Sensory testing versus nerve conduction velocity in diabetic polyneuropathy

We sought to evaluate the utility of quantitative sensory testing (QST) and nerve conduction velocity (NCV) studies as measures of distal symmetric polyneuropathy (DSP). We studied 36 diabetic patients divided into four clinical categories of increasing severity. QST included thermal testing and vibration thresholds. NCV studies included median, peroneal, and sural nerves. Results of QST and NCV were compared among clinical groups using survival methodology. The log-rank statistic showed significant differences among the groups; the direction of the differences were consonant with clinical severity. For each diabetic patient, the result of each measurement was classified as normal or abnormal; more diabetic patients had abnormal NCV than either vibration tests or thermal tests. In conclusion, findings of QST and NCV are in keeping with clinical categorization of patients, QST and NCV are complementary tests, and the sural sensory study is the best single predictor of DSP.

Preservation of hearing and facial nerve function in resection of acoustic neuroma

The surgical results in 78 recent cases of total removal of unilateral acoustic neuroma in which an attempt was made to preserve cochlear function have been added to the authors' previous series of 66 cases to evaluate the factors influencing the ability to preserve useful hearing. Useful hearing was defined by speech reception threshold no poorer than 70 dB and a discrimination score of at least 15%. Analysis using a logistic regression model showed that certain preoperative clinical parameters such as tumor size, speech discrimination score, and gender were significantly correlated with hearing outcome. Favorable outcome was significantly correlated with smaller tumor size, higher preoperative speech discrimination score, and male sex. From this data, an explicit formula was devised for predicting hearing outcome for an individual patient. In four cases with useful hearing preserved, there was improvement of greater than 15 percentage points in speech discrimination scores. While preoperative auditory brainstem responses were not predictive of hearing preservation, monitoring of intraoperative auditory evoked potentials was predictive of hearing outcome in selected cases. Specifically, when wave V was unchanged at the end of the operation, even if it may have been transiently lost during surgery, useful hearing was invariably preserved.

Differences in vitamin D status between countries in young adults and the elderly

PURPOSE

To compare vitamin D status between countries in young adults and in the elderly.

MATERIALS AND METHODS

Reports on vitamin D status (as assessed by serum 25-hydroxyvitamin D) from 1971 to 1990 were reviewed. Studies were grouped according to geographic regions: North America (including Canada and the United States); Scandinavia (including Denmark, Finland, Norway, and Sweden); and Central and Western Europe (including Belgium, France, Germany, Ireland, The Netherlands, Switzerland, and the United Kingdom).

RESULTS

Vitamin D status varies with the season in young adults and in the elderly, and is lower during the winter in Europe than in both North America and Scandinavia. Oral vitamin D intake is lower in Europe than in both North America and Scandinavia. Hypovitaminosis D and related abnormalities in bone chemistry are most common in elderly residents in Europe but are reported in all elderly populations.

CONCLUSIONS

The vitamin D status in young adults and the elderly varies widely with the country of residence. Adequate exposure to summer sunlight is the essential means to ample supply, but oral intake augmented by both fortification and supplementation is necessary to maintain baseline stores. All countries should adopt a fortification policy. It seems likely that the elderly would benefit additionally from a daily supplement of 10 micrograms of vitamin D.

Dependence of measured ionized calcium on protein concentration as measured by three ion-selective electrodes

A positive effect of protein on the measurement of ionized calcium in serum by ion-selective electrodes (ISEs) has been previously reported and the present study confirms this finding. Ionized calcium in serum was measured in the presence of increasing protein concentrations induced by venous stasis in 17 healthy volunteer subjects. Ionized calcium was measured using two commercial analysers, a Radiometer ICA2 analyser and a Baker Analyte+2 analyser, and a calcium cell devised by Covington for the calcium reference method (CRM). Both commercial analysers used charged ionophores and the CRM used a neutral carrier ionophore in the selective membrane. A small but significant rise in ionized calcium with increasing protein was measured on all analysers. Substitution of isotonic KCl for saturated KCl in the reference electrode of the CRM resulted in significantly reduced values for ionized calcium in paired serum samples when measured using the isotonic salt bridge. This study supports the premise that the positive effect of protein is related to the salt bridge concentration of the reference electrode rather than the ISE membrane composition.

Radiological evaluation of the facial nerve

The methodology for evaluation of the facial nerve (CT and MR technique) is presented and the need for routine use of gadolinium-DTPA with MRI is emphasized. The various disorders causing facial palsy with their clinical and radiological features are described. Although tumors only cause 6% of facial nerve disorders, they require a thorough radiologic workup. Schwannoma is the most common neoplasm arising from the facial nerve and can occur anywhere along the nerve course: cerebellopontine angle and internal auditory canal, geniculate ganglion, or tympanic, mastoid and intraparotid segments.

The Roles of Ionic Processes in Muscular Fatigue During Intense Exercise1

Muscular fatigue is manifested by a decline in force- or power-generating capacity and may be prominent in both submaximal and maximal contractions. Disturbances in muscle electrolytes play an important role in the development of muscular fatigue. Intense muscular contraction is accompanied by an increased muscle water content, distributed in both intracellular and extracellular spaces. This water influx will modify ionic changes in both compartments. Changes in muscle intracellular electrolyte concentrations with intense contraction may be summarised as including decreases in potassium (6 to 20%) and in creatine phosphate (up to 70 to 100%) and increases in lactate (more than 10-fold), sodium (2-fold) and small, variable increases in chloride. The net result of these intracellular ionic concentration changes with exercise will be a reduction in the intracellular strong ion difference, with a consequent marked rise in intracellular hydrogen ion concentration. This intracellular acidosis has been linked with fatigue via impairment of regulatory and contractile protein function, calcium regulation and metabolism. Potassium efflux from the contracting muscle cell dramatically decreases the intracellular to extracellular potassium ratio, leading to depolarisation of sarcolemmal and t-tubular membranes. Surprisingly little research has investigated the effects of intense exercise training on electrolyte regulation and fatigue.

Microalbuminuria in clinical practice

Albumin excretion rate measured by new immunoassays and semiquantitative tests is advocated as a means for early detection of diabetic nephropathy. We determined albumin excretion rate in 276 patients. Albumin excretion rate was normal in 66%, within the microalbuminuric range in 27%, and within the macroproteinuric range in 7%. Significant predictors of albumin excretion rate included presence of hypertension and glycosylated hemoglobin level in type I diabetes mellitus, and years since diagnosis in type II diabetes mellitus. A semiquantitative test was deemed to be of limited diagnostic value. We conclude that testing for early diabetic nephropathy in routine clinical practice gives valuable information and that determination by a quantitative immunoassay based on a single 24-hour urine sample is preferable. The optimal frequency of screening and the levels that determine progressive renal disease have yet to be established.

Physiologically based pharmacokinetic modeling with dichloromethane, its metabolite, carbon monoxide, and blood carboxyhemoglobin in rats and humans

Dichloromethane (methylene chloride, DCM) and other dihalomethanes are metabolized to carbon monoxide (CO) which reversibly binds hemoglobin and is eliminated by exhalation. We have developed a physiologically based pharmacokinetic (PB-PK) model which describes the kinetics of CO, carboxyhemoglobin (HbCO), and parent dihalomethane, and have applied this model to examine the inhalation kinetics of CO and of DCM in rats and humans. The portion of the model describing CO and HbCO kinetics was adapted from the Coburn-Forster-Kane equation, after modification to include production of CO by DCM oxidation. DCM kinetics and metabolism were described by a generic PB-PK model for volatile chemicals (RAMSEY AND ANDERSEN, Toxicol. Appl. Pharmacol. 73, 159-175, 1984). Physiological and biochemical constants for CO were first estimated by exposing rats to 200 ppm CO for 2 hr and examining the time course of HbCO after cessation of CO exposure. These CO inhalation studies provided estimates of CO diffusing capacity under free breathing and for the Haldane coefficient, the relative equilibrium distribution ratio for hemoglobin between CO and O2. The CO model was then coupled to a PB-PK model for DCM to predict HbCO time course behavior during and after DCM exposures in rats. By coupling the models it was possible to estimate the yield of CO from oxidation of DCM. In rats only about 0.7 mol of CO are produced from 1 mol of DCM during oxidation. The combined model adequately represented HbCO and DCM behavior following 4-hr exposures to 200 or 1000 ppm DCM, and HbCO behavior following 1/2-hr exposure to 5160 ppm DCM or 5000 ppm bromochloromethane. The rat PB-PK model was scaled to predict DCM, HbCO, and CO kinetics in humans exposed either to DCM or to CO. Three human data sets from the literature were examined: (1) inhalation of CO at 50, 100, 250, and 500 ppm; (2) seven 1/2-hr inhalation exposures to 50, 100, 250, and 500 ppm DCM; and (3) 2-hr inhalation exposures to 986 ppm DCM. An additional data set from human volunteers exposed to 100 or 350 ppm DCM for 6 hr is reported here for the first time. Endogenous CO production rates and the initial amount of CO in the blood compartment were varied in each study as necessary to give the baseline HbCO value, which varied from less than 0.5% to greater than 2% HbCO. The combined PB-PK model gave a good representation of the observed behavior in all four human studies.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunohistochemical localization of vimentin and S-100 antigen in small acoustic tumors and adjacent cochlear nerves

To clarify the involvement of cochlear nerves in small acoustic tumors, we used immunoperoxidase techniques to determine the presence and distribution of vimentin and S-100 antigens in two acoustic tumor specimens and a transected vestibular nerve. Schwann cells and acoustic tumor cells failed to react positively with monoclonal antibody to vimentin. Reaction was observed in mesenchymal-appearing cells within both the normal nerve and the acoustic tumors, predominantly in association with blood vessels. Normal schwann cells and acoustic tumor cells reacted with polyclonal antibody to S-100 antigen with a similar, uniform distribution. Mesenchymal-appearing cells did not react with antibody to S-100. Immunostaining of a vestibular nerve from a Meniere's disease patient, used as a control, did not differ significantly from nerves adjacent to acoustic tumors. Because tumor cells and normal schwann cells stained similarly with antibody to S-100, it was not possible to establish with certainty if tumor cells invaded adjacent nerves.

Screening for thyroid disease in children with IDDM

The aim of this study was to evaluate the usefulness of screening for thyroid disease by performing thyroid function tests and measuring thyroid autoantibodies in 371 children and adolescents with insulin-dependent diabetes mellitus (IDDM). We analyzed clinical data and results of serum thyroxine, triiodothyronine uptake, thyroid-stimulating hormone, and antibodies to thyroid microsomal antigen and thyroglobulin. Goiter was noted in 20% of subjects. Thyroid-specific autoantibody was positive in 19% of subjects. Twenty-seven subjects (7%) had thyroid dysfunction. Autoantibody testing identified subjects with thyroid dysfunction with a sensitivity of 50%, a specificity of 84%, a degree of misclassification of 17%, a positive predictive value of 13%, and a negative predictive value of 97%. We recommend that all children and adolescents be screened shortly after diagnosis of IDDM by determination of thyroid-stimulating hormone (measured by high-sensitivity assay) to identify thyroid dysfunction and by testing for antibody to thyroid microsomal antigen to characterize both risk of future thyroid dysfunction and the need for future testing.

Immunohistochemical evidence of measles virus antigens in active otosclerosis

Despite intensive investigation, the cause of otosclerosis remains uncertain. Recent studies of Paget's disease of bone have revealed a possible viral origin. Because of similarities between otosclerosis and Paget's disease, we have pursued investigation of a possible viral cause of otosclerosis. Four temporal bone specimens from patients with otosclerosis, processed for immunohistochemistry, demonstrated positive specific reactivity with monoclonal antibodies to measles virus antigens using the indirect immunofluorescent and immunoperoxidase techniques. Reactivity was most intense in active foci. Reactivity in the peroxidase assay was also observed in areas of acting otosclerosis with application of primary antisera from patients with subacute sclerosing panencephalitis, a disorder of the central nervous system in which a defective measles virus has been isolated. Other related paramyxoviruses, including mumps and respiratory syncytial virus, were negative, as were negative controls.

Effect of glucose polymer ingestion on energy and fluid balance during exercise

Nine male triathletes were studied during 160 min of exercise at 65% VO2 max on two occasions to examine the effect of glucose polymer ingestion on energy and fluid balance. During one trial they received 200 ml of a 10% glucose polymer solution at 20 min intervals during exercise (CHO), while in the other they received an equal volume of a sweet placebo (CON). On average, blood glucose levels (CON = 4.2 +/- 0.2 mmol l-1, CHO = 4.8 +/- 0.1, mean +/- S.E.) and respiratory exchange ratios (CON = 0.84 +/- 0.01, CHO = 0.87 +/- 0.01) during exercise were higher (P less than 0.05) as a result of the glucose polymer ingestion. There were no differences between trials, however, in the estimated plasma volume changes during exercise. Exercise time to exhaustion at an intensity corresponding to 110% VO2 max, performed 5 min after the submaximal exercise, was not influenced by glucose polymer ingestion. Relative to a control exercise bout conducted without prior exercise, however, sprint performance and postexercise blood lactate accumulation were impaired in both trials. It is concluded that glucose polymer ingestion maintains blood glucose levels and a high rate of carbohydrate oxidation during prolonged exercise, without compromising fluid balance.

Right upper lobe obstruction with right-sided double-lumen endobronchial tubes: A comparison of two tube types

Twenty-nine patients undergoing left thoracotomy consecutively were intubated with right-sided double-lumen endotracheal tubes in the conventional "blind" fashion. The first 20 received Leyland red-rubber double-lumen tubes, and the subsequent nine received Mallinckrodt polyvinylchloride double-lumen tubes. The patency of the right upper lobe bronchial orifice was then assessed by flexible fiberoptic bronchoscopy. Right upper lobe obstruction occurred in 89% of the polyvinylchloride tube intubations and in 10% of the red-rubber tube intubations.

Methylene chloride: a 2-year inhalation toxicity and oncogenicity study in rats

Male and female Sprague-Dawley rats were exposed to 0, 50, 200, or 500 ppm methylene chloride for 6 hr/day, 5 days/week for 2 years. Blood carboxyhemoglobin levels were elevated in a dose-dependent (less than linear) manner in rats exposed to 50-500 ppm methylene chloride. Histopathologic lesions related to methylene chloride exposure were confined to the liver and mammary tissue of rats. An increased incidence of hepatocellular vacuolization was observed in male and female rats exposed to 500 ppm methylene chloride. Female rats exposed to 500 ppm methylene chloride also had an increased incidence of multinucleated hepatocytes and number of spontaneous benign mammary tumors/tumor-bearing rat (adenomas, fibromas, and fibroadenomas with no progression toward malignancy); the incidence of benign mammary tumors in female rats exposed to 50 or 200 ppm methylene chloride was comparable to historical control values. No increase in the number of any malignant tumor type was observed in rats exposed to concentrations as high as 500 ppm methylene chloride. Additional groups of female rats were exposed to 500 ppm methylene chloride for the first 12 months or the last 12 months of the 24-month study. The response observed in female rats exposed to 500 ppm for the first 12 months was the same as that observed in female rats exposed to 500 ppm for 2 years. Conversely, the response observed in female rats exposed to 500 ppm during the last 12 months of the study was similar to that observed in control animals. Based upon the results of this study, the no-adverse-effect level for chronic inhalation exposure of Sprague-Dawley rats was judged to be 200 ppm methylene chloride.

Evaluation of a new chemical dip strip for detecting ketonemia in the emergency setting

The utility of a new urine dipstick, Chemstrip uK, was evaluated using serum in place of urine to quantify serum ketones in 29 acutely ill patients with suspected ketosis treated in the emergency department. The serum Chemstrip uK method accurately predicted the level of ketonemia as assessed by the Acetest tablet method (r = .94; P less than .0001). There were no false-negative and no false-positive results. The use of this strip is recommended for evaluating subjects with suspected ketosis.

Hormonal influences on osteoporosis

Osteoporosis has recently received increased attention in both the medical and lay literature. It is estimated that there are more than one million osteoporosis-related fractures yearly in the United States, which are responsible for between three and four billion dollars in health care expenditures. A discussion of osteoporosis requires consideration of both the physiology and pathophysiology of bone tissue. In a structural sense, bone exists in two forms, the outer compact cortex accounting for 80 percent of total bone volume, and the more porous inner trabecular bone. Bone-forming osteoblasts and bone-resorbing osteoclasts are responsible for the ongoing, life-long process of formation and resorption of bone. Sex hormone deficiency, as well as chronic illness, malnutrition, and childhood immobilization, has deleterious effects on growth and modeling, ultimately reducing peak bone mass and setting the stage for osteoporosis in later life. Estrogen is known to have a protective effect on the female skeleton. The mechanisms of this effect are unknown, although estrogen may protect against parathyroid hormone-mediated bone loss. There may be a particular subset of postmenopausal women who are particularly susceptible to estrogen deficiency. Calcitonin levels, which decrease postmenopausally, return to normal with estrogen; other hormones may also play important roles. Osteoporosis is not the result of a single hormonal deficiency or excess; it must be considered in relation to other pathogenetic and risk factors.

Atypical insufficiency fractures confused with Looser zones of osteomalacia

Six women, aged 24-67 years, had osteopenia and insufficiency fractures, which suggested a diagnosis of osteomalacia. The insufficiency fractures occurred at traditional sites for Looser zones, were multiple in number, were symmetrically distributed in three patients, and did not heal promptly. Bone mass was low, as assessed by single-energy photon absorptiometry at the midshaft of the radius. Two postmenopausal women had vertebral compression fractures. Biochemical indices and bone histomorphometric analysis excluded osteomalacia, and in vivo double tetracycline labeling in five patients revealed both high and low bone turnover states. We propose more stringent radiographic criteria for the designation of the term "Looser zone" that retains the customary association between the radiologic event and osteomalacia. This paper also outlines a diagnostic strategy for future cases of atypical insufficiency fractures and proposes reasons for their resemblance to true Looser zones.

Determination of ionised calcium by ion selective electrode is not independent of albumin concentration

The relationship of ionised calcium measurement to changes in serum total protein and albumin were studied both in vivo and in vitro. During venostasis serum ionised calcium was determined in 10 control subjects using an Orion SS20 analyser. A slight but significant increase in ionised calcium occurred only after prolonged venostasis (15 min), when gross changes in total protein and albumin were seen. The effect of albumin concentration on serum ionised calcium was studied in vitro by the dialysis technique of Payne. The increase in ionised calcium in 40 sera was 0.0198 mmol/l per 10 g albumin change. We conclude that albumin-related variation in serum ionised calcium determination required such gross changes that correction is rarely necessary in clinical practice. When gross albumin alteration occurs, the appropriate correction for the analyser used should be determined and applied.

Filamentous structures morphologically similar to viral nucleocapsids in otosclerotic lesions in two patients

Two of four patients with active stapedial otospongiosis had abnormal filamentous structures in osteoblast-like cells. These structures were rare in these cells and did not occur in any other cells. The structures were 17 nm wide and clustered in a loose skein in dilated cisternae of the rough endoplasmic reticulum. They resembled the nucleocapsids of subacute sclerosing panenecephalitis, a variant of measles virus.

Chronic toxicity and oncogenicity study on inhaled vinylidene chloride in rats

Male and female Sprague-Dawley rats (Spartan substrain) were exposed to vinylidene chloride (VDC) by inhalation for 18 months to assess chronic toxicity and oncogenic potential of the subject test material. Interim sacrifices were performed at 1, 6, and 12 months. Rats were exposed to VDC concentrations of 10 and 40 ppm for 6 hr/day, 5 days/week for the first 5 weeks of the study. Based upon the absence of observable treatment-related effects among rats sacrificed after 1 month of exposure, the exposure concentrations were increased to 25 and 75 ppm VDC. Exposures were continued at these concentrations through the 18th month of the study after which the surviving animals were held until 24 months and then sacrificed. Cytogenetic evaluations were performed on a separate group of animals, four rats/sex, exposed to 0, 25, or 75 ppm VDC for 6 months. There were no exposure-related changes in the following parameters: mortality, appearance and demeanor, body weight data, clinical chemistry determinations, hematologic evaluations, urinalysis, or cytogenetic evaluation of bone marrow preparations. A target organ effect, characterized by hepatocellular fatty change in the midzonal region of the hepatic lobule which was minimal in severity, was observed in both male and female rats of both the 25- and 75-ppm exposure groups as early as the 6-month interim sacrifice. The midzonal fatty change was also observed at the 12-month sacrifice but no indication of progression of this lesion in either severity or incidence was apparent. During the last 6 months of the study, after exposures had been discontinued, this effect was no longer discernible; therefore this alteration was readily reversible. The incidences of several tumors and/or tumor types were statistically increased or decreased in VDC-exposed rats when compared to their respective control groups; none of these differences were judged to be attributable to VDC exposure.

The mast cell and bone

The mast cell, which contains many potent bioactive substances, by its very location must have an effect on bone metabolism in health and disease. In this article, the early questions about mast cells in bone raised by Urist and McLean almost thirty years ago are only partially answered, but the work continues to stimulate new experimental and clinical research on the function of mast cells.

Hypovitaminosis D and response to supplementation in older patients with cystic fibrosis

This study reports serum 25-hydroxy vitamin D (25-(OH)D) levels, bone mineral content and bone maturation in 20 adolescent and adult patients with cystic fibrosis, and their response to the internationally recommended dose of supplementary vitamin D (800 iu/day; 20 micrograms/day). Serum 25-(OH)D values were below normal in 75 per cent of patients and serum alkaline phosphatase values, corrected for age, were increased in 60 per cent. Bone mineral content, measured by photon beam absorptiometry, was below the normal range in 45 per cent of patients and bone age retarded in 45 per cent. Following supplementation with vitamin D 40 per cent of patients failed to achieve normal serum 25-(OH)D levels. We concluded that hypovitaminosis D occurs frequently in older patients with cystic fibrosis and is accompanied by osteopenia and retarded bone maturation.

Hydrolysis of several glycol ether acetates and acrylate esters by nasal mucosal carboxylesterase in vitro

The in vitro activity of carboxylesterase recovered from the nasal mucosal tissue of B6C3F1/CrlBR mice toward several agents known to cause olfactory epithelial lesions when inhaled by rodents was determined. Apparent Vmax and Km values were obtained for mouse nasal carboxylesterase using ethylene glycol monomethyl ether acetate (EGMEAc), ethylene glycol monoethyl ether acetate (EGEEAc), propylene glycol monomethyl ether acetate (PGMEAc), methyl acrylate (ME), ethyl acrylate (EA), and butyl acrylate (BA) as substrates. The short straight-chained glycol ethers, EGMEAc and EGEEAc, appeared to be relatively good substrates for nasal carboxylesterase under enzyme saturating and subsaturating conditions as indicated by their high Vmax and Vmax/Km values. The short-chained acrylate esters MA and EA were also hydrolyzed to a greater extent than BA at enzyme-saturating levels; however, the reverse was true at subsaturating levels as indicated by the relatively high Vmax/Km ratio obtained for BA. MA and BA were observed to cause a loss of carboxylesterase activity at enzyme saturation levels while EA caused a loss of enzyme activity at only one-half Km concentration. Using EGMEAc as a substrate, no sex differences in nasal carboxylesterase activity were observed in mice or rabbits. The specific activity of nasal carboxylesterase was found to be equivalent to that of the liver and greater than that of the kidney, lung, or blood. Mice and dogs were found to have similar nasal carboxylesterase activities which were slightly higher than that found in rats and about six-fold higher than that found in rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypovitaminosis D and elevated serum alkaline phosphatase in elderly Irish people

The vitamin D status of 181 elderly Irish community-dwelling and institutionalized subjects was studied during Winter-Spring. The mean serum 25-hydroxyvitamin D level was 10 nmol/L (95% range less than 5.0-59 nmol/L); values were below 25 nmol/L in 79 percent of subjects. A significant seasonal variation of serum 25-hydroxyvitamin D levels was noted in elderly community-dwelling subjects. The previously documented age-related increase in serum alkaline phosphatase activity was significantly less in vitamin D replete subjects than in vitamin D deplete subjects in this study (P less than 0.005). The higher serum alkaline phosphatase values found in the vitamin D deplete subjects may represent mild secondary hyperparathyroidism or osteomalacia. The relationship of vitamin D status to both dietary intake and effective sunlight (latitude) is examined.

The comparative absorption and excretion of chemical vapors by the upper, lower, and intact respiratory tract of rats

Upper respiratory tract (URT) absorption of several compounds with differing water solubilities and potentials to cause lesions of the nasal mucosa were studied in rats. Absorption of propylene glycol monomethyl ether (PGME), PGME acetate (PGMEAc), ethyl acrylate (EA), epichlorohydrin (EPI), styrene (STY), nitroethane (NE), ethylene dibromide (EDB), and methylene chloride (MeCl2) vapors by the isolated URT was compared to that by the isolated lower respiratory tract (LRT) and the intact animal. Nearly all PGME and PGMEAc and 30-70% of EA, EPI, STY, NE, and EDB were absorbed when passed through the URT. In general, similar levels were absorbed by both the isolated LRT and intact animal. It was estimated that intact animals received more than 90% of their total dose of PGME and PGMEAc, and 50% of EA, NE, EPI, and EDB via the URT. Further, the dosage per unit of surface area in the URT may be 5000-6000 times that of the LRT. However, the extent of URT absorption was not related to the ability to cause lesions of the nasal mucosa. Absorption of compounds by the URT was not a simple function of water solubility or of blood or water/air partitioning coefficients suggesting that a more complex mechanism for controlling absorption may exist. In one case, it was demonstrated that URT enzymatic activity could influence the absorption of certain compounds by the URT.

Methylene chloride: a two-year inhalation toxicity and oncogenicity study in rats and hamsters

A long-term study was conducted to determine the possible chronic toxicity and oncogenicity of methylene chloride. Rats and hamsters were exposed by inhalation to 0, 500, 1500, or 3500 ppm of methylene chloride for 6 hr per day, 5 days a week, for 2 years. No exposure-related cytogenetic effects were present in male or female rats exposed to 500, 1500, or 3500 ppm. Females rats exposed to 3500 ppm had an increased mortality rate while female hamsters exposed to 1500 or 3500 ppm had decreased mortality rates. Carboxyhemoglobin values were elevated in rats and hamsters exposed to 500, 1500, or 3500 ppm with the percentage increase in hamsters greater than in rats. Minimal histopathologic effects were present in the livers of rats exposed to 500, 1500, or 3500 ppm. Decreased amyloidosis was observed in the liver and other organs in hamsters exposed to 500, 1500 or 3500 ppm. While the number of female rats with a benign tumor was not increased, the total number of benign mammary tumors was increased in female rats in an exposure-related manner. This effect was also evident in male rats in the 1500- and 3500-ppm exposure groups. Finally, male rats exposed to 1500 or 3500 ppm had an increased number of sarcomas in the ventral neck region located in or around the salivary glands. Therefore, in this 2-year study, some effects were observed in male and female rats exposed to 500, 1500, or 3500 ppm of methylene chloride. In contrast, hamsters exposed to the same exposure concentrations had less extensive spontaneous geriatric changes, decreased mortality (females), and lacked evidence of definite target organ toxicity.

Pulmonary physiology and inhalation dosimetry in rats: development of a method and two examples

Methods were developed to measure simultaneously respiratory frequency, tidal volume, minute volume, and net uptake of an inhaled vapor in rats. During steady state, if metabolism is the only significant route of elimination, net uptake rate of the inhaled vapor is equal to its rate of metabolism. The rates of metabolism of methyl chloride in 50- and 1000-ppm-exposed rats were 0.20 and 3.3 nmol/min/g, respectively; the rates of metabolism of methylene chloride in 50- and 1500-ppm-exposed rats were 0.57 and 2.8 nmol/min/g, respectively. The uptake values obtained for both solvents were consistent with pharmacokinetic and metabolism data that were previously obtained in our laboratory. A pharmacokinetic model incorporating the metabolic rate at steady state, blood concentration versus time, and respiratory minute volume was used to describe the fate of inhaled methyl chloride in F344 rats, and to estimate the inhaled "effective" dose in 50- and 1000-ppm 6-hr-exposed rats (3.8 and 67 mg/kg, respectively). The approach used in these studies appears to be a useful method for the evaluation of metabolic rates and for inhalation dosimetry.

Pharmacokinetics and metabolism of inhaled methyl chloride in the rat and dog

Methyl chloride (MeCl) metabolism and pharmacokinetics were studied in male Fischer 344 rats and male beagle dogs. Apparent steady-state blood MeCl concentrations were proportionate to exposure concentration in rats and dogs exposed to 50 and 1000 ppm. Furthermore, blood MeCl concentrations were similar in both species when they were exposed to the same concentration. A linear two-compartment open model described the blood MeCl data: alpha and beta phase elimination half-times corresponded to approximately 4 and 15 min, respectively, in rats, and 8 and 40 min in dogs. Rats exposed for 6 hr to 0, 50, 225, 600, or 1000 [14C]MeCl were evaluated for tissue nonprotein sulfhydryl (NPSH), total 14C activity, nonextractable tissue 14C activity, and urinary metabolites. MeCl-induced NPSH depletion was dose-related and was greatest in liver. Total 14C in liver and kidney was approximately proportionate to exposure concentrations. Relative concentrations of nonextractable 14C decreased at 600 to 1000 ppm MeCl suggesting a dose-dependent metabolic pathway for MeCl in the rat. Metabolites in urine included N-acetyl-S-methylcysteine, methylthioacetic acid sulfoxide, and N-(methylthioacetyl)glycine. These metabolites are likely to be products of a reaction between MeCl and glutathione. A nonradiometric analysis of a putative MeCl metabolite (S-methylcysteine) was performed in dogs exposed to MeCl; this method was not a sensitive indicator of MeCl exposure.

Osteomalacia and osteoporosis: evaluation of a diagnostic index

Data from a retrospective study in 41 patients is used to suggest an index of bone disease. This is designed as a means of collating available results, clarifying the significance of each in diagnosing either osteomalacia or osteoporosis, and reducing the significance of a single abnormal finding--for example, a raised alkaline phosphatase activity or low serum 25 hydroxy vitamin D, when the overall index score is low. Index scores above 35% would be diagnostic of osteomalacia; scores below 15% if associated with collapsed vertebrae suggest osteoporosis. Scores between 15% and 35% would indicate the need for a bone biopsy to discriminate between osteoporosis and osteomalacia.

Comparative metabolism and disposition of ethylene glycol monomethyl ether and propylene glycol monomethyl ether in male rats

Male Fischer 344 rats were given a single po dose of approximately 1 or 8.7 mmol/kg of [14C]EGME (ethylene glycol monomethyl ether) or [14C]PGME (propylene glycol monomethyl ether). After dosing, expired air, excreta, and tissues were analyzed for 14C; metabolites in urine were isolated and identified. There were pronounced differences in the metabolism and disposition of [14C]EGME and [14C]PGME. Approximately 50 to 60% of the administered 14C was excreted in urine, and about 12% was eliminated as 14CO2 within 48 hr after a single po dose of [14C]EGME. For PGME, only 10 to 20% of the administered 14C was excreted in urine, while 50 to 60% was eliminated as 14CO2 within 48 hr. Methoxyacetic acid was identified as the primary urinary metabolite of EGME, accounting for 80 to 90% of the total 14C in urine. PGME, propylene glycol(1,2-propanediol), and the sulfate and glucuronide conjugates of PGME were identified in urine of rats given PGME. Since methoxyacetic acid causes the same spectrum of toxicity as EGME in male rats, it is likely that the adverse effects of EGME are the result of its in vivo bioactivation to methoxyacetic acid. Hence, differences in routes of metabolism and types of metabolites appear to be the underlying basis for the remarkably different toxicologic properties of EGME and PGME, respectively.

Ethylene glycol monomethyl ether. I. Subchronic vapor inhalation study with rats and rabbits

Male and female Sprague-Dawley rats and New Zealand White rabbits were exposed to 0, 30, 100 or 300 ppm ethylene glycol monomethyl ether (EGME) vapors 6 hours per day, 5 days per week, for a total of 13 weeks. No rats died prior to scheduled sacrifice, but some rabbits in the 100 and 300 ppm exposure groups died or were sacrificed when moribund during the study. Body weights as well as thymus and testicular weights of rats and rabbits in the 300 ppm group were reduced as a result of the exposures. Hematologic changes occurred in rats and rabbits exposed to 300 ppm. Concentrations of total protein, albumin and globulins in serum of rats (but not rabbits) in the 300 ppm group were lower than for controls. Gross lesions in rats and rabbits exposed to 300 ppm EGME included decreased size of thymus in both sexes, decreased abdominal fat, and small flaccid testes in males. In addition there was decreased lymphoid tissue in some rabbits, as well as a slight-to-moderate decrease in size of testes in 4 of 5 rabbits in the 100 ppm group and in 2 of 5 rabbits exposed to 30 ppm. Treatment-related microscopic lesions included degenerative changes in germinal epithelium of testes in all male rats and rabbits in the 300 ppm group, as well as in 3 of 5 rabbits in the 100 ppm group and 1 of 5 male rabbits in the 30 ppm group. The only effects attributed to exposure to 30 ppm EGME in this study were slight microscopic changes in testes of 1 of 5 male rabbits.

Toxicity of methoxyacetic acid in rats

Male Fischer 344 rats were given eight daily doses of 0, 30, 100 or 300 mg/kg methoxyacetic acid by gavage. The high dose resulted in decreased body weight, severe degeneration of testicular germinal epithelium, decreased size of the thymus with depletion of thymic cortical lymphoid elements, and reductions in bone marrow cellularity resulting in depressions of red blood cell counts, hemoglobin concentration, packed cell volume, and white blood cell counts. Some of these observations were apparent to a lesser degree in rats given 100 mg/kg. The low dose produced no apparent effects during the course of the study. These toxicological properties of methoxyacetic acid are remarkably similar to ethylene glycol monomethyl ether (EGME), and the adverse effects of EGME in rats are probably the result of in vivo bioactivation of EGME to methoxyacetic acid.

Metabolism of acrylate esters in rat tissue homogenates

Methyl, ethyl and butyl acrylate were hydrolyzed to acrylic acid in rat liver, kidney and lung homogenates. The rates of hydrolysis of the various esters in these in vitro studies were comparable; hydrolysis rates were approximately 20 times higher in liver homogenates than in kidney or lung homogenates. The esters also disappeared rapidly when added to blood in vitro. However, the disappearance in blood was not associated with the appearance of acrylic acid. Ethyl acrylate was found to react spontaneously with GSH in vitro and this reaction was catalyzed greatly by enzymes in 100 000 x g liver supernatant. Acrylic acid did not react with GSH in vitro. Ethyl acrylate, but not acrylic acid, depletes non-protein sulfhydryls when added to blood in vitro. Thus, the disappearance of acrylate esters in blood in vitro could be due at least in part to binding with non-protein sulfhydryls in red blood cells rather than to hydrolysis.

Inhalation toxicity of acrylic acid

Male and female Fischer 344 rats and B6C3F1 mice were exposed to 0, 5, 25 or 75 ppm acrylic acid vapors 6 hours per day, 5 days per week, for 13 weeks. These exposure levels were selected after conducting a 2-week probe study in which 225 ppm caused pronounced growth retardation and nasal lesions in both rats and mice. The 13-week exposures had no adverse effect on the growth of male and female rats and male mice. However, mean body weight gains of female mice in the 25 and 75 ppm exposure groups were statistically significantly lower than for controls after 12 weeks of exposure. There were no pronounced treatment related effects on organ weights, hematologic parameters, clinical chemistry parameters or urinary parameters. Histopathologic examinations revealed lesions of the nasal mucosa in rats in the 75 ppm exposure group, and in some or all mice at each treatment level. The nasal lesions were primarily localized to the olfactory epithelium; the respiratory epithelium was relatively unaffected. The histopathologic observations in both rats and mice included degeneration, and inflammatory cell infiltration in the olfactory mucosa. In mice there were also instances of hyperplasia of the submucosal glands and, replacement of olfactory epithelium by respiratory epithelium. These effects were attributed to the irritant properties of acrylic acid vapors.

Improved methodology for generating controlled test atmospheres

Improved methodology has been developed for generating controlled test atmospheres. Vaporization of volatile liquids is accomplished in a 28 mm (O.D.) glass J-tube in conjunction with a compressed air flameless heat torch, a pressure-sensitive switch, and a positive displacement piston pump. The vaporization system has been very reliable with a variety of test materials in studies ranging from a few days to several months. The J-tube vaporization assembly minimizes the possibility of thermal decomposition of the test material and affords a better margin of safety when vaporizing potentially explosive materials.