Experimental study of arachnoiditis from iohexol, an investigational nonionic aqueous contrast medium

Myelography was performed in 16 monkeys using either metrizamide or iohexol, a new nonionic aqueous contrast medium. Eight of the animals received almost five times the recommended clinical dose of contrast medium per unit of body weight; the other eight received the equivalent of a high clinical dose. The severity of resultant arachnoiditis 12 weeks later was evaluated by repeat myelography and by histologic study of the arachnoid. No animals had severe arachnoiditis. Two of the four animals examined with the higher dose of metrizamide had moderate arachnoiditis and one had mild arachnoiditis; with the lower dose of metrizamide, two of four animals had mild arachnoiditis. No significant evidence of arachnoiditis was seen in any of the eight animals examined with iohexol.

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.

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.

Chromatin-negative Klinefelter's syndrome with focal megalencephaly

At autopsy, 72-year-old white male with chromatin-negative Klinefelter's syndrome, mental retardation, psychotic behavior, and carcinoma of the lung was noted to have right unilateral focal cerebral and cerebellar megalencephaly with broad gyri, a cytoarchitectually abnormal cortex, and thickened cerebral vessels. Literature about the neuropathology of Klinefelter's syndrome and several cases of other chromosome aberrations (XYY and XO syndromes) are reviewed. These neuropathological changes are thought to be related to clinical manifestation.

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.

Analysis of brain weight. II. Adult brain weight in relation to body height, weight, and surface area

Analysis of 1,261 adult subjects, ages 25 to 80 years, showed that there is a positive relationship between the brain weight and the body dimensions. The brain weight, however, increases at a slower rate than the body dimensions. There is indication that only a small portion of the brain varies with variation in the body dimensions. Among parameters, the brain weight correlates best with the body surface area, followed by the body height and body weight. The brain weight is related to the body weight partly because it increases with increasing height. When adjusted to body dimensions, the brain weight is greater for white men than for black men and for white women than for black men. Our study also shows that the loss of brain mass proceeds at a slightly faster rate than loss of body mass.

Analysis of brain weight. I. Adult brain weight in relation to sex, race, and age

The weights of fresh brains obtained at consecutive autopsies over a period of five years were reviewed. Brains with lesions, such as large tumor, hemorrhage, infarct, or edema, were excluded. Analysis of the brain weight of 1,261 subjects, aged 25 to 80 years, show that the mean brain weight decreases in order from white men to black men to white women to black women. These differences are statistically significant and become apparent at age 6 years. The rate of decrease for the brain weight after age 25 years is highest for white men, followed by black women, white women, and black men, and, except that between white men and white women, the differences are statistically insignificant. Contrary to earlier reports, the mass decreases rapidly after age 80 years. In evaluating an individual brain weight, it is important to compare it with the norm for each subgroup of a given age.

Arachnoiditis from myelography with iopamidol, metrizamide, and iocarmate compared in the animal model

A new aqueous myelographic contrast media, iopamidol, was compared to iocarmate and metrizamide with respect to the risk of arachnoiditis. Macaque monkeys underwent myelography with one of the three contrast media. Twelve weeks later, the animals were restudied with myelography, then sacrificed for histologic studies of the arachnoid. Results suggest that iopamidol is safer than iocarmate and equivalent to metrizamide with respect to the risk of arachnoiditis.

Excretion of aqueous myelographic contrast media in animals undergoing a repeat myelogram

The rate of elimination of contrast media may be a factor in side effects and complications of aqueous myelography. The authors studied the effect of a previous myelogram and arachnoiditis on the elimination of aqueous contrast media from the subarachnoid space. Serum and cisternal CSF iodine concentrations were measured after experimental myelography in subhuman primates. The transfer of the aqueous contrast media from CSF to serum was slowed and the circulation with the cerebrospinal fluid into the intracranial cisterns was increased by a previous myelogram or arachnoiditis.

The risk of arachnoiditis from experimental nonionic contrast media

Aqueous myelographic contrast media are needed that are less expensive and better tolerated than metrizamide. This study compares two new, nonionic aqueous contrast media, ioglunide and iopamidol, with two previously developed contrast media, metrizamide and iocarmate. Myelography was performed with one of the contrast media in monkeys; four weeks later the degree of arachnoid fibrosis was determined in each animal by myelographic and histologic studies of the dural sac. Iopamidol, ioglunide, and metrizamide produced no more arachnoid changes than were found in the control animals. Iocarmate produced moderate to severe arachnoiditis.

Metrizamide optic nerve sheath opacification

The safety of metrizamide in the optic nerve sheath has not been studied to our knowledge. We studied histologic changes produced by metrizamide in the optic nerve of cats with surgically created lesions simulating orbital tumors and trauma. Displacement, compression, and disruption of the optic nerve sheath were detectable by radiographing the opacified sheath. Arachnoiditis of the optic nerve sheath is unlikely from a single exposure to metrizamide in a concentration less than 300mg I/ml.

Taylor-Haughton line revisited

In 1900 Taylor and Haughton described a technique to define a line on the scalp directly above the central (rolandic) fissure. The Taylor-Haughton line was used to identify the central fissure in computed tomography (CT) images. Radiopaque catheters are placed on the scalp on either side of the Taylor-Haughton line prior to CT imaging. The accuracy of the Taylor-Haughton line for identifying the central fissure was also investigated in cadaver brains. The Taylor-Haughton line provides a good approximation of the location of the rolandic fissure.

The contracting cord sign of multiple sclerosis

A new sign of multiple sclerosis, the contracting cord sign, is described. The myelographic demonstration of a large cord that subsequently decreases in size may suggest multiple sclerosis. Multiple sclerosis must be considered in the differential diagnosis of an enlarged spinal cord. Distinguishing between the collapsing cord and the contracting cord is discussed.

CT detection of demyelinated plaques in multiple sclerosis

CT images and anatomic slices of two brains containing numerous demyelinated plaques were correlated. Demyelinated plaques smaller than 0.7 cm were not detected by CT. Some larger plaques were misinterpreted as normal structures. These and other considerations suggest that chronic cerebral demyelination cannot be excluded by negative nonenhanced CT scan.

Ineffectiveness of prophylactic intrathecal methylprednisolone in myelography with aqueous media

The effectiveness of prophylactic intrathecal methylprednisone (MP) in preventing arachnoiditis from iocarmate myelography was studied. Monkeys were injected intrathecally with locarmate, MP, or a combination of the two. Twelve weeks later the severity of arachnoiditis was determined in each animal. There was no significant prophylactic effect of intrathecal MP on arachnoiditis from locarmate. Some arachnoiditis was found in control animals treated with MP alone.

Computed tomography of anatomic specimens

To obtain high quality computed tomographic (CT) images of specimens, the specimens must be submerged in water and immobilized. We describe a simple, effective technique for imaging brain specimens in various CT scanners. Anatomic sections that correspond exactly to the plane of the CT image may be obtained

Comparison of arachnoiditis produced by meglumine iocarmate and metrizamide myelography in an animal model

Myelography in monkeys was performed with either meglumine iocarmate or metrizamide. The severity of resultant arachnoiditis in each animal 12 weeks later was evaluated by repeat myelography and by histologic study of the arachnoid. Three of the four animals examined with meglumine iocarmate had severe arachnoiditis; none of the four animals examined with metrizamide had as severe changes. The difference between the two groups was statistically significant (P less than .05).

Arachnoiditis from experimental myelography with aqueous contrast media

Myelography was performed on 80 monkeys to study postmyelographic arachnoiditis. Metrizamide myelography caused arachnoiditis when high concentrations were used, but not with the usual clinical concentrations. Arachnoiditis resulted after myelography with meglumine iocarmate; however, the risk of arachnoiditis was reduced by diluting the contrast medium. Prophylactic intrathecal methylprednisolone was not effective in preventing arachnoiditis. Blood in the cerebrospinal fluid did not affect the degree of arachnoiditis.

Severity of postmyelographic arachnoiditis and concentration of meglumine locarmate in primates

Myelography with meglumine iocarmate, a dilute meglumine iocarmate solution, or gas was performed in macaque monkeys. Twelve weeks later the animals were examined myelographically and histologically for evidence of arachnoiditis. Arachnoiditis in the animals treated with dilute meglumine iocarmate and gas was significantly less than in those treated with meglumine iocarmate.

Arachnoiditis following myelography with water-soluble agents. The role of contrast medium osmolality

The role of contrast medium osmolality in postmyelographic arachnoiditis was studied. Monkeys were injected intrathecally with isotonic saline (290 mOs/kg), hypertonic saline (1,449 mOs/kg), metrizamide (456 or 300 mOs/kg), or methylglucamine iocarnate (1,049 mOs/kg). After 12 weeks the animals were examined for evidence of arachnoiditis, with myelography just prior to sacrifice and microscopic examination of the excised dural sac and its contents. Intrathecal injections of methyglucamine iocarmate or metrizamide caused arachnoiditis while saline did not. Only one animal given 170 mg l/ml (300 mOs/kg) exhibited a more severe reaction than the controls. An increase in the cerebrospinal fluid osmolality alone does not cause arachnoiditis.

Experimental production of arachnoiditis with water-soluble myelographic media

After myelography with either metrizamide (300mg l/ml) or meglumine iocarmate (280 mg l/ml), mild to severe arachnoid fibrosis was demonstrated radiographically and histologically in primates. Intrathecal injections of metrizamide (170 mg l/ml) or autologous cerebrospinal fluid produced less arachnoiditis. The risk of arachnoiditis is probably minimized by the use of reduced volumes and concentrations of water-soluble media. Controlled studies of arachnoiditis following myelography are probably more reliable in the primate model than in other experimental animals.

The relation of axonal transport of mitochondria with microtubules and other axoplasmic organelles

Axonal transport of mitochondria was studied in frog sciatic nerves incubated in agents selected for their known or alleged effect on microtubules or axonal flow. Quantitative data on mitochondria, microtubules, neurofilaments, endoplasmic reticulum, and cross-sectional area of the axon indicate that axonal transport of mitochondria is dependent on microtubules. When more than half of the microtubules are destroyed, the axonal transport of mitochondria is diminished in proportion to the destruction of microtubules. Axonal transport of mitochondria is not related to neurofilaments and endoplasmic reticulum. Changes in the cross-sectional area of axons, even upon reduction to half the normal size, do not noticeably affect mitochondrial transport. Cyanide which blocks oxidative metabolism also blocks axonal transport of mitochondria, but analysis of fine structure indicates that cyanide is destructive to microtubules as well.

The SN mechanism in aromatic compounds. XXXII. Reactivity of some perhalogenobenzenes

Substituent effects in a series of pentafluorophenyl compounds (C6F5X) ranging from powerful activating to powerful deactivating substituents are considered, both as regards orientation and rates, and shown to be simply and reliably predicted by considering the change as made up of two components, viz. from C6F6 to C6F5H and from C6F5H to C6F5X. The same principle applies generally to C6Hal5X compounds, and the necessary orientation and rate data are obtainable from the existing large body of substituent effects in aromatic SN reactions. Comparisons are thus also easily possible with substituent effects in aromatic SE reactions, and more generally. The reasons for predominant para direction for almost all groups, except the more powerful deactivating substituents which are meta directing, and the expectation of a few borderline cases, emerge clearly from discussion. While orientation is largely known already, there have been very few precise rate determinations apart from the present work. Some brief consideration of the admixture of dioxan with protic solvent is given. The reactivities of hexafluorobenzene and hexachlorobenzene are compared. The substantially greater reactivity reported with the former is regarded as due solely to the greater mobility of fluorine than chlorine, with first row nucleophdes in protic solvents; whereas in contrast it is predicted that the C6Cl5 group is slightly more activating for aromatic S, reactions than the C,F, group. The relative reactivities of C6F6 and C6H5F, and C6Cl6 and C6H5Cl are also compared. Rate ratios are c.108; ΔΔE? c.15 kcal mole-1; and Δlog10B c.+1.