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At least 595 records · Page 33Linked to original sources

PubMed1999

Evaluation of apical root resorption following extraction therapy in subjects with Class I and Class II malocclusions.

The purpose of this study was to determine the amount of root resorption during orthodontic treatment, and to examine the relationship between tooth movement and apical root resorption. Twenty-seven Class I and 27 Class II patients treated with edgewise mechanics following first premolar extractions were selected. The following measurements were made on the pre- and post-treatment cephalograms: upper central incisor to palatal plane distance, the inclination of upper central incisor to the FH and AP planes, the perpendicular distances from the incisor tip to the AP and PTV planes, and incisor apex to PTV. The amount of apical root resorption of the maxillary central incisors was determined for each patient by subtracting the post-treatment tooth length from the pre-treatment tooth length measured directly on cephalograms. Intra-group differences were evaluated by the Student's t-test and inter-group differences by the Mann-Whitney U-test. For correlations the Pearson correlation coefficient was used. The results show that there was a mean of approximately 1 mm (P < 0.01) of apical root shortening in Class I patients, but in Class II division I subjects the mean root resorption was more than 2 mm (P < 0.001). The inter-group differences were statistically significant. No significant correlations were found between the amount of apical root resorption and tooth inclination, or the duration of active treatment.

Adolescent↗

PubMed1996

The decision to extract: part II. Analysis of clinicians' stated reasons for extraction.

In a recently reported study, the pretreatment records of each subject in a randomized clinical trial of 148 patients with Class I and Class II malocclusions presenting for orthodontic treatment were evaluated independently by five experienced clinicians (drawn from a panel of 14). The clinicians displayed a higher incidence of agreement with each other than had been expected with respect to the decision as to whether extraction was indicated in each specific case. To improve our understanding of how clinicians made their decisions on whether to extract or not, the records of a subset of 72 subjects randomly selected from the full sample of 148, have now been examined in greater detail. In 21 of these cases, all five clinicians decided to treat without extraction. Among the remaining 51 cases, there were 202 decisions to extract (31 unanimous decision cases and 20 split decision cases). The clinicians cited a total of 469 reasons to support these decisions. Crowding was cited as the first reason in 49% of decisions to extract, followed by incisor protrusion (14%), need for profile correction (8%), Class II severity (5%), and achievement of a stable result (5%). When all the reasons for extraction in each clinician's decision were considered as a group, crowding was cited in 73% of decisions, incisor protrusion in 35%, need for profile correction in 27%, Class II severity in 15% and posttreatment stability in 9%. Tooth size anomalies, midline deviations, reduced growth potential, severity of overjet, maintenance of existing profile, desire to close the bite, periodontal problems, and anticipation of poor cooperation accounted collectively for 12% of the first reasons and were mentioned in 54% of the decisions, implying that these considerations play a consequential, if secondary, role in the decision-making process. All other reasons taken together were mentioned in fewer than 20% of cases. In this sample at least, clinicians focused heavily on appearance-related factors that are qualitatively determinable by physical examination of the surface structures of the face and teeth. They appear to have made primary use of indicators available on study casts and facial photographs and relatively little use of information that is available only on cephalograms or that involves the application of specialized orthodontic theories.

Adolescent↗

PubMed2001

Eruption of third permanent molars after the extraction of second permanent molars. Part 2: Functional occlusion and periodontal status.

Functional occlusion and periodontal health were investigated after orthodontic treatment that involved extraction of second molars and after eruption of the third molars in 37 patients (25 female, 12 male). The mean age was 21 years 9 months (range, 16 years 1 month-30 years 5 months). The third permanent molars invariably erupted into a position that maintained good functional occlusion. Sixty-three percent of patients had canine guidance in lateral excursion; the remainder of patients had satisfactory group function. There were only 2 non-working side interferences in the sample, 1 from a recently erupted mandibular third molar. The periodontal health of the sample was generally excellent. Plaque score and bleeding on probing was very low (1.7% of sites). Periodontal health around both maxillary and mandibular teeth was extremely good. When attachment loss was assessed, 2238 of 2240 sites were clinically healthy. One patient, who had generally poor oral hygiene, had a 4-mm probing depth interproximally on the maxillary first and third molar contact. There was no correlation between periodontal health and mandibular third molar position. Therefore, both functional occlusion and periodontal health in the sample were good after loss of second permanent molars and eruption of the third molars.

Adolescent↗

PubMed2002

A study of the effectiveness of oral midazolam sedation for orthodontic extraction of permanent teeth in children: a prospective, randomised, controlled, crossover trial.

OBJECTIVES: To assess the safety, effectiveness and acceptability of o:ral midazolam sedation for orthodontic extraction of permanent teeth in children. DESIGN: A prospective, randomised, controlled, crossover trial. METHODS: A total of 26 children aged 10-16 (ASA I), referred for orthodontic extraction of premolar or canine teeth under sedation, were included in the study. Each child required two treatment sessions for the extraction of equivalent teeth on opposite sides of the mouth. Each subject was sedated with either ora midazolam (0.5 mg/kg) or nitrous oxide and oxygen (30%/70%) at the first visit and the alternative form at the second visit. At each visit two teeth were extracted, one upper and one lower. Heart rate, arterial oxygen saturation, respiration rate, sedation and behavioural scores were recorded every five minutes. Overall behaviour, patient acceptance and patient satisfaction were recorded at the end of treatment. RESULTS: Of the 26 children included in the study there were 12 males and 14 females. The mean age was 12.5 years. The mean heart rate and respiratory rate for both groups were similar and within acceptable clinical limits. The lowest mean arterial oxygen saturation levels for nitrous oxide and midazolam sedation were 97.7% and 95.0% respectively. Although midazolam caused greater oxygen desaturation, the range (91%-100%) was within safe limits for conscious sedation. The mean level of sedation was greater in the midazolam group compared with the nitrous oxide group and all but one case completed treatment. A total of 23 patients (88%) said they would be prepared to have ora midazolam sedation again and 17 (65%) actually preferred oral midazolam to nitrous oxide sedation. CONCLUSION: Oral midazolam (0.5mg/kg) appears to be a safe and acceptable form of sedation for 10-16 year old paediatric dental patients.

Administration, Oral↗

PubMed2001

Eruption of third permanent molars after the extraction of second permanent molars. Part 1: Assessment of third molar position and size.

The eruptive path of third molars after extraction of second molars was examined in 63 patients. Panoramic radiographs from the start and the end of active treatment and 3 or more years after treatment were assessed. Study models were used to compare the size of the second and third molars and to assess the final position of the third molars. All third molars erupted; none became impacted. During eruption, maxillary third molar crowns uprighted and maintained their angulation as they came into occlusion. Mandibular third molar crowns continued to upright significantly mesiodistally after active treatment, with space closure the result of horizontal translation rather than mesial tipping. Further uprighting occurred once occlusion was established, although few became as upright as the second molars they replaced. However, mandibular third molar roots were frequently curved distally, thus the third molar crown position was invariably better than the overall tooth angulation would suggest, by 16.5 degrees on average. Model analysis (Richardsons' scoring system) showed 96% of mandibular and 99% of maxillary third molars erupted into a good or acceptable position. Limitations of this scoring system are discussed. The mesiodistal size of third molars was suitable to replace second molars; on average, mandibular third molars were 0.55 mm larger and maxillary third molars were 0.7 mm smaller than second molars.

Adolescent↗

PubMed2004

Gingival endothelial and inducible nitric oxide synthase levels during orthodontic treatment: a cross-sectional study.

This study uses a cross-sectional design to examine the endothelial and inducible nitric oxide synthase (eNOS and iNOS, respectively) levels of gingival tissue. Fifteen subjects, 10 female and 5 male individuals (aged 14.6-21.2 years; mean 17.4 +/- 1.8 years), who needed extraction of the four first premolars for orthodontic reasons and who had indications for a gingivectomy were enrolled in the study. In each patient, two maxillary/mandibular premolars were extracted, and two months later an orthodontic appliance was placed in the same arch. A canine undergoing treatment for distal movement served as the test tooth (TT), whereas its contralateral canine was used as the control tooth (CT). The CT was included in the orthodontic appliance but was not subjected to the orthodontic force. Two weeks after the orthodontic appliance placement, clinical data consisting of the presence of supragingival plaque, bleeding on probing, and probing depth were collected from each experimental tooth. Immediately after, gingival tissue was collected from the distal aspect of each TT and CT for immunohistochemistry, messenger RNA reverse transcription by polymerase chain reaction, and Western blot analysis for both eNOS and iNOS. The results showed that no differences in clinical conditions occurred between the experimental teeth. On the contrary, both the eNOS and iNOS levels and the expression of the TTs were significantly greater than those of the CTs (all comparisons significant to P < .01). Our results indicate a role for gingival eNOS and iNOS during the early phases of orthodontic treatment in humans.

Adolescent↗

PubMed1978

A cephalometric evaluation of high-pull molar headgear and face-bow neck strap therapy.

The effects of two different extraoral appliances were evaluated over a 1-year period. Of the thirty-seven cases selected for study, twenty were treated with a face-bow neck strap and seventeen were treated with a high-pull molar headgear. Patients ranged in age from 10.10 to 16.6 years and averaged 13.4 years. The appliances exerted less than 600 Gm. of force per side and were worn for 12 to 16 hours per day. All cases were fully banded, and extraction and nonextraction treatment were included. An analysis of pretreatment data revealed a high degree of selection. Patients selected for high-pull treatment generally exhibited larger anterior face heights, steeper mandibular plane angles, and a greater amount of tooth eruption of the upper first molars than the patients selected for neck strap therapy. A control group of ten untreated subjects was matched to each treatment group to permit assessment of the impact of treatment on growth. Relative to normal growth, treatment with face-bow neck strap traction tended to direct the maxilla and mandible downward and backward. The palatal plane was lowered anteriorly and point A was retracted. The maxillary molars were extruded, and concomitantly an increase in anterior face height and mandibular plane angle was observed. On the other hand, the high-pull molar headgear traction resulted only in increased mandibular molar eruption. However, there was also a nonsignificant tendency for point A to be held back and for lower anterior face height to increase. The comparison of the two treatment samples revealed that the functional occlusal plane was tipped down at the back as the maxillary molars were more extruded in the neck strap sample. In the high-pull sample, the functional occlusal plane was unchanged and the mandibular molars were more extruded than they were in the neck strap group.

Adolescent↗

PubMed1996

Canine retraction with rare earth magnets: an investigation into the validity of the constant force hypothesis.

The objective of this study was to test the hypothesis that a prolonged constant force provides more effective tooth movement than an impulsive force of short duration. Six human subjects were selected, the main criterion being a need for extraction of their upper first premolars. Canine retraction on these subjects was executed on one side with the application of a force rapidly declining in magnitude, produced by a vertical loop, and on the other side with the application of a relatively constant force. This type of force was achieved by a similar vertical loop which was constantly activated by three parylene-coated neodymium-iron-boron (Nd2Fe14P) block magnets. The vertical loop on the control side was reactivated 6 weeks after the initial activation. No reactivation was necessary on the experimental side for the duration of the experiment. The rate of tooth movement on the two sides was compared over a period of 3 months, on the basis of maxillary impressions taken at frequent intervals during the course of the study. The canines retracted with a constant force moved statistically significantly more than the control canines (p < 0.05) during the experimental period. The average differences in the mean rates of tooth movement between the two sides were in the order of 2:1 in favor of the experimental side. There were no statistically significant differences in the changes of angulation (tipping) or rotation about the y axis between the two sides. The duration of force application seems to be a critical factor in regulating rate of tooth movement. Conversely, magnitude of the applied force did not appear to be of primary significance.

Bicuspid↗

PubMed2005

Third molar angulation during and after treatment of adolescent orthodontic patients.

The purpose of this study was to analyse the effect of premolar extraction therapy on third molar angulation during active treatment, and to test the significance of such changes on subsequent impaction of the third molars. Lateral cephalograms made before (T1) and after (T2) treatment and at long-term follow-up (T3) of 157 patients treated non-extraction (non-ex) or with extraction of four premolars (ex), all accurately diagnosed for impaction versus eruption of at least one third molar at T3, were evaluated. Linear regression models demonstrated that the maxillary third molars uprighted more from T1 to T2 (P < 0.05) and were less distally angulated at T2 (P < 0.01) in the ex than in the non-ex patients. No such differences were detected in the mandible (P > 0.05). The regression models also showed similar uprighting of the maxillary and mandibular third molars from T1 to T2 and similar angulation of the maxillary third molars at T2 in those patients with subsequent eruption and impaction (P > 0.05), but more mesially angulated mandibular third molars at T2 in the impaction patients (P < 0.01). Chi square testing demonstrated a higher frequency of distal tipping of the maxillary third molars from T1 to T2 in the impaction patients (P < 0.01), while mesial tipping from T1 to T2 of the mandibular third molars occurred with similar frequency in the two patient groups (P > 0.05). Chi square analysis also showed a higher frequency of greater than 30 degree distal angulation as well as an amount mesial angulation of the maxillary third molars at T2 (P < 0.01), and a higher frequency of greater than 40 degree mesial angulation of the mandibular third molars at T2 (P < 0.01) in patients with impaction than in those with eruption.

Adolescent↗

PubMed2005

Determinants of successful treatment of bimaxillary protrusion: orthodontic treatment versus anterior segmental osteotomy.

The purpose of this study was to investigate the differences in initial skeletal, dental, and soft tissue characteristics of bimaxillary protrusion (BP) patients to determine poor or good results with orthodontic treatment (OT) or anterior segmental osteotomy (ASO) with extraction of four first premolars. Lateral cephalometric radiographs of 46 adult Korean females with BP were analyzed before treatment (T0) and after treatment (T1). According to the measurements at T1, patients were classified into group 1 (poor result with OT, n = 12), group 2 (good result with OT, n = 11), group 3 (poor result with ASO, n = 5), and group 4 (good result with ASO, n = 18). Sagittal, vertical, dental, and soft tissue variables were measured. The differences at T0 among the four groups were compared by one way analysis of variance test and verified by Scheffe's multiple comparison test. Stepwise discriminant analysis was performed to find decisive predictors. Skeletal class II malocclusion tendency, less developed chin, and vertical facial growth pattern were related with group 1. Overly uprighted and less protrusive upper and lower incisor, near normal interincisal angle (IIA), less protrusive upper lip, and more obtuse lower nasolabial angle (NLA) were related with group 3. IIA, U1-NA distance, combination factor, interlabial gap, lower NLA, pterygomaxillary fissure-N, and posterior nasal spine-anterior nasal spine were selected as significant variables for discriminating the four groups. The percentage of correctly classified cases was 91.3%. In particular, the discriminant function showed the highest accuracy in the prediction of group 4. These variables and discriminant functions contributed to the differential diagnosis on BP to make a procedural decision between OT and ASO.

Adult↗

PubMed2004

Effects of continuous and interrupted orthodontic force on interleukin-1beta and prostaglandin E2 production in gingival crevicular fluid.

The purpose of this study was to evaluate the effects of a light continuous force and an interrupted force with weekly reactivation on interleukin-1beta (IL-1beta) and prostaglandin E(2) (PGE(2)); possible interactions between these 2 potent mediators of the bone resorption process were assessed in vivo. Ten healthy young adults (mean age 20.6 years, 2 men, 8 women) with 4 premolars extracted were assessed. In each subject, 1 maxillary canine (E1) received continuous force with a nickel-titanium coil spring. The opposite canine (E2) received an interrupted force with a screw-attached retractor; the force was reactivated weekly by 2 turns of the screw. An antagonistic canine was used as a control. Gingival crevicular fluid was collected from the distal side of each tooth, 10 times in 3 weeks, and IL-1beta and PGE(2) levels were measured. For E1, the IL-1beta level showed a significant elevation at 24 hours and then decreased and maintained an insignificant but high mean concentration, compared with the control site. The PGE(2) level showed a significant elevation at 24 hours and then decreased. For E2, a significant elevation of IL-1beta level was observed at 24 hours and a greater significant elevation at 24 hours after the first reactivation, compared with the control sites. The PGE(2) level increased significantly at 24 hours and remained high for 1 week. The synergistic up-regulation of PGE(2) by appliance reactivation and secreted IL-1beta was not evident with either type of force after 1 week. Both experimental sites showed significant tooth movement compared with the control sites at 3 weeks; however, there was no significant difference between the 2 experimental sites. A well-controlled mechanical stress with timely reactivation can effectively upregulate IL-1beta secretion, but there might be limitations in increasing the mediator levels, because of the feedback mechanisms in vivo. In addition, the analysis of crevicular fluid is a useful method for assessing cellular response to orthodontic force in vivo.

Adolescent↗

PubMed2000

Realistic late-mixed dentition treatment of Class I and II malocclusions.

In contemporary orthodontic practice, a large number of Class I and Class II patients, with and without crowding, are treated without premolar extractions. A wide range of philosophies and devices have been introduced with the aims of providing more space within the arches for the accommodation of the teeth, and influencing the relationships between the upper and lower arches. Some of these philosophies and devices are new--others have been recycled from previously-used models, which may or may not have been discarded for a number of reasons. Much descriptive and anecdotal material has been presented to support these developments. There have also been isolated studies of the effects of various mechanical component parts on dentofacial structures, some using homogenous subject-material, others using quite non-homogenous material. Little quantitative assessment has been made, however, of the effects of holding the E-spaces, uprighting the permanent first molars and redirecting the erupting permanent second molars, on attempts to provide sufficient space within the arches for alignment and levelling, correcting Class II anterior and posterior relationships and finding space for the uncomplicated eruption of the third molars. In addition, none of these space-holding or gaining effects has really been assessed alongside the effects of various attempts to orthopaedically-modify maxillary growth, if necessary, as the mandible naturally moves forward with its dentition. If a likely range of growth and treatment effects could be demonstrated in large relatively homogenous samples, one would have gone someway towards explaining the anecdotal phrase "unlocking the malocclusion", which has so often appeared in the literature. One might also have challenged another widely-held concept--that, when relieving crowding within the dental arches, one is either an extractionist or an expansionist. It might then be possible to show that, in a growing patient with a Class I or II malocclusion, crowding may well be relieved by providing space within the arches (perhaps, at the expense of the third molars), and by allowing the mandible and its dentition to move forward with growth, while forward movement of the maxilla and its dentition is inhibited.

Dental Arch↗

PubMed2000

Cell-cycle control in cell-biomaterial interactions: expression of p53 and Ki67 in human umbilical vein endothelial cells in direct contact and extract testing of biomaterials.

Current biocompatibility testing involves the demonstration of cell proliferation, which is usually interpreted as a sign of positive biocompatibility when the materials sustain cell proliferation. As the field of biomaterials research is rapidly moving toward tissue-engineered devices and hybrid organs, control of cell function has become a main topic. Cell function, which involves specific differentiation pathways, cannot be separated from cell-cycle control. The study of cell-cycle control is an important extension of routine proliferation assays and has extensive roots in developmental and tumor biology. We studied the expression of the tumour suppressor gene p53 and the proliferation-associated antigen Ki67 of endothelial cells in response to biomaterial contact. Cells were seeded in six- or 24-well plates, in which one or three 12-mm-diameter biomaterial disks were laid down. After 48- and 72-h incubation periods, cells were processed for flow cytometry, immunofluorescence, or Western blotting. The following materials were used: titanium, NiCr alloy, and CoCr alloy. Cells were also exposed to 24-h (ISO-norm) extracts in 25-cm(2) culture flasks (600, 000 cells) for 24 and 48 h. For extract testing, serially diluted Ni-ion suspensions were also used. Human umbilical vein endothelial cells adhered to metal surfaces and started forming a monolayer within 3 days. Ki67 expression was positive in more than 60% after 2 days and decreased markedly after 3 days of adhesion. During this time cells developed focal contacts and produced a fibronectin matrix. p53 expression could be demonstrated with Western blotting and flow cytometry, but not with immunofluorescence. Differences due to both culturing time and material were found in expression patterns with both methods. Inverse correlations between Ki67 and p53 expression were detected, which are probably based on culture kinetics. The results indicate that expression of p53 and also Ki67 is clearly influenced by biomaterials in direct contact testing, despite the absence of obvious morphological differences. The p53 marker can be used for defining cell function in more detail, although the correlation with specific physiological function has still to be clarified.

Biocompatible Materials↗

PubMed1988

Increased content of chondroitin sulfate proteoglycan in human colorectal carcinoma metastases compared with the primary tumor as determined by an anti-chondroitin-sulfate monoclonal antibody.

To determine if the amount of chondroitin sulfate proteoglycan (CSPG) in human colorectal tumor tissue correlates with the tumor's aggressiveness we immunochemically determined the CSPG levels in colorectal carcinomas at different stages. A total of 50 specimens--4 polyps, 15 stage B tumors, 9 stage C tumors, 12 stage D tumors, 7 liver metastases, and 3 lymph node metastases--were examined. Tumor tissues were extracted with 4 M guanidine hydrochloride containing protease inhibitors. The extracts were serially diluted and blotted onto nitrocellulose membranes. Reactivity of a chondroitin sulfate-specific mouse monoclonal antibody (CS-56) was determined by biotinylated goat antimouse Ig and avidin-biotin-peroxidase complex. After comparing tissues from tumors at different stages (classified by the presence or absence of metastasis), we could not find a positive or negative correlation between the amount of CSPG in primary colorectal carcinoma tissues and the tumor's metastatic potential. However, the metastatic foci in the liver or lymph node contained higher amounts of CSPG than the primary tumors did. Immunohistochemical staining of colon carcinoma tissue with CS-56 revealed that CSPG is predominantly localized in fibrotic portions in the tumor tissues. Two-year follow-up studies indicated that a high level of CSPG in primary tumors was not predictive of recurrence.

Adenocarcinoma↗

PubMed1992

Automated microparticle enzyme immunoassay for neural thread protein in cerebrospinal fluid from Alzheimer's disease patients.

An automated microparticle enzyme immunoassay (MEIA) with the IMx analyzer for the detection of neural thread protein (NTP) in cerebrospinal fluid (CSF) from Alzheimer's disease (AD) patients was developed. This assay uses monoclonal antibodies produced against the purified pancreatic form of the protein. The assay employs one monoclonal antibody covalently coupled to the microparticle to capture immunoreactive material in CSF or brain tissue. The second monoclonal antibody was conjugated to alkaline phosphatase and serves as detection antibody. The assay provides results in approximately 45 minutes with a sensitivity of 60 pg/ml (3 fmoles/ml). The titration curve of both normal and AD CSF resulted in a linear relationship with respect to the volume of CSF used. A similar relationship was observed when normal and AD brain tissue extracts were serially diluted. The molecular weight of NTP in CSF was approximately 20 kD as determined by gel filtration method under non-denaturing conditions. The recovery for pancreatic thread protein (PTP) spiked in either normal or AD CSF was 104% and 108%, respectively. Intra-, inter-, and total assay CVs (coefficient of variation) for controls were less than 2.9%, 3.3% and 3.0%, respectively. This assay will provide a useful tool in the study of the Alzheimer's disease and may help research in diagnosis and prognosis of Alzheimer's disease and related disorders.

Alzheimer Disease↗

PubMed2003

Patterns of circulating hepatitis B virus serum nucleic acids during lamivudine therapy.

We examined whether lamivudine treatment, in addition to the rapid decline of HBV serum DNA described in a large number of laboratories, causes changes in composition and amount of discernable circulating viral DNA and RNA. Nucleic acids were extracted from serial serum samples of a patient infected chronically and treated with lamivudine for 14 weeks. Three sequence segments of the HBV genome synthesized successively during replication, X, C, and X-preC, were analyzed by competitive PCR and RT/PCR. In addition, RNA was examined for differential polyadenylation. Before treatment, identical DNA copy numbers (10(9)/ml) were found in all three segments. C segment DNA displayed the expected rapid decline. X-preC, a target contiguous only on plus-strand DNA behaved similarly. In contrast, the X segment DNA copy numbers showed a less pronounced decrease remaining at higher values (10(7)/ml) than the C and X-preC segment (both about 2 x 10(5)/ml) at the end of therapy. X segment RNA displayed a persisting copy number of about 10(7)/ml, while C and X-preC RNA decreased to about 10(5) copies/ml. Polyadenylated HBV RNA, full-length and truncated, persisted initially at 10(5) but decreased to 10(4) to 10(3) copies/ml at the end of treatment. The major conclusions are the actual numbers of virus particles during lamivudine therapy can only be assessed via X segment DNA, since it is reverse transcribed first, and Lamivudine induced coexistence of DNA and RNA for the C and X segment at similar levels indicates drug-arrested intermediates of reverse transcribed HBV DNA minus-strand. Packaged RNA lacks a poly(A) tail whereas polyadenylated RNA is likely not packaged.

Antiviral Agents↗

PubMed2004

Involvement of Hevea latex organelle membrane proteins in the rubber biosynthesis activity and regulatory function.

Centrifugation of fresh Hevea rubber latex yields three distinct fractions. The sediment bottom fraction (BF) content of membrane-bound organelles is ca. 20 vol.-% of latex. Prolonged storage or delayed use of fresh latex will result in disintegration and loss of the bottom fraction. This is due to the osmotically sensitive BF rupture and its membrane debris being tightly bound to the top rubber particles (RP) phase. The BF membrane was found to be highly active for rubber biosynthesis (RB), in contrast to previous reports that describe RB only occurring on the RP surface. It was clearly shown that washed BF membrane (WBM) was much more active than fresh RP for RB activity. WBM was highly activated by SDS for RB in a biphasic manner, but SDS strongly inhibited the RP. Probably WBM micelle formation resulted in a highly increased active surface area for RB. C55-PP (UPP) was a very active allylic for WBM in RB function, but inactive for RP. Serial acetone extraction of WBM proteins showed a distinct profile of the fractions with different RB activity. WBM isolated proteins suspended in 2% sodium dodecyl sulfate (SDS) with an RB activity equal to that of intact WBM was with the 20% acetone protein fraction. The 60 and 80% fractions were inactive. Combining the 20 with 80% fractions showed a complete inhibition of RB activity. Complete RB loss was also found when WBM was mixed with the 80% fraction, indicating that WBM has both an enzyme system and a factor for regulation of the RB activity in a well controlled metabolic function for the latex RB process.

Acetone↗

PubMed1997

Detection of Rift Valley fever virus in mosquitoes by RT-PCR.

A reverse transcriptase-polymerase chain reaction (RT-PCR) assay to detect Rift Valley fever (RVF) virus RNA in experimentally infected mosquitoes was developed. The specificity of the assay was evaluated with three other phleboviruses; sandfly fever Sicilian (Sabin), sandfly fever Naples (Sabin) and Punta Toro (MSP 3) viruses. The relative sensitivity of the assay, determined by using RVF virus RNA extracted from serial dilutions of virus culture, was approximately 50 plaque forming units. This sensitivity level was 100-fold higher when a nested PCR procedure was used. When the RT-PCR assay was used with coded samples of intrathoracically-infected and uninfected mosquito, the assay detected the virus in all infected mosquitoes. With this assay, it was possible to detect RVF virus RNA in a single infected mosquito in the background of 10, 25 or 50 uninfected mosquitoes.

Animals↗