Neonatal mouse model: review of methods and results

The neonatal mouse model, in various forms, has been used experimentally since 1959 and a large number of chemicals have been tested. The neonatal model is known to be very sensitive for the detection of carcinogens that operate via a genotoxic mode of action. In contrast, it is known not to respond to chemicals that act via epigenetic mechanisms, commonly observed in the two-year carcinogenicity studies. As such, the model has a high sensitivity and specificity in its response. Dose selection for the neonatal model is based on the maximum tolerated or feasible dose. Traditionally, compounds have been tested via the IP route of administration in this model. In some cases, this has limited the amount of material that can be administered because of the low dosing volumes (10 to 20 microL) that can be administered IP. For the ILSI project, the neonatal model was adapted for oral administration, which has the advantages of being the same route for which most pharmaceuticals are administered. In addition, a 10-fold increase in the volume of administration (100 to 200 microL) and the ability to dose drugs in suspension, permits much higher doses to be used as compared to the IP route of administration. The spontaneous tumors in the neonatal model occurred mainly in the liver of male mice and lung of male and female mice with a few tumors observed in the Harderian gland. The positive control, DEN produced a robust, uniform, and reproducible tumor response with the target organs essentially limited to liver and lung. A total of 13 compounds out of the 21 ILSI ACT compounds were evaluated in the neonatal model involving 18 studies with duplicate studies for some compounds. The genotoxic carcinogens including those used as positive controls were clearly positive (cyclophosphamide, diethylnitrosamine, 6-nitrochrysene). The non-genotoxic rodent carcinogens were clearly negative (chlorpromazine, sulfisoxazole, sulfamethoxazole, clofibrate, DEHP, haloperidol, metaproteranol, and phenobarbital). The non-genotoxic human carcinogen (cyclosporin) was clearly negative. The two other human carcinogens phenacetin and DES were negative and interestingly estradiol was negative in one of the two oral studies, but was clearly positive in the other. Considering the mode of action for three of the human carcinogens (DES, cyclosporin and phenacetin), which were negative in this model, the mode of action in humans is likely to be epigenetic. Overall, for the 3 clearly genotoxic chemicals, all were positive. For the 9 clearly non-genotoxic chemicals, all 9 were negative. The two human carcinogens for which genotoxicity may or may not play a role (DES and phenacetin) were negative and estradiol was positive in I of the two oral studies. Overall, the extensive database for compounds tested in the neonatal mouse model would support its use as an alternative model for the assessment of the carcinogenic potential of a chemical. The model responds to chemicals that act via a genotoxic mode of action that represent a greater concern for human cancer risk.

Phase I clinical and pharmacokinetic trial of irofulven

PURPOSE

To evaluate the clinical tolerability of a new schedule of 6-hydroxymethylacylfulvene (irofulven, MGI 114, HMAF, NSC 683863), a semisynthetic sesquiterpene derived from the cytotoxic mushroom metabolite illudin S. Irofulven has been shown to induce DNA damage and apoptosis in vitro and has shown activity in a number of human tumor xenograft models. A number of drug-resistant cell lines including those that express the mdr phenotype, retain sensitivity to irofulven.

METHODS

We conducted a phase I trial of irofulven given as an intravenous infusion (30 min) on a daily x5 schedule every 28 days. A total of ten patients were enrolled and treated at three dose levels, 6, 8, and 11 mg/m2 per day.

RESULTS

Irofulven reached steady-state concentrations during the 30-min infusions with biexponential kinetics. Irofulven disappeared rapidly from plasma and was detectable for only 15-30 min after the end of the infusion. The mean half-life was 4.91 min and the mean clearance was 4.57 l/mm per m2. Peak plasma concentrations of irofulven of approximately 300 ng/ml were achieved. Pharmacokinetic parameters did not differ significantly from day 1 to day 5. Irofulven was highly emetogenic. Other prominent toxicities included anorexia and fatigue. One case of delayed-onset metabolic acidosis possibly secondary to irofulven was observed. No other renal or metabolic toxicity was encountered. One patient experienced a late-onset grade 3 extravasation skin injury thought to be secondary to extravasation of irofulven. Minimal marrow suppression was observed. No objective tumor responses were observed.

CONCLUSIONS

The recommended phase II dose on this schedule is 6 mg/m2.

Diagnosis and surgical treatment of thyroid adenoma-induced hyperthyroidism in a green iguana (Iguana iguana)

An adult female green iguana (Iguana iguana) presented with polyphagia, loss of the dorsal spines, hyperactivity, increased aggression, tachycardia, and a bilobate mass palpable anterior to the thoracic inlet. Diagnosis of hyperthyroidism was based on a total T4 (30.0 nmol/L) elevated above that of clinically healthy iguanas (3.81 +/- 0.84 nmol/L), and histopathology confirmed a functional thyroid adenoma. Surgical thyroidectomy safely returned the lizard to a euthyroid state.

Epidermal growth factor in the lungs of infants developing chronic lung disease

Growth factors important to lung growth and fibrosis have been poorly studied in chronic lung disease (CLD) of prematurity. Epidermal growth factor (EGF) promotes epithelial cell maturation, and vascular endothelial growth factor (VEGF) is important in angiogenesis. The concentration of these growth factors was determined in 111 bronchoalveolar lavage fluid (BALF) samples from 35 ventilated infants: 13 developed CLD (median gestation 27 weeks, birthweight 820 g), 16 developed and recovered from respiratory distress syndrome (RDS) (31 weeks, 1,415 g) and six control infants (33 weeks, 2,075 g) were ventilated for nonpulmonary reasons. At birth, EGF in BALF from the CLD and RDS infants was lower than in the control infants (control versus CLD, 7.3 versus 0.0 pg x mL(-1), p<0.01; control versus RDS, 7.3 versus 5.0, p=0.08). EGF increased in all groups with a more rapid increase in control infants. A close relationship was noted between BALF EGF and gestational age (R=0.73). VEGF was undetectable at birth but increased at a similar rate in all three groups and did not correlate with gestation. In conclusion, these data suggest that epidermal growth factor is closely correlated to gestation and that it may predispose preterm infants to develop chronic lung disease.

Alternative models for carcinogenicity testing

The International Conference on Harmonisation Expert Working Group on Safety suggested that under certain circumstances, data from alternative assays could be used in safety evaluation in place of a second bioassay. Several alternatives were discussed. Six of these models were evaluated in a collaborative effort under the auspices of the Health and Environmental Sciences Institute (HESI) branch of the International Life Sciences Institute (ILSI). Standard protocols, pathology review, and statistical evaluations were developed. Twenty-one chemicals were evaluated, including genotoxic, nongenotoxic, carcinogenic, and noncarcinogenic chemicals. The models that were evaluated included the p53(+/-) heterozygous knockout mouse, the rasH2 transgenic mouse, the TgAC transgenic mouse (dermal and oral administration), the homozygous XPA knockout and the XPA/p53 knockout mouse models. Also evaluated were the neonatal mouse models and the Syrian Hamster Embryo (SHE) transformation assay. The results of this comprehensive study suggest that some of these models might be useful in hazard identification if used in conjunction with information from other sources in a weight of evidence, integrated analysis approach to risk assessment.

Aluminum output fluxes from forest ecosystems in Europe: a regional assessment

Data from 89 forested catchments and plots across Europe were used to define empirical relationships between aluminum leaching and input fluxes of major ions, output fluxes of major ions, ecosystem parameters such as soil pH, and combinations of these. Forests that release dissolved Al to seepage or surface waters are located primarily in areas receiving the highest loading of acid rain, and the output flux of Al shows the highest correlations to the throughfall flux of inorganic nitrogen, the output fluxes of NO3-, H+, and SO4(2-), and the mineral soil pH. If the speciation of Al is taken to be Al3+ (an overestimate), Al is released in a nearly 1:1 molar charge ratio with the sum of NO3- and SO4(2-) in runoff or seepage water over a wide range of basepoor bedrock types and acid deposition across Europe. The empirical data point to a threshold range of N deposition of 80 to 150 mmolc N m(-2) yr(-1) and a (less clearly defined) range of S deposition of 100 to 200 mmolc SO4(-2) m(-2) yr(-1) above which Al released from forests exceeds 100 mmolc Al m(-2) yr(-1). Within this threshold range, the sites that release little or no dissolved Al are those that continue to assimilate input N and/or have high soil pH (>4.5).

Dealing with emergencies in rural areas of Europe: proceedings from WONCA Europe 2000

On 4 July 2000, two workshops on handling emergencies in rural areas of Europe were held at the WONCA (World Organisation of National Colleges and Academies of Family Medicine/General Practice) conference in Vienna under the auspices of EURIPA (European Rural and Isolated Practitioners' Association). Papers submitted covered varying patterns of service provision and examples of short intensive training for emergencies at resident and general practitioner levels. Ways of collecting data routinely for accident prevention were also discussed. The workshops concluded that there was a need for more research in the application of emergency skills, that lack of confidence in dealing with emergencies may contribute to recruitment problems, and that further work towards a document detailing training requirements for emergencies was needed. This will be developed at a EURIPA workshop at WONCA in Tampere, June 2001.

Effects of Stachybotrys chartarum on surfactant convertase activity in juvenile mice

We have shown recently that alveolar type II cells are sensitive to exposure to Stachybotrys chartarum spores, both in vitro and in an in vivo juvenile mouse model. In mice, this sensitivity is manifest in part as a significant increase in the newly secreted, biologically active, heavy aggregate form of alveolar surfactant (H) and the accumulation of the lighter, "metabolically used", biologically inactive alveolar surfactant forms (L(vivo)) in the interalveolar space. Conversion of the heavy, surface-active alveolar surfactant to the light metabolically used, nonsurface active forms is believed to involve the activity of an enzyme, namely convertase, which is thought to be derived from lamellar bodies (LB) in alveolar type II cells. The purpose of this study was to evaluate the effects of S. chartarum spores on mouse H and LB convertase activity by measuring their rates of conversion to L(vivo) using the in vitro surface area cycling technique. It was determined whether there were concurrent changes in the protein and phospholipid concentrations of the raw bronchoalveolar lavage fluid (RL) and LB fractions that could be correlated with changes in convertase activity. Conversions of H to L(vivo) in untreated control mice and saline-, isosatratoxin F-, and Cladosporium cladosporioides-exposed mice were not significantly different (p > 0.05). However, conversion from H to L(vivo) in the mice exposed to S. chartarum spores was significantly higher than all other treatment groups (p < 0.001). LB to L(vivo) conversions in untreated and saline-exposed mice were not significantly different, although they were significantly higher than the H to L(vivo) conversions in these two animal treatment groups (p < 0.005), which supports the position that LB is a source of convertase activity in animals. LB to L(vivo) conversion from C. cladosporioides-, isosatrotoxin F-, and S. chartarum-exposed mice were all significantly depressed (p < 0.003) compared to the LB to L(vivo) conversion values obtained from untreated and saline-exposed mice. Protein concentrations in RL, H, L(vivo), and LB from mice exposed to S. chartarum spores were significantly elevated compared to those from the other treatment groups (p < 0.001). Protein concentration in H isolated from C. cladosporioides-exposed mice was also significantly elevated above untreated and saline control animal levels. Phospholipid concentrations in H isolated from S. chartarum-exposed mice were significantly elevated compared to those from other treatment groups, while LB phospholipid concentrations were significantly increased compared to saline and untreated control animal groups. These results show that S. chartarum spores significantly alter convertase activity in both the H and LB surfactant fractions in juvenile mice and that these changes can be related to changes in protein and phospholipid concentrations in alveolar lavage fractions. As surfactant promotes lung stability by reducing the surface tension of the air-alveolar interface, these results further support our position that inhalation exposure to S. chartarum spores in exposed individuals may lead to altered surfactant metabolism, and possibly to lung dysfunction through diminished alveolar surfactant surface tension attributes, and lung stability.

Endothelium-derived hyperpolarizing factor : identification and mechanisms of action in human subcutaneous resistance arteries

BACKGROUND

Both a vascular endothelial cytochrome P450 (CYP450) product of arachidonic acid metabolism and the potassium ion (K(+)) have been identified as endothelium-derived hyperpolarizing factors (EDHFs) in animal vascular tissues. We studied the relative importance of EDHF, nitric oxide (NO), and prostacyclin (PGI(2)) as vasodilators in human subcutaneous arteries. We also examined the mechanisms underlying the vasodilator action of EDHF to elucidate its identity.

METHODS AND RESULTS

Subcutaneous resistance arteries were obtained from 41 healthy volunteers. The contribution of EDHF to the vasodilation induced by acetylcholine was assessed by inhibiting production of NO, PGI(2), and membrane hyperpolarization. The mechanisms underlying the relaxation evoked by K(+) and EDHF were elucidated. EDHF was found to account for approximately 80% of acetylcholine-mediated vasorelaxation. Its action was insensitive to the combination of barium and ouabain, whereas barium and ouabain reversed K(+)-mediated vasorelaxation. EDHF-mediated vasorelaxation, however, was sensitive to the phospholipase A(2) inhibitor oleyloxyethyl phosphorylcholine and the CYP450 inhibitor ketoconazole.

CONCLUSIONS

EDHF is the major contributor to endothelium-dependent vasorelaxation in human subcutaneous resistance arteries. A product of phospholipase A(2)/CYP450-dependent metabolism of arachidonic acid and not K(+) is the likely identity of EDHF in human subcutaneous resistance arteries.

Measurement of CP-violating asymmetries in B0 decays to CP eigenstates

We present measurements of time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurement uses a data sample of 23x10(6) Upsilon(4S)-->BbarB decays collected by the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we find events in which one neutral B meson is fully reconstructed in a CP eigenstate containing charmonium and the flavor of the other neutral B meson is determined from its decay products. The amplitude of the CP-violating asymmetry, which in the standard model is proportional to sin2beta, is derived from the decay time distributions in such events. The result is sin2beta = 0.34+/-0.20 (stat)+/-0.05 (syst).

Hearing by eye: how much spatial degradation can be tolerated?

In the McGurk effect (McGurk and MacDonald, 1976 Nature 264 746-748), illusory auditory perception is produced if the visual information from lip movements is discrepant from the auditory information from the voice. A study is reported of the tolerance of the effect to varying levels of spatial degradation (videotaped images of a speaker's face were quantised by a mosaic transform). The illusory effect systematically decreased with an increase in the coarseness of the spatial quantisation. However, even with the coarsest level (11.2 pixels/face) the illusion did not completely disappear. In addition, those participants who did not experience the illusion nevertheless showed the effects of auditory-visual interaction in their clarity ratings of the auditory stimulus. It is concluded that auditory-visual interaction in visible speech perception is based on relatively coarse-spatial-scale information.

Analysis of pulmonary surfactant by Fourier-transform infrared spectroscopy following exposure to Stachybotrys chartarum (atra) spores

Lung cells are among the first tissues of the body to be exposed to air-borne environmental contaminants. Consequently the function of these cells may be altered before other cells are affected. As gas exchange takes place in the lungs, changes in cellular function may have serious implications for the processes of oxygen uptake and carbon dioxide elimination. In order for these processes to occur, the lung must maintain a high degree of expandability. This latter function is accomplished in part by the pulmonary surfactant which is synthesized and released by alveolar type II cells. Earlier studies have shown that exposure to gas phase materials such as smoke or organic solvents can alter the composition and function of the surfactant. The present study examines the ability of highly toxigenic mold spores to alter surfactant composition. Stachybotrys chartarum spores suspended in saline were instilled into mouse trachea as described earlier. After 24 h, the lungs were lavaged and the different processing stages of surfactant isolated by repeated centrifugation. Intracellular surfactant was isolated from the homogenized lung tissue by centrifugation on a discontinuous sucrose gradient. Samples were extracted into chloroform-methanol, dried and analyzed by Fourier-Transform infrared spectroscopy (FTIR). Exposure to S. chartarum induced an overall reduction of phospholipid among the three surfactant subfractions. The intermediate and spent surfactant fractions in particular were reduced to about half of the values observed in the saline-treated group. The relative distribution of phospholipid was also altered by spore exposure. Within the intracellular surfactant pool, higher levels of phospholipid were detected after spore exposure. In addition, changes were observed in the nature of the phospholipids. In particular strong intramolecular hydrogen bonding, together with other changes, suggested that spore exposure was associated with absence of an acyl chain esterified on the glycerol backbone, resulting in elevated levels of lysophospholipid in the samples. This study shows that mold spores and their products induce changes in regulation of both secretion and synthesis of surfactant, as well as alterations in the pattern of phospholipid targeting to the pulmonary surfactant pools.

Idiopathic hepatic uptake of (99m)Tc methylene diphosphonate: a case report

OBJECTIVE

Two sequential (99m)Tc methylene diphosphonate (MDP) scans were performed on a 42-y-old woman with insulin-dependent diabetes mellitus, chronic right pyelonephritis and anemia. The initial scan showed reduced skeletal uptake with intense and diffuse hepatic uptake. Because these findings were similar to those seen when excessive hydrolyzed-reduced (99m)Tc colloids are present in the radiopharmaceutical, the scan was repeated after an adequate time delay. Increased skeletal uptake was evident in the second scan, but the hepatic uptake persisted. Although there are numerous causes of soft tissue activity on (99m)Tc MDP bone scans, the responsible pathologic entity is not always clear. This study reviews several possible reasons for such uptake, although the exact mechanism in this case remains conjectural.

Signalling mechanisms underlying the myogenic response in human subcutaneous resistance arteries

OBJECTIVE

In this study we have examined for the first time the signal transduction mechanisms involved in the generation of pressure-dependent myogenic tone in human small resistance arteries from the subcutaneous vascular bed.

METHODS

Myogenic responses and the subcellular mechanisms involved in the generation of this response were studied on a pressure myograph.

RESULTS AND CONCLUSION

Human subcutaneous resistance arteries constricted 14.1+/-1.1% in response to an increases in intraluminal pressure from 40 to 80 mmHg and a further 3.5+/-1.7% in response to the 80-120-mmHg pressure step. Ca(2+) depletion or nifedipine abolished this response, whereas BAY K 8644 increased this response to 20.6+/-2.1% (P<0.05, response vs. control). The phospholipase C inhibitor U-73122 reduced the myogenic response to 2.5+/-1.0% at 80 mmHg (P<0.01, response vs. control) and abolished it at 120 mmHg. Diacylglycerol lipase inhibition with RHC-80267 abolished all myogenic responses to pressure. The protein kinase C (PKC) activator phorbol 12,13-dibutyrate increased the maximal myogenic response to 20.9+/-1.8% (P<0.05, response vs. control), whereas the PKC inhibitor calphostin C abolished myogenic responses. These data show that the generation of pressure-dependent myogenic tone in human subcutaneous arteries is dependent on Ca(2+) influx via voltage operated Ca(2+) channels (VOCCs) and a concomitant requirement for the activation of phospholipase C (PLC), diacylglycerol, and PKC.

Personal radon dosimetry from eyeglass lenses

Eyeglass lenses are commonly composed of allyl-diglycol carbonate (CR-39), an alpha-particle detecting plastic, thus making such lenses personal radon dosemeters. Samples of such lenses have been obtained, etched to reveal that radon and radon progeny alpha tracks can be seen in abundance, and sensitivities have been calibrated in radon chambers as a primary calibration, and with a uranium-based source of alpha particles as a convenient secondary standard. With one exception natural, environmental (fossil) track densities ranged from less than 3,000 to nearly 70,000 per cm2 for eyeglasses that had been worn for various times from one to nearly five years. Average radon concentrations to which those wearers were exposed are inferred to be in the range 14 to 130 Bq x m(-3) (0.4 to 3.5 pCi x l(-1)). A protocol for consistent, meaningful readout is derived and used. In the exceptional case the fossil track density was 1,780,000 cm(-2) and the inferred (24 h) average radon concentration was 6500 Bq x m(-3) (175 pCi x l(-1)) for a worker at an inactive uranium mine that is used for therapy.

Alveolar metabolism of natural vs. synthetic surfactants in preterm newborn rabbits

We compared the recoveries of four surfactant preparations: two natural [term fetal rabbit surfactant (FRS) and adult rabbit surfactant (ARS)] and two commercially available preparations [apoprotein-based Survanta (S) and synthetic Exosurf (E)] from 27-day gestation rabbit pups treated at birth and ventilated up to 120 min. At 5, 60, and 120 min, we measured the recovery of the heavy-aggregate, metabolically active form (H) and the light-aggregate, nonsurface active metabolic breakdown form (L) of alveolar surfactant and determined the phospholipid content and composition of the intracellularly stored lamellar body (LB) pool. Pups treated with FRS had <15% loss of H by 2 h. ARS-treated pups had a >50% loss of H by 1 h, and E- and S-treated pups had approximately 50% loss by 5 min, with a slower rate of continuing loss of up to 80% by 2 h. The major losses of H phospholipid were not explained by the L-form recovery. LB phospholipid significantly increased only in the E-treated pups and only at 2 h. FRS provides a biologically active form (H) of surfactant that appeared to remain in the airway for a significantly longer time than the other surfactant preparations. The unique properties of FRS merit further study.

Medical complications after stroke: a multicenter study

BACKGROUND AND PURPOSE

This prospective, multicenter study was performed to determine the frequency of symptomatic complications up to 30 months after stroke using prespecified definitions of complications.

METHODS

We recruited 311 consecutive stroke patients admitted to hospital. Research nurses reviewed their progress on a weekly basis until hospital discharge and again at 6, 18, and 30 months after stroke.

RESULTS

Complications during hospital admission were recorded in 265 (85%) of stroke patients. Specific complications were as follows: neurological-recurrent stroke (9% of patients), epileptic seizure (3%); infections-urinary tract infection (24%), chest infection (22%), others (19%); mobility related-falls (25%), falls with serious injury (5%), pressure sores (21%); thromboembolism-deep venous thrombosis (2%), pulmonary embolism (1%); pain-shoulder pain (9%), other pain (34%); and psychological-depression (16%), anxiety (14%), emotionalism (12%), and confusion (56%). During follow-up, infections, falls, "blackouts, " pain, and symptoms of depression and anxiety remained common. Complications were observed across all 3 hospital sites, and their frequency was related to patient dependency and duration after stroke.

CONCLUSIONS

Our prospective cohort study has confirmed that poststroke complications, particularly infections and falls, are common. However, we have also identified complications relating to pain and cognitive or affective symptoms that are potentially preventable and may previously have been underestimated.

Using telephone prompts to improve initial attendance at a community mental health center

Contacting patients by telephone before their appointment has been shown to increase clinic attendance in various settings. However, no such studies have been conducted in New Zealand, which has a unique mix of publicly funded secondary care and largely privately funded primary care. A controlled prospective study of telephone prompting was carried out in a New Zealand publicly funded community mental health center. One group of 190 patients was phoned the day before their initial appointment, and their attendance rate was compared with that of 496 patients not phoned. Ninety-six percent of the patients who were successfully contacted kept their appointment, compared with 76 percent of those not contacted.

Psychiatric training in New Zealand

OBJECTIVE

The aims of this study were to develop a profile of current psychiatric trainees in New Zealand, to identify factors important in their recruitment to and retention in psychiatric training and to identify factors that predict failure to complete training.

METHOD

A survey was sent to all current psychiatric trainees in New Zealand and to all trainees who could be traced who had left psychiatric training in New Zealand In the last 5 years without completing the Fellowship of the Royal Australian and New Zealand College of Psychiatrists.

RESULTS

General characteristics of the two groups are presented, as well as information about recruitment, burnout, general health and experiences of work and training. The only significant difference in general characteristics between the two groups was that more of those who had left training prematurely had been born overseas. The levels of family and personal mental illness were high, but there was no difference in these rates between those who had stayed in training and those who had left permaturely. Most trainees had decided to pursue a psychiatric career during their house-officer years. The most important factors determining the choice of a career in psychiatry were philosophical interest and house-officer experience in psychiatry. With respect to retention, despite high rates of burnout and psychological morbidity, and dissatisfaction with various aspects of the work setting, 94% of current trainees indicated satisfaction with their decision to train in psychiatry and over 90% intended to practise in New Zealand in the future. Most trainees who left training prematurely did so during the first 2 years of training. Dissatisfaction with work conditions, and stress or burnout were the main reasons for leaving.

CONCLUSIONS

This study provides information on some of the complex determinants of psychiatric recruitment and retention in the New Zealand setting. Areas that could be addressed in order to improve recruitment, work satisfaction and retention in training are considered.