Development of a retroviral construct containing a human mutated dihydrofolate reductase cDNA for hematopoietic stem cell transduction

A double-copy Moloney leukemia virus-based retroviral construct containing both the NeoR gene and a mutant human dihydrofolate reductase (DHFR) cDNA (Ser31 mutant) was used to transduce NIH 3T3 and mouse bone marrow (BM) progenitor cells. This resulted in increased resistance of these cells to methotrexate (MTX). The transduced BM progenitor cells were returned to lethally irradiated mice. The recipients transplanted with marrow cells infected with the recombinant virus showed protection from lethal MTX toxicity as compared with mock- infected animals. Evidence for integration of the proviral DNA was obtained by amplification of proviral DNA by polymerase chain reaction (PCR) and Southern analysis. Sequencing a portion of the PCR-amplified human DHFR cDNA showed the presence of the mutation. These studies with the human Ser31 mutant DHFR cDNA gave results comparable with those obtained with the mutant murine DHFR cDNA (Leu to Arg22) in developing MTX-resistant BM. The Ser31 mutant human DHFR cDNA is currently being tested for infection of human CD34+ human BM and peripheral blood stem cells in vitro.     

Cardiovascular and Adrenal Proliferative Lesions in Fischer 344 Rats Induced by Long-term Treatment with Type III Phosphodiesterase Inhibitors (Positive Inotropic Agents), Isomazole and Indolidan

Male and female Fischer 344 rats were treated with the positiveinotropic agents, isomazole or indolidan, in the diet for 104weeks. The doses were 0.0, 11.5, 23.5, or 48.0 mg\kg and 0.0,0.12, 0.40, or 1.3 mg\kg, respectively. Only 17% of the malestreated with 48.0 mg\kg isomazole survived the duration of thestudy. The male component of the indolidan study was terminatedat 22 months, with only 18% of the high-dose males surviving.Sixty-five percent of the males treated with 48.0 mg\kg isomazoleand 70% of the males treated with 1.3 mg\kg indolidan were foundto have severe periarteritis, often with thrombi located mainlyin the mesenteric arteries. Fifty-four percent of the male ratstreated with 48.0 mg\kg isomazole and 55% of the male rats treatedwith 1.3 mg\kg indolidan died from cardiovascular disease comparedto 1–2% among the control males. Animals in the low- andmiddle-dose groups of both studies had a lower incidence ofcardiovascular disease than did those in the high-dose group.Additional lesions associated with the long-term administrationof both drugs were markedly increased incidence of adrenal medullaryproliferative lesions (both hyperplasia and pheochromocytomas)and increased incidence of chronic progressive glomerulonephrosis.These lesions, like those in the cardiovascular system, occurredin a dose-dependent manner and were more frequent in males thanin females. Treatment-related effects in these studies werejudged to be related to the pharmacologic action of these compounds.     

Triphenyl Phosphite and Diisopropylphosphorofluoridate Produce Separate and Distinct Axonal Degeneration Patterns in the Central Nervous System of the Rat

This study compared the neurotoxic effects of triphenyl phosphite(TPP) in the rat with those seen after exposure to diisopropylphosphorofluoridate(DFP), a compound known to produce organophosphorus-induceddelayed neurotoxicity (OPIDN). Animals received either threesubcutaneous injections of TPP (1184 mg/kg body wt each dose)administered at 3-day intervals or a single subcutaneous injectionof DFP (4 mg/kg body wt). TPP-induced clinical signs were initiallyobserved 2 to 18 days after the last injection and includedataxia, flaccid paresis, stereotyped alternating side-to-sidemovements, and circling behavior. Axonal and terminal degenerationwere present in the cerebellum, vestibular nuclear complex,cochlear nuclei, and superior and inferior colliculi. The subthalamicnucleus, substantia nigra, septal region, hypothalamus, thalamus,hippocampus, and cerebral cortex also contained degeneratingaxons and terminals. Degeneration was particularly evident inthe sensorimotor cerebral cortex, mediodorsal, ventromedial,and medial geniculate thalamic nuclei and in the magnocellularpreoptic and medial mammillary nuclei of the hypothalamus. Verylight degeneration was present in the gracile fasciculus andnucleus. In contrast, rats injected with DFP showed moderatedegeneration in the gracile fasciculus and nucleus but did notdisplay degeneration in any other brain region. Injections ofDFP did not produce delayed onset clinical signs. The resultsindicate that in the rat, different central nervous system cellgroups are affected by these two organophosphorus compoundsand that TPP affects nuclei and tracts at all levels of theneuraxis, including those associated with higher-order processingand cognitive functions. In addition, the distinct degenerationpatterns produced by these two compounds support the view thatTPP-induced neurotoxicity should not be considered as a typeof OPIDN, but rather as a separate category of organophosphorus-inducedneurotoxicity.     

Storage of feature conjunction in transient auditor memory

The purpose of this study was to determine whether feature conjunction are stored in transient auditory memory. The mismatch negativity (MMN), an event-related potential that is elicited by stimuli that differ from a series of preceding stimuli was used in this endeavour. A tone that differed from the preceding series of stimuli in the conjunction of tow of its features, both present in preceding stimuli but in different combination, was found to elicit the MMN, the data are interpreted to indicate that information about the conjunction of feature is stored in the memory.     

Giant thrombosed aneurysm associated with an arteriovenous malformation: Case report and review of the literature

The association of cerebral arteriovenous malformations and intracranial aneurysms has been well documented. Among these are a subset of giant aneurysms in association with arteriovenous malformations which are relatively rare. We present a case report and a brief review of the literature regarding this entity.     

MRI in ankle tuberculosis: Review of 14 cases

We reviewed the MR imaging features of ankle tuberculosis and determined the role of MR in its diagnosis. A retrospective analysis of 14 cases of ankle tuberculosis imaged with MRI was performed. Plain radiographs were also reviewed where available, and the imaging characteristics were noted. We also reviewed the medical records in order to assess the impact of the imaging findings on management of these patients. Magnetic resonance imaging is extremely helpful for detection, mapping the extent and resolution of the disease. It can identify cases, enables early institution of antituberculous chemotherapy and might obviate the need for surgery.