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Biomedical subjects

D Chambers

Publications and source records attributed to D Chambers.

At least 55 records · Page 3Linked to original sources
PubMed1994

Dentists troubled by the administration of anesthetic injections: long-term stresses and effects.

A questionnaire was mailed to 3,000 practicing dentists to inquire about their physical and psychological responses to the task of administering local anesthesia. Surprisingly, 18.8% of the 711 responding dentists reported that the administration of injections causes them enough distress to have (at least at some time) reconsidered dentistry as a career. Six percent of respondents considered their thoughts and feelings to be a serious problem, whereas only 2% reported no negative reactions to this aspect of clinical practice. Self-reported reactions to various anesthetic procedures were compared, and the various responses are discussed. It is concluded that the administration of anesthetic injections is a rarely discussed but significant contributor to the overall professional stress and difficulty for many, but not all, dentists.

Adult↗
PubMed1992

What an image depicts depends on what an image means.

Previous research has shown that subjects visually imaging the classical ambiguous figures have great difficulty in reconstruing these images. To explain this finding, we propose that subjects' construal of their image strongly influences what is depicted in the image, leading to the inclusion of some aspects of an imaged figure and the exclusion of others. Thus, images of (supposedly) ambiguous figures may literally omit information necessary for the reconstrual. To test this claim, we asked subjects to form an image of the duck/rabbit figure, and then to compare their image to drawings that departed slightly from the original figure. We hypothesized that subjects would have a clear image of the side of the figure they understood as the "face" (the left side if the image is understood as a duck, the right side for the rabbit). Conversely, subjects would have only a vague image of the "back" of the head. Consequently, in comparing their image to test stimuli, subjects should be able to detect variations in the contour of the "face," but not in the contour of the "back" of the animal's head. These predictions were confirmed, strongly suggesting that the construal of an image does dictate what is depicted within the image.

Attention↗
PubMed1991

Neither pictures nor propositions: what can we learn from a mental image?

In an earlier paper, we reported that subjects have great difficulty in finding alternative construals of their own mental images. In the present paper, we examine how subjects can nonetheless learn from their mental images. We argue that mental images, like percepts, are meaningful depictions. As such, mental images do depict appearance but are also inherently understood in a certain way, and this understanding influences the phenomenal appearance of the represented form. This, in turn, governs what the form will be seen to resemble and what the form is likely to call from memory. We report four experiments in support of this view. In each experiment, subjects are briefly shown outline shapes and asked to form a mental image of each shape. Subjects are then asked what familiar form the imaged shape resembles. Subjects routinely find target shapes in their images when the target is compatible both with the imaged geometry and with how that geometry is organized and understood. When the sought-for target is compatible with image geometry but not with how the image is understood, subjects reliably fail to find the target shape in their images.

Adult↗
PubMed1990

Characterization of TRP-1 mRNA levels in dominant and recessive mutations at the mouse brown (b) locus.

The mouse brown locus encodes a putative membrane-bound metalloenzyme, tyrosinase-related protein-1 (TRP-1). We have examined the effect on mRNA expression of the locus of a number of mutant alleles. The common null mutant allele, brown, produces wild-type levels of TRP-1 mRNA, which is nonfunctional. Another recessive allele, cordovan-Harwell, has an intermediate, dark-brown phenotype and produces only very low levels of presumably normal TRP-1 mRNA. Two dominant alleles appear to act by killing the melanocyte in which they are expressed. One of them, Light, has normal size and amounts of TRP-1 mRNA. The other, White-based brown, produces no detectable TRP-1 mRNA. It has a gross DNA rearrangement at the 5' end, and we speculate that this results in activation of transcription of sequences not usually seen in melanocytes, and that this is toxic to the cell. The relationship between phenotype and molecular structure at the locus is discussed, and we draw some general principles applicable to other developmental genes.

Animals↗
PubMed1990

Endometrial adenocarcinoma presenting as pituitary apoplexy.

The novel combination of disseminated primary endometrial adenocarcinoma and a symptomatic pituitary metastasis presenting as pituitary apoplexy is described for the first time. Pituitary apoplexy is an unusual manifestation of metastatic pituitary disease. The more common clinical features of pituitary metastases and an approach to their management are discussed. The usefulness of magnetic resonance imaging in assessing the base of skull is emphasised.

Adenocarcinoma↗
PubMed1989

Methyl 2-[4-(2-chloroethyl)-2,3-dihydro-7-nitroquinoxalin-1-yl]benzoate from intramolecular cyclization of a nitroaromatic mustard.

C18H18CIN3O4, Mr = 375.81, orthorhombic, P212121, a = 11.000 (3), b = 8.023 (2), c = 19.316 (5) A, V = 1704.68 A3, Z = 4, Dm = 1.46 (1), Dx = 1.417 g cm-3, Mo Kalpha, lambda = 0.71069 A, mu = 1.82 cm-1, F(000) = 760, T = 293 (1) K, R = 0.051 for 985 [I greater than 2.5 sigma(I)] reflections. X-ray analysis confirms that the nitroaromatic mustard methyl N-(2-[bis(2-chloroethyl)amino]- 5-nitrophenyl)anthranilate undergoes rapid intramolecular cyclization, but the product is the 7-nitro rather than the 6-nitro derivative previously reported [Chambers & Denny (1986).

Antineoplastic Agents↗
PubMed1989

Evidence for distinguishable transcripts of the putative testis determining gene (ZFY) and mapping of homologous cDNA sequences to chromosomes X,Y and 9.

Oligonucleotide sequences based on the amino acid sequence of the putative testis determining gene ZFY have been used to isolate a 1.3 Kb Hind III Y genomic DNA fragment CMPXY1 and three human testis cDNA sequences (CMPXY2, CMPXY3 and CMPXY4). These sequences detect at least four potential exons on the Y (Y1, Y3, Y4 and Y5), three on the X (X1, X2 and X3) and three of autosomal origin (A1, A2 and A3) as determined by comparing the fragments detected by different clones. Analysis with subfragments of CMPXY4 shows that Y3 is unique to the Y and that Y4 and X1 are homologous. Y5 and X3 are detected by the same subfragment of CMPXY4. This is also the case for Y1, X2, A1, A2 and A3. Thus these exons may contain further regions of homology between the X, Y and an autosomal locus. The X-linked sequences all lie in Xp21.2-Xp22.1 and studies with XX males have placed the Y-linked sequences in distal Yp adjacent to the Y-autosomal homologous sequence GMGY3. We have confirmed these localizations by in situ hybridization with CMPXY4 and have shown additionally that the autosomal sequences of both the CMPXY4 sequence and GMGY3 map to 9p22-9pter. Restriction analysis demonstrates that CMPXY1/XY2/XY3 differ in sequence from CMPXY4 at three restriction enzyme sites, thus suggesting that they are transcribed from different but closely related genes and that CMPXY4 must be either X-linked or autosomal in origin. This indicates that more than one of the loci containing ZFY-related sequences are transcribed and potentially fulfil functionally distinct roles in the human sex determining pathway. Northern blot analysis of human foetal testis RNA has shown that three low abundance transcripts of 5, 6 and 8 Kb can be detected by ZFY-related DNA sequences.

Base Sequence↗
PubMed1989

Periodontal implications of orthodontic treatment in adults with reduced or normal periodontal tissues versus those of adolescents.

This longitudinal study monitored periodontal status in 20 adults and 20 adolescents undergoing fixed orthodontic treatment. Ten adults had generalized periodontitis and received periodontal treatment, including periodontal surgery, before orthodontic treatment. They also received periodontal maintenance at 3-month intervals during orthodontic treatment. The other 10 adults had normal periodontal tissues. Neither these latter adults nor the adolescents received periodontal maintenance during orthodontic treatment. Periodontal status was determined (1) at six standard sites before fixed appliances were placed (baseline), (2) at 1, 3, 6, 9, 12, and 18 months after appliances had been placed, and (3) 1, 3, 6, and 12 months after appliances had been removed. At each of these visits, these sites were assessed for plaque index, gingival index, bleeding tendency, and pocket depth. Loss of attachment between baseline and 3 months after appliances were removed and tooth loss were also determined. Complete data were obtained for 15 adolescents and 14 adults. During orthodontic treatment the adolescent group showed significantly more (p less than 0.05) periodontal inflammation and supragingival plaque than the adults; after appliances were removed, this pattern was no longer statistically significant. For loss of attachment, there were no significant differences among adolescents, adults with normal periodontal tissues, or adults with reduced but healthy periodontal tissues who had undergone treatment for periodontal disease. For tooth loss, three nonstudy site teeth with pockets deeper than 6 mm and/or furcation involvements were lost because of periodontal abscesses in the adult group treated for periodontal disease.

Adolescent↗
PubMed1988

Postfusional latency in stereoscopic slant perception and the primitives of stereopsis.

Random dot stereograms of slanted surfaces were constructed, each representing one or two slanted surfaces in different relative arrangements and with different axes. Latency to fusion and from fusion to stereoscopic resolution was measured for each stimulus. It was found that latency to fusion was always very brief but that latency to stereoscopic resolution varied markedly, depending upon the orientation and arrangement of the stereoscopic surfaces. A gradient of discontinuities at a surface boundary produced an instant slant response for that surface, whereas a gradient of absolute disparities across the surface did not, except under conditions where vertical declination (a form of orientation disparity) was present. We conclude that stereopsis is not based on the primitives used in matching the images for fusion and that it is, at least initially, a response to disparity discontinuities which play no role in the fusion process. We also conclude that vertical declination is responded to globally as a slant around a horizontal axis but that other forms of orientation disparity are ineffective. The evidence from our experiments does not support the existence of a stereoscopic ability to respond globally to differences in magnification (or spatial frequency). It is suggested that stereoscopic perception of slant around a vertical axis is slow because it results from the integration of local processes.

Attention↗
PubMed1987

Long-term survival rates after prolonged aortic cross-clamping with St. Thomas' Hospital cardioplegia.

Prolonged aortic cross-clamping (in excess of 120 min) was necessary in 154 cardiac surgical patients. St. Thomas' Hospital cardioplegia was used for myocardial preservation. Quantitative polarization microscopy enabling quantitative birefringence measurements to assess the change in birefringence of the muscle fibres in response to the addition of buffer containing ATP and calcium (i.e. myocardial contractility) was used to detect whether there had been any deterioration in right or left ventricular myocardium during the bypass period. 30 day survival was 90%, long-term (60 months) survival was 80%. In single valve replacements, patients with aortic valvular replacement had 100% survival up to 92 months, whereas patients with mitral valvular replacement had survival rates of 83% after 12 months and 27% after 60 months. Survival rates after 60 months were 89% for coronary artery bypass grafting, 80% for multiple valve replacements, and 74% for combined valvular and coronary artery bypass grafting surgery. Quantitative birefringence assessment of function showed that in the surviving patients 5% had functional deterioration during bypass whereas in the non-surviving patients 70% had functional deterioration. It may be concluded that after cardiac surgery necessitating prolonged aortic cross-clamping--once the initial operative problems are overcome--reasonable long-term results can be obtained by using St. Thomas' Hospital cardioplegia.

Bicarbonates↗
PubMed1986

Potential antitumor agents. 46. Structure-activity relationships for acridine monosubstituted derivatives of the antitumor agent N-[2-(dimethylamino)ethyl]-9-aminoacridine-4-carboxamide.

A series of monosubstituted derivatives of the new antitumor agent N-[2-(dimethylamino)ethyl]-9-aminoacridine-4-carboxamide has been prepared, bearing methyl, methoxy, and chloro groups at available acridine positions. The physicochemical properties and antitumor activity of these compounds varied more with the position than with the nature of the substituent groups. The highest levels of both in vitro and in vivo antileukemic activity were shown by 5-substituted derivatives, while 7- and 8-substituted derivatives possessed the highest selectivity toward the HCT-8 human colon carcinoma line compared to the L1210 mouse leukemia line in vitro.

Aminoacridines↗
PubMed1985

Perceived position and saccadic eye movements.

Data are reported which support the conclusion that saccades which occur 600 msec or more after the brief, presentation of a target stimulus are directed to its perceived position when that differs from both its retinal and spatial position.

Animals↗
PubMed1985

Effect of self-administered daily irrigation with 0.02% SnF2 on periodontal disease activity.

To determine the effect on periodontal health of a daily self-administered irrigation with 0.02% stannous fluoride (SnF2) solution, 28 subjects who had moderate to advanced periodontitis were randomly divided into 3 groups: a control group (n = 9) which used no irrigation, a group (n = 8) which used a self-administered water irrigation device (Water Pik) daily with water (H2O group) and a group (n = 11) which used the Water Pik in a similar manner but with SnF2 solution (SnF2 group). All subjects were instructed in routine tooth brushing and flossing but received no other periodontal treatment. 4 study sites were selected from each patient which had pocket depths greater than 4 mm and bleeding upon probing. Plaque index, gingival index, bleeding tendency, pocket depth, loss of attachment, and microbiologic samples of subgingival plaque for morphologic determinations were collected from all study sites at baseline, 2, 6, and 10 weeks. A cross-over was then initiated for 2 additional monthly checks in which the H2O group changed to SnF2 and the SnF2 group was divided into 2 subgroups which either continued to use SnF2 or changed to H2O. The control group completed the study at the beginning of the crossover. The clinical data showed significantly more improvement in periodontal health during the first 10 weeks for the SnF2 group (p less than 0.01). After cross-over, the clinical data indicated the group that changed from H2O to SnF2 significantly improved their periodontal health, while the group that changed from SnF2 to H2O became worse. The microbiologic data showed trends which agreed with the clinical data during the first 10 weeks but were less significant. After cross-over, the %s of motile rods and spirochetes were too small (0-7%) to establish statistically significant changes considering the accuracy of the technique used.

Bacteria↗