The histopathological, immunohistochemical and electron microscopic findings in eight patients with polycystic lipomembranous osteodysplasia and sclerosing leukoencephalopathy (PLO-SL) are described. This autosomally recessively inherited disease is first manifested by multiple bone cysts, which are later followed around the age of 30 by severe neuropsychiatric syndrome. The pathogenesis of PLO-SL has not been established, and the search for the most suspected error in lipid metabolism has been unsuccessful. The typical macroscopic features were marked hydrocephalus ex vacuo due to severe destruction of the white matter (WM) with extensive secondary astrocytic gliosis, and with relatively better preserved gray matter (GM). The basement membranes of blood vessels with plump endothelium were thickened and often multiplied, most prominently in the WM. Extravasation of plasma constituents was demonstrated immunohistochemically. On the basis of the vascular changes, also present in bone lesions, it is proposed that severe chronic vasogenic brain edema is the main pathogenetic mechanism of the severe leukoencephalopathy in this disease entity.

Biopsy material was obtained from cortical epileptogenic zones (eight temporal, one occipital, one parietal and one frontal) of eleven patients aged 1.5-47 years with therapy-resistant partial epilepsy (TRPE) undergoing epilepsy surgery. Control autopsy material (two temporal, two occipital, one parietal and one frontal) was removed from six neurologically healthy cases within 6-10 hours postmortem delay. In each specimen, 100-300 pyramidal and non-pyramidal neurons were visualized by intracellular Lucifer Yellow microinjection. Single neurons were imaged using CLSM generated serial optical sections; 2-D reconstruction of each neuron was made using z-projection of serial optical images, and 3-D reconstructions and rotations were computerized. Neuronal maps from TRPE biopsies, compared to control autopsies, show markedly increased numbers of dendritic abnormalities of single pyramidal and non-pyramidal neurons in layers I, II-III, V-VII, and in the subcortical white matter. The abnormalities include: (1) increased number of non-pyramidal cells in layer I; (2) many pyramidal cells with two or three dendrites originating apically, rather than one single apical dendrite, in layers II-III; (3) atypical orientation of oblique apical and basal dendrites in pyramidal neurons of layers II-VII; (4) increased number of atypical 'dinosaur-like' and fusiform cells in layers V-VII; (5) numerous neurons in the white matter. These abnormalities may be etiological in cases with early onset, and predisposing in cases with late onset.

The cerebellar pathology at autopsy of 5 patients with Rett syndrome is described. The patients ranged in age from 7–30 years. All had markedly reduced brain weights with proportionately small cerebella. Microscopic examination revealed loss of Purkinje cells, atrophy, astrocytic gliosis of the molecular and granular cell layers, and gliosis and loss of myelin in the white matter. Cortical atrophy occurred focally along the folia and was often more marked in the tips of the folia. The 2 oldest patients had been treated with phenytoin which may have contributed to the morphologic changes. Atrophy and gliosis increased with age or in patients without phenytoin treatment; the youngest patient demonstrated only minor microscopic changes. In addition to the generalized alterations, 1 patient had several adjacent folia with severe atrophy. The results indicate that cerebellar changes in Rett syndrome consist of general hypoplasia with the addition of atrophy beginning in childhood and progressing over many years.

The historical background of lipid research with particular reference to the nervous system is outlined. Attention is called to the early studies of Swedish investigators on the morphology and physical properties of the lipid rich myelin sheath. The pioneering research of the late Gunnar Brante on quantitative topical lipid chemistry of the human nervous system in health and disease is pointed out. A selection of lipid histochemical methods for various spingolipids is presented. Results are reported of their application to cases of four genetically determined sphingolipidoses. The morphological changes characterizing these diseases are interpreted in terms of histochemistry and biochemistry. The recently developed method by Dowson for the characterization of autofluorescence emission spectra from neuronal lipopigment in various ceroidoses (ceroid-lipofuscinosis) has been applied to cases of Sanfilippo's syndrome and Salla disease. The results are briefly commented upon.

The distribution of lead in the cerebellum of suckling Sprague-Dawley rats was examined using a nuclear microprobe for elemental mapping of tissue sections (particle-induced X-ray emission, 3-μm beam of 2.5 MeV protons; micro-PIXE). The rats were injected intraperitoneally with a lead-containing vehicle or vehicle only from ages 1 to 14 days. The calculated doses were 7.8 (low-dose) and 15.6 (high-dose) μg lead/g body weight. The rats were killed at 20 days of age. The vascular system was rinsed quickly with 0.15 M ammonium acetate to obtain determinations of intra-parenchymal lead with minimal influence of lead bound to erythrocytes and plasma proteins. Brains were frozen in propane/propylene in liquid nitrogen. Cryostat sections, 15 μm thick, were air dried on formvar coats that covered a hole, 15 mm in diameter, in a plastic disc, and were used for lead analysis by micro-PIXE. Very low concentrations of lead were found in the brain of controls. Lead levels in homogenates from cerebrum and cerebellum measured by atomic absorption spectrometry (AAS) were: low-dose 1.2–2.2 μg/g wet weight and high-dose 1.4–2.4 μg/g wet weight. The lead levels measured with the micro-PIXE method were in good agreement with the levels found with AAS. Lead was present in the cerebellar white matter in two to three times higher amounts than in the cortical grey (low-dose white matter 11–18 μg/g dry weight, grey matter 2.0–5.5 μg/g dry weight). This was true for both low and high dose exposed rats. Lead concentrations in rats subjected the high-dose lead exposure were approximately 60% higher than those in low-dose exposed rats. Concentrations were lower in the Purkinje cell layer than in other parts of the cortex. These new findings on the distribution of lead in suckling rats are discussed in relation to the pathogenesis of experimental lead encephalopathy.

Characteristics of intraneuronal lipopigment in two siblings with Sanfilippo's syndrome are reported. A lipopigment emission spectrum probably reflects its composition and the (uncorrected) autofluorescence emission spectra results are compared with spectra from non-diseased tissue and from previously reported childhood-onset neuronal ceroidlipofuscinoses (ceroidoses), adult-onset ceroidosis (Kufs' disease) and animal ceroidoses. Values derived from the emission spectra from Sanfilippo's syndrome could be distinguished from those obtained from equivalent regions of non-diseased brains and were within the range of abnormal values previously reported from accumulations of pigment in various types of neuronal ceroidosis. Some abnormal lipopigment in Sanfilippo tissue was indistinguishable from some lipopigment in childhood-onset ceroidosis and in Kufs' disease. These results indicate that the intraneuronal lipopigment which accumulates to an abnormal extent in Sanfilippo's syndrome should not be termed "lipofuscin", which is a normal cerebral constituent, but "ceroid" to denote lipopigment with abnormal characteristics.

A neuropathological study was performed on two patients with Salla disease, one male and one female, from different families. They both died at the age of 41 years. Both patients showed increased excretion of free sialic acid in the urine, psychomotor retardation starting in the 1st year of life, ataxia and spasticity. Several family members of both families were affected with the same disease indicating the hereditary character of the disorder. The neuropathological investigation revealed strikingly similar changes in the two cases. Macroscopically the cerebral white matter was severely reduced. Histologically marked loss of axons and myelin sheaths was accompanied by pronounced astrocytic proliferation. The remaining axons frequently showed ovoid swellings surrounded by a myelin sheath. The reduction of the number of myelin sheaths seemed proportional to the numerical reduction of axons. Many cortical nerve cells displayed in relation to age an abnormal amount of lipofuscin. Neurofibrillary tangles were observed in nerve cells of the neo-cortex, nucleus basalis of Meynert and locus ceruleus. Cerebellum showed moderate loss of Purkinje cells. In the spinal cord axonal degeneration was observed in both ascending and descending tracts.

Splenectomy in children with the Norrbottnian type of Gaucher disease is followed by increased blood levels of glucosylceramide and imparied neurological and mental status. High blood levels are associated with an increased accumulation of glucosylceramide in perivascular Gaucher cells in the brain compared to non-splenectomised cases. Surrounding the Gaucher cell infiltrates there is loss of neurons and slight demyelinaton in the brain parenchyma. The brains of four cases with the Norrbottnian type of Gaucher disease were examined by immunohistochemical stains in an attempt to further characterize the perivascular Gaucher cells and to examine the reactions of the vessel walls and brain parenchyma to the accumulation of Gaucher cells. The perivascular storage cells showed granular staining with antibodies to muramidase and α1-antichymotrypsin confirming that they are blood-derived macrophages belonging to the monocyte-macrophage system. The Gaucher cells contained material positive for antisera to plasma proteins strongly suggesting that large molecules (including glucosylceramide) can escape from the blood and be taken up by the macrophages in Gaucher disease. The storage cells were surrounded by a reticulin network stained by antisera to collagen type III, type IV and laminin. The infiltrates were bounded from the brain parenchyma by a membrane strongly positive with antiserum for the basal lamina protein collagen type IV and laminin. The formation of a basal lamina around the Gaucher cell cuffs probably constitutes a protective phenomenon governing the brain parenchyma against the foreign cells. A focal loss of neurons but only minor loss of axons could be demonstrated with the antiserum to neurofilament. The brain parenchyma surrounding the Gaucher cell infiltrates showed marked astrogliosis in the anti-glial fibrillary acidic protein stain.

We performed a neuropathological study on 5 fetuses with an autosomal recessive, lethal syndrome of congenital contractures diagnosed by fetal hydrops on ultrasonography. The fetuses showed a typical pattern of malpositioning of hips and knees with occasional pterygia of the neck and elbows. The muscles were hypoplastic and the spinal cords showed severe thinning, most markedly affecting the ventral half. A total loss of axons in the ventral and lateral funiculi, subtotal loss of anterior horn motor neurons with accompanying astrocytosis and astrogliosis, and similar but less severe changes at the brain stem level suggested a degenerative rather than a dysmorphogenetic mechanism. Sensory nuclei and pathways were distinctly less severely affected, if at all. The findings further delineate this condition as a genetically and pathoanatomically distinct autosomal recessive syndrome.

The morphologic changes of the spinal cord in Rett syndrome are described in 2 young women who died at 20 and 30 years of age. Both patients had been in a severely disabled state for many years with tetraparesis and extreme muscle wasting. Degeneration and loss of spinal ganglion nerve cells, in addition to gliosis of both the white and gray matter of the spinal cord, were evident. The number of motor neurons appeared to be reduced and axonal changes suggestive of degeneration were observed in both the ascending and descending tracts.

The specific gravity of the cerebral cortex of normal and protein-deprived rats aged 15, 21 and 25 days was determined. The increase in specific gravity seen in control rats in the course of their development was reduced in protein-deprived rats in the course of the period between 15 and 21 days of age. The results are in agreement with previous reports on delayed maturation of the brain in protein-deprived rats and indicate that determination of brain specific gravity may serve as a suitable screening method in situations when a disturbed brain maturation is suspected.

The effect of severe protein deprivation and subsequent nutritional rehabilitation on the fibre size and mitochondrial enzyme activity of the extensor digitorum longus (EDL) and soleus muscles of the young rat has been examined. Protein deprived rats showed atrophy of type 2 fibres predominantly, reduced histochemical activity of succinic dehydrogenase (SDH) and reduced biochemical activity of citrate synthase. Nutritional rehabilitation indicated by resumption of the original body weight resulted in complete restitution of the weight of the muscles and the size of type 1 and type 2 fibres, but not of the activity of SDH and citrate synthase. The results indicate that regarding size, type 2 fibres tend to be more influenced than type 1 fibres by the nutritional supply. The mitochondrial enzyme activity which is decreased by protein deprivation does not regain the normal levels as quickly as the muscle fibres resume their normal size.

The influence of maternal protein deprivation on body and brain growth and on serum immunoreactive insulin-like growth factor I (IGF-I) levels was examined in rats during development. The offspring of protein-deprived mothers were significantly growth-retarded postnatally and showed an altered developmental pattern of serum immunoreactive IGF-I levels. In contrast to control animals, between days 5 and 20 postnatally, a significant elevation in serum immunoreactive IGF-I levels which peaked at day 15 was found. However, in adult growth-retarded rats a significant reduction in serum immunoreactive IGF-I levels was found. These findings suggested the preweaning period to be critical for the development of the mature somatomedin system.

Previous studies on the toxic effects of lead on the brains of young animals have shown damage to the blood-brain barrier (BBB) which in severe forms appears as hemorrhagic encephalopathy. In those studies the doses of lead have been of such magnitude that lead-induced anorexia resulting in growth retardation has contributed to the extent of the injury (Sundström et al. 1984). The growth retardation can be prevented by using low lead doses (Sundström et al. 1983). Consequently, we have examined to which extent the BBB is injured in suckling rats with low dose lead encephalopathy. This was done by a) testing the permeability of the BBB to plasma proteins and b) assessing the possible occurrence of vasogenic edema by measuring the specific gravity of brain tissue. Low dose lead encephalopathy was induced by daily i.p. injections of lead nitrate 10 mg/kg body weight (b.wt.) for the first 15 days. The lead contents of the blood and homogenates of the cerebrum and cerebellum were assayed by atomic absorption spectrophotometry.

The effects of exercise on atroph of muscle fibres and loss of mitochondria in the extensor digitorum longus (EDL) and soleus muscles were studied in protein deprived rats. They had smaller muscle fibres than aged-matched control rats, the difference being more evident in type 2 than type 1 fibres both in the fast EDL and slow soleus muscles. The loss of weight was more pronounced in the EDL muscle which is composed mainly of type 2 fibres than in the soleus muscle which is composed mainly of type 1 fibres. Protein deprived rats subjected to a programme of periodic running on a treadmill for 12 weeks showed less muscle atrophy than sedentary, protein deprived rats. This effect of exercise in diminishing the degree of atrophy was more pronounced in the type 2 than type 1 fibres. The protein deprived rats which had been sedentary showed a marked loss of subsarcolemmal mitochondria, which was not seen in protein deprived rats undergoing exercise.

Most studies on lead toxicity in the suckling rat have been performed with doses leading to growth retardation. In a previous paper (Sundström et al. 1983), the effects of different lead doses on normal suckling rats were described. The dose of 10 mg/kg body weight daily given on days 1–15 pp produced minute hemorrhagic lesions on day 15 in the cerebellum, whereas rats given 5 mg/kg body weight daily lacked microscopically discernible pathologic changes in the brain. None of these groups exhibited growth retardation.