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Biomedical subjects

W E Roberts

Publications and source records attributed to W E Roberts.

At least 127 records · Page 7Linked to original sources
PubMed1980

Cell kinetics of the initial response to orthodontically induced osteogenesis in rat molar periodontal ligament.

Initial cell kinetics (15 min-20 h) of mechanically induced osteogenesis was studied with 3H-thymidine (3H-Tdr) autoradiography. Continuous orthodontic force elicited a three-stage cell proliferative reaction within rat molar periodontal ligament (PDL): (a) brief, generalized response, characterized by a burst of mitotic activity from 75 min to 2 h and a cyclic change (decrease, increase and return to control levels) in percent labeled cells from 15 to 2 h; (b) transient, generalized response, involving an increased mitotic index (MI) from 2 to 13 h, associated with elevated labeling index (LI) from 6 to 12 h; and (c) sustained, localized osteogenic response (12 h to several days) in which cell proliferation was confined primarily to the immediate area of new bone formation. These results suggest that the initial effect of mechanical perturbation on relatively quiescent adult bone progenitor cells is a generalized, transient release of G1 and G2 blocked cells. This response may correlate clinically with the regional acceleration phenomenon (RAP), which follows bone trauma, fracture, or surgical injury.

Animals↗
PubMed1979

Circadian periodicity of the cell kinetics of rat molar periodontal ligament.

Circadian periodicity of DNA synthesis (S) phase and mitosis over a complete 12-hour light/12-hour dark cycle was studied in rat molar periodontal ligament (PDL) with 3H-thymidine autoradiography. Maximum percent labeled cells was at 10 A.M. in all regions, and mean labeling (24-hour average) was 1.44, 0.93, and 1.46 percent for the crest, midroot, and apical areas of the PDL, respectively. Maximum percent mitotic figures were also at 10 A.M. in all areas studied, and the mean number of mitoses averaged over 24 hours was 0.19, 0.12, and 0.14, respectively for crest, midroot, and apical areas. Ratios of mean labeling and mitotic indices were 7.58, 7.75, and 10.43 from crest to apex. Duration of mitosis and S phase were estimated at 1.2 and 9 hours, respectively. Analysis of data suggested that stress/strain within the PDL, associated with masticatory function, has a regional influence on duration of S phase, mitotic rate, and percentage of cells in the S phase. These results help define an in vivo experimental model for assessing the PDL cellular response to biomechanically defined force systems. Clinical implications are discussed.

Animals↗
PubMed1975

Cell population dynamics of periodontal ligament stimulated with parathyroid extract.

Young adult rats were injected with parathyroid extract (PTE). Periodontal ligament (PDL) adjacent to a previously resorbing alveolar bone surface was divided into four zones number I to IV, from bone to cementum. Zones I and IV were within 25 mmu of the bone and cementum surfaces, respectively, while a line bisecting the center of the PDL separated Zones II and III. A net increase of about 16 total nuclei in all zones was observed during the first five hours after PTE administration. Since local mitosis accounted for no more than two nuclei, approximately 14 cells apparently migrated into the area. Over the first five hours Zones I and II combined showed a 21-cell increase, being apparently the sole recipients of cells migrating into the field (14) plus approximately seven more from Zone III, which lost cells during the time period. The concurrent histological observation in Zone II, of increased intravascular monocytes and perivascular macrophages during the first five hours, suggests cells are migrating into Zone II via vascular channels. The data suggest two sources for increased PDL cellularity associated with stimulated osteoclast histogenesis: (1) local PDL cellular proliferation and (2) influx of migrating cells (probably through vascular channels) during first five hours after PTE.

Animals↗
PubMedDate not supplied

Shoulder dystocia and operative vaginal delivery.

Our objective was to determine the factors involved in the development of shoulder dystocia in association with operative vaginal delivery. In this prospective study, patients who were candidates for operative vaginal delivery were randomized either to forceps (N = 315) or vacuum with M-cup (N = 322) and timed from initial placement of instrument to final delivery. Data were gathered prior to and after instrumental delivery. Statistics used were Pearson chi square, Fisher's exact, analysis of variance, and multiple logistic regression. There were a total of 21 patients with shoulder dystocia in both groups (3.3% incidence). Discriminant factors that did nor meet significance included use of epidural analgesia (P = .12), station (P = .99), previous vaginal delivery (P = .99), fetal gender (P = .54), indication for operative vaginal delivery (P = .63), > 45 degrees rotation (P = .68), use of episiotomy (P = .62), maternal weight (P = .26), and maternal diabetes (P = .08). Nearly attaining significance in univariate analysis was randomization to vacuum (P = .052). Significant factors included gestational age (P = .03), time required to effect delivery (P = .007), and birthweight (P = .0001). When these factors were subjected to stepwise multiple logistic regression, three factors remained as significant associations with shoulder dystocia: randomization to vacuum (P = .04), time for delivery (P = .03), and birthweight (P = .0001). In this operative vaginal delivery trial, shoulder dystocia was strongly associated with large fetal size, longer time to delivery, and the use of vacuum for delivery.

Birth Injuries↗
PubMedDate not supplied

Detection of intra-amniotic infection by gas-liquid chromatography.

The use of gas-liquid chromatography to detect short-chain organic acids in the amniotic fluid of patients with amnionitis has been previously described. Most of the studies describe patients in the early third trimester with such infections. The purpose of the current study was to confirm the correlation of infection with increased production of organic acids and to assess the effect of gestational age on the presence of these short-chain fatty acids in the amniotic fluid. Six patients with confirmed chorioamnionitis were used as positive control subjects. Seventy-two patients at various gestational ages from 18 to 42 weeks with negative Gram's stain and culture results from the amniotic fluid were used as negative control subjects. The data revealed an increased production of organic acids, particularly pyruvic, oxalic and succinic, in patients with amnionitis regardless of gestational age. Interestingly, patients with noninfected amniotic fluid also revealed an increase in the concentrations of volatile organic acids between 27 and 32 weeks' gestation. It appears from this study that previous results correlating chorioamnionitis with an increased production of organic acids in the amniotic fluid may have been confounded by gestational age.

Amniotic Fluid↗
PubMedDate not supplied

Mechanical response to functional loading around the threads of retromolar endosseous implants utilized for orthodontic anchorage: coordinated histomorphometric and finite element analysis.

A 3-dimensional bone-implant finite element model was created. The objective was to further investigate the mechanical environment of cortical bone adjacent to the threads of a retromolar endosseous implant used for orthodontic anchorage to mesially translate mandibular molars in response to normal functional loading. This study emphasizes the stress invariants around and between the threads of the implant for future comparison to histomorphometric data from an ongoing clinical study. A strong stress pattern change was found immediately around the implant, which was reflected by a moderate change of stresses between the threads and a significant increase in stress at the tips of the threads.

Compressive Strength↗
PubMedDate not supplied

A manpower study of orthodontic specialists for the State of Indiana: a preliminary report.

To develop current manpower data and project the future need for orthodontic specialists, a survey questionnaire was mailed to Indiana orthodontists (90 percent response). In addition, a telephone survey of orthodontic receptionists was conducted during the same time period (95 percent response). In general, orthodontists perceived a lower state of business than did their staffs. About 77 orthodontists are expected to retire by the year 2010. Based on maintaining the adjusted potential patient-to-orthodontist ratio (increasing adult and declining children in the population), it was projected that only about 66 (86 percent) of the retirees require replacement. To maintain manpower at eight percent fewer orthodontists than are currently in practice, three to four new orthodontists per year will be needed in Indiana over the next two decades.

Chi-Square Distribution↗
PubMedDate not supplied

State findings on pesticide residues in food--1988 and 1989.

Findings of pesticide and related chemical residues are presented for 27,065 samples of foods collected and analyzed in 10 state food laboratories over 1988 and 1989 (fiscal years (FY) 88 and 89). These laboratories conduct food regulatory programs compatible with national programs of the U.S. Food and Drug Administration. Of the findings, 6325 samples contained detectable levels of 1 or more pesticide analytes and 418 (or 1.5%) of the total number of samples were deemed to be of regulatory significance.

Food Analysis↗
PubMedDate not supplied

Remodeling of devitalized bone threatens periosteal margin integrity of endosseous titanium implants with threaded or smooth surfaces: indications for provisional loading and axially directed occlusion.

Microradiographic analysis of endosseous implants in dogs revealed similar patterns of healing and remodeling of the alveolar process adjacent to both types of implants. However, substantial differences were noted in bone morphology both at the periosteal margin and within the cervical half of the interface. The grooves of the threaded implant were filled with relatively immature composite bone. In contrast, the smooth cylindrical implant was bordered by a dense cortex of relatively avascular bone except for a 1 mm at the periosteal margin that was remodeled and vital. For both types of implants, areas of apparently nonvital, hypermineralized bone were remodeling near the interface and in subperiosteal areas of the alveolar process. The integrity of the periosteal margin may be threatened by undermining remodeling of adjacent bone during the late healing period. The cervical (alveolar) crest and particularly the periosteal margin of the interface are high stress bearing areas. If overloaded, these areas are subject to "cervical cratering," a common prelude to implant failure. The results of this study suggest that axially directed occlusion and a progressive loading scheme are indicated.

Bone and Bones↗
PubMedDate not supplied

State programs for pesticide residues in foods.

Two U.S. data collection and dissemination programs, FEEDCON and FOODCONTAM, are described. FEEDCON provides information on contamination levels in animal feeds of toxic chemical residues (pesticides, industrial chemicals, heavy metals, mycotoxins, natural plant toxins, salmonella, and therapeutic drug cross-contaminations). FEEDCON data are collected from approximately 40 state feed regulatory agencies, feed manufacturers, and related groups who subscribe ($100-$200 per year) to the program, which is sponsored by the Association of American Feed Control Officials. FOODCONTAM provides similar information, but is limited to pesticides, heavy metals and industrial chemicals (polychlorinated and polybrominated biphenyls, etc.) in human foods. Both programs have been developed and initiated under U.S. Food and Drug Administration contracts with the Mississippi State Chemical Laboratory. Program structures of both are outlined conceptually, and FOODCONTAM is described in detail. FOODCONTAM data-sharing program development is essentially complete, but expansion by incorporating FDA data with State Laboratory data is nearing reality.

Food Contamination↗
PubMedDate not supplied

Treatment for hyperemesis gravidarum in the home: an alternative to hospitalization.

Our objective was to determine whether medical therapy in the home for patients with hyperemesis gravidarum is safe, efficacious, and cost effective compared with hospitalization. In this retrospective, matched control study 50 women with hyperemesis were treated in the home and were matched for gravidity, gestational age, and weight loss from prepregnancy weight with 47 patients who were hospitalized for traditional treatment. Both groups had similar intravenous fluid and medical support until they could tolerate adequate oral intake. Women in the home had 9.7 +/- 8.0 days of intravenous therapy compared with 9.5 +/- 6.2 days in hospitalized patients (not significant). The mean percent of weight loss at initiation of therapy was similar in both groups (4.6% +/- 5.7% vs 4.5% +/- 6.1%, not significant). The mean weight change during therapy in the home group was + 1.0 +/- 4.3 pounds compared with +1.2 +/- 8.6 pounds in the hospitalized group (not significant). The only complication was infiltration of the intravenous site, the occurrence of which was similar in the two groups (40% vs 57%, not significant). At discontinuation of therapy 90% of the home patients no longer required any supportive therapy; 10% (n = 5) required hospitalization because of relapse. The cost of therapy was significantly lower for patients in the home group ($708 +/- $533 vs $2701 +/- $1717, p < 0.001). These data show that management of hyperemesis in the home is both safe and efficacious. Furthermore, successful therapy can be achieved in the home at a significantly reduced cost.

Adult↗