Oligonucleotide sequences selected from the 16S rRNA genes of various species of ammonia-oxidizing bacteria were evaluated as specific PCR amplification primers and probes. The specificities of primer pairs for eubacterial, Nitrosospira and Nitrosomonas rRNA genes were established with sequence databases, and the primer pairs were used to amplify DNA from laboratory cultures and environmental samples. Eubacterial rRNA genes amplified from samples of soil and activated sludge hybridized with an oligonucleotide probe specific for Nitrosospira spp., but not with a Nitrosomonas-specific probe. Lakewater and sediment samples were analysed using a nested PCR technique in which eubacterial rRNA genes were subjected to a secondary amplification with Nitrosomonas or Nitrosospira specific primers. Again, the presence of Nitrosospira DNA, but not Nitrosomonas DNA, was detected and this was confirmed by hybridization of the amplified DNA with an internal oligonucleotide probe. Enrichments of lakewater and sediment samples, incubated for two weeks in the presence of ammonium, produced nitrite and were found to contain DNA from both Nitrosospira and Nitrosomonas as determined by nested PCR amplification and probing of 16S rRNA genes. This demonstrates that Nitrosospira spp. are widespread in the environment. The implications of the detection of Nitrosomonas DNA only after enrichment culture are discussed.

Ammonia↗

PubMed1994

Genetic testing and insurance. Withholding test results sidesteps ethical problems.

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Ethics, Medical↗

PubMed1992

Blood-brain exchange routes and distribution of 65Zn in rat brain.

Zinc is essential for normal development and function of the CNS although much is to be learned about brain Zn homeostasis. In these experiments adult male Wistar rats within the weight range 500-600 g were used. Ventriculo-cisternal perfusion was performed to allow the measurement of 65Zn fluxes between blood and csf across the choroid plexuses. Blood-brain or blood-cerebrospinal fluid barrier permeability to 65Zn has been determined by graphical analysis in experiments that lasted between 5 and 180 minutes. Cerebral capillary permeability to 65Zn was found to be low with a K(in) of about 5 x 10(-4)ml/min/g. Choroid plexus permeability to 65Zn was about 12 fold greater, although Zn influx to brain via this route was less than 5% that across cerebral capillaries. The autoradiographic distribution of 65Zn in brain showed regional variation with lowest levels in white matter and high levels in the dentate gyrus and hippocampus.

Animals↗

PubMed1991

Coronary risk-disk.

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Coronary Disease↗

PubMed1991

65Zn uptake from blood into brain in the rat.

Zinc is essential for the normal development and function of the CNS, although little is known about brain zinc homeostasis. Therefore, in this investigation we have studied 65Zn uptake by brain from blood and have measured the blood-brain barrier permeability to 65Zn in the anaesthetised rat in vivo. Adult male Wistar rats within the weight range 500-600 g were used. 65ZnCl2 and 125I-albumin, the latter serving as a vascular marker, were injected intravenously in a bolus of normal saline. Sequential arterial blood samples were taken during experiments that lasted between 5 min and 5 h, after which the whole brain was removed, dissected, and analysed for radioisotope activity. Data have been analysed by graphical analysis, which suggests that after 30 min of circulation, 65Zn uptake by brain from blood is unidirectional with an influx rate constant, Kin, of approximately 5 X 10(-4) ml/min/g. At circulation times of less than 30 min, 65Zn fluxes between blood and brain are bidirectional, where influx has a K value of greater than 5 X 10(-4) ml/min/g. In addition to the blood space, the brain appears to contain a rapidly exchanging compartment(s) for 65Zn of approximately 4 ml/100 g, which is not CSF.

Animals↗

PubMed1990

65zinc uptake from blood into brain and other tissues in the rat.

Zinc is essential for normal growth, development and brain function although little is known about brain zinc homeostasis. Therefore, in this investigation we have studied 65Zn uptake from blood into brain and other tissues and have measured the blood-brain barrier permeability to 65Zn in the anaesthetized rat in vivo. Adult male Wistar rats within the weight range 500-600 g were used. 65ZnCl2 and [125I]albumin, the latter serving as a vascular marker, were injected in a bolus of normal saline I.V. Sequential arterial blood samples were taken during experiments that lasted between 5 min and 5 hr. At termination, samples from the liver, spleen, pancreas, lung, heart, muscle, kidney, bone, testis, ileum, blood cells, csf, and whole brain were taken and analysed for radio-isotope activity. Data have been analysed by Graphical Analysis which suggests 65Zn uptake from blood by all tissues sampled was unidirectional during this experimental period except brain, where at circulation times less than 30 min, 65Zn fluxes were bidirectional. In addition to the blood space, the brain appears to contain a rapidly exchanging compartment(s) for 65Zn of about 4 ml/100g which is not csf.

Animals↗

PubMed1990

Bayes theorem for the clinician.

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Bayes Theorem↗

PubMed1990

A comparison of methods for nasal mast cell demonstration.

Nasal turbinates were studied from 14 rhinitis patients following surgical turbinectomy, and from five subjects at autopsy. Mast cell counts on turbinectomy specimens were compared following staining with toluidine blue or Alcian blue and safranin after fixation in either paraformaldehyde or neutral buffered formalin. Mast cell numbers were significantly greater in the superficial submucosa than in the epithelium or deep submucosa in both the rhinitis group and the autopsy subjects. The combination of PFA fixation and ABS staining gave maximum mast cell counts, revealed two morphological mast cell sub-types and gave optimal demonstration of nasal tissue. Nasal mast cells are thus not uniformly distributed, appear heterogeneous under light microscopy, are present in large numbers even in the elderly, and are best demonstrated using PFA fixation and ABS staining.

Adolescent↗

PubMed1987