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Biomedical subjects

M Woo

Publications and source records attributed to M Woo.

82 records · Page 5Linked to original sources
PubMed1985

Computed tomography in young children with herpes simplex virus encephalitis.

Computed tomographic (CT) scans were obtained from eight infants and young children with herpes simplex virus encephalitis. In two cases the initial scan showed diffuse edematous changes as a mass effect without laterality. Unilateral localized low attenuation in the initial scan was evident 4 days after the onset in one patient, and high attenuation in the initial scan appeared on the 6th day in another patient, but in general, it was not possible to establish an early diagnosis of herpes simplex virus encephalitis from CT scan. In the longitudinal study the calcification with ventriculomegaly appeared in 3 of 5 survivors, and gyriform calcification in 2 of 3 patients, respectively. The appearance of multicystic encephalomalacia was evident in one patient 6 months after the onset of neonatal herpes simplex encephalitis. It is shown that the CT findings of neonates and young children with herpes simplex encephalitis are different from those of older children and adults, and the importance of longitudinal CT studies was stressed in clarifying the pathophysiology of the central nervous system involvement in survivors.

Child, Preschool↗
PubMed1971

Two classes of slowly adapting mechanoreceptor fibres in reptile cutaneous nerve.

1. The myelinated fibre spectrum of the plantar nerve of reptile consists of a unimodal distribution corresponding approximately to the delta elevation in mammalian nerve and contains a variety of receptor categories similar to those of mammals except for the obvious absence of structures related to hairs.2. The various receptor types of reptilian skin do not fall into discrete groups on the basis of conduction velocity.3. Only a few thermoreceptor fibres were identified but a large proportion of slowly adapting mechanoreceptors responded to rapid temperature transients.4. Two distinct categories of slowly adapting receptors whose discharge is related to the amplitude of skin displacement have been identified and studied in detail. These two receptors can be distinguished by their patterns of discharge, and display several distinctive features including differences in resting discharge, receptive field size, threshold, response to DC polarization, etc.5. The mathematical functions describing the response to stimuli of varying magnitude for one receptor type is markedly affected by the sequence of stimulus presentation.

Animals↗
PubMedDate not supplied

Vascular involvement in benign infantile mitochondrial myopathy caused by reversible cytochrome c oxidase deficiency.

A 1-month-old Japanese girl had profound generalized weakness, hypotonia, and severe lactic acidosis. The infant improved gradually: she held her head at 9 months, learned to walk by 15 months. At the first muscle biopsy at 11 weeks of age, the specimen was characterized by numerous ragged-red fibers and decreased enzyme activity on cytochrome c oxidase (COX) staining. Electron microscopic findings were characterized by the presence of excessive abnormal mitochondria not only in skeletal muscle fibers but also in blood vessels. Vascular abnormalities consisted of an increased number of enlarged mitochondria in endothelial and smooth muscle cells of small arteries. Biochemical analysis showed an isolated defect of COX activity, which was only 16% of the mean control level. At the second biopsy at 44 months of age, the COX activity had increased to normal in the entire specimen. On electron microscopy, the abnormal mitochondria present on the first biopsy specimen had disappeared both in muscle fibers and blood vessels; nearly all mitochondria were morphologically normal at the second biopsy. Now at 5 years of age she can run and does not show muscle weakness. We report reversibility of abnormal mitochondria with age not only in skeletal muscle fibers but also in blood vessels in a patient, who had reversible COX deficiency with a benign clinical course.

Arteries↗
PubMedDate not supplied

Hepatotoxicity in rat following administration of valproic acid.

Chronic injections of valproic acid (VPA), VPA with phenobarbital (PB), and PB were studied for their effects on liver mitochondrial morphology and carnitine metabolism in rats. Mitochondrial enlargement was induced by the administration of VPA (500 mg/kg/day) for a period of 7 consecutive days. The administration of VPA (500 mg/kg/day)-plus-PB (20 mg/kg/day) for 7 days, however, did not induce megamitochondrial formation, but in these livers an unusual increase was observed in the number of liver mitochondria, microvesicular steatoses, and myeloid bodies. VPA-treated rats had significantly lower levels of serum-free and total carnitine and higher levels of acylcarnitine and acyl to free ratio than those of the controls. The free carnitine concentrations in serum and liver of the rats treated with VPA-plus-PB were much lower as compared with those treated with either VPA or PB. These morphological and biochemical results, especially of carnitine metabolism, suggest that inhibition of beta-oxidation in liver mitochondria occurred in rats treated with VPA and PB and that, in particular, polytherapy with VPA-plus-PB could be clinically hazardous in causing hepatic injury.

Animals↗
PubMedDate not supplied

Hepatotoxicity in rat following administration of valproic acid: effect of L-carnitine supplementation.

The effect of prolonged administration (7 days) of valproate (VPA, 500 mg/kg/day), or VPA (500 mg/kg/day) with L-carnitine (200 mg/kg/day) on blood carnitine levels and the appearance of liver mitochondria were assessed in the rat. VPA-treated rats showed hypocarnitinemia and enlarged mitochondria when compared with saline-injected control rats. In rats treated with both VPA and L-carnitine, serum and liver carnitine levels were increased by the L-carnitine supplement and the liver mitochondria were not enlarged. L-Carnitine supplement in VPA-medicated patients seems to prevent hepatotoxicity, especially mitochondrial dysfunction.

Animals↗
PubMedDate not supplied

The dependence of mass energy absorption coefficient ratios on beam size and depth in a phantom.

The Monte Carlo computer code "electron gamma shower" (EGS) has been used to determine photon spectra in a water phantom. Spectra used by Johns and Cunningham and for the AAPM dosimetry protocol have been used as input data and ratios of average mass energy absorption coefficients have been calculated for a number of depths and field sizes. The results show that there is a slight dependence on both of these parameters. For example, (mu en/P) water graphite for cobalt-60 varies from a value of 1.111 for the primary spectrum in air, to 1.135 at a depth of 20 cm in a phantom for a beam approximately 1 m2 in area. This variation of over 2% is relevant for dosimetry. The variation is less than this for high-energy radiation beams and in most cases can be ignored. The effect is greater for high atomic materials such as bone, where the range of variation of (mu en/P)bone water, again for cobalt radiation, may be as great as 15%. This too is less for high-energy bremsstrahlung spectra.

Cobalt Radioisotopes↗