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Biomedical subjects

D C Moore

Publications and source records attributed to D C Moore.

At least 19 recordsLinked to original sources
PubMed1997

Restoration of pedicle screw fixation with an in situ setting calcium phosphate cement.

STUDY DESIGN: Pedicle screws were pulled out of human cadaveric vertebrae before and after augmentation with polymethylmethacrylate or in situ-setting calcium phosphate cement. The fixation strength of screws augmented with calcium phosphate cement was compared with that of screws augmented with polymethylmethacrylate. OBJECTIVES: To determine whether a new in situ-setting calcium phosphate cement might be suitable for augmenting the fixation of pedicle screws. The principle objective was to compare the pull-out resistance of screws augmented with calcium phosphate cement with the pull-out behavior of screws augmented with polymethylmethacrylate. Polymethylmethacrylate augmentation was chosen as the standard because of its current clinical use. Five types of screws were tested to determine whether screw design had an effect on the efficacy of augmentation. SUMMARY OF BACKGROUND DATA: Although many factors affect the pull-out resistance of pedicle screws, a key determinant of their performance is the strength of their attachment to the spine. In elderly, osteopenic patients, the screw-bone interface is especially at risk for stripping during insertion or pull-out after surgery. In these patients, polymethylmethacrylate has been used to augment pedicle screw fixation, although its use is not without risk. In situ-setting calcium phosphate cements may provide an alternative to polymethylmethacrylate in this application. Like polymethylmethacrylate, calcium phosphate cements can be injected into the prepared screw hole. They have the added advantage of being resorbed and replaced during healing and normal bone remodeling. METHODS: Thirty human lower lumbar vertebrae (L3-L5) were implanted bilaterally with one of five types of pedicle screws (n = 6 for each screw type). The screws were pulled out 3.0 mm at 0.25 mm/sec with a servohydraulic materials testing machine. The 3.0-mm pull-out distance, which was slightly longer than one thread pitch, was designed to strip the screw-bone interface but to leave the pedicle otherwise intact. After the initial testing, the screws in each vertebrae were removed, and the screw tracks were filled with 2.0 cc of polymethylmethacrylate (one side) or calcium phosphate cement (contralateral side). After augmentation, the screws were reinserted, and the cements were allowed to harden for 24 hours. Postaugmentation testing followed the protocols for preaugmentation testing, and the pull-out resistance of screws augmented with calcium phosphate cement was compared with the pull-out resistance of screws augmented with polymethylmethacrylate. RESULTS: Mechanically, calcium phosphate cement compared favorably with polymethylmethacrylate for augmenting pedicle screws. Both restored the strength of the screw-bone interface: across all screw types, the average increase in pull-out strength was 147% with polymethylmethacrylate augmentation and 102% with calcium phosphate cement. There were no significant differences because of screw type with either type of augmentation. CONCLUSIONS: The in situ-setting calcium phosphate cement investigated in this study compared favorably with polymethylmethacrylate in a single-cycle, pull-out test of augmented pedicle screws in senile trabecular bone. With further evaluation, this cement may offer an alternative to polymethylmethacrylate for the enhancement of pedicle screw fixation clinically.

Bone Cements↗
PubMed1996

The role of pediculolaminar fixation in compromised pedicle bone.

STUDY DESIGN: This in vitro study analyzed the effects of a supralaminar hook on pedicle screw fixation in compromised pedicle bone. OBJECTIVES: To determine the ability of pediculolaminar fixation to restore pedicle screw pull-out strength after stripping of senile pedicle bone. SUMMARY OF BACKGROUND DATA: Despite improvements in pedicle screw design, the bone-screw interface remains the "weakest link" in pedicle screw fixation. This interface is especially vulnerable in osteoporotic bone previously instrumented pedicles, and at the ends of long instrumentation constructs. METHODS: Side-to-side testing between a pedicle screw and a pedicle screw supplemented with a supralaminar hook (pediculolaminar fixation) was performed in human cadaveric lumbar vertebrae. Comparisons were made for intact and compromised pedicle bone. RESULTS: Pediculolaminar fixation restored 89% of intact pedicle screw pull-out strength whereas the pedicle screw alone restored only 19% of intact pull-out strength. The role of pediculolaminar fixation was greatest in weaker bone. Significant differences were noted in energy to failure and post-failure energy. In intact bone, the pediculolaminar construct did not increase pull-out strength or energy to failure, although it did have a greater post-failure energy. CONCLUSIONS: Pediculolaminar fixation can augment pedicle screw fixation in pedicle bone compromised by previous stripping or significant osteoporosis or both.

Aged↗
PubMed1996

Natural course of 'subclinical' hypothyroidism in childhood and adolescence.

OBJECTIVES: To describe the natural course of "subclinical" hypothyroidism due to autoimmune thyroiditis in children and adolescents, and to determine whether, like euthyroid childhood autoimmune thyroiditis, it would also run a more benign course in this age group than in adults. DESIGN: Case series. SETTING: Pediatric endocrine clinic in a tertiary medical center. PATIENTS: Eighteen patients (age range, 5 to 19 years) with juvenile autoimmune thyroiditis and an initially elevated serum thyrotropin (thyroid-stimulating hormone) concentration were followed up from documentation of the elevated serum thyrotropin concentration for a mean of 5.8 years. Eleven patients never received treatment, and seven were followed up after discontinuation of therapy. MAIN OUTCOME MEASURES: Changes in the serum thyrotropin and thyroxine concentrations and thyroid gland size, as well as signs and symptoms of hypothyroidism, were monitored throughout the observation period. RESULTS: The mean duration of observation during which the patients did not receive any therapy was 47.3 months. At the end of the observation period, seven patients were euthyroid, 10 continued to have an elevated serum thyrotropin concentration with a normal serum thyroxine concentration, and one became hypothyroid. CONCLUSIONS: "Subclinical" juvenile hypothyroidism may be a benign and remitting process in many older children and adolescents. In view of the undefined risks of levothyroxine sodium therapy, it may be possible to follow up expectantly selected younger patients with a minimally elevated serum thyrotropin concentration, rather than to treat them empirically.

Adolescent↗
PubMed1996

Anatomy of the palmar cutaneous branch of the median nerve: clinical significance.

A detailed anatomic, histologic, and immunohistochemical study of the palmar cutaneous branch of the median nerve (PCBMN) and its distal arborization was undertaken on 12 fresh human cadaveric hands. Small unmyelinated fibers terminated in the superficial loose connective tissue of the transverse carpal ligament. There were no nerve fibers detected in the deep, dense collagen aspect of the ligament. Based on these findings, during open carpal tunnel release, the skin incision should be placed along the axis of the ring finger to avoid injury to the superficial branches of the PCBMN. When open release is used, the very small terminal branches in the loose tissue of the ligament will be transected; this may in part be responsible for postoperative soft tissue pain. For endoscopic releases, some risk for transection of the main trunk of the PCBMN at the proximal incision exists. Repeated passes of the endoscopic knife should be avoided in an attempt to limit damage to the small fibers in the superficial aspect of the ligament.

Aged↗
PubMed1996

Detection of human papillomavirus in cervical biopsies of summer camp ROTC cadets with abnormal papanicolaou smears.

STUDY OBJECTIVE: Human papillomavirus (HPV) infections may be the most common sexually transmitted disease (STD) among adolescents and young adults. A strong association exists for certain "high-risk" HPV-type cervical infections and subsequent evolution of cervical cancer and its precursor lesions. The objective of this study was to detect HPV in cervical biopsies of reserve officer training corps (ROTC) cadets attending a regional summer camp who had abnormal screening Papanicolaou (Pap) smears and to better define the spectrum of HPV oncogenic risk types for this population. It was hypothesized that HPV would be detected in the majority of cervical biopsies in keeping with the evolving concept of cervical cancer and its precursors as an STD and the central role of HPV in its development. DESIGN: On arrival for summer military camp training, college women cadets underwent physical examinations that included pelvic examinations for Pap smears. Study participants completed confidential questionnaires after informed consent was obtained. Subjects, who had abnormal Pap smears as defined by reports of atypical squamous cells of undetermined significance (ASCUS) or low- or high-grade squamous intra-epithelial lesions (LGSIL or HGSIL), underwent colposcopic evaluations with cervical biopsies. Subsequently, biopsies were processed for detection of HPV-specific DNA by gel electrophoresis, chemiluminescent oligonucleotide probing, and DNA-RNA hybridization methods after polymerase chain reaction (PCR) amplification. PARTICIPANTS: All female summer camp enrollees presented to the Madigan Army Medical Center Gynecology Clinic for complete physicals before the onset of the training program and were solicited for study inclusion. MAIN OUTCOME MEASURES: All colposcopic biopsy specimens were evaluated for the presence of HPV DNA and subtyped if positive. RESULTS: Representing 42 states, 95% (332) of eligible subjects participated. Mean age was 21.9 years. Racial composition included 70% white, 16% black, 4% Hispanic, 4% Asian, and 6% "other." Eighty-five percent had a history of hetero-sexual activity, with 17.7 years as the mean age at onset. Of the subjects, 12.6% reported a previous diagnosis of a sexually transmitted disease, and 7.8% (26 of 332) had abnormal Pap smears. Of these, colposcopic biopsy results were available for 25 of the 26 abnormal Pap smears. Ninety-six percent (24 of 25) of the colpobiopsies had detectable HPV. Eighty-eight percent (22 of 25) of the subjects with abnormal Pap smears had concurrent abnormal biopsy results. All of these had detectable HPV, confirmed by three different methods, and 29% had dual HPV infection. Sixty percent had "intermediate" or "high-risk" types identified by specific genotyping, 8% had "low-risk" types, and 28% had nontypable HPV. CONCLUSIONS: The data confirm that abnormal Pap smears in this young adult college population are almost always associated with HPV infection, a significant proportion of it being other than low-risk types. The prognostic significance of type-specific cervical HPV infection still needs to be better defined in relation to potential cofactors and host immune response. However, clinicians who provide primary gynecologic care to adolescents and young adults should be aware of the high correlation between abnormal Pap smears and HPV cervical infection and should follow up the patient with the potential risk in mind.

Adolescent↗
PubMed1995

Sunlight--can it prevent as well as cause cancer?

Excessive exposure to sunlight is known to damage the skin. However, the emphasis of most studies has been on the consequences of sunlight exposure to fair-skinned individuals, and the situation of people with heavy skin pigmentation residing in, or migrating to, geographic locations with limited sunlight incidence has been largely neglected. Recent epidemiological studies suggested the hypothesis that sunlight deprivation, and the associated reduction in the circulating levels of vitamin D3 (vit D3) derivatives may lead to the increased incidence of the carcinomas of the breast, colon, and prostate. Two endocrine pathways may mediate these effects. The pineal function can potentially be involved, but the formation of vit D3 derivatives is gaining credibility as a mechanism for the retardation of cancer progression. Evidence is accumulating that such compounds, e.g., 1,25-dihydroxyvitamin D3 (1,25D3) induce differentiation of several neoplastic cell types, arrest or retard their proliferation, and act as chemopreventive agents in animal carcinogenesis. We also propose that the antineoplastic effects of vit D3 derivatives are exerted at several steps in tumor progression and that immunomodulating effects of 1,25D3 may contribute to these effects of sunlight. The recent findings that common cancers, e.g., carcinoma of the prostate and the breast, behave more aggressively in black Americans than in white Americans may be explained on this basis. Although more data are needed on the effects of sunlight on the circulating levels of 1,25D3, a corollary of this hypothesis is that there should be no broad condemnation of moderate sunlight exposure, as it may be available in insufficient amounts to some Americans.

Animals↗
PubMed1995

Acclimation of a non-indigenous sub-Arctic population: seasonal variation in thyroid function in interior Alaska.

Total, as well as free, T4 and T3 levels were obtained over four seasons for young male infantry soldiers assigned to interior Alaska. Significant seasonal variations were found in both T3 and T4. Total T4 and T3 levels were highest in winter, while free T4 and T3 levels were highest in early spring. Correlations with melatonin levels from a concurrent study showed an association between late day (17.00) mean spot melatonin levels during the preceding summer and T3 levels in winter and spring. Differences in seasonal T4 and T3 levels between indigenous and newly arrived people in the sub-Arctic may be related not only to cold acclimation but also to light.

Acclimatization↗
PubMed1994

Hypothalamic hamartoma in oral-facial-digital syndrome type VI (Váradi syndrome).

Oral-facial-digital syndrome (OFDS) type VI (Váradi syndrome) is an autosomal recessive trait of orofacial anomalies, cerebellar dysgenesis, and polysyndactyly. Developmental anomalies of the posterior fossa, including cerebellar hypoplasia and variants of the Dandy-Walker complex, are the most common central nervous system malformations reported in patients with this syndrome. We report hypothalamic hamartoma, supernumerary maxillary incisor, and precocious puberty in a boy with OFDS type VI. We propose that hypothalamic hamartoma is an occasional manifestation of OFDS type VI.

Genes, Recessive↗
PubMed1993

Body image and eating behavior in adolescents.

Approximately two-thirds of adolescent girls at any age are dissatisfied with their weight, the proportion increasing with actual weight. Slightly more than half of all girls are dissatisfied with the shape of their bodies, an attitude which also is positively correlated with body weight. Girls are most likely to be distressed about excess size of their thighs, hips, waist and buttocks, and inadequate size of their breasts. Those who are dissatisfied with their bodies are more likely to engage in potentially harmful weight control behaviors, such as dieting, fasting, self-induced vomiting, diuretic use, laxative use and diet pill use. Those who diet are more likely to begin in early adolescence, to be white than black, to be of higher socioeconomic status, to engage in other eating-related practices and to have a poor body image and self esteem. Boys who are underweight are most likely to be dissatisfied with their weight and many with normal weight wish to weigh more. Approximately one-third of boys are dissatisfied with their body shape, desiring larger upper arms, chest and shoulders. Dieting and purging are less likely than exercise to be chosen by boys as methods of weight control. Dieting among boys is more likely to be associated with increased body weight and some sports, such as wrestling. Body consciousness and altered body image are widespread among adolescents, and may be associated with potentially harmful eating practices in both sexes, but more so in girls.

Adolescent↗
PubMed1992

Inhibition by 1,25 dihydroxyvitamin D3 of c-myc down-regulation and DNA fragmentation in cytosine arabinoside-induced erythroid differentiation of K562 cells.

The effect of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on DNA fragmentation, altered expression of the heat shock protein (hsp) 70 gene, and protooncogenes c-myc and c-myb was studied during chemical induction of erythroid differentiation in K562 cells. Preincubation of K562 cells with 1,25(OH)2D3 did not alter the concentration of hemoglobin in cells which did differentiate, but led to a reduction in the accumulation of low molecular weight DNA generated by Ara-C administration. The extent of this reduction was similar to the degree of inhibition of hemoglobin formation in the culture as the whole. Preincubation with 1,25(OH)2D3 had no effect on the increase of hsp 70 gene expression induced by a 48-hr treatment with Ara-C, but prevented the Ara-C-induced down-regulation of the protooncogene c-myc. The protooncogene c-myb was down-regulated after 15 min of treatment with Ara-C, and exposure to 1,25(OH)2D3 prior to Ara-C caused a further down-regulation of its expression. The data suggest that the events associated with erythroid differentiation may be separable into at least two groups; one of these may have an influence on the kinetics of the cell cycle traverse, and the other may be related to the expression of the erythroid phenotype.

Blotting, Northern↗