Susan Billings-Gagliardi

Hypomyelinated mutant mice: Description of jpmsd and comparison with jp and qk on their present genetic backgrounds

Hypomyelinated mutant mice are valuable natural animal systems for analysis of CNS myelin development, chemistry and diseases. One mutant, jpmsd, has never received thorough morphological description. We here describe the detailed morphology of jpmsd, compare it with well-studied jp and qk on their present genetic backgrounds, and discuss the genetic histories of all 3 mutants. Region for region, jpmsd has twice as much myelin as jp, but 1/2--1/5 as much as qk. Both jp and jpmsd have scarce oligodendrocytes, rare nodes of Ranvier, clustering of myelin segments, abnormal lipid-filled cells, frequent degenerating cells, and rare distorted myelin profiles. In contrast, qk has abnormally numerous oligodendrocytes, frequent nodes of Ranvier, no obvious myelin clustering, no lipid-filled cells, rare degenerating cells, and frequent abnormal or distorted myelin profiles. jp and jpmsd are quantitatively different, but qualitatively similar. Since its origin, the jpmsd disease has inadvertently been ameliorated by transferring the mutation to a different background. Persistent differences in the remainder of the genome might account for all remaining apparent differences between jp and jpmsd. In contrast, qk is totally dissimilar in morphology and presumably in pathophysiology.

Development and Validation of the Stroke Action Test

Background and Purpose— Accurately assessing the public’s readiness to respond to stroke is important. Most published measures are based on recall or recognition of stroke symptoms, or knowledge of the best action for stroke when the diagnosis is provided. The purpose of this study was to develop and evaluate a new written instrument whose items require the respondent to associate individual symptoms with the most appropriate action. Methods— The Stroke Action Test (STAT) contains 21 items that name or describe stroke symptoms from all 5 groups of warning signs and 7 items that are nonstroke symptoms. For each item, the respondent selects 1 of 4 options: call 911, call doctor, wait 1 hour, or wait 1 day. The instrument validation sample included 249 subjects from community-based organizations. Score reliability and validity were analyzed using multiple data and information sources. Results— The mean overall STAT score (all 28 items) for the lay people was 36.8%. On average, they chose call 911 for 34.1% of the stroke symptoms. They chose call doctor for 39.4% of the stroke symptoms, wait 1 hour for 20.1%, and wait 1 day for 6.0%. Score reliability is good (&agr;=0.83). Evidence confirming score validity is presented based on analysis of item content and response patterns, and examination of the relationships between test scores and key variables related to stroke knowledge. Conclusions— STAT directly assesses a critical aspect of practical stroke knowledge that has been largely overlooked and provides scores with good reliability and validity.

Distribution of myosin heavy chain mRNA in embryonic muscle tissue visualized by ultrastructural in situ hybridization

We have localized myosin heavy chain (MHC) mRNAs in cells of intact embryonic chick muscle using high resolution in situ hybridization. Blocks of muscle were aldehyde-fixed prior to detergent treatment and hybridized with a biotinated cDNA probe, followed by colloidal gold-labeled antibodies, before embedment. Labeling was determined to represent MHC mRNA by extensive quantitative comparisons of electron micrographs from experimental and four different types of control samples. MHC mRNA was localized primarily to peripheral regions of 14-day chick pectoral muscle cells, where the majority of developing myofibrils were found. MHC mRNAs were consistently associated with the nonmyofibrillar cytoskeletal filaments which had diameters ranging from 4 to 10 nm. They were often oriented parallel to the longitudinal axis of the cell. The resolution of the ultrastructural approach allowed us to demonstrate that the mRNA molecules visualized were not directly associated with myofilaments, suggesting that nascent chains read from those messages do not assemble directly into myofilaments simultaneous with translation.

Shiverer jimpy double mutant mice. IV. Five combinations of allelic mutations produce three morphological phenotypes.

Mice which simultaneously express mutant genes at both the shi and jp loci (double mutant mice) have phenotypes much more complex than simple addition of individual mutant characteristics. Morphological study of shi jpmsd, shimld jp, and shi/shimld jp, and comparison with previously studied shi jp and shimld jpmsd, shows that 3 classes of central nervous system (CNS) white matter morphology are produced. (1) shi jp shows suppression of most jp characteristics: it is like shi except for more major dense line, and possibly more myelin, than shi alone. No other combination has as much myelin or any major dense line at all. (2) shi jpmsd has qualitative and quantitative characteristics intermediate between the two single mutants. (3) All combinations studied involving shimld have much less myelin than either single mutant. Qualitatively they express most jp locus features but suppress all shi locus features except abnormalities of myelin compaction. The difference between shi and shimld has more influence on the double mutant morphology than the difference between jp and jpmsd. In the 3-mutant combination, shi/shimld jp, the influence of shimld completely overrides that of shi. These morphological phenotypes resist assignment to any hierarchy of normalcy, and their specific features have no simple explanation in presently known molecular biology of the shi and jp locus mutations. They suggest the possibility of multiple copies and multiple primary functions of the messages at these loci.

Myelin deficient (shimld) mutant allele: Morphological comparison with shiverer (shi) allele on a B6C3 mouse stock

A new B6C3 stock of shimld mutant mice is compared in terms of behavior and CNS morphology with both a B6C3 shi stock and reports on other shimld animals. Defects of B6C3 shimld myelination seen at postnatal day 21 (P-21) are comparable to those in B6C3 shi with respect to % axons myelinated, sheath thickness, errors in the wrapping and targeting of myelin and abnormal oligodendrocyte shape. The two mutations are similarly expressed in cerebellar organotypic cultures. However, the major dense line (MDL) is present in a few shimld myelin sheaths at P-21 and a few sheaths show myelin basic protein by immunocytochemistry, while neither phenomenon is seen in shi at this age in the same CNS regions. Shimld mice survive their disease significantly better than shi. The shimld stock currently under study elsewhere differs from this B6C3 stock in that MDL was reported only in older animals, and behavior and survival were severely compromised.

Interpreting course evaluation results: insights from thinkaloud interviews with medical students

Purpose  To determine whether some of the fundamental assumptions that frequently underlie interpretation of course evaluation results are justified by investigating what medical students are thinking as they complete a typical basic science course evaluation.

Hypomyelinated mutant mice. V. Relationship between jp and jpmsd re-examined on identical genetic backgrounds

jp and jpmsd, two allelic mutations in the mouse that sharply reduce the amount of CNS myelin, produce diseases that can be distinguished morphologically only by their severity. This has raised the question of whether the two mutations are truly distinguishable. Since the two mutations have never been maintained on the same genetic background, correct quantitative and morphological comparison have not been possible. We have prepared a B6C3H stock of jp on the same genetic background as the available stock of jpmsd. In this jp stock, behavioral abnormalities, relative proportion of myelinated axons, and major morphological characteristics of the disease in situ are unchanged from the previous jp stock. The jp disease continues to be more severe than that of jpmsd. However, tissue from the new B6C3H stock myelinates better in organotypic culture than previous jp stocks. The increase in myelination is advantageous, not only for accurate comparison of the two alleles but for all culture studies of jp. Strictly comparable strains or stocks should be utilized in any comparative studies of closely related mutations such as jp and jpmsd.

Shiverer*jimpy double mutant mice. II. Morphological evidence supports reciprocal intergenic suppression

Mice which carry both the shiverer (shi) and the jimpy (jp) mutations have a morphological phenotype with features of each single mutation by itself but in milder form: the number of myelin sheaths is increased relative to jp, the thickness of sheaths and amount of major dense line is increased relative to shi, and the abnormal, lipid-filled cells characteristic of jp are not seen. However, the abnormal bundles of oligodendrocyte microprocesses and errors in the targeting of myelination which characterize shi are not altered by the presence of the jp mutation. This morphological evidence suggests partial reciprocal intergenic suppression in shiverer jimpy double mutant mice and therefore agrees with conclusions based on biochemical data presented by Kerner and Carson (Brain Research, 374 (1986) 45-53).

Does reading about stroke increase stroke knowledge?: The impact of different print materials

The purpose of this study was to determine whether print materials on stroke resulted in increased knowledge in a sample of lay people. One hundred and seventy-seven participants received (at random) one of five versions of a stroke information packet, or a control packet on colorectal cancer. Participants rated the materials on readability, understandability and usefulness immediately after reading. After a delay of 18 days on average, participants answered questions assessing stroke knowledge. Ratings of all packets were generally positive; however, stroke knowledge scores were significantly higher for the stroke information groups compared to the control group only for knowledge of causal mechanisms (stroke pathophysiology). While there was some indication that the fictionalized material on stroke was more effective than the expository materials, overall the impact of print materials on stroke knowledge, measured after a delay of at least 1 week, was minimal at best. Further research is needed to determine whether fictional contexts make some information more memorable.

Jimpy-4J Mouse Has a Missense Mutation in Exon 2 of the Plp Gene

We previously showed that the jimpy-4J mouse mutation is located on the X chromosome, in or closely linked to the proteolipid protein (Plp) gene. The phenotype is characterized by the most severe hypomyelination of any of the naturally occurring myelin mutant mice, sharp reduction in oligodendrocyte number, and virtual absence of PLP protein. Affected animals show tremor, seizures, and die at about 24 postnatal days. We now report that sequencing of Plp genomic and cDNAs identifies a single nucleotide substitution in exon 2 that predicts an Ala38Ser substitutions in a hydrophilic region of PLP/DM20 protein close to a transmembrane domain. This mutation occurs in a very different region of the mouse Plp gene than that jimpy-msd mutations, yet all three produce qualitatively similar phenotypes.