Search PubMed⌕ Search

Biomedical subjects

K C Ho

Publications and source records attributed to K C Ho.

At least 91 records · Page 5Linked to original sources
PubMed1986

Correlation of perinatal brain growth with age, body size, sex, and race.

This study compares the weight of the human brain to gestational age and body dimensions. A new formula for calculating the rate of growth is proposed. It consists of a second order polynomial function: Y = A0 + A1X + A2X2, in which Y is brain weight, body weight, height, or body surface area; X is gestational age in weeks and A0, A1, and A2 are statistically estimated coefficients. In utero, the growth rate is most rapid for body weight, followed in decreasing order by brain weight, body surface area, and height. Brain growth is the same for both sexes in black and white races; it accelerates between the 20th and 45th weeks of gestation. The size of the newborn infant brain is directly related to gestational age and body size and is not determined by sex or race.

Birth Weight↗
PubMed1985

Nucleotide sequence of the transcription initiation region for rRNA in the sea urchin Lytechinus variegatus.

The 1191-bp sequence which includes the 5' end of 18S X rDNA and its adjacent spacer have been determined for a cloned fragment of sea urchin rDNA. The 5' end of 33S precursor rRNA (pre-rRNA) has been located by S1 nuclease mapping and primer extension. Pre-rRNA appears to be initiated at an A, 658 bp upstream from the 5' terminus of 18S rRNA. The first nucleotide of 18S rRNA was also analyzed by S1 nuclease mapping and found to correspond to T in the nontranscribed DNA strand. Comparisons of the transcription initiation region in rDNA and the 5' end of 18S X rDNA with the corresponding regions in other eukaryotes reveal no significant nucleotide sequence homology in the precursor portion while the 5' end of 18S X rDNA is highly conserved.

Animals↗
PubMed1985

The diethyldithiocarbamate concentration effects and interactions with other cytotoxic agents on Chinese Hamster cells (V79).

A metal chelator, diethyldithiocarbamate (DDC) perturbs the chromosome condensation processes in dividing cells. The length of the metaphase chromosomes in Chinese hamster cells (V79) treated with 17.2 micrograms/ml of DDC for 2 hr is about half of that in untreated cells. However, concentrations of 1.7 microgram or 172 micrograms/ml DDC apparently do not produce this effect. DDC at 17.2 micrograms/ml also disrupts spindle fibers. Penicillamine, EDTA, EGTA, and diamide show no effect on chromosome condensation. Bleomycin, but not mitomycin and cisplatin, added simultaneously with DDC can prevent the DDC effect on chromosomes. The cytotoxic effect of increasing concentrations of DDC to V79 cells incubated at 37 degrees C exhibits a similar biphasic response. This concentration biphasic toxic effect is not altered when the cells are treated with DDC in combination with radiation, heat, or other cytotoxic drugs. These observations suggest that the different effects of DDC concentrations on chromosome condensation should be considered as one important modification factor for DDC related toxicity.

Animals↗
PubMed1985

Mixed glioma of the cerebellopontine angle.

A rare case of mixed ependymoma and astrocytoma of the cerebellopontine angle is reported. Its clinical presentation, characteristics on evaluation, and prognosis are compared with those of the acoustic neuroma and glioma. The central form of von Recklinghausen's disease and familial multiple lipomatosis as it applies to the patient is also discussed.

Astrocytoma↗
PubMed1984

Modification of membrane function, protein synthesis, and heat killing effect in cultured Chinese hamster cells by glycerol and D2O1.

Glycerol and D2O can provide a protective effect to Chinese hamster V79 cells receiving heat treatment. The mechanism for this effect is assumed to be the ability of these agents to stabilize proteins which implies that one of the possible heat-killing mechanisms is the inactivation of a heat-sensitive molecule (protein?). In addition, we observed that heat can alter the membrane permeability rapidly, and glycerol can reduce the initial heat-induced membrane permeability changes (determined by aminoisobutyric acid uptake). Although not as effective as cycloheximide, glycerol and D2O can retard protein synthesis. These two processes can add to the protective effect of stabilizing cellular protein against heat killing. Since glycerol and D2O added during the heat-conditioning period can interfere with the appearance of thermotolerance, the mechanisms for the protective effect of glycerol and D2O are likely to be different from heat-induced thermotolerance. We propose that the heat-sensitive molecule protected by D2O or glycerol may also play a role in the triggering process of the thermotolerance phenomenon. If the conditioning heat treatment is sufficient to affect this molecule but not other cellular targets, thus allowing the cell to survive, thermotolerance may be observed in surviving cells in response to second or continued heat treatment. Depending on the severity of the heat effect, this heat-sensitive molecule may continue to exist after a conditioning heat treatment in medium containing glycerol or D2O, and therefore, the response of the cells to the challenging heat is altered little. This proposed mechanism is capable of explaining several thermotolerance experimental protocols. Since glycerol can also reduce the toxicity of vincristine, microtubule-related protein is probably one of the proteins stabilized by this agent. D2O also probably affects microtubule protein, because the cells heated in medium containing D2O show little topological changes.

Aminoisobutyric Acids↗
PubMed1983

Epidemiologic methodology as used in China.

Seven epidemiological methods commonly used in China are discussed. A communicable disease reporting system is in place but this does not include rheumatic diseases. Death registers include cause of death only in selected pilot study points. Field studies using either mobile clinics or nation-wide treatment and prevention programs are useful for infectious diseases. Disease specific surveys of mortality and prevalence are available for hypertension and tuberculosis. Some case control and efficacy studies are also undertaken. Thirty longterm disease surveillance points have been established throughout China.

China↗
PubMed1982

Fatal misonidazole-induced encephalopathy: an RTOG case report.

A case of fatal encephalopathy following administration of misonidazole (MISO) is reported. Anorexia and dehydration preceded signs of encephalopathy after a cumulative dose of 18 g (11 g/m2) of MISO in five weekly doses. Serum MISO levels four hours after weekly administrations were markedly elevated. Postmortem examination revealed focal cortical neuronal necrosis and hemorrhage with focal demyelination. The possible relationship of dehydration or altered drug metabolism to the development of MISO central nervous system toxicity is noted.

Brain Diseases↗
PubMed1982

Chemodectoma involving the cavernous sinus and semilunar ganglion.

This paper reports a case of paraganglioma involving the cavernous sinus and semilunar ganglion. The origin of the tumor cells, from paraganglia in this region, is also discussed. Recognition of paraganglia in this area may aid the clinician and pathologist in the differential diagnosis of tumors in this region.

Aged↗
PubMed1982

The weight of the infratentorial portion of the adult brain and analysis of the infratentorial/whole brain weight ratio.

A direct relationship exists between the weights of the infratentorial portion (ITP) of the brain and the whole brain. With aging, the weight of the ITP decreases, but the decrease begins later and is smaller than for the forebrain. With whole brain weights, there are significant differences in the weight of the ITP between sexes and between the races. The weight of the ITP increases slightly with increase in body weight. The infratentorial/whole brain ratio is stable during adult life and does not vary with body dimensions. The ratio increases after age 80 because of the accelerated loss of mass of the forebrain. The ratio is the same for both races, but it is significantly higher for the females than for the males. The difference is best accounted for by an arrest in the growth of the forebrain in the female during adolescence.

Adult↗
PubMed1982

Computed tomographic appearance of the bulging annulus.

Criteria have not been established for differentiating herniated nucleus pulposus and bulging annulus fibrosus by computed tomography (CT). The CT diagnosis of a bulging annulus was evaluated by correlating the CT and anatomic appearance of cadaver lumbar spines, and by comparing CT and surgical findings in patients undergoing lumbar laminectomy. We found that in anatomically or surgically verified bulging annulus, CT showed generalized extension of the disk margin beyond the vertebral body margins. Therefore, bulging annulus can be distinguished by CT from herniated nucleus, which has a focal, usually posterolateral, protrusion of the disk margin.

Adolescent↗
PubMed1982

Arachnoid response to contrast media: a comparison of iophendylate and metrizamide in experimental animals.

Arachnoiditis resulting from administration of intrathecal iophendylate (Pantopaque) was compared with that from metrizamide (Amipaque) in 16 monkeys. Four animals initially underwent metrizamide myelography, eight underwent iophendylate myelography, and four control animals received only cerebrospinal fluid. Twelve weeks later, all 16 animals underwent metrizamide myelography and then histologic studies. Animals receiving iophendylate for the first myelogram differed significantly from the other two groups on inflammation, fibrosis, and myelographic evidence of arachnoiditis. The arachnoiditis produced by iophendylate was more severe than that produced by metrizamide; the iophendylate also produced a more cellular reaction that was qualitatively different from the reaction to metrizamide. This more severe reaction to iophendylate has clinical implications for patients undergoing myelography if the contrast medium is not completely removed from the system after myelography.

Animals↗
PubMed1982

Effect of blood on arachnoiditis from aqueous myelographic contrast media.

Bloody cerebrospinal fluid is thought to increase the risk of arachnoiditis from myelography with iophendylate, but not with aqueous media. An experimental study was undertaken of the effects of metrizamide, iocarmate, and blood, independently and in mixtures, on the production of arachnoid fibrosis. Monkeys exposed to a mixture of iocarmate or metrizamide and blood developed no more significant arachnoid fibrosis than animals exposed to the contrast medium alone. Lumbar puncture with bloody cerebrospinal fluid, although a possible cause of adverse effects, is not a contraindication to proceeding with metrizamide myelography.

Animals↗
PubMed1981

Newborn brain weight in relation to maturity, sex, and race.

Fresh brain weight, gestational age, body weight, sex, and race were collected from autopsy records of 782 newborns over a 10-year period. The brain weight of the mature newborn does not differ between males and females or between white and black infants. For the premature, however, brain weight is heavier in white males than in black males and in white females than in black females. These differences are similar to those found for adults in our previous studies, and they correspond to differences in gestational age and body weight in the subgroups. The differences in brain weight between races are best explained on the basis of environmental factors.

Black People↗
PubMed1981

The morphological changes in unmyelinated peripheral nerve fibers exposed to low sodium and high potassium concentrations.

Frog sciatic nerves were incubated in vitro in isotonic solutions in which the relative concentrations of sodium and potassium were varied. The cross-sectional areas of the unmyelinated axons, the Schwann cells ensheathing the axons, and the periaxonal spaces were measured, and the densities of the axoplasmic organelles were determined. It was found that the nerve fibers were relatively resistant to solutions with low sodium and high potassium concentrations. At very low sodium and high potassium concentrations, there was swelling of the Schwann cells with compression of the axons. A slight degeneration of the axoplasmic organelles was also noted. In an extremely low sodium and high potassium solution, the mesaxons of a few nerve fibers opened up; this was associated with swelling of the axons and slippage of the opposing surfaces of the axolemma and schwann cell membrane. The width of the periaxonal space remained unchanged even with extreme shrinkage or swelling of the axons. These findings indicate that the Schwann cell and axon react differently to low sodium and high potassium concentrations and that the Schwann cell appears to act as a buffer zone, protecting the axon by maintaining optimal ionic concentrations in the periaxonal space.

Animals↗
PubMed1980

Detection of demyelinated plaques with xenon-enhanced computed tomography.

Studies of xenon-enhanced CT for detecting cerebral demyelination have produced conflicting results. Therefore, we studied the effect of xenon inhalation on the CT appearance of five demyelinated plaques. The plaques and the surrounding white matter increased commensurately in attenuation during xenon inhalation. Therefore, xenon enhancement does not generally increase the sensitivity of CT for detecting cerebral demyelination.

Brain↗