PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “CHROMIUM ISOTOPES”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed2006

Discovery of a 25-cm asteroid clast in the giant Morokweng impact crater, South Africa.

Meteorites provide a sample of Solar System bodies and so constrain the types of objects that have collided with Earth over time. Meteorites analysed to date, however, are unlikely to be representative of the entire population and it is also possible that changes in their nature have occurred with time. Large objects are widely believed to be completely melted or vaporized during high-angle impact with the Earth. Consequently, identification of large impactors relies on indirect chemical tracers, notably the platinum-group elements. Here we report the discovery of a large (25-cm), unaltered, fossil meteorite, and several smaller fragments within the impact melt of the giant (> 70 km diameter), 145-Myr-old Morokweng crater, South Africa. The large fragment (clast) resembles an LL6 chondrite breccia, but contains anomalously iron-rich silicates, Fe-Ni sulphides, and no troilite or metal. It has chondritic chromium isotope ratios and identical platinum-group element ratios to the bulk impact melt. These features allow the unambiguous characterization of an impactor at a large crater. Furthermore, the unusual composition of the meteorite suggests that the Morokweng asteroid incorporated part of the LL chondrite parent body not represented by objects at present reaching the Earth.

Journal Article↗
PubMed1969

The renal handling of hemoglobin. II. Catabolism.

The fate of small doses of isotopically labeled isologous hemoglobin was studied in the rat. When haptoglobin depleted animals were given 2.0 mg of (59)Fe hemoglobin intravenously, nearly half was trapped by the kidneys. Kidney (59)Fe activity disappeared slowly over several weeks. Whatever iron was lost from the kidneys was largely reutilized. In contrast, the porphyrin of hemoglobin absorbed by the kidneys appeared to be rapidly catabolized, since 5 hr after the injection of (14)C or (59)Fe heme-labeled hemoglobin only a small fraction was recovered as hematin. Likewise, after injection of globin-labeled hemoglobin, rapid disappearance of kidney protein activity indicated that the absorbed globin was readily catabolized in situ.

Animals↗
PubMed1973

Mechanism of graft-versus-host-induced lymphadenopathy in mice. Trapping vs. proliferation.

Graft-vs.-host (GVH)-induced lymphadenopathy of the popliteal lymph node has been produced in C57BL/6 x A/J F(1) (BAF(1)) mice by injecting A/J spleen cells into the rear footpads. By giving (51)Cr-labeled BAF(1) lymphoid cells intravenously to the hosts, 24 h before sacrifice, we have demonstrated that a large portion of the GVH-induced lymphadenopathy is due to the trapping of circuating lymphocytes in the challenged lymph nodes. Most of the remaining enlargement can be attributed to proliferation of host cells within the reacting lymph nodes. Conditions have been defined under which the weights and [(14)C]thymidine incorporation of the popliteal nodes can be plotted against the dose of injected A/J spleen cells on a double-log scale to give a linear dose-response. The popliteal lymph node GVH assay is a simple and effective means of quantitating immune reactivity to histocompatibility antigens in mice.

Animals↗
PubMed1990

Selenium utilization during human lactation by use of stable-isotope tracers.

We examined utilization of selenomethionine (SeMet) and selenite in six lactating (L) and six nonlactating (NL) women, 2-3 mo postpartum, and seven never-pregnant (NP) women by use of stable-isotope tracers. All groups had similar selenium status at the start of the study. Significantly more selenium from SeMet than from selenite was absorbed and appeared in plasma in all groups. Milk contained more selenium from apparently absorbed SeMet than from selenite. More selenium from apparently absorbed selenite than from SeMet appeared in urine of NP and NL subjects whereas L subjects had approximately the same amount of selenium from apparently absorbed selenite and SeMet in their urine. All groups retained significantly more selenium from SeMet than from selenite; L women retained more selenium from selenite than did the other two groups. Absorption and retention of selenium from SeMet in L women did not appear to be significantly different from that in other women, suggesting that selenium requirements during lactation are increased mainly because of milk losses.

Absorption↗
PubMed2003

Determination of the s-wave scattering length of chromium.

We have measured the deca-triplet s-wave scattering length of the bosonic chromium isotopes 52Cr and 50Cr. From the time constants for cross-dimensional thermalization in ultracold atomic samples, we have determined the magnitudes |a(52Cr)|=(170+/-39)a(0) and |a(50Cr)|=(40+/-15)a(0), where a(0)=0.053 nm. By measuring the rethermalization rate of 52Cr over a wide temperature range and comparing the temperature dependence with the effective-range theory and numerical single-channel calculations, we have obtained strong evidence that the sign of a(52Cr) is positive. Rescaling our 52Cr model potential to 50Cr strongly suggests that a(50Cr) is positive also.

Journal Article↗
PubMed1985

Preparation of monoclonal antibody to hepatocellular membranes and its application to induction of liver cell membrane damage.

Monoclonal antibody (MoAb) to rat liver plasma membranes was prepared by hybridization of mouse immune lymphocytes with mouse myeloma cells, and was identified by the immunodiffusion method in a fraction of IgM secreted from the hybridoma thus obtained. In indirect immunofluorescence tests, specific fluorescence was detected only on the surface of rat hepatocytes, but neither on the cells from other organs of the rat nor on the hepatocytes of other species of animals, suggesting that the antibody may be organ- and species-specific. When the primary culture rat hepatocytes, labelled with isotopic chromium (51Cr), were treated with the MoAb together with complement, a specific release of 51Cr from the cells was found shortly after treatment, accompanied with bubbling of the cell membranes, and a significant release of 51Cr was observed at an MoAb concentration of 15 micrograms/ml or more. Without complement, or with inactivated complement, these reactions were not observed. These facts suggest strongly that the cell surface of the hepatocytes was damaged by the MoAb in the presence of complement.

Animals↗
PubMed1972

Effects of vasopressin and isoprenaline infusions on the distribution of blod flow in the intestine; criteria for the validity of microsphere studies.

1. The distribution of superior mesenteric arterial flow was investigated by radioactive microspheres. The small intestine received 83% of the flow ((85 ml/min)/100 g intestine) and flow was uniform along the length of the small intestine.2. The intestinal wall was separated into 3 layers-muscle, submucosa and mucosa. The muscle received (8 ml/min)/100 g intestine and the combined submucosa and mucosa (77 ml/min)/100 g intestine.3. The distribution of microspheres between the mucosa and submucosa depended on the size of the microspheres; the smaller the spheres, the more were found in the mucosa. It also depended on the state of the vascular bed; if microspheres were given during an infusion of vasopressin, a subsequent infusion of isoprenaline resulted in movement of some of the spheres from the submucosa into the mucosa.4. Histological studies after India ink injection showed few capillary-sized vessels but many large vessels in the submucosa. Capillary-sized vessels arose close to the junction with the mucosa and passed into the mucosa.5. These and other data suggest that the intestine consists of two parallel-coupled sections, one to the muscle and the other through the submucosa to the mucosa. The vessels in the submucosa are in series with those in the mucosa and submucosal shunts do not exist. Redistributions of flow between mucosa and submucosa cannot therefore occur during stimulation of the sympathetic nerves or infusions of drugs such as noradrenaline or adrenaline.6. When microspheres are used in pharmacological investigations on distribution of blood flow in organs, controls to validate the method for the particular areas being studied are essential. If the vessels in the areas studied are in series rather than in parallel, the method is invalid.

Animals↗