Considerations involved with the use of semipermeable membrane devices for monitoring environmental contaminants.

Semipermeable membrane devices (SPMDs) are used with increasing frequency, and throughout the world as samplers of organic contaminants. The devices can be used to detect a variety of lipophilic chemicals in water, sediment/soil, and air. SPMDs are designed to sample nonpolar, hydrophobic chemicals. The maximum concentration factor achievable for a particular chemical is proportional to its octanol-water partition coefficient. Techniques used for cleanup of SPMD extracts for targeted analytes and for general screening by full-scan mass spectrometry do not differ greatly from techniques used for extracts of other matrices. However, SPMD extracts contain potential interferences that are specific to the membrane-lipid matrix. Procedures have been developed or modified to alleviate these potential interferences. The SPMD approach has been demonstrated to be applicable to sequestering and analyzing a wide array of environmental contaminants including organochlorine pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polychlorinated dioxins and dibenzofurans, selected organophosphate pesticides and pyrethroid insecticides, and other nonpolar organic chemicals. We present herein an overview of effective procedural steps for analyzing exposed SPMDs for trace to ultra-trace levels of contaminants sequestered from environmental matrices.

Effects of 3,3',4,4',5-pentachlorobiphenyl (PCB 126) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) injected into the yolks of chicken (Gallus domesticus) eggs prior to incubation.

The yolks of White Leghorn chicken (Gallus domesticus) eggs were injected prior to incubation with either 3,3',4,4',5-pentachlorobiphenyl (PCB 126) at doses ranging from 0.1 to 12.8 microg/kg egg or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) at doses ranging from 0.04 to 0.64 microg/kg egg. Chicks were subjected to necropsy within 24 h of hatching. The brain, bursa, heart, liver, and spleen were removed and weighed. Assessment of the rate of hatching indicated an LD50+/-S.E. of 2.3+/-0.19 microg/kg egg (7. 1+/-0.58 nmol/kg egg) for PCB 126 and 0.15 +/- 0.012 microg/kg egg (0.47 +/- 0.037 nmol/kg egg) for TCDD. No significant differences in the incidence of developmental abnormalities (structural defects and edema) were observed in TCDD-exposed embryos, while PCB 126 caused significantly more developmental abnormalities at 3.2, 6.4, and 12.8 microg/kg egg than the vehicle control. PCB 126 caused lower hatchling weights and greater relative brain, heart, and liver weights when compared to the vehicle control group at a dose of 3.2 microg/kg egg which is greater than the LD50. TCDD at 0.08 microg/kg egg caused relative bursa weights to be less than those of the vehicle control. A toxic equivalency factor (TEF) of 0.07 was determined for PCB 126 in relation to TCDD based on overt lethality.

Organochlorine contaminants in double-crested cormorants from Green Bay, WI: I. Large-scale extraction and isolation from eggs using semi-permeable membrane dialysis.

A 41.3-kg sample of double-crested cormorant (Phalacrocorax auritus) egg contents was extracted, yielding over 2 L of egg lipid. The double-crested cormorant (DCC) egg extract, after clean-up and concentration, was intended for use in egg injection studies to determine the embryotoxicity of the organic contaminants found within the eggs. Large-scale dialysis was used as a preliminary treatment to separate the extracted contaminants from the co-extracted sample lipids. The lipid was dialyzed in 80x5 cm semi-permeable membrane devices (SPMDs) in 50-ml aliquants. After the removal of 87 g of cholesterol by freeze-fractionation, the remaining lipid carryover (56 g) was removed by 100 routine gel permeation chromatography (GPC) operations. A 41,293-g sample was thus extracted and purified to the extent that it could easily be placed at a volume of 5 ml, the volume calculated to be necessary for the egg injection study. Analyses were performed comparing contaminant concentrations in the final purified extract to those present in the original egg material, in the extract after dialysis and cholesterol removal, and in the excluded materials. Recoveries of organochlorine pesticides through dialysis and cholesterol ranged from 96% to 135%. Total polychlorinated biphenyls in the final extract were 96% of those measured in the original egg material. Analysis of excluded lipid and cholesterol indicated that 92% of the polychlorinated dibenzo-dioxins and -furans were separated into the final extract.

The in vitro and in vivo effects of isoflurane and nitrous oxide on platelet aggregation.

In view of the possible antiaggregation effects of newer general anesthetics we investigated the in vitro and in vivo effects of isoflurane and nitrous oxide on platelet aggregation. Platelets obtained from 18 healthy volunteers, were exposed in vitro for 30 min in a closed chamber to oxygen-carbon dioxide (90%, 5%) (control), oxygen-carbon dioxide-nitrous oxide (80%), or oxygen-carbon dioxide-isoflurane (1.5%) with or without nitrous oxide (80%). Samples were tested in ADP- and collagen-induced aggregation tests. Both nitrous oxide and isoflurane produced statistically significant inhibition of ADP-induced aggregation. Inhibition of collagen-induced aggregation was not statistically significant. In 18 patients who received nitrous oxide (3 L/min) and isoflurane (1-2%) during anesthesia, platelet aggregation was reduced significantly. We conclude that both nitrous oxide and isoflurane cause moderate but statistically significant inhibition of platelet aggregation that may be clinically important in some patients.

Private physicians in ambulatory care training in U.S. medical schools.

The contribution of private physicians to medical student education in ambulatory care was determined by a questionnaire directed to departments of family practice, internal medicine, and pediatrics in 124 U.S. medical schools and their branch campuses. The response rate was 84 percent. Of the responding departments, 82 percent offered an ambulatory care course in curricular years three and/or four, and 56 percent utilized private physicians in their courses. Departments of internal medicine were least likely to offer such a course, and their courses less frequently included teaching by private physicians (p less than 0.0001). When offered, internal medicine courses in ambulatory care were least likely to be required for graduation and involved the fewer students. Departments of family practice were most likely to offer ambulatory care courses and were most likely to utilize private physicians in their courses.

Early onset of the "on-off" phenomenon in children with symptomatic Parkinsonism.

Many patients with idiopathic Parkinson's disease treated with levodopa for more than five years develop fluctuations in their clinical response to this drug. Such fluctuations may be unpredictable, but more commonly occur in a regular pattern related to the size and timing of the levodopa dosage. Theories as to their cause have emphasised both the progression of the underlying Parkinson's disease and the possibility of a late side-effect of levodopa. We report two children with Parkinsonism, one after recurrent obstructive hydrocephalus and the other following an encephalitic illness. Both patients had striking improvement with levodopa, but developed predictable and unpredictable dramatic response fluctuations within weeks of starting levodopa therapy. This suggests that neither the pathology of idiopathic Parkinson's disease, nor the long-term use of levodopa are essential for the development of predictable or unpredictable fluctuations in response to levodopa therapy.

Cerebral color blindness: an acquired defect in hue discrimination.

In contrast to the traditional view that striate visual cortex (area 17) is surrounded by two homogeneous cortical areas (areas 18 and 19), recent studies have shown that mammalian extrastriate visual cortex contains several anatomically and functionally distinct subregions. One such region, the V-4 complex of the rhesus monkey, is highly specialized for the analysis of color information, suggesting that a lesion in a homologous region might produce a defect in color vision while sparing other visual functions. We have studied a patient whose clinical syndrome supports this suggestion: a 44-year-old man with normal color vision suffered two cerebral infarctions that produced first a right and then a left superior homonymous quadrantanopia and also caused prosopagnosia, topographical disorientation, and severely impaired color vision. Computed tomography demonstrated extensive lesions in both inferior occipital lobes in the territories of the lateral branches of the posterior cerebral arteries, involving the lingual and medial occipitotemporal gyri bilaterally; these gyri contain the inferior portion of striate cortex and segments of extrastriate visual cortex. The patient had no difficulty in giving the correct color names associated with common objects presented either verbally or in outline drawings. Standardized testing with the Farnsworth-Munsell 100-hue test, the Nagel anomaloscope, and a method that tests for just-noticeable differences between monochromatic stimuli all showed that the patient's ability to distinguish one color from another was markedly imparied but not totally absent. In contrast, visual acuity, reading, visually guided eye movements, and stereopsis were normal. Cells in the V-4 complex of monkey extrastriate cortex are highly specialized for distinguishing one color from another; the hue discrimination deficit that was demonstrated in this patient with cerebral color blindness indicates that a region or regions with similar function has been damaged.

Palinopsia.

Three cases of palinopsia (visual perseveration) are described. In case, evidence pointed to a lesion in the right occipitotemporal region. Pathological findings are reported in one of the three. Previous reports have stressed the importance of posteriorly placed cerebral lesions, more commonly right sided than left, but have not demonstrated more precise localisation within the hemisphere.

Reduplicative paramnesia.

A striking behavioral abnormality is described in three individuals who had severe head trauma. At a point when general mnestic capabilities had returned to a near normal level, the patients persistently relocated the hospital at another geographical site, even in the face of compelling counter-evidence. The strong parallels in the etiology and course of the three cases justify the positing of a syndrome, here termed reduplicative paramnesia. A neuropsychologic analysis of the disorder stresses the cognitive operations entailed in geographical localization and confabulation. Clinical-pathologic considerations underline the role of right hemisphere and frontal lobe structures in the syndrome.

The anatomical basis of prosopagnosia.

Evidence is presented that patients with prosopagnosia have right anterior inferior occipital lesions in the region of the occipital temporal junction. Many if not all cases have an additional lesion in the left hemisphere; this is often but apparently not always symmetrical with the right hemisphere lesion. This evidence is discussed in relation to the anatomical connections of these regions and the results of experiments in animals.

Dysphagia in unilateral cerebral lesions.

Dysphagia may in rare instances be a presenting feature of unilateral cerebral lesions. Normally, bilateral lesions are necessary to cause neurological disturbance of swallowing but there appear to be occasional subjects where this is not so. Cases are presented and the literature reviewed to illustrate this. The dysphagia may occur in isolation and is not necessarily accompanied by dysarthria, facial apraxia, or obvious paralysis. The lesion may be on either side and usually involves the low posterior frontal region. Cases that have come to necropsy have shown involvement of the lowest part of the precentral gyrus or the posterior part of the inferior frontal gyrus.