Morphological observations of peripheral nerves by the scanning electron microscope

In order to observe a normal peripheral nerve and a changed peripheral nerve by means of a scanning electron microscope, the present study was carried out. In the changed nerve fibers, they were enveloped by many processes of hypertrophied Schwann cells, and the processes of the Schwann cells seemed to make a pseudosyntitium-like structure with each other. From this finding, it was speculated that these Schwann cells seemed to follow the reverse process in the development of normal peripheral nerve fibers.

Membranous glomerulonephropathy and nephrotic syndrome associated with iatrogenic metallic mercury poisoning in a cat

The nephrotic syndrome, characterized by nonselective proteinuria, hypoproteinemia, hypoalbuminemia, and ascites, was observed in a 10-month-old male cat. Profound glomerular changes and renal tubular changes appear to have been induced by iatrogenic chronic exposure to metallic mercury originally contained in a rectal thermometer. Large concentrations of mercury were present in the kidneys, liver, spleen, and urine. Evaluation of glomeruli by immunofluorescent microscopy revealed interrupted granular deposition of immuno-globulin G and the third component of complement in glomerular capillary walls and the mesangium. Electron microscopic evaluation of glomeruli revealed diffuse alterations in glomerular basement membranes and visceral epithelial cells. Small electron dense deposits were observed in capillary walls, but they were not characteristic of immune complexes. The mechanism(s) responsible for the mercury induced glomerulonephropathy in this patient could not be determined on the basis of available data.

Acute mercury vapor poisoning. Fatality in an infant

A 7-month-old girl succumbed to respiratory failure following exposure to high-density mercury vapor produced by heating of the metal in the home. Her course typified inhalation mercury toxic reaction, which in its focus on pulmonary damage creates a clinical picture distinct from that of chronic and oral mercury poisoning.

Glycogen deposition in distal tubular cells during HgCl2 induced acute renal failure

An unusual cytoplasmic accumulation of glycogen within the distal tubular epithelium of the kidney was produced by subcutaneouse administration of a single dose of HgCl2 (4 mg/kg body weight), used to induce acute renal failure. Since the plasma immune-reactive insulin was increased while plasma and urine glucose levels remained normal, it was concluded that activation of glycogen synthase might have lead to this effect. Furthermore, the accumulated glycogen was considered to contribute to the protection of distal tubular cells against HgCl2-induced injury, since oxidative energy metabolism was severely depressed after HgCl2 administration.

Comparison of standard chelating agents for acute mercuric chloride poisoning in mice

A comparison in mice has been made of the effectiveness of five chelating agents used clinically for acute mercuric chloride poisoning, or recommended for such use. The compounds examined were N-Acetyl-D,L-penicillamine (NAPA), D-penicillamine (DPA), 2,3-dimercaptosuccinic acid (DMSA), sodium 2,3-dimercaptopropanesulfonate (DMPS), and 2,3-dimercaptopropanol-1 (BAL). The test of effectiveness was their ability to reduce the mortality of acute mercuric chloride poisoning when administered 20 minutes after the mercury at chelate:mercury mole ratios of 10, 15, 20, and 30. All except BAL were found to be effective at the highest mole ratio tested, but N-Acetyl-D,L-penicillamine and sodium 2,3-dimercaptopropanesulfonate were significantly more effective than DMSA and BAL at mole ratios of 10:1. The relative effectiveness does not correlate with available data on stability constants. The toxicity of BAL itself becomes apparent at mole ratios of 20:1 and above.

[Regeneration of the proximal kidney tubules (experimental study with the use of scanning electron microscopy)]

Necrosis of proximal tubules in white rats was produced by inoculation of a comparatively low dose (1.5 mg/kg) of mercuric chloride. Necrosis and regeneration of the epithelium were studied in scanning electron microscope during 10 days lfter the inoculation. The relationship between destructive and regenerative processes was established. The membrane naked as a result of epithelial necrosis is first covered by a flat epithelial plate without microvilli. Soon (presumably within a few hours) microvilli appeared on the surface of the plate and gradually a proper striated border and interdigitation between the cells absent early in regeneration are formed. Within 7-10 days the newly formed epithelium became differentiated and could not be distinguished from normal epithelium by electron microscopy.

Toxic effects of metals from the environment on hair growth and structure

Diffuse alopecia related to ingestion of toxic metals from the environment has been observed in 36 patients. Copper, arsenic, mercury and cadmium were involved and the intensity of disturbance of the hair cycle, heralded by presence of dystrophic hairs, was proportional to the amount of toxic material detected in blood and urine. Toxicity can be observed in vitro by measuring labeled cells on squash preparations after incorporation of tritiated uridine and thymidine in plucked hairs. The labeling indexes, as well as the ratio between cells entering the S phase and the viable cells were always lower in toxic alopecia than in normal hair. Toxic metals do not seem to affect the morphology of the hair shaft.

[Renal failure caused by mercury and lead poisoning in the calf (author's transl)]

The renal lesions in three calves with mercury poisoning (phenylmercuric acetate) and two calves with lead poisoning are described. In addition of slight tubular degeneration, glomerulonephritis occurred in the animals with mercury poisoning. Moreover, uraemia, oedema and haemorrhages were present. Lesions of the brain not were found. In the animals with lead poisoning, chronic renal tubular changes and characteristic intranuclear inclusion bodies in the proximal tubular cells were observed. The juxtamedullary glomeruli showed proliferative mesangial lesions. In one calf, the cerebral cortex showed oedema, necrosis of neurons and an increase in glial cells.

[Chronic mercury poisoning following topical application of skin bleachers (author's transl)]

In two female patients chronic mercurialism following topical application of skin bleachers for the treatment of freckles was diagnosed. Over 20 to 25 years 3 to 10% mercurial ointments were applied twice daily. Recurrent attacks of headache, dyspnoea and abdominal colic-like cramps had lead repeatedly to emergency hospitalisations, multiple medical check-ups and surgical exploratory procedures. The diagnosis of mercurialism was made clinically because of a slate-grayish skin hyperpigmentation in the presence of freckles, and the drug-history. Metallic deposits in facial biopsies were demonstrated by electron microscopy. On admission 15.4 microgram% and 5.0 microgram % total Hg respectively were found in the two patients (normal values up to 2.0 microgram %). Following D-penicillamine treatment the mercury excretion via the urine could be elevated up to 25 microgram %. Neither the slate-gray facial discoloration nor the neurasthenic complaints were affected by this therapeutic trial. In one patient, a maculo-papular drug-induced skin rash to D-penicillamine developed. Persistent unsolved neurological complaints and cramp-like abdominal pains should remind that percutaneous mercury intoxication through intact skin following skin bleachers is still possible today.

Histochemical demonstration of mercury induced changes in rat neurons

A histochemical method modified for ultrastructural studies of mercury induced changes is described. Rat neurons from areas known to be influenced by mercury are used as examples. The histochemical reaction, suggested to be caused by polymercury sulphide complexes, is localized to "dense bodies" where it is visible 14 days after initiation of peroral mercury treatment (20 mg HgCl2/l drinking water).

Abnormal neuronal migration, deranged cerebral cortical organization, and diffuse white matter astrocytosis of human fetal brain: a major effect of methylmercury poisoning in utero

Detailed clinical and neuropathological studies have been made in two fullterm newborn human infants who were exposed to methylmercury in utero as a result of maternal ingestion of methylmercury-contaminated bread in early phases of pregnancy. High levels of mercury were detected in various regions of the brain at autopsy. Study of the brains revealed a disturbance in the development in both cases, consisting essentially of an incomplete or abnormal migration of neurons to the cerebellar and cerebral cortices, and deranged cortical organization of the cerebrum. There were numerous heterotopic neurons, both isolated and in groups, in the white matter of cerebrum and cerebellum and the laminar cortical pattern of the laminar cortical pattern of the cerebrum was disturbed in many regions as was shown by the irregular groupings and the deranged alignment of cortical. Prominent in the white matter of the cerebrum and the cerebellum was diffuse gemistocytic astrocytosis accompanied by an accumulation of mercury grains in their cytoplasm. These findings indicate a high degree of vulnerability of human fetal brain to maternal intoxication by methylmercury. A major effect appears to be related to faulty development and not to destructive focal neuronal damage as has been observed in mercury intoxicaiton in adults and children exposed postnatally.

[Behavioral changes in the rats following inhalation of mercury vapor (author's transl)]

The present study was designed to determine critical brain mercury concentrations associated with specific behavioral changes during exposure to mercury vapor. Rats exposed to 3 mg of Hg/m3 for 3 hours, 5 days per week, for 15-42 weeks, showed a decline in conditioned avoidance response. The latency of escape response also increased in pole climb shock escape. The time to the onset of effects varied from 12 to 39 weeks among 14 rats exposed to mercury. All rats recovered to preexposure baseline within 12 weeks after the termination of exposure. A significantly poor behavioral performance was noticed in rats with brain mercury concentration of approximately 20 microgram Hg/g. Behavioral recovery was seen when the mercury concentrations decreased to 10 microgram Hg/g brain tissue. These results suggest that the critical concentration of inorganic mercury in the brain associated with behavioral changes in the rat ranges about 10 ppm to 20 ppm. In spite of the high concentration of mercury, the nervous tissues of rats in this experiment with mercury vapor intoxication were normal.

Heavy metal nephropathy of rodents

Heavy metal nephropathy is a pathologic entity of the renal tubular epithelium of rats, evoked by lead, gold, and other heavy metals. It is characterized acutely by coagulative necrosis, subacutely by cortical fibrosis, and chronically by cytomegaly and karyomegaly. Finally, adenomas develop, some of which become malignant.

A fine structural study of liver (littoral) cells of methylmercury fed Japanese quail (Coturnix coturnix japonica)

Tissues of Japanese quails were subjected to electron microscopical study. The birds had received 0-8 ppm methylmercury added to their diets for 6 weeks. The ultrastructural changes in the littoral cells of the liver were swollen mitochondria, with dilatation of the endoplasmic reticulum, loss of ribosomes from the rough endoplasmic reticulum and an increase in the number of vesicles in the cytoplasm. The nuclear membrane in some littoral cells became dilated, and the nuclear chromatin was condensed. The physiological effect of the destruction of the littoral cells is discussed.

A pathological study of prolonged cases of Minamata disease. With particular reference to 83 autopsy cses

This study consists of 83 autopsy cases including 64 prolonged cases of Minamata disease. Lesions were severe in the prolonged cases with an acute onset, while they tended to be mild in those with chronic onset. Cerebral cortex showed loss of nerve cells in many of the former, with the cortex often being in a loosening or spongy state, while the thinning-out or decrease of neurons not exceeding 30% of all cells was frequent in the latter. Glial reaction was also intense in the former, but relatively weak in the latter; gradual loss of degenerative neurons without glial reaction was not rare. A given selectivity was found in the localization of lesions of the cerebral cortex, but it was not so conspicuous in those with a chronic onset as in those with an acute onset. Secondary changes corresponding to the lesions of the cortex appeared in the medulla. Cerebellar lesions in the chronic onset cases, as compared with those in the acute onset ones, were milder. The selectively localized area was diminished; the nodulus, uvula and lingula of the vermis and the medial surface of the semilunar lobules were the most likely to be damaged. Of the spinal peripheral nerves, damages to the spinal sensory nerve were found, which were more predominant than those to the motor nerve system, and in which was noted prominent regeneration and repair. The deposited mercury found in organs tended to remain in the nervous system and the kidneys during the prolonged course of this disease, and the prolonged accumulation of mercury in the nervous system appeared to have an influence on the pathogenesis of chronic Minamata disease.

Whole-body retention of mercury and selenium and histopathological and morphological studies of kidneys and liver of rats exposed repeatedly to mercuric chloride and sodium selenite

Distribution and retention of mercury and selenium was studied in rats exposed repeatedly to HgCl2 injections (0.5 mg Hg/kg to the tail vein every other day) and intragastrically to Na2SeO3 (0.5 mg Se/kg every day), applying combined and separate administration of these metals for 2 weeks. Whole-body retention of mercury in the presence of selenium was augmented by 20% and that of selenium in the presence of mercury by 4% with respect to the administered dose. Combined administration of mercuric chloride and sodium selenite brought about damage to the epithelial cells of renal proximal convolutions and formation of protein casts in their lumen. These changes had the same pattern as those induced by administration of mercuric chloride alone, but the intensity was lower. Submicroscopic studies revealed that repeated combined administration of sodium selenite and mercuric chloride did not completely abolish the mercury-induced mitochondrial swelling and contributed to chromatin destruction in the hepatocyte nuclei.

Ultrastructural changes of human sural nerves in the neuropathy induced by intrauterine methylmercury poisoning (so-called fetal Minamata disease)

Biopsy of the sural nerve was performed on three patients with severe Minamata disease of more than 10 years duration. There were so many unmyelinated and poorly myelinated nerve fibers that myelinated fibers scattered irregularly in small numbers or in groups of peculiar features in the intraneural bundle. Abnormaly thin or poorly formed myelin sheaths were noticed. Incomplete myelination and abnormal myelination varied in size and shape appeared as fetal anomaly. Regenerated axons extremely small in size remained singly or in groups following regenerative sprouting. Sometimes, extremely small axons with normal myelination were noticeable, while the axons were lost, leaving myelin sheaths. Axons occasionally contained increased neurofilaments. Schwann cells were not so increased as in adult Minamata disease. Degenerative changes of nerve fibers still proceeded, presumably because the patients lived in the mercury-contaminated district. Myelin degenerations and glycogen deposits in the axoplasm were identified.

Cochlear pathology following exposure to mercury

The sensory and secretory epithelia may become morphologically changed following the exposure to mercury chloride. The earliest and most sever change in the sensory epithelium appeared in the apical part of the cochlea, while the basal coils were only seldom damaged (cytocochleogram studies). Acute intoxication mostly affected both afferent and efferent nerve terminals and the hair cells, while chronic poisoning could also damage the stria vascularis.