Lowell W. Lapham

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 cerebrum was disturbed in many regions as was shown by the irregular groupings and the deranged alignment of cortical neurons. 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 intoxication in adults and children exposed postnatally.

Postnatal development of electrical and enzyme histochemical activity in Purkinje cells

Abstract Extracellular action potentials were recorded from Purkinje cells of rats, from several hours after birth to adult in age, anesthetized with Nembutal and paralyzed with curare. Lactate and succinate dehydrogenase and γ-amino butyrate-α-ketoglutarate transaminase activities were histochemically determined using tetrazolium reduction techniques. Action potentials were observed as early as several hours after birth with regular sustained spontaneous activity beginning at 1–2 days. There is a sharp increase in activity of all three enzymes between 0 and 3 days restricted in the cerebellar cortex to Purkinje-cell soma. Maximum activities of these enzymes were found at 7 days. Spontaneous climbing-fiber bursts were observed by 7 days. Between 10 and 15 days after birth there occurs an increase in spontaneous firing rates, a decrease in spike duration, and a shift from regular to irregular discharge patterns. There is a simultaneous appearance of histochemical activity in the neuropil of the molecular layer, the glomeruli, and the cerebellar interneurons at this time.

Tetraploid DNA content of Purkinje neurons of human cerebellar cortex.

Microspectrophotometric analysis of single cells in Feulgen preparations revealed tetraploid amounts of DNA in Purkinje neurons of human cerebellar cortex.

Late onset hereditary distal myopathy

A kindred is described in which six members, and probably a seventh, have been affected by a late-onset distal myopathy. Detailed clinical, laboratory, biopsy and autopsy findings are described in two family members. Myopathic histologic changes were observed in numerous biopsy and autopsy muscle specimens. Cardiomyopathy was present in one case.

The astrocyte response in experimental portal-systemic encephalopathy: an electron microscopic study.

The ultrastructural features of Alzheimer type II astrocytes are described in an experimental model of hepatic encephalopathy. Encephalopathy was produced in rats by constructing a portacaval shunt followed by gavage feedings of an ammoniated eation exchange resin. There was hyperplasia and hypertrophy of astrocytes in the cerebral cortex. By electron microscopy the astrocytes exhibited an expanded cytoplasmic compartment associated with proliferation of mitochondria and endoplasmic reticulum. Some astrocytes in addition displayed increased cytoplasmic electron-lucency and vacuolar changes. The implication of these alterations for the role of astrocytes in the pathogenesis of hepatic coma is discussed.

Cell counts in cerebral cortex of an autistic patient

Numbers of neurons and glia were counted in the cerebral cortex of one well-documented case of autism and two age and sexmatched controls. Areas in which cell counts were made were primary auditory cortex, Brocas speech area, and auditory association cortex. No consistent differences in cell density were found between the brains of the autistic patient and the control patients.

Neuronal polyploidy and nuclear volumes in the cat central nervous system

Abstract Nuclear DNA content has been measured cytophotometrically in neurons and glia of motor cortex, cerebellum, and spinal cord ventral horn of the cat. Betz cells, Purkinje cells and large neurons of ventral horn are tetraploid, while remaining neurons and glia in these areas are diploid, with the exception of an octaploid class in a small number of spinal cord neurons in 2 of 5 animals. The tetraploid neurons are the efferent neurons of their respective areas, and their nuclei are significantly larger than diploid nuclei. However, ploidy levels are not strictly proportional to nuclear volume in the cat central nervous system. Nuclear volumes vary among the different tetraploid neuronal types, Betz cell and tetraploid spinal cord nuclei having larger volumes than Purkinje cell nuclei. The nuclei of diploid neurons are significantly larger than those of diploid glial cells.

Effects of methylmercury on human fetal neurons and astrocytes in vitro: A time-lapse cinematographic, phase and electron microscopic study☆

Abstract Time-lapse cinematography of organotypic cultures of human fetal cerebrum demon-strated cessation of neuronal migration following the addition of 0.02 m m methylmercuric chloride (MMC) to the culture medium. This was due to rapid cytotoxic effects of MMC characterized by cessation of filopodial activity, focal swelling, and partial fragmentation of neurites. Separation of the membrane from neurites associated with marked swelling of the matrix was prominent, especially at growth cones. Soon total fragmentation occurred at these sites resulting in separation of degenerated neurites from neuronal cell bodies in 1 to 4 hr. Addition of 0.1 m m MMC caused fragmentation and separation of neurites from most neuronal cell bodies in approximately 40 min while exposures to 0.2 m m MMC caused a similar phenomenon in approximately 20 min. The cytotoxic effect of MMC was stopped immediately and further degeneration did not occur when cultures exposed to MMC were washed and replaced with normal complete culture medium. When mercury was given in a highly polar sulfonic acid form ( p -chloromercuriphenyl sulfonic acid) the membrane of neurites and astrocytes remained intact, indicating that penetration of the membrane by mercury is necessary to initiate the toxic effects of MMC. At the ultrastructural level damage to plasma membranes and neurotubular injury are conspicuous early features of methylmercury toxicity, taking place more rapidly in neurons than astrocytes, and eventuating in irreversible degeneration of both cell types.

Effects of methylmercury on DNA synthesis of human fetal astrocytes: a radioautographic study.

A number of studies have demonstrated that prenatal intoxication by methylmercury (MeHg) significantly influences prenatal development of the central nervous system (CNS) both in human and experimental animals 3,4,9,13. The mechanism or pathogenesis of this toxic influence remains obscure at the present time. One of the prominent features observed in the offspring of mothers who were intoxicated by MeHg during pregnancy has been a significant reduction in body weight as well as brain weight3,4, 9,13. Weight reduction could be the result of diminished proliferation of cells, increased cell death, diminished biosynthetic activity of cells resulting in smaller cells or a combination of these mechanisms. No detailed information is currently available concerning the effects of MeHg on proliferating elements in developing CNS. This study was an attempt to investigate the pattern of DNA synthetic activity in human fetal brain cells, specifically astrocytes in these experiments, exposed to various concentrations of MeHg. Our previous studies of early human fetal brainS, 6 have indicated much earlier development of astroglial cells than traditionally believed, and have further suggested that these cells play important roles during neuronal migration as well as modulation of various CNS functions during development. Human fetal astrocytes were established in cultures of human fetal brains obtained by hysterotomy*. The cells were grown routinely in medium containing 76 parts nutrient mixture F-12 (GIBCO), 20 parts fetal serum, one part L-glutamine, one part non-essential amino acids (GIBCO), one part 50~ glucose in water, and one part antibiotics. Monolayer cultures of pure astrocytes were used in experiments. Identification of cell type was established by correlating features observed by phase contrast microscopy of living cultures with the findings by electron microscopy and immunohistochemistry using glial fibrillary acidic protein as a marker for astrocytes (Fig. 1).

Peripheral neuropathy presenting with respiratory insufficiency as the primary complaint: Problem of recognizing alveolar hypoventilation due to neuromuscular disorders

Abstract A 57 year old farmer, initially believed to have hypoventilation secondary to medullary respiratory insensitivity, died with a peripheral neuropathy and marked involvement of the phrenic nerves. Peripheral neuropathy has not previously been reported to present in this manner. Routine pulmonary function tests that would help to distinguish patients with hypoventilation due to neuromuscular disorders from patients with hypoventilation due to diseases of the lung parenchyma and depression of the medullary respiratory centers were investigated. Five subjects with severe neuromuscular disease were studied (arterial carbon dioxide tension [pCO2]48 to 69 mm Hg, vital capacity [VC] 13 to 79 per cent of predicted and 1 second forced expiratory volume [FEV1] 76 to 96 per cent of VC). The mean ratio of maximum mid-inspiratory flow (MMIF) to maximum mid-expiratory flow (MMEF) was 0.79. In age-matched control subjects this ratio was 1.41. In addition to observing the ratio of MMIF to MMEF other effective clinical screening procedures to distinguish patients with hypoventilation secondary to neuromuscular disorders from patients with medullary respiratory insensitivity include (1) identification of weakness of the muscles used for ventilation by measuring the static maximum inspiratory and expiratory airway pressures, (2) determination of ability to lower the arterial pCO2 with voluntary hyperventilation, and (3) comparison of the maximum breathing capacity to the minute ventilation while breathing 7.5 per cent carbon dioxide for 3 minutes. The latter two measurements permit assessment of central hypoventilation in the presence of intrinsic lung disease.