The tagging of red cells and plasma proteins with radioactive chromium

Comparison of radioisotope methods and a nonradioisotope method to measure the RBC volume and RBC survival in the baboon

BACKGROUND

RBC volume, 24-hour posttransfusion survival, and life span can be measured with radio-isotopes and nonradioactive procedures.

STUDY DESIGN AND METHODS

RBC volume was measured directly with autologous baboon RBCs labeled with biotin-X-N-hydroxysuccinimide (NHS), 51Cr, 99mTc, and 111In-oxine and indirectly from the 125I plasma volume and the total body Hct. Twenty-four-hour posttransfusion survival and life span were measured in autologous fresh baboon RBCs labeled with 51Cr, 111In-oxine, 99mTc, and biotin-X-NHS.

RESULTS

Significantly larger RBC volumes were observed when the fresh autologous RBCs were labeled with 51Cr, 111In-oxine, or 99mTc than when they were labeled with the nonradioactive biotin-X-NHS. Twenty-four-hour posttransfusion survival values were significantly lower in the RBCs labeled with 111In-oxine or 99mTc than in the RBCs labeled with 51Cr.

CONCLUSIONS

The greater in vivo elution of 51Cr, 111In-oxine, and 99mTc than that of biotin-X-NHS influenced the measurements of RBC volume, 24-hour posttransfusion survival, and life span of the fresh baboon RBCs.

Human health risk and exposure assessment of chromium (VI) in tap water

Hexavalent chromium [Cr(VI)] has been detected in groundwater across the United States due to industrial and military operations, including plating, painting, cooling-tower water, and chromate production. Because inhalation of Cr(VI) can cause lung cancer in some persons exposed to a sufficient airborne concentration, questions have been raised about the possible hazards associated with exposure to Cr(VI) in tap water via ingestion, inhalation, and dermal contact. Although ingested Cr(VI) is generally known to be converted to Cr(III) in the stomach following ingestion, prior to the mid-1980s a quantitative analysis of the reduction capacity of the human stomach had not been conducted. Thus, risk assessments of the human health hazard posed by contaminated drinking water contained some degree of uncertainty. This article presents the results of nine studies, including seven dose reconstruction or simulation studies involving human volunteers, that quantitatively characterize the absorbed dose of Cr(VI) following contact with tap water via all routes of exposure. The methodology used here illustrates an approach that permits one to understand, within a very narrow range, the possible intake of Cr(VI) and the associated health risks for situations where little is known about historical concentrations of Cr(VI). Using red blood cell uptake and sequestration of chromium as an in vivo metric of Cr(VI) absorption, the primary conclusions of these studies were that: (1) oral exposure to concentrations of Cr(VI) in water up to 10 mg/L (ppm) does not overwhelm the reductive capacity of the stomach and blood, (2) the inhaled dose of Cr(VI) associated with showering at concentrations up to 10 mg/L is so small as to pose a de minimis cancer hazard, and (3) dermal exposures to Cr(VI) in water at concentrations as high as 22 mg/L do not overwhelm the reductive capacity of the skin or blood. Because Cr(VI) in water appears yellow at approximately 1-2 mg/L, the studies represent conditions beyond the worst-case scenario for voluntary human exposure. Based on a physiologically based pharmacokinetic model for chromium derived from published studies, coupled with the dose reconstruction studies presented in this article, the available information clearly indicates that (1) Cr(VI) ingested in tap water at concentrations below 2 mg/L is rapidly reduced to Cr(III), and (2) even trace amounts of Cr(VI) are not systemically circulated. This assessment indicates that exposure to Cr(VI) in tap water via all plausible routes of exposure, at concentrations well in excess of the current U.S. Environmental Protection Agency (EPA) maximum contaminant level of 100 microg/L (ppb), and perhaps those as high as several parts per million, should not pose an acute or chronic health hazard to humans. These conclusions are consistent with those recently reached by a panel of experts convened by the State of California.

Metal content of biopsies adjacent to dental cast alloys

Single case reports indicate that components of dental alloys accumulate in the adjacent soft tissue of the oral cavity. However, data on a wider range of dental alloys and patient groups are scarce. Therefore, the aim of the present study was to examine the metal content of oral tissues adjacent to dental alloys showing persisting signs of inflammation or other discoloration (affected sites) and of healthy control sites with no adjacent metal restoration in 28 patients. The composition of the adjacent alloys was analyzed and compared to the alloy components in the affected sites. Tissue analysis was performed using atomic absorption spectroscopy. Alloy analysis was performed with energy-dispersive X-ray analysis. In the affected sites, the metals Ag, Au, Cu, and Pd prevailed compared to control sites, reflecting the frequency distribution of single metals in the adjacent alloys. In most cases (84%), at least one of the analyzed metals was a component of the alloy and also detected in the tissue. Metal components from almost all dental cast alloys can be detected in adjacent tissue.

Is hexavalent chromium carcinogenic via ingestion? A weight-of-evidence review

Hexavalent chromium [Cr(VI)] is recognized as a human carcinogen via inhalation, based on elevated rates of lung cancer among occupationally exposed workers in certain industries. Cr(VI) is also genotoxic in bacterial and mammalian cell lines. In contrast, scientific panels in the United States and abroad have reviewed the weight of evidence (WOE) and decided that the available data are insufficient to conclude that Cr(VI) is an oral carcinogen. A criterion of 0.2 ppb was established by a California agency for Cr(VI) in drinking water to prevent cancer, however, this criterion was withdrawn in November, 2001. This criterion was remarkably lower than the promulgated California and federal drinking-water standards for total chromium of 50 ppb and 100 ppb, respectively. Both of the promulgated standards are designed to be protective of humans who ingest Cr(VI). This article describes a WOE analysis to examine the likelihood that Cr(VI) in drinking water poses a cancer hazard at the current U.S. drinking-water standard. The results indicate that: (1) From the historical epidemiological studies, there are a few reports of increased rates of digestive system cancer among Cr(VI)-exposed workers, although most are not statistically significant; (2) the preponderance of evidence from recent epidemiological studies of Cr(VI)-exposed workers does not support an increased risk of cancer outside of the respiratory system; (3) studies of four environmentally exposed populations are negative; (4) there is only one lifetime animal feeding study, and the findings from that study are considered to be flawed and inconclusive; and (5) recent kinetics and in vivo genotoxicity data demonstrate that Cr(VI) is reduced to nontoxic Cr(III) in saliva, in the acidic conditions of the stomach, and in blood. In short, at concentrations at least as high as the current U.S. maximum contaminant level (100 ppb), and probably at least an order of magnitude higher, Cr(VI) is reduced to Cr(III) prior to or upon systemic absorption. The weight of scientific evidence supports that Cr(VI) is not carcinogenic in humans via the oral route of exposure at permissible drinking-water concentrations.

Mechanisms of chromium toxicity, carcinogenicity and allergenicity: review of the literature from 1985 to 2000

Laboratory and clinical reports about the pathogenesis of the carcinogenicity and allergenicity of chromium compounds published between 1985 and 2000 have been reviewed as a basis for consideration of the pathogenetic mechanisms involved. There is good evidence from the clinic and the laboratory that Cr[VI] is the ion responsible for most of the toxic actions, although much of the underlying molecular damage may be due to its intracellular reduction to the even more highly reactive and short-lived chemical species Cr[III] and Cr[V]. Exposure to Cr[VI] can result in various point mutations in DNA and to chromosomal damage, as well as to oxidative changes in proteins and to adduct formation. The relative importance of these effects of chromium ions and of the free oxidising radicals they may generate in the body in causing tumours and allergic sensitisation remain to be demonstrated. Biochemical studies of the DNA-damaging effects and of the pathogenesis of the allergic reactions to chromium ions have not kept up with advances in understanding of the molecular basis of the effects of other carcinogens and allergens.

Inhibition of mesothelioma cell growth in vitro by doxycycline

Malignant mesothelioma causes profound morbidity and nearly universal mortality that is often refractory to conventional treatment modalities of aggressive surgery, radiotherapy, or chemotherapy. Doxycycline, a commonly used antibiotic, has anti-tumor activity against several malignancies, but its anti-tumor effects on malignant mesothelioma have not been evaluated. We report here that concentrations of doxycycline achievable in serum with typical oral doses had cytostatic effects to varying extent on all eight of the mesothelioma cell lines studied but did not affect normal lung fibroblasts. Doxycycline inhibited the production of mitochondrial cytochrome c oxidase, especially in mesothelioma cells more sensitive to its cytostatic effects, and directly inhibited gelatinase A activity; both of these activities are putative mechanisms for the cytostatic activity of doxycycline in other tumor cells. Thus doxycycline may have a role as adjuvant therapy for malignant mesothelioma.

Cytochrome b(5) plays a key role in human microsomal chromium(VI) reduction

The reduction of chromium(VI) to Cr(III) results in the formation of reactive intermediates that contribute to the cytotoxicity, genotoxicity, and carcinogenicity of Cr(VI)-containing compounds. Previous studies suggest that human microsomal Cr(VI) reduction likely proceeds through cytochrome b(5). In order to better understand Cr(VI) toxicity in humans, the role of cytochrome b(5) in combination with P450 reductase was examined in the reductive transformation of Cr(VI). Proteoliposomes containing human recombinant cytochrome b(5) and P450 reductase were constructed. The ability of P450 reductase to mediate efficient electron transfer from NADPH to cytochrome b(5) was confirmed by spectral analysis. The NADPH-dependent Cr(VI) reduction rate mediated by proteoliposomes was then compared to that of human microsomes. When these rates were normalized to equivalent cytochrome b(5) concentrations, the NADPH-dependent Cr(VI) reduction rates mediated by human microsomes were essentially identical to those for proteoliposomes containing cytochrome b(5) plus P450 reductase. Proteoliposomes containing only P450 reductase or cytochrome b(5) exhibited poor Cr(VI) reducing capabilities. Since it had been previously shown that trace amounts of iron (Fe) could dramatically stimulate microsomal Cr(VI) reduction, the ability of Fe to stimulate Cr(VI) reduction by proteoliposomes was examined. Both ferric chloride (FeCl(3)) and ferric adenosine-5'-diphosphate (FeADP) were shown to stimulate Cr(VI) reduction; this stimulation could be abolished by the addition of deferoxamine, a specific Fe(III) chelator. The NADPH-dependent reduction rates of various ferric complexes by proteoliposomes were sufficient to account for the increased Cr(VI) reduction rates seen with the addition of FeCl(3) or FeADP. Cr(V) was detected by electron paramagnetic resonance (EPR) spectroscopy as a transient intermediate formed during NADPH-dependent Cr(VI) reduction mediated by proteoliposomes containing cytochrome b(5) and P450 reductase. Overall, cytochrome b(5) in combination with P450 reductase can account for the majority of the NADPH-dependent Cr(VI) reduction seen with human microsomes.

Reflections on the early years of nuclear medicine

In the early years of nuclear medicine, physicians explored applied nuclear physics, and physicists pursued uncharted areas in medicine. Reflections from Jim Adelstein, MD, PhD, John McAfee, MD, Henry Wagner, MD, Fred Bonte, MD, Dave Kuhl, MD, and Alex Gottschalk, MD, add to the appreciation of the diversity in those early years. These reflections may serve many purposes. For some, they may provoke nostalgia for the better life gone by. For others, reflections may create an awareness of the people and the process of what it took to be where we are today. For still others, this may provide some impetus to better understand the origins of modern imaging technologies and their diffusion. Which techniques in use today will be in use 30 years from now? Why will some survive and others go by the wayside? From research into the process of technology transfer and diffusion, can we learn to put our efforts today where they will have the greatest benefits to human beings some 30 years from now? How can we maximize the present value of our efforts to improve diagnostic imaging? Reflections from the past may help.

Increased blood cobalt and chromium after total hip replacement

OBJECTIVE

To determine metal concentrations in blood and urine of patients who received cobalt-chromium-alloy metal on metal hip implants.

METHODS

Cobalt and chromium were determined in blood and urine of 76 patients and 26 controls by electrothermal atomic absorption spectroscopy.

RESULTS

A significant postoperative elevation of the metal concentrations was observed for total hip replacement patients in contrast to the control group. Twenty-nine patients exceeded the EKA (Expositionäquivalente für Krebserzeugende Arbeitsstoffe) threshold limits for cobalt in blood and for cobalt and chromium in urine. We obtained a significant correlation between cobalt in blood and cobalt in urine (r = 0.79; p < 0.005), chromium in blood and chromium in urine (r = 0.79; p < 0.005), cobalt in blood and chromium in blood (r = 0.69; p = 0.008), and cobalt in urine and chromium in urine (r = 0.95; p = 0.004).

CONCLUSION

Our findings suggest that in total hip replacements using metal-metal pairings, metal ions of the alloys are released. This release may lead to significantly elevated metal concentrations in biological fluids. Long-term studies are needed to determine the risk of metal-metal implants as a potential cause of cobalt and chromium toxicity.

Paper tests for occult blood in faeces and some observations on the fate of swallowed red cells

Paper tests for occult blood were assessed on faecal specimens from adults. An orthotolidine/sodium perborate and a modified orthotolidine/peroxide test were found to be reasonably satisfactory. The Hematest and Occultest tablets and a paper guaiac test were unsatisfactory.A large number of false positive results was obtained in children and infants. It is suggested that this might be due to meat derivatives reaching the faeces more easily in the young. Red cells labelled with either Cr(51) or Fe(59) were swallowed by human volunteers. Although between 45% and 73% of the red cell iron reappeared in the faeces, the peroxidase activity of the labelled material dropped six-fold on passage through the alimentary canal.

Studies on anemia in F1 hybrid mice injected with parental strain lymphoid cells

The survival of ⁵¹Cr-labeled erythrocytes has been studied in F₁ hybrid mice in which wasting disease was produced by injection of parental lymphoid cells taken either from lymph nodes and thymus or from the spleen. Coincident with the development of the disease syndrome, there occurred a severe anemia accompanied by a sudden loss of circulating labeled erythrocytes, whether host or parental. This finding suggests that the anemia is not due solely to specific immunologic reaction of donor tissue against host erythrocytes.

Effects of posture on plasma volume and some blood constituents

When the posture was changed from horizontal to vertical, or the reverse, the alteration in plasma volume and in the levels of haematocrit, haemoglobin, and plasma protein was much greater in patients with oedema or low plasma protein or albumin concentrations ("the pathological group") than in patients without these abnormalities ("the control group"). This larger fluid shift, and the larger concentration changes dependent on it, are explained in terms of Starling's hypothesis. In the control group there was scarcely any change in the total mass of intravascular plasma protein with change in posture, but in the pathological group this was often considerable. This was interpreted as indicating increased permeability of the capillaries to protein. Attention is drawn to the influence of uncontrolled alterations in posture on biochemical and haematological measurements and a recommendation is made in order to standardize conditions before taking blood for the analysis of non-diffusible constituents.

Cardiac index during intravenous levarterenol infusion in man

Cardiac indices were determined by the Stewart-Hamilton indicator-dilution method during intravenous infusions of levarterenol in 25 human subjects. The rate and duration of the infusion as well as the increase in arterial pressure and bradycardia were varied in order to study their influences on the cardiac index.

In vitro reduction kinetics of hexavalent chromium in human blood

This study examines time- and concentration-dependent changes in distribution of hexavalent chromium [Cr(VI)] and total chromium [Cr-(TOT)] in reconstituted human blood following addition of potassium dichromate. Fresh human blood stabilized with EDTA was obtained from human volunteers soon after meal ingestion and at 2.5 h after a light meal (herein defined as "2.5-h fasted" conditions). Cr(VI) spiked into plasma under 2.5-h fasting conditions at 3.0-12.5 micrograms/L was stable for several hours, indicating a lack of appreciable reductive capacity in isolated plasma. Spiked plasma following a recent meal exhibited immediate but variable reduction of Cr(VI) up to 300 micrograms/L. When the spiked plasma was recombined with the red blood cell (RBC) fraction, rapid reduction occurred in both the plasma and the RBC fractions based on measurement of Cr(VI) and Cr(TOT). The data indicate that plasma reduction capacity is enhanced by a recent meal, but may be overwhelmed at Cr(VI) concentrations between 2000 and 10,000 micrograms/L. These data also suggest that the RBC fraction apparently has the capacity to reduce Cr(VI) at concentrations in blood up to 15,000 micrograms/L, and that the rate of Cr(VI) uptake into RBCs may not exceed the rate of intracellular reduction at these concentrations.

DNA fragmentation, DNA-protein crosslinks, postlabeled nucleotidic modifications, and 8-hydroxy-2'-deoxyguanosine in the lung but not in the liver of rats receiving intratracheal instillations of chromium(VI). Chemoprevention by oral N-acetylcysteine

An in vivo study was carried out with the objectives of evaluating (a) the localization of DNA lesions resulting from exposure to chromium(VI) by the respiratory route, (b) the molecular nature of DNA alterations, and (c) modulation of DNA damage by a known chemopreventive agent. To this purpose, Sprague-Dawley rats received intratracheal instillations of sodium dichromate (0.25 mg/kg body weight) for three consecutive days, and the day after the last treatment lung and liver were removed for DNA purification. The results showed a selective localization of DNA lesions in the lung but not in the liver, which can be ascribed to toxicokinetics and metabolic characteristics of chromium(VI). DNA alterations included DNA-protein crosslinks, DNA fragmentation, nucleotidic modifications, and 8-hydroxy-2'-deoxyguanosine. The last two endpoints were evaluated, for the first time in chromium toxicology, by means of postlabeling procedures. This methodology was adapted to the detection of the DNA damage produced by those reactive oxygen species which result from the intracellular reduction of chromium(VI). The oral administration of the thiol N-acetylcysteine completely prevented any induction of DNA lesions in lung cells.

Urinary chromium as a biological marker of environmental exposure: what are the limitations?

Public concern has mounted recently about environmental exposures to chromium in soil, tap water, and ambient air. In response, agencies charged with protecting public health have attempted to study exposure by monitoring urinary chromium levels among potentially exposed populations. While urinary biomonitoring of occupationally exposed workers has been successfully used to assess high-level inhalation exposures in the workplace, evaluating low-level environmental exposures has been problematic. Due to these problems, before an extensive biological monitoring study is conducted of those exposed to low levels of environmental chromium, several issues must be resolved. First, exposures to chromium must occur at the same time as sampling, because the biological half-life of chromium in urine is very short (less than 2 days). Second, reduced bioavailability and bioaccessibility via the oral and dermal routes of exposure limit the capacity of urinary monitoring to measure environmental exposures (e.g., systemic dose is too small to be measured). Third, the dose of chromium must be sufficient such that it may be reliably measured above background levels in urine (range of 0.2 to 2 microg/liter) and above the analytical limit of detection (0.2 microg/liter). Fourth, the inter- and intrapersonal variability in background levels of urinary chromium is known to be significant and influenced by food and beverage intake, smoking, and exercise. Thus, the role of each factor must be carefully understood. Finally, it is imperative to have developed a complete understanding of the clinical significance of elevated urinary chromium levels before a study is performed, because higher than background levels, in and of themselves, are not indicative of a significant health concern. The route of exposure, valence of chromium to which people were exposed, exposure time, and duration must all be understood before the biological data can be implemented. We have conducted a total of nine human exposure studies over the past 3 years in an attempt to understand the kinetics of chromium and the impact on urinary, red blood cell (RBC), and plasma biomonitoring programs. The results of these studies are described here and our recommendations are offered for how to design and implement a urinary chromium biomonitoring study. In our view, given some evidence that the dose of hexavalent chromium [Cr(VI)] is sufficient to be measurable above background concentrations of total chromium [Cr(III) and Cr(VI)], duplicated measurements of chromium in plasma and RBCs are, in most cases, a more definitive gauge of environmental exposure than urinary biomonitoring.

Distribution of cobalt chromium wear and corrosion products and biologic reactions

Replacement hip arthroplasty with the use of ultrahigh molecular weight polyethylene for the cup articulating with a metal head has provided a low friction arthroplasty with years of success. However, the search for improved materials and designs for articulating surfaces continues. The use of metallic heads articulating with metallic cups is now being reconsidered for total hip replacements. Success will be enhanced if wear and corrosion of the articulating surfaces can be kept below that of the metal on ultrahigh molecular weight polyethylene couple. Concern has been raised about the release, and biologic fate, of metal species from corrosion and wear. Titanium alloys have been shown to have limitations as an articulating surface showing significant wear, and the alloy per se should not be considered for wear couples in total hip replacements. The cobalt chromium alloys are known to have reasonable wear and corrosion properties and continue to be evaluated. The issue of cobalt chromium wear and corrosion products and how this relates to the biologic performance of total hip replacement devices is reviewed. Under the condition of wear as currently experienced at the articulating surfaces of cobalt chromium alloys and ultrahigh molecular weight polyethylene, the amount of metallic products transferred to the tissues is sufficiently low to be well tolerated by the biologic system. Nickel and cobalt ions arc, rapidly transported from the implant site and eliminated in the urine. Chromium is stored in the tissue and eliminated more slowly. The issue of host hypersensitivity to these elements remains of concern. All 3 elements, in ionic form, are known to cause contact dermatitis. Untoward biologic reactions, including hypersensitivity, should be minimized if wear and corrosion phenomena are minimized.

Investigation of the effect of poorly controlled diabetes mellitus on erythrocyte life

Erythrocyte half-life (Et-1/2) has been measured in 11 patients with poorly controlled blood sugar levels and compared with a normal control group to determine whether decreased red cell deformability, which occurs in diabetic patients, causes shortening of erythrocyte life or not. No difference was seen (Et-1/2 = 28.1 days in diabetic patients and 28.5 days in controls). There was also no correlation between Et-1/2 and glycosylated hemoglobin (HbA1) levels. It has been concluded that poorly controlled diabetes mellitus has no effect upon erythrocyte life.

Release of hexavalent chromium from corrosion of stainless steel and cobalt-chromium alloys

Experiments were undertaken to determine whether hexavalent chromium was released during corrosion of orthopedic implants. Uptake of chromium (Cr) by cells and separation using amberlite resin were the methods used to determine that hexavalent Cr was present. We used salts of chromium as trivalent chromium (chromic chloride) and hexavalent chromium (potassium dichromate) to verify that the amberlite separation technique separates hexavalent Cr into the upper phase and trivalent Cr into the lower phase. The use of the salts also verified that only the hexavalent Cr became red blood cell-associated and that most of this was intracellular rather than membrane bound. The use of the amberlite separation technique demonstrated that the hexavalent Cr in the red blood cells was rapidly reduced to trivalent Cr. Cellular uptake of chromium was documented in red blood cells following corrosion of stainless-steel and cobalt-chromium implants in vivo, in the red blood cells of patients undergoing total joint revisions, and in fibroblasts subjected to products of fretting corrosion of stainless-steel and cobalt-chromium implants. Thus, corrosion of implants can lead to the release of the biologically active hexavalent chromium into the body. This chromium is rapidly reduced to trivalent chromium in cells.

Primates: models for red cell transfusion studies--cryopreservation and survival of transfused red cells in primates

Primates are excellent models for study of blood transfusion in humans. Erythrocytes of chimpanzees, gibbons, baboons, and rhesus monkeys have a half life (T/2) of 14 to 16 days and a life span (T/10) of approximately 50 to 60 days, which is about half of that found in man. Red cells of primates were cryopreserved by freezing using either a droplet method or the low-glycerol rapid-freeze procedure. Thawed cells survive normally when transfused into the same species. Transfusion of incompatible isologous blood in alloimmunized baboons, in the presence of high titer antibodies, showed survival with small volumes to be virtually nil, but with large volumes, a short normal survival period was followed by a "collapse" phenomenon similar to that seen in humans.

Protective effects of thiol compounds on chromate-induced toxicity in vitro and in vivo

The effects of thiol compounds (L-cysteine ethyl ester, 2,3-dimercaptosuccinic acid, or 2,3-dimercapto-1-propanesulfonic acid) on the toxicity induced by chromate (potassium dichromate) were investigated in HeLa cells and mice. Chromate-induced cytotoxicity evaluated by inhibition of cell growth and chromium content of the cells was diminished by all of the thiol compounds tested when the cells were incubated in the medium with both chromate and one of the thiol compounds. In mice injected ip with a thiol compound immediately after injection of chromate, mortality, ornithine carbamyl transferase activity in the serum, and chromium content in the liver were diminished remarkably compared with mice injected with chromate alone. These thiol compounds also caused an increase of urinary chromium excretion. These results suggest that the thiol compounds tested are useful for treating chromate-induced toxicity when they are given immediately after intake of the metal.

Haemodynamic changes in the rat femur and tibia following femoral vein ligation

Interference with venous outflow from a limb to stimulate fracture repair and bone growth has a long history, and its beneficial effects have been confirmed by many experimental and clinical studies. With the development of fracture fixation systems, the therapeutic use of circulatory intervention became redundant. Recently, a venous tourniquet effect has been cited to explain the enhancement of bone healing observed after fracture fixation with the Aircast system. As bone appears to be altered by venous stasis, it is important to characterise the vascular perturbations leading to these changes. Previous studies have often given conflicting results. This study investigated the short and long term haemodynamic effects of femoral vein ligation. Changes in blood flow rate and blood volume in the distal femur and proximal tibia of the rat were examined at 6 h and 1, 3 and 7 d following unilateral femoral vein ligation, and at 8 and 16 wk. Blood flows and volumes were generally reduced in the ligated limb 6 h after femoral vein ligation. This initial depression was followed by a relative increase (comparing the ligated limb with the contralateral unoperated bone) in blood volume during the 1st week. A significant relative reduction in epiphyseal vascular space was observed after 16 wk. A sustained reduction of arterial input to whole femora and tibiae was present in the ligated limb throughout the investigation although, for the cancellous knee joint epiphysis of the tibia, a localised relative increase in flow was apparent during the 1st week, again comparing the ligated limb with the nonligated contralateral bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of increasing doses of angiotensin II infused into normal and hypertensive Wistar rats on low density lipoprotein and fibrinogen uptake by aortic walls

The effect of 6 days' s.c. infusions of angiotensin II at increasing doses was determined on the uptake of rat or human low density lipoprotein (LDL) and of human fibrinogen by aorta in normal and spontaneously hypertensive rats. Rat or human LDL or human fibrinogen was injected i.v. 5 days after the start of infusion, and 24 hr later the radioactivity of aortic walls was determined. Body weight was almost constant in control rats and moderately decreased in a dose-dependent way by angiotensin II. Diastolic blood pressure decreased slightly over 6 days in control rats and increased transiently at the lowest dose of angiotensin II and progressively with two higher concentrations. All three angiotensin II concentrations significantly increased the uptake of rat and human LDL and of fibrinogen by aorta. The increase was dose related for rat LDL but not for human LDL or fibrinogen. In spontaneously hypertensive rats of the same age in which blood pressure was higher than in angiotensin II-infused rats, protein uptakes were not increased. The blood content of aortic walls was negligible and not altered by angiotensin II. Therefore, the uptake of atherogenic plasma proteins by rat aorta is increased by angiotensin II, but this effect may be independent of its pressor action.

Designing a biological monitoring program to assess community exposure to chromium: conclusions of an expert panel

The possible benefits of biological monitoring of large groups of people potentially exposed to environmental contaminants has become an area of much interest in recent years. Because chromite-ore processing residue has been found in some soils in northern New Jersey, urinary chromium monitoring of people in the community was evaluated as a potentially useful tool. In an attempt to identify those who could be exposed and to quantify the magnitude of exposure to the chromium in these soils, the New Jersey Department of Health (NJDOH) initiated a public health screening project. In 1992, the NJDOH proposed to evaluate over 4000 people who lived or worked near these sites. Volunteers were administered a questionnaire and were given a limited physical examination, and a single spot urine sample was collected. Because of the difficulties in using urinary chromium to assess low-level exposure and the potential implications of any regulatory decisions that could be based on the results of this project, a panel of experts was convened to evaluate the protocol. The panel consisted of five scientists and physicians with expertise in toxicology, dermatology, epidemiology, biological monitoring, and analytical chemistry. Like a World Health Organization group, the panel concluded that although urine biomonitoring can be useful in evaluating high levels of exposure to chromium, it is not reliable for assessing low-level exposure similar to that which may have occurred in northern New Jersey. The panel also noted that when urinary biomonitoring is to be used to assess the public's possible exposure, a large number of precautions must be taken to ensure the accuracy and usefulness of the results. The single most important recommendation was to collect a second, and perhaps a third, spot urine (or 24-h urine) sample before concluding that a person may be routinely overexposed. These suggestions are applicable to designing a biomonitoring program for nearly any environmental contaminant to which a community may be exposed. A review of scientific literature associated with biological monitoring of chromium is provided.

Radioisotopic labels for blood cell survival studies: a review

The different methods of labeling blood cells, in particular erythrocytes and platelets, for survival studies are reviewed. Besides the technical information about these procedures, attention is also paid to the indications of blood cell survival studies, the effective dose equivalent involved and the interpretation of the resulting data. In the final section the possibilities created by dual-labeling procedures are discussed.