起低平的持续分泌。     

On the clonal origin of tumours--lessons from studies of intestinal epithelium

Clonal studies of adult chimaeric mouse epithelium have demonstrated the monoclonal composition of crypts of Lieberkühn. In neonatal life, however, polyclonal crypts have been found, indicating that crypts are of polyclonal origin. We here relate these findings to studies of mosaic tissues which have addressed the question whether solid tumours are of monoclonal or polyclonal origin. The issues has so far remained unresolved because the expected frequencies of polyclonal tumours, given polyclonal origins, have not previously been estimated. A general approach for the calculation of such expected values is suggested. The consistent reports of tumours with polyclonal components suggest that autocrine or paracrine mechanisms play an important role during tumorigenesis.     

Heat resistance of Listeria: strain differences and effects of meat type and curing salts

The heat resistances of 27 strains of Listeria monocytogenes and two strains of L. innocua were compared in broth heated at 57°C. No strain was exceptionally resistant. The heat resistance of a representative isolate of L. monocytogenes was compared in fresh and cured beef and chicken, and an equation was derived to predict the time necessary to achieve a '7D' inactivation at temperatures between 50 and 70°C.     

High speed DNA sequencing by capillary electrophoresis.

A major challenge of the Human Genome Initiative is the development of a rapid, accurate, and efficient DNA sequencing technology. A major limitation of current technology is the relatively long time required to perform the gel electrophoretic separations of DNA fragments produced in the sequencing reactions. We demonstrate here that it is possible to increase the speed of sequence analysis by over an order of magnitude by performing the electrophoresis and detection in ultra thin capillary gels. An instrument which utilizes these high speed separations to simultaneously analyze many samples will constitute a second generation automated DNA sequencer suitable for large-scale sequence analysis.     

Detection of the site of contamination by Staphylococcus aureus within the defeathering machinery of a poultry processing plant

Counts of Staphylococcus aureus from samples of neck skin taken from poultry carcasses at different stages of processing showed that the numbers decreased approximately 10-fold during scalding but increased by almost 1000-fold during plucking, reaching up to 10⁴/g. Swab samples taken from the defeathering machinery yielded counts of ca. 10³/swab at the entry to the first plucker but these increased to ca. 10⁷at the exit, with a subsequent decrease through the second and third machines. Counts of other organisms growing on the Baird-Parker isolation medium showed much lower levels at the exit to the first plucker, suggesting that this was the major site of contamination at which S. aureus grew preferentially. Data obtained from four visits to the processing plant over a period of 10 months suggested that the incidence of S. aureus on the birds is affected by the season (summer or winter) whereas levels in the plucking machines depended on the day of sampling.     

Field inversion gel electrophoretic separation of Cryptosporidium spp. chromosome-sized DNA

Chromosomal DNA from 5 isolates of Cryptosporidium parvum and 1 of C. baileyi were compared by field-inversion gel electrophoresis (FIGE). FIGE analyses of parasite DNA prepared from purified sporozoites versus intact oocysts showed no observable differences. Chromosomal DNA migration patterns of the 5 C. parvum isolates were indistinguishable, whereas similar but distinct differences were evident between C. baileyi and the isolates of C. parvum. Oocyst-reactive monoclonal antibodies differentiated oocysts of C. parvum from those of C. baileyi but were unable to distinguish oocysts of 1 isolate of C. parvum from another.     

Relationship between maximal expiratory flows and lung volumes in growing humans

We examined airway vs. lung parenchymal growth, as inferred from maximal expiratory flows (MEF) and lung volumes (V), respectively, to determine whether the interindividual variability of airway size (inferred from MEF) changes during lung growth and whether a young child with large (or small) airways for his parenchymal size (inferred from V) maintains relatively large (or small) airways for his lung size as he grows to adulthood. Serial measurements of MEF and V were obtained from a cohort of healthy 6- to 27-yr-old males (n = 26) and females (n = 21) over a period of 18 yr. Data were analyzed using logarithmic transformation of the power law equation, MEF = aVb, to fit a regression line to each subject's data points. These growth trajectories were satisfactorily modeled as parallel lines with 20-30% variability of their y-intercepts, indicating that substantial intersubject variability of MEF relative to V is present in early childhood and remains constant during growth. The results further indicate that MEF does track V during lung growth. We conclude that dysanapsis originates in early childhood.     

Development of captive bongos (Tragelaphus eurycerus): Activity budgets and developmental milestones

The development of changes in visual orientation, posture, activity budgets, and behavioral milestones was examined in five bongo calves which were observed from birth to 4 or 6 months of age. The only significant change in the calves' visual orientation was an increase in orientation to food. Reclining declined significantly over weeks, while standing increased and moving did not change. Overall, stationary behaviors dominated the activity budget, but decreased significantly over the study. The category that included locomotion, object exploration, and auto-play did not change, while forage and rumination increased significantly. Contrary to expectation, the decline in suckling was not significant. Affiliative interactions with the dam decreased significantly during the study, but increases in affiliation with other bongos were not significant. Levels of agonistic behavior between the calves and their dams and other herd members were low throughout the study, and did not change significantly. One female calf achieved several developmental milestones later than the others. It is suggested that these differences may have been influenced by the dominance status of her dam. The results conform to the general developmental pattern of “hider” bovids. Bongos, however, show somewhat different patterns of social development than eland, which are reported to be more precocial in expression of aggressive and sexual behaviors. © 1992 Wiley-Liss, Inc.