Lung Biopersistence and in Vitro Dissolution Rate Predict the Pathogenic Potential of Synthetic Vitreous Fibers

Here we review the past decade of research on inorganic fiber toxicology, which demonstrates that fiber biopersistence and in vitro dissolution rate correlate well with fiber pathogenicity. Test fibers for these studies included eight synthetic vitreous fibers (SVFs)-refractory ceramic fiber (RCF1), four fiber glasses (FCs), rock wool, slag wool, HT stone wool-and two asbestos types (crocidolite and amosite). Fiber toxicology and biopersistence were investigated using rodents exposed by inhalation. To evaluate chronic inhalation toxicity, rodents were exposed nose-only to ∼ 100 fibers >20 µm in length (F > 20 µm)/cm(3), 6 h/day, 5 days/wk, for 2 yr (rats) or 1½ yr (hamsters). To evaluate lung biopersistence, rats were exposed nose-only for 5 days to fiber aerosol; lung burdens were then analyzed during 1 yr postexposure. In vitro dissolution rate was evaluated in a flow-through system using physiological solutions that mimic the inorganic components of extra- and intracellular lung fluids. The 10 test fibers encompassed a range of respiratory toxicities, from transient inflammation only to carcinogenesis. Lung clearance weighted half-times (WT½) for F > 20 µm were 6-15 days for stonewool, building insulation FCs, and slag wool; 50-80 days for rock wool, 2 special-application FCs, and RCFI; and >400 days for asbestos. WT½ correlated with pathogenicity: The rapidly clearing fibers were innocuous (insulation FCs, slag wool, and stonewool), but the more biopersistent fibers were fibrogenic (rock wool) or fibrogenic and carcinogenic (special-application FCs, RCFI, amosite and crocidolite asbestos). In vitro dissolution rates (k dis= ng/cm(2)/h) of the 10 fibers at pH 7.4 or 4.5 ranged from < 1 to >600. Fibers that dissolved rapidly in vitro also cleared quickly from the lung and induced only transient inflammation in the chronic studies. In contrast, fibers that dissolved slowly in vitro were biopersistent in the lung and tended to induce permanent pathogenicity. Other in vitro studies of fiber degradation suggest that, in addition to fiber dissolution, fiber leaching and subsequent transverse breakage may also be important mechanisms in lung biopersistence and hence pathogenicity. The validity of using lung biopersistence for predicting the potential pathogenicity of SVFs is confirmed by this research. The research also supports the use of in vitro fiber degradation at pH 7.4 and/or pH 4.5 as an indicator of SVF potential pathogenicity.

Cytotoxicity of refractory ceramic fibres to Chinese hamster ovary cells in culture

The toxicity/oncogenicity of refractory ceramic fibres have been tested in chronic inhalation studies in rodents. Because these studies are time consuming and expensive, there is a need to develop and validate short-term models to screen fibres for their toxicological potential. In the present study, the toxic effects of four different compositions of refractory ceramic fibres were determined using Chinese hamster ovary cells grown in culture. These refractory ceramic fibres were the same size-selected fibres that had been used in animal inhalation studies, thus facilitating a direct comparison of findings in the two systems. Chinese hamster ovary cells were treated with refractory ceramic fibres 24 hr after seeding into 60-mm culture dishes in Ham's F12 medium with 10% serum. Inhibition of cell proliferation and colony formation were determined after 3-5 days of fibre exposure. Crocidolite and chrysotile asbestos were used as positive controls. Concentration-dependent inhibition of both cell proliferation and colony formation was observed after treatment with refractory ceramic fibres. The LC(50) for the different refractory ceramic fibres ranged from 10 to 30 mug/cm(2). The LC(50)s for crocidolite and chrysotile were 5 mug/cm(2) and 1 mug/cm(2), respectively. To assess the genotoxic potential of these fibres, fibre-exposed Chinese hamster ovary cell cultures were stained with acridine orange and scored for the incidence of micronuclei and other nuclear abnormalities. The incidence of nuclear abnormalities for refractory ceramic fibres at 20 mug/cm(2) ranged from 20 to 40%. Toxic endpoints of the in vitro studies were compared with those of the chronic animal inhalation studies. The latter included induction of lung fibrosis and pleural and airway tumours. A correlation was observed between the in vitro and in vivo toxicological potencies of the respective four refractory ceramic fibres: the fibres that were most toxic in vitro were also the most toxic in the chronic animal inhalation studies. A direct relationship was also observed, both in vitro and in vivo, between average fibre length and the severity of the toxic effect.

New insight into rectal function in pediatric defecation disorders: disturbed rectal compliance is an essential mechanism in pediatric constipation

OBJECTIVE

To evaluate rectal sensitivity in patients with pediatric constipation (PC) and nonretentive fecal soiling (FNRFS) using pressure-controlled distention (barostat).

STUDY DESIGN

Thresholds for rectal sensitivity (first sensation, urge to defecate, and pain), and rectal compliance were determined using a barostat.

RESULTS

A total of 69 patients with PC (50 males; mean age, 10.9 +/- 2.2 years) and 19 patients with FNRFS (15 males; mean age, 10.0 +/- 1.9 years) were compared with 22 healthy volunteers (HVs) (11 males; mean age, 12.7 +/- 2.6 years). Sensitivity thresholds were not significantly different among the 3 groups. Rectal compliance was increased in 58% of the patients with PC (P < .0001 vs HVs). Rectal compliance did not differ between patients with FNRFS and HVs. Children with PC with abnormal rectal function required significantly larger rectal volumes at urge to defecate.

CONCLUSIONS

Increased compliance is the most prominent feature in patients with PC. Because of higher compliance in these children, larger stool volumes are required to reach the intrarectal pressure of the urge to defecate. Children with FNRFS have normal rectal function.

Use of short-term assays to evaluate the potential toxicity of two new biosoluble glasswool fibers

Two new glasswools were developed for optimal biosolubility in the lung: JM 902, for insulation and filtration; and JM 901F, for standard thermal and acoustical insulation. Both were tested for lung biopersistence and their potential to induce persistent pulmonary inflammation in rats. Their dissolution rate constants (k(dis)) were estimated in vitro. Results for 902 were: in vitro k(dis) (pH 7.4) = 150 ng/cm2/h; after 5 days of fiber inhalation (IH), lung clearance of fibers > 20 microm length (F > 20 microm) indicated a weighted half-time (WT(1/2)) of 6.8 days and 90% clearance time (T90) of 33 days; following intratracheal instillation (IT), lung clearance half-time (T(1/2)) for F > 5 microm was 20 days. Results for 901F were: k(dis) (pH 7.4) = 500-560; after 5 days of fiber inhalation exposure, WT(1/2) (F > 20 microm) = 8.1 days and T90 = 38 days. After 5 days of fiber inhalation, both fibers induced initial pulmonary inflammation followed by return to normal within 3 wk postexposure. Lung clearance half-times for 902 and 901F passed the European Union (EU) criteria for noncarcinogenic fibers (IH WT(1/2) F > 20 microm was < 10 days); 902 passed the noncarcinogenic criterion of the German government (IT T(1/2) F > 5 microm was < 45 days). Thus, carcinogenicity labeling is not required for either fiber in the EU. Short-term test results for 902 and 901F were similar to results for synthetic vitreous fibers (SVFs) that were innocuous in rodent chronic inhalation studies, but short-term test results for 902 and 901F differed sharply from results for other SVFs that were pathogenic in chronic studies. Thus, these short-term tests indicate that 902 and 901F are biosoluble fibers and would be nonpathogenic in the rat exposed by inhalation.

Potential pulmonary effects of man-made organic fiber (MMOF) dusts

In the first half of the twentieth century epidemiologic evidence linked elevated incidences of pulmonary fibrosis and cancer with inhalation of chrysotile and crocidolite asbestos, a family of naturally occurring inorganic fibrous materials. As the serpentine and amphibole forms of asbestos were phased out, synthetic vitreous fibers (SVFs; fiber glass, mineral wool, and refractory fiber) became increasingly utilized, and concerns were raised that they too might cause adverse health effects. Extensive toxicological research on SVFs has demonstrated that their pulmonary effects are directly related to fiber dose in the lung over time. This is the result of deposition (thin fibers deposit in the lower lung more efficiently than thick fibers) and lung-persistence ("biopersistence" is directly related to fiber length and inversely related to dissolution and fragmentation rates). In rat inhalation studies, asbestos was determined to be 7- to 10-fold more biopersistent in the lung than SVFs. Other than its effect on biopersistence, fiber composition did not appear to play a direct role in the biological activity of SVFs. Recently, the utilization of man-made organic fibers (MMOFs) (also referred to by some as synthetic organic fibers) has increased rapidly for a variety of applications. In contrast to SVFs, research on the potential pulmonary effects of MMOFs is relatively limited, because traditionally MMOFs were manufactured in diameters too thick to be respirable (inhalable into the lower lung). However, new developments in the MMOF industry have resulted in the production of increasingly fine-diameter fibers for special applications, and certain post-manufacturing processes (e.g., chopping) generate respirable-sized MMOF dust. Until the mid-1990s, there was no consistent evidence of human health affects attributed to occupational exposure to MMOFs. Very recently, however, a unique form of interstitial lung disease has been reported in nylon flock workers in three different plants, and respirable-sized nylon shreds (including fibers) were identified in workplace air samples. Whether nylon dust or other occupational exposures are responsible for the development of lung disease in these workers remains to be determined. It is also unknown whether the biological mechanisms that determine the respirability and toxicity of SVFs apply to MMOFs. Thus, it is appropriate and timely to review the current data regarding MMOF workplace exposure and pulmonary health effects, including the database on epidemiological, exposure assessment, and toxicology studies.

Synthetic vitreous fibers: a review of toxicology research and its impact on hazard classification

Because the inhalation of asbestos, a naturally occurring, inorganic fibrous material, is associated with lung fibrosis and thoracic cancers, concerns have been raised about the possible health effects of synthetic vitreous fibers (SVFs). SVFs include a very broad variety of inorganic fibrous materials with an amorphous molecular structure. Traditionally, SVFs have been divided into three subcategories based on composition: fiberglass, mineral wool (rock, stone, and slag wools), and refractory ceramic fiber. For more than 50 years, the toxicologic potential of SVFs has been researched extensively using human epidemiology and a variety of laboratory studies. Here we review the research and its impact on hazard classification and regulation of SVFs. Large, ongoing epidemiology studies of SVF manufacturing workers have provided very little evidence of harmful effects in humans. Several decades of research using rodents exposed by inhalation have confirmed that SVF pulmonary effects are determined by the "Three D's", fiber dose (lung), dimension, and durability. Lung dose over time is determined by fiber deposition and biopersistence in the lung. Deposition is inversely related to fiber diameter. Biopersistence is directly related to fiber length and inversely related to fiber dissolution and fragmentation rates. Inhaled short fibers are cleared from the lung relatively quickly by mobile phagocytic cells, but long fibers persist until they dissolve or fragment. In contrast to asbestos, most of the SVFs tested in rodent inhalation studies cleared rapidly from the lung (were nonbiopersistent) and were innocuous. However, several relativley biopersistent SVFs induced chronic inflammation, lung scarring (fibrosis), and thoracic neoplasms. Thus, biopersistence of fibers is now generally recognized as a key determinant of the toxicologic potential of SVFs. In vitro dissolution of fibers in simulated extracellular fluid correlates fairly well with fiber biopersistence in the lung and pulmonary toxicity, but several exceptions suggest that biopersistence involves more than dissolution rate. Research demonstrating the relationship between biopersistence and SVF toxicity has provided a scientific basis for hazard classification and regulation of SVFs. For a nonhazardous classification, legislation recently passed by the European Union requires a respirable insulation wool to have a low lung-biopersistence or be noncarcinogenic in laboratory rats. U.S. fiberglass and mineral wool industries and the Occupational Health and Safety Administration (OSHA) have formed a voluntary Health and Safety Partnership Program (HSPP) that include: a voluntary permissible exposure level (PEL) in the workplace of 1 fiber/cc, a respiratory protection program for specified tasks, continued workplace air monitoring, and, where possible, the development of fiber formulations that do not persist in the lung. RCF manufacturers have implemented a Product Stewardship Program that includes: a recommended exposure guideline of 0.5 fibers/cc; a 5-year workplace air monitoring program; and research into the development of high-temperature-resistant, biosoluble fibers.

Ethics in the practice of psychiatry in South Africa

OBJECTIVE

To determine attitudes with regard to ethics in the practice of psychiatry in South Africa.

DESIGN

Cross-sectional survey.

METHOD

The study utilised clinical vignettes, with gender and race of the patient as potential modifying variables in diagnosis and management. Open-ended questions pertaining to potential abuses were included.

SETTING AND SUBJECTS

Questionnaires were mailed to all practising psychiatrists in South Africa in 1993 and 1994.

OUTCOME MEASURES

Responses to questionnaire.

RESULTS

A 40% response rate was obtained (N = 73). Patient race and gender did not influence diagnosis or have a marked impact on the prescription of treatment. Pressure from the patient's family on the psychiatrist did alter case management, as did the psychiatrist's age and gender in some instances. Racial discrimination, sexual misconduct and economic abuses were the most frequently cited areas of observed abuse.

CONCLUSION

The development of an ethical framework for the practice of psychiatry in South Africa would appear to be of critical importance.

Effect of radiotherapy and chemotherapy on pulmonary function after treatment for breast cancer and lymphoma: A follow-up study

PURPOSE

To determine the changes in pulmonary function tests (PFTs) 0 to 48 months after treatment for breast cancer and lymphoma.

PATIENTS AND METHODS

The alveolar volume (V(A)), vital capacity, forced expiratory volume in 1 second, and corrected transfer factor of carbon monoxide (T(L,COc)) were measured in 69 breast cancer and 41 lymphoma patients before treatment and 3, 18, and 48 months after treatment with radiotherapy alone or radiotherapy in combination with chemotherapy (mechlorethamine, vincristine, procarbazine, prednisone, doxorubicin, bleomycin, vinblastine; cyclophosphamide, epidoxorubicin, fluorouracil; cyclophosphamide, thiotepa, carboplatin; cyclophosphamide, methotrexate, fluorouracil). The three-dimensional dose distribution in the lung of each patient was converted to the mean lung dose. Statistical analysis was used to evaluate the changes in PFT values over time in relation to age, sex, smoking, chemotherapy, and the mean lung dose.

RESULTS

After an initial reduction in PFT values at 3 months, significant recovery was seen at 18 months for all patients. Thereafter, no further improvement could be demonstrated. Reductions in spirometry values and V(A) were related to the mean lung dose only (0.9% per Gy at 3 months and 0.4% per Gy mean dose at 18 months). T(L,COc) decreased 1. 1% per Gy mean dose and additionally decreased 6% when chemotherapy was given after radiotherapy. Chemotherapy administered before radiotherapy reduced baseline T(L,COc) values by 8% to 21%. All patients showed an improvement of 5% at 18 months.

CONCLUSION

On the basis of the mean lung dose and the chemotherapy regimen, the changes in PFT values can be estimated before treatment within 10% of the values actually observed in 72% to 85% of our patients with healthy lungs.

Studies on the inhalation toxicology of two fiberglasses and amosite asbestos in the syrian golden hamster. Part I. Results of a subchronic study and dose selection for a chronic study

A multidose, subchronic inhalation study was used to estimate the maximum tolerated dose (MTD) of 901 fiberglass (MMVF10.1) for a chronic inhalation study using hamsters. Subchronic study results indicated that 30 mg/m(3) [250-300 WHO fibers (>5 microm long)/cm(3) and 100-130 fibers/cm(3) >20 microm long] meets or exceeds the estimated MTD, and chronic study results confirmed this. For the subchronic study, hamsters were exposed 6 h/day, 5 days/wk, for 13 wk to MMVF10.1 at 3, 16, 30, 45, and 60 mg/m(3) (36, 206, 316, 552, or 714 WHO fibers/cm(3)), then monitored for 10 wk. Results demonstrating MTD were: inflammatory response (all fiber exposures); elevated lung cell proliferation with @ges;16 mg/m(3); lung lavage neutrophil elevations with @ges;16 mg/m(3) and lactate dehydrogenase (LDH) and protein elevations with > or = 30 mg/m(3); and persistent abnormal macrophage/fiber clumps in lungs exposed to 45 and 60 mg/m(3), which suggest overloading of clearance mechanisms. For the chronic study, hamsters were exposed for 78 wk to MMVF10a (901 fiber glass) or MMVF33 (special-application 475 fiberglass) at approximately 300 WHO fibers/cm(3) ( approximately 100 fibers/cm(3) @gt;20 @mu;m long), or to amosite asbestos at an equivalent concentration and 2 lower concentrations. All fiber-exposed animals had pulmonary inflammation, elevated lung lavage cells, and increased lung cell proliferation. Between 52 and 78 wk of exposure, lung burdens of all fibers increased at an accelerated rate, suggesting impairment of clearance mechanisms. MMVF33 and amosite induced fibrosis and pleural mesothelioma. These findings substantiate that exposures in the chronic study adequately tested the toxic potential of fiberglass.

Relation between limb toxicity and treatment outcomes after isolated limb perfusion for recurrent melanoma

BACKGROUND

The optimal toxic reaction of the normal tissues in perfused limbs after isolated limb perfusion (ILP) is unknown. Theoretically, more severe limb toxicity could reflect a concomitant increased toxic effect to the tumor and improved outcomes. We determined whether there is a relation between limb toxicity and treatment outcomes after ILP for recurrent limb melanoma.

STUDY DESIGN

Among 252 patients with recurrent melanoma of the limbs, treatment outcomes in 192 patients (76%) with no or mild acute limb toxicity were compared with those in 60 (24%) with more severe reactions. Multivariate analysis was used to identify prognostic factors for complete response, limb recurrence-free interval, and survival.

RESULTS

Among 112 patients with measurable disease, 65 patients (58%) had a complete response and 27 (42%) experienced a relapse in the perfused limb. For complete response, uninvolved regional lymph nodes (p = 0.0025) and ILP using tumor necrosis factor-alpha (p = 0.0076) appeared to be favorable prognostic factors in multivariate analysis. There was no evidence of a relation between limb toxicity and complete response either in univariate (p = 0.16) or multivariate analysis (p = 0.46). For limb recurrent-free interval, only the number of lesions was a significant prognostic factor (p = 0.047); limb toxicity was not (p = 0.095). In 140 patients with recurrent melanoma excised before or at the moment of ILP, independent prognostic factors for survival were gender, the number of positive nodes, and stage of disease. There was no relation between limb toxicity and survival in either univariate (p = 0.53) or multivariate analysis (p = 0.94). Forty-eight (34%) of the 140 patients had a relapse in the perfused limb. No prognostic factors for limb recurrent-free interval could be identified; limb toxicity was not related to relapse time in univariate or multivariate analyses (p = 0.16 and p = 0.14, respectively).

CONCLUSIONS

More severe acute limb toxicity is not associated with improved outcomes. One should aim at grade II toxicity (slight erythema or edema, compatible with complete recovery) at the most to increase the therapeutic ratio of ILP.

The importance of fiber biopersistence and lung dose in determining the chronic inhalation effects of X607, RCF1, and chrysotile asbestos in rats

The chronic inhalation effects in rats of X607 (a rapidly dissolving synthetic vitreous fiber) were compared with those previously reported for RCF1 (a refractory ceramic synthetic vitreous fiber) and chrysotile asbestos. Of primary concern was the importance of biopersistence as a mechanism of fiber toxicity. Fischer rats were exposed to fiber aerosol by nose-only inhalation for 6 h/day, 5 days/week for 2 years. X607 and RCF1 aerosols were similar in concentration (approximately 200 fibers/cc) and average dimensions (approximately 20 x 1 microns). Chrysotile aerosol was higher in concentration (10,600 fibers/cc) and an order of magnitude smaller in average dimensions. Lung fiber deposition after 6 h inhalation was greater for X607 than for RCF1. However, at later time points, fibers/lung (especially long fibers) were much lower for X607 than for RCF1, suggesting less biopersistence for X607. X607 was neither fibrogenic nor tumorigenic and induced only minimal lung cellularity that reversed after exposure was terminated. In contrast, RCF1 and chrysotile asbestos induced pulmonary fibrosis and thoracic neoplasms (chrysotile induced 32% more pulmonary neoplasms than RCF1). Lung deposition and fiber lengths did not explain the toxicologic differences between the three fibers. Fiber biodurability, including chemical and physical parameters, appears to be a major toxicologic determinant here. Chemical analysis of lung fibers revealed rapid leaching of X607 compared to RCF1. In in vitro dissolution tests, X607 underwent rapid dissolution (kdis = 990 ng/cm2/h) and transverse fragmentation, RCF1 dissolved slowly (kdis = 6 ng/cm2/h) and did not fragment, and chrysotile dissolution was negligible (< 0.1 ng/cm2/h).

In vitro toxicity of respirable-size particles of diatomaceous earth and crystalline silica compared with asbestos and titanium dioxide

The relationship between particle characteristics and in vitro toxicity was investigated using Chinese hamster ovary cells. Test dusts included respirable natural (Nat) and flux-calcined (FC) diatomaceous earth (DE), quartz, cristobalite, TiO2, and chrysotile and crocidolite asbestos. All dusts elicited a qualitatively similar, concentration-dependent response: particle uptake, induction of micro- and polynuclei, and reduction in cell proliferation. However, similar mass concentrations of the dusts yielded a 35-fold range of toxicity: chrysotile > crocidolite > Nat DE > FC DE > quartz > Cristobalite > TiO2. In vitro toxicity did not correlate with crystalline silica content, surface area, composition, volume, particles/cm2, or fibrous geometry. Toxicity was closely associated with the number of particles/cm2 culture surface that had at least one dimension > 7.5 mu. Thus particle size but not shape could be a determinant of in vitro toxicity. Particle size might also impact in vivo pathogenesis.

Histological grading in gastric lymphoma: pretreatment criteria and clinical relevance

BACKGROUND & AIMS

Stomach-conserving therapy in primary gastric non-Hodgkin's lymphoma (mucosa-associated lymphoid tissue [MALT]-NHL) is increasingly gaining importance as an alternative to surgery. As a consequence, surgical pathologists have to define histological criteria in pretreatment endoscopic biopsy specimen samples not only to make the diagnosis but also to recognize minor tumor components that may infer a significantly adverse impact on prognosis. The aim of this study was to define histological criteria for clinically significant tumor progression in pretreatment endoscopic biopsy specimens.

METHODS

In a consecutive series of 106 patients with gastric MALT-NHL, the prognostic impact of large cell components was assessed by semiquantitative analysis of clusters and diffusely intermingled malignant blasts.

RESULTS

In low-grade MALT-NHL, a category with a diffuse large cell component of 1%-10% with or without nonconfluent clusters of blasts could be separated with a significantly worse prognosis (10-year disease-specific survival, 90% vs. 75%). No clinical parameters of known prognostic significance could account for this difference.

CONCLUSIONS

It is possible to define criteria in endoscopic biopsy specimens to recognize clinically relevant tumor progression. To serve as a guideline in the choice of treatment, these criteria should be validated prospectively in future clinical trials.

Clinical evaluation of the Byk LIA-mat CA125 II assay: discussion of a reference value

The Byk LIA-mat CA125 II assay was compared with the Centocor IRMA CA125 II. Serum samples studied (n = 1012) were obtained from 652 apparently healthy females, 61 pregnant women, and 299 patients with benign and malignant gynecological tumors. The CA125 II assay value at the 95th percentile of the total healthy group was 29 kU/L for the LIA-mat and 32 kU/L for the Centocor assay. For the LIA-mat assay the 95th percentile was 31 kU/L (Centocor 36 kU/L) for the group < 45 years and 21 kU/L (Centocor 25 kU/L) for women > 55 years of age. By using ROC curves we found the optimal pretreatment Byk LIA-mat CA125 II value differentiating between benign and malignant ovarian tumors to be 95 kU/L. Pretreatment CA125 values > 1000 kU/L were detected in serum samples of patients with advanced epithelial ovarian cancer.

Quality of life, sexual functioning and sex role identity after surgical orchidectomy in patients with prostatic cancer

Surgical orchidectomy is a simple procedure with few physical side effects, low mortality, and cost effectiveness. Nevertheless, there can be negative sequelae such as sexual dysfunction, impaired quality of life, and poor body image. Although it is a frequent treatment approach for prostate cancer, it is not clear whether these sequelae are problematic for this patient group. It is possible that relief from painful metastases and the prolongation of life outweigh these negative factors. The present study investigated quality of life, sex-role identity, and sexual function in 15 patients with stage D prostate cancer, before and after surgery. Orchidectomy did not appear to affect quality of life, or sex-role identity. However, loss of sexual function did present as an area of concern. It was noted that 55% of premorbidly sexually active patients found this loss disturbing. These patients, premorbidly, appeared to have higher sex-role stereotypy.

A comparison of human exposures to fiberglass with those used in a recent rat chronic inhalation study

In a recent rat inhalation study, 2 years of exposure to high concentrations of fiberglass (FG) resulted in no treatment-related fibrosis or thoracic tumors. To determine the relevancy of this study for human risk assessment, it is important to compare the rat experimental exposure levels with those of humans. Data on human exposures were taken from several studies and included FG manufacturing, installation and removal, and ambient air. FG levels in the rat aerosol were 200,000-fold higher than indoor air, > 2000-fold higher than during FG insulation manufacturing, and > 1000-fold higher than FG batt installation. The rat aerosol was 30-fold more concentrated than the highest human exposure (blowing installation of unbound FG). Rat FG lung burden also vastly exceeded that of FG workers, which was not significantly elevated above nonworker levels. The amount of fibers/mg dry lung for the rat after lifetime exposure was > 4000-fold greater than for the FG worker, average exposure 11 years. Aerosol and lung fiber dimensions in the rat study were comparable to those of human exposures. From these comparisons, it can be concluded that the exposure level in the rat inhalation study was sufficiently, if not excessively, high in comparison to human exposures. Increasing the experimental exposure in the rat studies would not serve to mirror human environmental or occupational exposures.

Patient- and treatment-related factors associated with acute regional toxicity after isolated perfusion for melanoma of the extremities

In order to gain some insight into the cause of acute regional toxicity after isolated perfusion using melphalan, 15 patient-related and perfusion-technique-related factors were tested in a logistic regression model. Acute toxicity was graded according to Wieberdink's grading system. In a group of 425 patients, 362 (85%) encountered no or slight toxicity with a grade I or II reaction, and 63 (15%) patients encountered more severe toxicity with a grade III, IV, or V reaction. Most patients were treated with a standard dose of 10 or 13 mg melphalan per liter of perfused tissue for leg and arm perfusions, respectively. Factors associated with a more severe toxicity reaction proved to be tissue temperatures of 40 degrees C or higher, female gender, a deterioration of the gas values of the venous perfusate during perfusion, and perfusion at a proximal level of isolation. Consideration of these prognostic factors may lead to a further decrease of acute regional toxicity in perfusion.

In vitro cytotoxicity of asbestos and man-made vitreous fibers: roles of fiber length, diameter and composition

The present study investigated (i) the impact of various fiber parameters on in vitro toxicity to cells and (ii) the validity of an in vitro test system as a toxic screen for fibrous materials. Chinese hamster ovary cells were exposed in vitro to a series of size-selected inorganic test fibers that represented a range of different diameters, lengths and compositions (glass, refractory ceramic, mineral wool, asbestos). Toxic end-points included inhibition of proliferation, induction of micronuclei and polynuclei and viability. For all compositions tested, toxic effects were similar: a concentration-dependent decrease in proliferation and increase in incidence of morphologically abnormal nuclei with minor decreases in viability. Diameter-dependent differences in toxicity were slight or absent for fiber diameters ranging from 0.3-7 microns when concentration was expressed as number of fibers/cm2. Length-dependent differences in toxicity were, however, striking. EC50 values (concentration in fibers/cm2 that reduced cell proliferation to 50% of unexposed control cultures) plotted against fiber length produced a hyperbolic curve, demonstrating that toxicity increases with fiber length up to 20 microns. All fibers tested fell on this hyperbola. These data suggest that: (a) the primary toxic effect of fibers on CHO cells is the induction of nuclear morphologic alterations resulting in cytostasis; (b) fiber diameter has little or no impact on in vitro toxicity when concentration is calculated as fibers/cm2; (c) fiber length is directly proportional to in vitro toxicity; and (d) toxicity of asbestos and vitreous fibers to CHO cells is not affected by composition. The lack of compositional effect in CHO cells does not correlate with findings from recent rodent inhalation studies using the same test fibers. Thus CHO cells may not be an appropriate in vitro model of fiber pathogenesis and would not constitute a valid toxicologic screening system for fibers.

Moclobemide twice daily in the treatment of major depressive episode: a double-blind, multicenter comparison with different three-times-daily dosage schedules

Data on a twice-daily dosage schedule with moclobemide in the treatment of depression is limited. In this study, moclobemide 150 mg twice daily (b.i.d.) was compared to two different three-times-daily (t.i.d.) regimens with total daily dosages of 300 and 450 mg, respectively, over a 6-week period. The study was randomized, double-blind, and conducted at three university centers. Efficacy was measured on the Hamilton Depression and Anxiety Rating Scales, on the Zung Scale, and on clinical global impression. Tolerability and safety were assessed through adverse events and vital signs and on clinical global impression. One hundred seventy-eight depressed outpatients were included, and 158 completed the study. The treatment groups were comparable at baseline. No clear differences between the treatment groups could be shown with respect to efficacy. There was, however, a slightly larger decrease in the total HAM-A score in the groups receiving 150 mg b.i.d. and t.i.d. than in the third group. There were no marked differences between the groups with respect to tolerability and safety. Tolerability was rated "good" or "excellent" in 94% of patients, and there was no appreciable change in vital signs in any of the treatment groups. Moclobemide 150 mg b.i.d. is the optimal initial schedule for treatment of depression.

Laser beam propagation in turbulent conditions

Diffraction-limited low power laser beams at 1.06 and 3.8 microm were focused by a 91-cm diam aperture onto a receiver located 10.5 km away on a low slant angle path over a desert basin. The analysis of beam areas and turbulence levels was used to determine a new scaling law for tilt-corrected turbulence-induced beam spread.

Carcinoma of the tonsillar region: comparison of two staging systems and analysis of prognostic factors

Between 1966 and 1985, 92 patients with local or locoregional tonsillar carcinoma were treated in the Netherlands Cancer Institute. Treatment consisted of radiotherapy in 79 patients, combination of surgery and postoperative radiotherapy in 10 patients, and surgery alone in 3 patients. The 5-year crude survival rate was 43% and the disease-free interval 57%. Patients were classified according to the UICC 1982 and the UICC 1987/AJCC 1988 criteria. The changes in the lymph node classification proposed in UICC 1987 lead to inversion in sizes of N1 and N2 groups, and of stages III and IV. The most important prognostic factor for disease-free interval is T stage (P = .03). Prognosis is significantly worse in stage IV (UICC 1982) compared to stages I to III (41% vs. 65%, respectively, P = .03). Crude survival is lower in males (P = .031) and in patients who smoked (P = .019).

Dietary influences on cell proliferation in bone marrow

Oral dietary protein-calorie malnutrition was used in rats to study the influence of malnutrition on the distribution of the dividing cells in the bone marrow (stem cells) over the compartments of the cell cycle. A 5-day period of malnutrition induced an increase in the percentage of cells in the G0/G1 phase of the cell cycle while simultaneously inducing a statistically significant decrease in the percentage of cells in S phase. Similar results were obtained after a 14-day period of malnutrition. Nutritional replenishment after 5 and 14 days of dietary deprivation induced a rapid recovery of the percentage of S phase cells and a decrease in the percentage of cells in the G0/G1 phase of the cell cycle. Malnutrition and nutritional replenishment did not influence hemoglobin concentration and platelet numbers in the peripheral blood, but leucocyte numbers increased significantly after short-term replenishment. These results demonstrate a decrease in the percentage of proliferating bone marrow cells after short periods of deficiency and general malnutrition. The results also demonstrate that bone marrow cells recover quickly after nutritional replenishment. In malnourished cancer patients, suspected of bone marrow insufficiency and receiving therapy that potentially impairs bone marrow proliferation, a short period of nutritional replenishment preceding treatment could possibly be marrow-protective.

Alterations in serum levels, anti-tumor activity and toxicity of methotrexate in rats after a short period of nutritional depletion

The alterations in serum levels, anti-tumor activity and host toxicity of methotrexate (MTX) were tested in tumor bearing rats following a period of dietary manipulation. A protein deprived (PD) diet or a diet containing a normal protein content (NP) was administered for 5 days and MTX injected intra-peritoneally (i.p.) at the end of the 5 day period. The MTX serum levels were significantly elevated in rats which received the PD diet, as compared to NP dietary rats. This elevation correlated with an enhanced tumor response to MTX administration. In addition, bone marrow toxicity and intestinal tract toxicity, measured with flow cytometry (FCM) of the bone marrow and morphometry of the jejunal mucosa respectively was increased in rats receiving the PD diet. These results indicate that the serum clearance of MTX is delayed in animals suffering from malnutrition, leading to both enhanced tumor response and increased host toxicity.

Determination of transferrin receptors on frozen sections of malignant B-cell lymphomas by immunofluorescence with a monoclonal antibody

A series of 34 B-cell lymphomas was studied for the presence of transferrin receptors by immunofluorescence on frozen tissue sections with a monoclonal antibody. These lymphomas were classified by light microscopic study and furthermore investigated by immunohistochemical and morphometric methods. There were diffuse centrocytic, diffuse centroblastic, and follicular and diffuse centrocytic/centroblastic lymphomas. Significant differences in log mean nuclear area in these four histologic groups were found, as well as a significant correlation between log nuclear area and transferrin receptors as measured semiquantitatively by fluorescence intensity of the cell membranes. In addition, it was found that there is a strong correlation between the transferrin receptor activity and malignancy grading on histologic and morphometric basis. Therefore, the transferrin receptor determination on frozen sections appears to be a good method of malignancy grading.

Therapeutic enhancement in mice by clinically relevant dose and fractionation schedules of cis-diamminedichloroplatinum (II) and irradiation

The interaction of cis-diamminedichloroplatinum(II) (c-DDP) and irradiation was investigated in the RIF-1 tumor, skin and duodenum in C3H/Km mice. The c-DDP enhanced the effects of fractionated irradiation in the tumor, as measured by both growth delay and cell survival determined by excision and colony formation in vitro. This enhancement was at least additive and possibly supra-additive. The combined treatment was effective in clinically relevant treatment regimens. The same doses of c-DDP failed to enhance acute radiation skin reactions and caused only a moderate enhancement of the radiation-induced cell killing in duodenal crypt cells. The latter was found when c-DDP was administered immediately before each irradiation dose in a fractionated treatment schedule, but not when it was given in a single larger dose 24 h before the start of fractionated radiotherapy. Comparing the effects on tumor with those on normal tissues, the optimum treatment appeared to be c-DDP given once a week 24 h before daily fractionated irradiation.

The Denver type for peritoneovenous shunting of malignant ascites

Peritoneovenous shunts of the Denver type were inserted into 36 patients to control malignant ascites. The Denver system features a compressible pump chamber bearing a pressure sensitive valve. Initially, all the shunts functioned well. The shunt remained open until death in 21 patients, and at the beginning of the analysis, another two patients were still alive with an open shunt. Blockage of the shunt occurred in 13 patients before death. The cumulative survival time for patients after shunt insertion was 129 months and the cumulative shunt functioning time was 92 months. The over-all median survival time after shunt installation was 13 weeks, and calculated actuarially, the median shunt functioning time for long term survivors was 14 weeks. The cytologic state of the ascitic fluid did not make a statistically significant difference to the blockage-free interval (p = 0.99), neither did the type of primary tumor (p = 0.37). Complications were of a minor type. There was no laboratory or clinical evidence of disseminated intravascular coagulation. Tumor spread through the tubing was seen in one of the three autopsies performed. Denver type peritoneovenous shunting appears to provide effective palliation in the majority of patients. It should, however, only be performed as a last resort.

Pharmacokinetics of free and total platinum species after rapid and prolonged infusions of cisplatin

Pharmacokinetic studies were performed in 51 patients who received cisplatin infusions. Two treatment regimens (single-day or daily for 5 days) and three infusion schedules (for 4 to 15 minutes, 2 to 3 hours, or 24 hours) were used. The daily dose of cisplatin varied from 20 to 120 mg/m2. The kinetics of total platinum studied up to day 5 revealed differences only during the initial period after the infusion. Peak levels were both dose and schedule dependent and initial t1/2 values in the decay curves were only schedule dependent (mean values: 13 minutes for rapid infusions, 40.3 minutes for 2 to 3-hour infusions, and 220.5 minutes for 24-hour infusion). The t1/2 values between days 1 and 5 were neither dose nor schedule dependent (mean 5.0 to 7.3 days). Concentrations of free platinum declined biexponentially after the rapid and 2 to 3-hour infusions, but they declined monoexponentially after 24-hour infusions. Final t1/2 values ranged from 26.0 to 78.8 minutes. In patients with normal renal and hepatic function, the free platinum AUC was identical for cisplatin infusions of different duration when equal doses were given. Free platinum clearance correlated with creatinine clearance (P = 0.017). The uptake of platinum in red blood cells was rapid, and peak concentrations correlated with the free platinum AUC (P = 0.0006), independent of the infusion schedule. The decay of platinum levels in red blood cells was biphasic. The mean terminal t1/2 for the interval between days 5 and 15 was 29.8 days. This suggests a breakdown of red blood cells that results from cisplatin dosing.

Research avenues in anxiety and its treatment

Research into anxiety and related disorders requires the systematic collection of much new data. The areas of research most likely to produce clinically useful information are considered. The richest area of research will probably be biopharmacological. Biological and pharmacological research may be usefully coupled to behavioural recording in order to increase our knowledge of the behavioural/physiological relationships. More data are, however, needed on the social/environmental areas of anxiety and on the natural history of these conditions. Cognitive/behavioural approaches are more likely to be useful than depth psychological approaches.

Early-stage rectal cancer: electrofulguration in comparison to abdominoperineal extirpation or low-anterior resection

For some small rectal cancers electrofulguration can be an attractive alternative to more extensive surgical procedures. This report is a review of 49 patients who, after careful selection, were considered ideal candidates for curative fulguration in the period 1959-1982. All had rectal adenocarcinomas and were clinically staged as Dukes' A tumors. To put the results of this analysis into perspective, they are compared to the results of those patients (34) who also had early clinical stage rectal adenocarcinomas, but for a variety of reasons underwent abdominoperineal excisions (APE, 11 patients) or low-anterior resections (LAR, 23 patients) instead of fulguration. Postoperative complications after fulguration were minimal, there were no postoperative deaths, and all patients retained anal continence. After APE or LAR there were two postoperative deaths (one myocardial infarction, one ruptured iliac aneurysm); postoperative morbidity was greater. All LAR-treated patients remained continent. Of the patients at risk 55% remained disease-free after fulguration, while 77% remained disease-free after APE or LAR (P = 0.023). This is due to a higher percentage of loco-regional recurrences occurring after fulguration than after APE or LAR (31% vs 9%, respectively, P = 0.021). The percentage of patients with distant metastases in both groups are similar. It seems that electrofulguration of rectal cancers, even in strictly selected patients in a specialized institution, can lead to an unacceptably high percentage of patients with loco-regional recurrences. Nearly all local failures occurred in patients with tumors that measured more than 3 cm in diameter and/or occupied more than one-third of the rectal circumference. Salvage operations for loco-regional failure were performed in 13 patients, 5 of whom are alive with no evidence of disease. Since there seems to be a direct relation between tumor size and the chance of loco-regional recurrence and since salvage operations for local failure are not uniformly successful, electrofulguration for cure must be reserved for the very rare patient with a very small early-stage rectal cancer.

Aspect of the pharmacokinetics of slow-release lithium carbonate

The bio-availability of two forms of lithium carbonate, Lentolith and Camcolit, was investigated. Serum levels of lithium were measured over 24 hours after different oral dosages. Lentolith gave very adequate serum levels on single daily dosage schedules. Advantages for long-term treatment are discussed.

Depression and its pharmacological management

Clinical factors of importance in the treatment of primary affective disorder with antidepressants are reviewed, and the selection of drugs is discussed on both clinical and biological grounds. Two recently validated neuro-endocrine tests used in the assessment of major depressive disorder are referred to, and research trends with regard to the neurobiology of these disorders are commented upon.

Dose-effect relations for tumour control and complication rate after fast neutron therapy for pelvic-tumours

The effects of fast neutrons and high-energy photons were analysed for tumour control and skin and bowel damage after treatment of bladder and rectal cancers. A combination of statistical models was used for this analysis. A steep dose-effect curve was found for local tumour control as well as for the risk of complications. Some estimates were made of RBE values for control of bladder tumour and for normal-tissue damage. The implication of these data for neutron therapy is discussed.

Prediction of infarct size from serial CK determinations: evaluation by clinical studies and computer simulation

To assess reduction of infarct size by therapeutic intervention, a high predictive accuracy is mandatory. The CK release in the circulation (CKr) was studied in 12 consecutive patients after uncomplicated myocardial infarction, admitted within 5 h after onset of symptoms. Despite improvement of existing methods, such as a more frequent sampling, CK-MB determination instead of total CK determination and use of a gamma-exponential instead of a log-normal curve-fitting technique, the correlation between CKr predicted from measurements within 7 h after the start of CK rise and CKr calculated after completion of the CK curve remained poor. Computer simulations were done to investigate measurement errors as a cause of this failure. Normally distributed noise, with standard deviations ranging from 0.2% to 8.0% of peak CK-MB, was added to the first points of an ideal gamma-exponential CK-MB curve and predictions were made from these "noisy" points. A small noise already produced a great variation in prediction: 0.8% noise resulted in a deviation of predicted CKr from calculated CKr ranging from --20 to +6%. It is concluded that adequate prediction of infarct size from serial CK determinations in the first 7 h after onset of the CK rise must fail if the precision of the biochemical determination is not less than 0.4%.