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Biomedical subjects

L R Allen

Publications and source records attributed to L R Allen.

17 recordsLinked to original sources
PubMed2001

Aberrant apoptosis in the neurological mutant Flathead is associated with defective cytokinesis of neural progenitor cells.

Flathead is a rat neurological mutant which is phenotypically characterized by a flattened cranium, resting tremor, ataxia, progressive paralysis of the hind limbs, and death at 3-4 weeks after birth. Previous studies showed that rats homozygous for the mutation have a dramatically reduced brain size caused by a burst of apoptosis that begins after embryonic day 16 (E16) and which peaks at about E18. Late-developing structures such as the dentate gyrus, internal granule layer of the cerebellum, and superficial layers of the neocortex are severely depleted of cells. In the present study we have found that neurons and glia are both affected by the mutation. Immunohistochemical analysis with TAG-1, a marker for migratory neurons, revealed reduced staining in Fh neocortex and cerebellum, indicating that the mutation affects neuronal migration or a developmental event prior to it. Analysis of acutely dissociated neocortical cultures showed an accumulation of nestin-positive progenitor cells. Moreover, a substantial proportion of these progenitor cells were multinucleated with the nuclei organized as rosettes. Such multinucleated cells were also found in intact sections of the neocortex and the cerebellum where their presence was restricted to proliferative zones. Within the neocortex, the abundance of multinucleated progenitors is highest at E18 and decreases thereafter, thus correlating with the profile of cell death. This, along with the dramatically higher frequency of apoptosis among multinucleated cells, suggests that the aberrant cell death in Fh is due to defective cytokinesis that occurs in progenitor cells during late stages of brain development.

Animals↗
PubMed2000

New mutations in MID1 provide support for loss of function as the cause of X-linked Opitz syndrome.

Opitz syndrome (OS) is a genetically heterogeneous malformation disorder. Patients with OS may present with a variable array of malformations that are indicative of a disturbance of the primary midline developmental field. Mutations in the C-terminal half of MID1, an RBCC (RING, B-box and coiled-coil) protein, have recently been shown to underlie the X-linked form of OS. Here we show that the MID1 gene spans at least 400 kb, almost twice the distance originally reported and has a minimum of six mRNA isoforms as a result of the alternative use of 5' untranslated exons. In addition, our detailed mutational analysis of MID1 in a cohort of 15 patients with OS has resulted in the identification of seven novel mutations, two of which disrupt the N-terminus of the protein. The most severe of these (E115X) is predicted to truncate the protein before the B-box motifs. In a separate patient, a missense change (L626P) was found that also represents the most C-terminal alteration reported to date. As noted with other C-terminal mutations, GFP fusion constructs demonstrated that the L626P mutant formed cytoplasmic clumps in contrast to the microtubular distribution seen with the wild-type sequence. Notably, however, both N-terminal mutants showed no evidence of cytoplasmic aggregation, inferring that this feature is not pathognomonic for X-linked OS. These new data and the finding of linkage to MID1 in the absence of a demonstrable open reading frame mutation in a further family support the conclusion that X-linked OS results from loss of function of MID1.

Abnormalities, Multiple↗
PubMed1994

A Delphi study on research priorities for trauma nursing.

OBJECTIVES: To identify and prioritize research questions of importance to trauma patient care and of interest to trauma nurses. METHOD: A three-round Delphi technique was used to solicit, identify, and prioritize problems for trauma nursing research. In round 1, experienced trauma nurses (N = 208) generated 513 problems, which were analyzed, categorized, and collapsed into 111 items for subsequent rounds. Round 2 participants rated each research question on a 1 to 7 scale on two criteria: impact on patient welfare and value for practicing nurses. Group median scores provided by 166 round 2 respondents and respondents' individual round 2 scores were indicated on the round 3 questionnaire. Subjects rated the questions again on the same criteria and indicated whether nurses, independently or in collaboration with other health professionals, should assume responsibility for that research. Median and mean scores and rank order were determined for each item. RESULTS: Respondents who completed all three rounds (n = 137) had a mean of 8.3 years of trauma experience. Nine research questions ranked within the top 20 on both criteria. The two research questions that ranked highest on both criteria were: What are the most effective nursing interventions in the prevention of pulmonary and circulatory complications in trauma patients? and What are the most effective methods for preventing aspiration in trauma patients during the postoperative phase? The third-ranked question regarding patient welfare was: What psychological and lifestyle changes result from traumatic injury? Regarding value for practicing nurses, What are the most effective educational methods to prepare and maintain proficiency in trauma care providers? ranked third. CONCLUSION: These research priorities provide impetus and direction for nursing and collaborative investigation in trauma care.

Adult↗
PubMed1993

Disordered eating attitudes and behaviors, psychological adjustment, and ethnic identity: a comparison of black and white female college students.

The low prevalence of restrictive eating disorders among black women has been attributed primarily to cultural differences in the definition of beauty. Utilizing self-report measures, this study examined differences in the nature of disordered eating behaviors for black and for white female college students. Analyses of covariance and correlational tests revealed that white females demonstrated significantly greater disordered eating attitudes and behaviors than black females. Additionally, the data indicated that although disordered eating behaviors and attitudes are related to actual weight problems for black females, this is not the case for white females. Furthermore, this study is the first to provide evidence that restrictive eating disorders among black women are related to the degree to which they assimilate to mainstream culture. Finally disordered eating behaviors and attitudes were related to depression, anxiety, and low self-esteem in both groups.

Acculturation↗
PubMed1985

The effect of social support on educational outcomes.

A review of the social support literature identified the theoretical framework for this prospective descriptive correlational study. The relationship of social support to educational outcomes was investigated in a convenience sample of 67 junior and 60 senior nursing students. Social support was measured by the Inventory of Socially Supportive Behavior (ISSB), indicating the frequency with which respondents were recipients of supportive actions from their total support network. Outcomes included the cumulative grade point averages of all participants and the NCLEX scores of graduating seniors. Social Support was also examined in relation to self-esteem, measured by the Coopersmith Self-Concept scale and test anxiety, measured by the Spielberger Test Anxiety Inventory. Hypotheses tested were: (1) There is a positive relationship between social support and both cumulative grade point average and NCLEX scores. (2) There is a positive relationship between social support and self-esteem. (3) Social support will have greater influence on outcomes under conditions of stress, defined as high test anxiety. Hypotheses 1 and 3 were not supported. Hypothesis 2 was supported at the .05 significance level, using a Pearson Correlation Coefficient. Additional information included a significant inverse correlation for test anxiety and both grade point average (p = .01) and NCLEX results (p = .05). Implications for educational experiences and future research are discussed.

Achievement↗
PubMedDate not supplied

The maintenance nitrogen requirement of the zebra finch Taeniopygia guttata.

A procedure is described for the accurate determination of the maintenance nitrogen requirement (MNR) of small granivorous birds. When used with the zebra finch (Taeniopygia guttata), it yielded a MNR of 403 mg kgW(-0.75) d(-1). This is lower than most other passerines so far measured and more similar to some nonpasserine species. Similarly, the value for endogenous nitrogen loss estimated for the zebra finch (153 mg kgW(-0.75) d(-1)) is less than that for passerines in general but higher than the nonpasserine value. We suggest that the low MNR of the strictly granivorous zebra finch is primarily an adaptation to seed diets in which high-quality protein is a limiting factor. Comparison with a wider range of species reported in the literature was restricted because inappropriate methods have been used to estimate MNR in many cases, including the use of growing or reproducing birds and the assumption that maintenance of body mass necessarily coincides with maintenance of zero nitrogen balance.

Animals↗