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Biomedical subjects

K Skov

Publications and source records attributed to K Skov.

11 recordsLinked to original sources
PubMed1994

Number and size of renal glomeruli in spontaneously hypertensive rats.

OBJECTIVE: A reduced number of nephrons, whether acquired or congenital, as has been observed in certain inbred rat strains, may lead to systemic hypertension. The present study estimated the total number of glomeruli and mean glomerular size in kidneys of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. METHODS: Unbiased stereological methods were used on immersion-fixed kidneys from 12-week-old male SHR (n = 9) and age-matched WKY rats (n = 11). RESULTS: The total number of glomeruli was significantly reduced in the SHR compared with in the WKY rats. Sclerotic glomeruli were not found in either group. No significant difference in mean glomerular volume was observed, but the total glomerular volume was reduced by 25% in the SHR compared with in the WKY rats. CONCLUSION: SHR have fewer glomeruli than WKY rats, but of similar size, resulting in a reduced total glomerular volume in adult SHR. These findings are consistent with the hypothesis that the kidney plays an important role in the pathogenesis of genetic hypertension.

Animals↗
PubMed1994

The effect of two topoisomerase inhibitors on low-dose hypersensitivity and increased radioresistance in Chinese hamster V79 cells.

A preliminary investigation of the effect of topoisomerase inhibitors on the structure of the survival curve at low doses has been carried out in Chinese hamster V79 cells, where there is a deviation from the predicted response to radiation (Marples and Joiner, Radiat. Res. 113, 41-51, 1993). Cells were treated with one representative drug for each enzyme (topoisomerase I or II) prior to X irradiation in air and assessed for cell survival using automated microscopic location of cells. VP-16 causes little or no effect, while camptothecin has a measurable effect up to 2 Gy. The results are discussed in terms of the role of DNA damage and cell cycle in increased radioresistance, which encourage further investigation of the effects of this class of drugs at low doses.

Animals↗
PubMed1994

A preliminary investigation into the extent of increased radioresistance or hyper-radiosensitivity in cells of hamster cell lines known to be deficient in DNA repair.

The response to low doses of X rays was assessed in cells of three hamster cell lines which are defective in DNA repair and was compared with their parental lines. Cells of the V79-derived double-strand break repair-deficient line XR-V15B showed no radioresistance in the 0.5-Gy range compared with the V79B wild type, but instead showed an exponential response. Cells of the single-strand break repair-deficient line EM9 showed hyper-radiosensitivity and exhibited increased radioresistance. Most interestingly, cells of the UV-20 cell line appeared to respond exponentially, as a continuation of the hyper-radiosensitive portion of the curve, with no evidence of increased radioresistance. This line is defective in an incision step of excision repair and is sensitive to crosslinking agents. Further studies are warranted to address the possible role of single- and double-strand break repair and excision repair in hyper-radiosensitivity and increased radioresistance.

Animals↗
PubMed1994

Can colony size be used to detect low-dose effects?

Many insults at low doses are defined as nontoxic, even though obvious effects do occur. Among these are changes in colony size when clonogenic survival is assessed. Early attempts to quantify radiation effects on colony size have been reported, but the time-consuming nature of these experiments did not encourage the use of this parameter as an end point. Recently, however, developments in image cytometry technology have provided alternative, less labor-intensive means of measuring colony size. These techniques have been used in our ongoing investigations of radiation effects at low doses. Data accumulated to date show a measurable dose dependence of colony size in clones classed as survivors. This dose dependence is characterized by fluctuations in the 0-1.5-Gy dose range, followed by a gradual decrease in colony size at higher doses. The fluctuations at low doses correspond qualitatively to the concavity, thought to be indicative of inducible repair phenomena, that has been observed in cell survival curves in the same dose range. This concavity was also seen in the current study, but its detection appeared to be dependent on the method used to score survivors.

Animals↗
PubMed1992

Morphology of renal afferent arterioles in spontaneously hypertensive rats.

We present a new perfusion technique that allows arteries down to the level of capillaries to be fixed while relaxed and under a known intravascular pressure. Through a catheter inserted into the right renal artery of 12-week-old male spontaneously hypertensive rats (n = 9) and control Wistar-Kyoto rats (n = 11), the kidney vessels were rinsed with human plasma, relaxed by papaverine, and perfused with a casting resin containing microspheres. The microspheres (12 microns) became trapped in the glomeruli of the kidney and, together with a closing of the venous outflow, they caused the flow through the kidney to stop, so that the intravascular pressure was raised to the level of the input perfusion pressure (100 mm Hg). The resin material was allowed to harden, and the kidney was immersion-fixed and prepared for histomorphometrical investigations. This technique made it possible to measure both the structurally determined lumen diameter and the corresponding media thickness under clearly defined conditions. The lumen diameter of afferent arterioles close to the glomeruli showed a 17% reduction in spontaneously hypertensive rats (15.4 +/- 0.6 microns; mean +/- SEM) compared with Wistar-Kyoto rat arterioles (18.5 +/- 0.3 microns, p < 0.001). However, this was not due to media hypertrophy, because media cross-sectional area was smaller (p < 0.001) in spontaneously hypertensive rats (210 +/- 6 microns 2) compared with Wistar-Kyoto rats (274 +/- 16 microns 2). We conclude that the lumen reduction in renal afferent arterioles in spontaneously hypertensive rats is not the result of an encroachment on the lumen by a hypertrophic media.

Analysis of Variance↗
PubMed1991

Interaction of platinum drugs with clinically relevant x-ray doses in mammalian cells: a comparison of cisplatin, carboplatin, iproplatin, and tetraplatin.

Whereas the interaction between radiation and platinum complexes has never been pronounced in radiobiological experiments (to 30 Gy in mammalian cells), there have been reports of interest in this combination in the clinic, where fractionated doses of approximately 2 Gy are used. Our studies on the marked interaction in hypoxia at the 80% survival level (1-2.5 Gy) with cisplatin have been extended to second generation platinum drugs of clinical interest. The studies in the lower radiation dose region have been facilitated by the use of the cell analyzer DMIPS to identify individual cells and follow them microscopically to assess for clonogenic ability. Chinese hamster V79 cells were used, which were exposed to drug for 1 hr prior to irradiation in hypoxia (or air). None of the drugs give an enhancement ratio (ER) greater than 1.3 in the high radiation dose region, whereas all can produce ER80% (ER calculated at iso-survival of 80%) of 2 or higher at low doses in hypoxic cells. The enhancement of radiation kill in oxic V79 cells (ER's to 1.1 at 1-2% S) disappears at low doses (ER80% = 1.0) except for tetraplatin, where a moderate ER80% (to 1.64) was measured. Comparison of the hypoxic interaction on a concentration basis suggests that cisplatin is the best drug at low x-ray doses and low concentrations, but the interaction reaches a plateau at ER80% approximately 2.0. Tetraplatin continues to give better interaction with increasing concentration (up to ER80% = 3.7 at 25 microM). Interaction of radiation with the less toxic drugs, iproplatin and carboplatin, used at around 100 microM can be improved by longer exposure times prior to irradiation. Comparison on the basis of toxicity, for which the plating efficiency was used, suggests that cisplatin gives a better interaction than the three newer drugs for a given level of toxicity in hypoxic V79 cells.

Animals↗
PubMed1978

In-111 transferrin labeling studied by perturbed angular correlations.

The technique of perturbed angular correlations (P.A.C.) was used to study transferrin labeled with radioactive indium. Three forms of the labeled system were studied: a) the In-111 was bound to transferrin with no iron present at either of the binding sites; b) the In-111 probe was used to label transferrin that was 33% saturated with iron; and c) the label was attached to saturated Fe-transferrin. The measured perturbation factors, G22(t), indicate that the three binding states are clearly differentiated. Cases (a) and (b) exhibit characteristic features of time-independent quadrupole interactions and the average quadrupole interaction frequencies, omegaq, were determined in these cases.

Binding Sites↗
PubMedDate not supplied

Misonidazole and potentially lethal damage.

The existence of potentially lethal damage (PLD) is demonstrated in exponentially growing CHO cells exposed to misonidazole in hypoxia. The method of hypertonic post-treatment of cells was used in these studies. Misonidazole-induced PLD differs in many characteristics from radiation-induced PLD. The repair kinetics of misonidazole-induced PLD are much slower than for the repair of radiation-induced PLD (hours vs. minutes). No significant repair of misonidazole-induced PLD took place at 25 degrees C. Other differences are discussed. Hypertonic post-treatment of irradiated cells which had been pre-incubated with misonidazole to non-toxic levels, gave survival data consistent with the interpretation that no radiation PLD can be induced in such cells.

Aerobiosis↗