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Biomedical subjects

D L Allen

Publications and source records attributed to D L Allen.

At least 73 records · Page 4Linked to original sources
PubMed1994

Talin, vinculin and DRP (utrophin) concentrations are increased at mdx myotendinous junctions following onset of necrosis.

Duchenne muscular dystrophy (DMD) and the myopathy seen in the mdx mouse both result from absence of the protein dystrophin. Structural similarities between dystrophin and other cytoskeletal proteins, its enrichment at myotendinous junctions, and its indirect association with laminin mediated by a transmembrane glycoprotein complex suggest that one of dystrophin's functions in normal muscle is to form one of the links between the actin cytoskeleton and the extracellular matrix. Unlike Duchenne muscular dystrophy patients, mdx mice suffer only transient muscle necrosis, and are able to regenerate damaged muscle tissue. The present study tests the hypothesis that mdx mice partially compensate for dystrophin's absence by upregulating one or more dystrophin-independent mechanisms of cytoskeleton-membrane association. Quantitative analysis of immunoblots of adult mdx muscle samples showed an increase of approximately 200% for vinculin and talin, cytoskeletal proteins that mediate thin filament-membrane interactions at myotendinous junctions. Blots also showed an increase (143%) in the dystrophin-related protein called utrophin, another myotendinous junction constituent, which may be able to substitute for dystrophin directly. Muscle samples from 2-week-old animals, a period immediately preceding the onset of muscle necrosis, showed no significant differences in protein concentration between mdx and controls. Quantitative analyses of confocal images of myotendinous junctions from mdx and control muscles show significantly higher concentrations of talin and vinculin at the myotendinous junctions of mdx muscle. These findings indicate that mdx mice may compensate in part for the absence of dystrophin by increased expression of other molecules that subsume dystrophin's mechanical function.

Age Factors↗
PubMed1994

Participatory continuing dental education.

The significance of continuing education for the development of a professional person is indisputable. There is evidence that participatory continuing education is the most effective form for this activity to take in relation to dentists and clinical practice. Working Group 15, appointed by the FDI Commission, specifically studied this form of continuing education by use of a questionnaire to 26 representative national dental associations. The majority of countries surveyed have at least some education of this sort although it forms only a small proportion overall. Little evaluation seems to take place to measure the subsequent value to the practitioners attending. The results of the information gathered are discussed and recommendations are made.

Africa↗
PubMed1994

Some aspects of trends and relationships in dental and medical education.

Dental education is dynamic. Many factors--economic, pedagogical, managerial, logistic, trends in disease patterns and delivery systems--are influencing its future directions and relationships with medical and other health professions' education. This article attempts to highlight those trends and relationships, at least in part of the world.

Biological Science Disciplines↗
PubMed1993

Mitogenic and receptor activities of human growth hormone 108-129.

We have selectively synthesized a number of peptides encompassing the region of helix 3 of growth hormone (GH). These peptides and native human (h) GH have been evaluated for mitogenic and receptor activities in 3T3-F442A preadipocytes. In this system, wild type hGH is anti-mitogenic. In contrast, hGH 108-129 stimulated DNA synthesis while other GH-derived peptides were ineffective. hGH (L) 108-129 had an EC50 of about 0.2 nM and was maximally effective at about 0.5 nM in stimulating [3H]thymidine incorporation in 3T3-F442A cells. hGH (L) 108-129 was mitogenically as active as insulin-like growth factor-I and more active than insulin. It was less effective than transforming growth factor-beta. By cell cycle analysis, hGH (L) 108-129 increased the proportion of cells in S/G2/M phases to 28%. hGH, when coincubated with hGH (L) 108-129, blocked the mitogenic response of the peptide. A monoclonal antibody to the GH receptor significantly reduced binding of 125I-hGH to its receptor but had no effect on binding of 125I-hGH (L) 108-129. Affinity cross-linking of 125I-hGH to its receptor was not duplicated with 125I-hGH (L) 108-129. No other GH peptides or insulin competed for binding of 125I-hGH 108-129. Scatchard analysis indicated a Kd of 5.2 nM with 5.6 x 10(5) binding sites/cell for hGH (L) 108-129. These studies indicate that hGH (L) 108-129, a sequence encompassing helix 3 of hGH, acts by binding to a site other than the GH receptor and evokes high mitogenic responses.

3T3 Cells↗
PubMed1993

Serotonergic lesions decrease mu- and delta-opiate receptor binding in discrete areas of the hypothalamus and in the midbrain central gray.

Serotonergic nerve terminals in the brain were lesioned by intraventricular infusion of the selective neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) and levels of mu- and delta-opiate binding were measured in brain areas implicated in reproductive behavior and gonadotropin secretion. The lesion decreased mu-receptor binding in the preoptic area (mPOA) and the midbrain central gray, while delta-receptor binding was decreased in the mPOA and the dorsomedial nucleus of the hypothalamus. Hypothalamic serotonergic lesions also attenuated morphine inhibition of female sexual behavior. These results indicate the existence of serotonergic-opiate interactions in select regions of the brain and suggest that these interactions may be important in the regulation of lordosis behavior.

Animals↗
PubMed1993

Pargyline-induced increase in serotonin levels: correlation with inhibition of lordosis in rats.

The effect of intrahypothalamic infusion of the monoamine oxidase inhibitor pargyline on lordosis behavior and monamine levels in the preoptic area and hypothalamus was examined. Progesterone-facilitated lordosis was blocked by pargyline in half the treated rats. The inhibition of lordosis was correlated with increases in serotonin and dopamine levels in the ventromedial nucleus of the hypothalamus and serotonin levels in the arcuate nucleus-median eminence when compared to controls or pargyline-treated rats with high levels of lordosis responding. Changes in norepinephrine levels were not correlated with changes in behavior. The results provide further evidence for an inhibitory role of basomedial hypothalamic serotonin in the control of female sexual behavior.

Animals↗
PubMed1993

A potential complication of early blood patching following inadvertent dural puncture.

Early blood patching following inadvertent dural puncture has been recommended by some workers. We describe a case in which this resulted in the injection of blood contaminated with group B haemolytic streptococci. Although no complications ensued, the potential for injecting bacteraemic blood following parturition limits the application of this technique in obstetric patients.

Journal Article↗
PubMed1992

A microcomputer program for determining turnover rates during non-steady state conditions: application to monoamine turnover.

A program to calculate the turnover rate of monoaminergic neurotransmitters was written for use on microcomputers. The program is based on non-steady state models, i.e., measuring the rate of change of levels of neurotransmitters or their metabolites after pharmacological inhibition of synthetic or degradative enzymes. Methods have been developed to estimate monoamine turnover by measuring the rate of decrease of catecholamine levels after treatment with alpha-methyl-p-tyrosine (AMPT), a tyrosine hydroxylase inhibitor, or the increase in serotonin levels after pargyline, an inhibitor of monoamine oxidase. This program is suitable for examining either linear increases or exponential decreases in monoamine levels. The program has been tested in our laboratory for the determination of serotonin, dopamine or norepinephrine turnover after hormonal or pharmacological manipulations. The program is readily adaptable for calculation of the turnover rate of other biological molecules under non-steady state conditions.

Biogenic Monoamines↗
PubMed1992

Neonatal alloimmune thrombocytopenia due to anti-HPA-5b (Br(a), Zav(a), Hca): the importance of third-generation platelet antibody detection techniques, a case report.

Investigation of the maternal serum in a case of suspected alloimmune neonatal thrombocytopenia by conventional, second-generation platelet serological assays (platelet radioactive antiglobulin test [PRAT], platelet suspension immunofluorescence test [PSIFT] and solid-phase adherence assay (SPAA, 'Capture-P') demonstrated only the presence of HLA class-I antibodies of limited specificities: no platelet-specific antibodies were detectable. The use of a third generation, glycoprotein capture assay (monoclonal antibody-specific immobilization of platelet antigens, MAIPA) revealed the additional presence of anti-HPA-5b with a titre of 1 in 32. Despite this relatively high titre, and the fact that it was able to induce a prolonged thrombocytopenia, this antibody was not detectable by conventional assays. In view of these findings we conclude that the use of MAIPA is essential when investigating cases of suspected alloimmune neonatal thrombocytopenia.

Abnormalities, Multiple↗
PubMed1992

Positive correlation between proopiomelanocortin and tyrosine hydroxylase mRNA levels in the mediobasohypothalamus of ovariectomized rats: response to estradiol replacement and withdrawal.

We have investigated putative dopaminergic regulation of opiomelanotropinergic activity in the arcuate/periarcuate mediobasohypothalamus (MBH) by assessing the changes in MBH tyrosine hydroxylase (TH; rate-limiting enzyme in catecholamine synthesis) and proopiomelanocortin (POMC; opiomelanotropin precursor) mRNA levels under conditions in which endogenous tuberinfundibular dopaminergic activity exhibits marked changes. Adult Sprague-Dawley rats were sacrificed at 09.00 and 15.00 h, and individual MBH POMC and TH cytoplasmic mRNA levels were simultaneously quantified by multiplex solution hybridization-RNase protection assay with protected fragments separated by polyacrylamide gel electrophoresis. In ovariectomized (OVX) rats treated for 3 days with low-dose estradiol (E2) implants (resulting in 18 +/- 4 pg E2/ml serum), the MBH levels of POMC and TH mRNAs were approximately 17 and 31% lower than those measured in OVX controls, respectively. In OVX rats implanted for 20 days with larger E2 implants (99 +/- 9 pg E2/ml serum), POMC and TH mRNA levels were approximately 29 and 41% lower than in OVX controls, respectively. Additional groups were exposed to the higher E2 dose for 20 days and then killed 10 or 20 days after removal of the E2 implant. In these rats, POMC mRNA levels rebounded to the same level seen in OVX controls, while TH mRNA levels even exceeded control values by 22-27%. TH and POMC mRNA levels did not change significantly between 09.00 and 15.00 h, except 10 days after removal of the E2 implants, when 09.00 h POMC mRNA levels were higher than the 15.00 h levels. MBH POMC and TH mRNA levels were positively correlated with each other within individual animals. This correlation is maintained when both POMC and TH mRNA levels are suppressed in response to both 3-day low-dose and 20-day high-dose E2 treatment. However, although rat MBH opiomelanotropinergic and tuberoinfundibular dopaminergic mRNA biosynthesis thus appear to be positively correlated, the coregulation or functional interactions of these two neuronal systems remain to be determined.

Amino Acid Isomerases↗
PubMed1992

Growth hormone and fibronectin expression in 3T3 preadipose cells.

In the present study we focused on the relationship between GH action and the extracellular matrix in 3T3-F442A preadipose cells. Results from Northern blotting indicated that in serum-free medium, the presence of 2 nM met-human GH down-regulated levels of fibronectin messenger RNA by approximately 40, 60, and 70% as compared with control levels on days 1, 2, and 4, respectively. GH-dependent reduction of levels of collagen alpha 1(I) mRNA expression occurred later and was less pronounced than effects on levels of fibronectin mRNA, suggesting a specificity in the matrix-altering function of GH. Western blot analyses and immunoprecipitation studies revealed that between 2 and 5 days of culture, matrix-associated fibronectin protein was reduced 70 to 90% by GH treatment. Down-regulation of fibronectin protein expression by met-human GH was dose-dependent between 2 and 0.02 nM. The presence of 2 nM insulin or insulin-like growth factor-1 promoted a 30-40% increase in fibronectin levels compared to control cells. The GH-promoted down-regulation of fibronectin expression was eliminated by concomitant addition of insulin. These data demonstrated that GH effects on matrix-associated fibronectin expression were independent of, and in opposition to, effects promoted by insulin and insulin-like growth factor-1. Treatment of culture dishes with fibronectin or collagen inhibited GH-stimulated adipogenesis 50 and 80%, respectively, compared with controls, as judged by levels of glycerol-3-phosphate dehydrogenase activity. Thus, composition of the extracellular matrix was a critical factor in GH-induced adipogenesis of 3T3-F442A fibroblasts. Our results demonstrate that GH action in 3T3 preadipose cells is intimately coupled to the biology of extracellular matrix.

3T3 Cells↗
PubMed1992

Thrombocytopenia in malaria.

The relationship between platelet counts and platelet bound (direct) or platelet directed (indirect) serum antibody concentrations was studied in 17 patients with Plasmodium falciparum malaria and 12 patients with P. vivax malaria. Platelet counts rose with recovery from infection from 196 +/- 84 x 10(9)/l (mean +/- SD) and 195 +/- 34 x 10(9)/l to 319 +/- 99 and 283 +/- 62 x 10(9)/l respectively (p less than 0.002), but there was no relationship between either absolute platelet count or changes in counts and either indirect or direct platelet antibody levels. These findings suggest that a non-immunologically mediated mechanism is involved in the pathogenesis of thrombocytopenia in malaria.

Adolescent↗
PubMed1991

Effect of a year-long primary care clerkship on graduates' selection of family practice residencies.

This report compares the selection of family practice residencies from 1981 through 1989 by graduates trained at two campuses of the State University of New York (SUNY)-Health Science Center at Syracuse College of Medicine, at other New York State campuses, and at all U.S. medical schools. One of the SUNY-Syracuse cohorts comprised the students who had completed all their work at the Syracuse campus, while the other comprised those who had spent their third year at the campus in Binghamton, which has a year-long, half-day-a-week primary care clerkship that is not available at the Syracuse campus, which has no primary care clerkship. Comparison of the proportions of the graduates in the two SUNY-Syracuse cohorts who chose family practice residencies, and comparisons of the proportions of graduates from other New York state schools and from all U.S. schools who selected family practice residencies during the same nine-year period, indicate that the proportion of students trained during their third year at the Binghamton campus who selected family practice residencies was significantly greater (21%; p less than .001). Additional investigation is required to determine whether the year-long nature of the required clerkship affects graduates' choices more than does the primary care content of the clerkship.

Career Choice↗
PubMed1991

'Partial D' women with anti-D alloimmunization in pregnancy.

We report five women with Rh 'partial D' who were found to have anti-D during pregnancy. Two patients were category IVa, their red cells typing as Go(a+); one was category VI; and two had a 'partial Du' which could not be categorized. The maternal anti-D concentration increased during four of the eight pregnancies studied, but none reached significant levels. Three of six D-positive cord blood samples had a positive direct antiglobulin test (DAGT). Although one baby became jaundiced, no treatment was required. The policy in the Oxford Region for the management of patients with a weak expression of D is outlined.

England↗
PubMed1990

Dental laboratory work authorization forms: a survey.

Dental laboratory work authorization forms embrace a diversity of material content and design. This survey examined 51 dental laboratory work authorization forms and delineated each content item and format features into a frequency percentage. This information has a high potential for use in changing prospective dental laboratory and authorization form design.

Dental Records↗