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R Carpenter

Publications and source records attributed to R Carpenter.

At least 145 records · Page 8Linked to original sources
PubMed1990

Floral homeotic mutations produced by transposon-mutagenesis in Antirrhinum majus.

To isolate and study genes controlling floral development, we have carried out a large-scale transposon-mutagenesis experiment in Antirrhinum majus. Ten independent floral homeotic mutations were obtained that could be divided into three classes, depending on whether they affect (1) the identity of organs within the same whorl; (2) the identity and sometimes also the number of whorls; and (3) the fate of the axillary meristem that normally gives rise to the flower. The classes of floral phenotypes suggest a model for the genetic control of primordium fate in which class 2 genes are proposed to act in overlapping pairs of adjacent whorls so that their combinations at different positions along the radius of the flower can specify the fate and number of whorls. These could interact with class 1 genes, which vary in their action along the vertical axis of the flower to generate bilateral symmetry. Both of these classes may be ultimately regulated by class 3 genes required for flower initiation. The similarity between some of the homeotic phenotypes with those of other species suggests that the mechanisms controlling whorl identity and number have been highly conserved in plant evolution. Many of the mutations obtained show somatic and germinal instability characteristic of transposon insertions, allowing the cell-autonomy of floral homeotic genes to be tested for the first time. In addition, we show that the deficiens (def) gene (class 2) acts throughout organ development, but its action may be different at various developmental stages, accounting for the intermediate phenotypes conferred by certain def alleles. Expression of def early in development is not necessary for its later expression, indicating that other genes act throughout the development of specific organs to maintain def expression. Direct evidence that the mutations obtained were caused by transposons came from molecular analysis of leaf or flower pigmentation mutants, indicating that isolation of the homeotic genes should now be possible.

DNA Transposable Elements↗
PubMed1990

Poor response of breast cancer to tamoxifen.

Fifty eight (58) patients with early breast cancer (mean age 78.3 years) and 37 patients with advanced breast cancer (mean age 65.9 years) were treated with tamoxifen orally 20 mg daily or twice daily. The mean follow-up time was 19.1 months in the early group and 18.4 months in the late group. The drug was extremely well tolerated. All patients had cytological or histological evidence of breast cancer. A complete or partial response was found in only 36% of the patients with early breast cancer and only 13% in the advanced group. We conclude that tamoxifen was disappointing as a primary therapy in our patients. Although because of its lack of toxicity it can be seen as initial therapy for patients with breast cancer, it may have to be supplanted rapidly by other forms of therapy in the substantial proportion of patients in whom a response will not occur.

Administration, Oral↗
PubMed1989

Management of screen detected ductal carcinoma in situ of the female breast.

Thirty eight ductal carcinomas in situ of the female breast detected during the first 7 years of screening by the Guildford Breast Screening Unit have been treated by one surgeon. Twenty-eight cases were treated conservatively and ten by mastectomy. In the group treated conservatively there have been five local recurrences: four as ductal carcinoma in situ and one as node negative microinvasive carcinoma. There were no clinical or pathological features that predicted local recurrence, which was detected only by follow-up mammography. Based on these early results, an initially conservative approach to screen detected ductal carcinoma in situ is advocated.

Aged↗
PubMed1989

A chromosome rearrangement suggests that donor and recipient sites are associated during Tam3 transposition in Antirrhinum majus.

We describe the structure of a chromosome rearrangement which changes the spatial pattern of expression of the pallida gene of Antirrhinum majus. The rearrangement involves a chromosome inversion of ~6 map units with one breakpoint at the end of a copy of the transposable element Tam3 located in the promoter region of the pallida locus. The sequence at the breakpoints shows that 5-7 bp, present once in the progenitor, has been duplicated and flanks both ends of the inversion. We propose that this structure arose from an aberrant Tam3 transposition, suggesting a model for normal transposition which involves physical association between donor and recipient sites. This may explain why transposition of plant transposable elements such as Ac in maize occurs preferentially to recipient sites closely linked to the donor site. Excision of the Tam3 copy located at the end of the chromosome inversion, results in a unique spatial pattern of pallida gene expression as a consequence of replacing all sequence 70 bp upstream of transcription by a new sequence. This pattern may be the result of deleting specific upstream components which regulate pallida expression and/or of changing the relative chromosome position of the pallida gene.

Journal Article↗
PubMed1989

Elevated blood serotonin in autistic probands and their first-degree relatives.

Whole blood serotonin levels and platelet counts were studied in 14 families, representing 57 family members and 15 probands who met DSM III criteria for infantile autism. High serotonin appeared to segregate in families. When two parents had high serotonin, the serotonin level in their offspring was twice the parental level. When one parent had high serotonin, the serotonin level in the offspring approximated the level of serotonin in either the high serotonin parent or the low serotonin parent. For the case where both parents had low serotonin, in one family the children had low serotonin and in a second family, high serotonin levels were present in the autistic proband, and a sibling with severe mental retardation. Mean serotonin levels were higher for both male and female, autistics and family members, in the four black families than in the 10 Caucasian families.

Adolescent↗
PubMed1989

Clinical efficacy of 99mtechnetium mercaptoacetylglycine kit formulation in routine renal scintigraphy.

99mTechnetium mercaptoacetylglycine is a promising new renal radiopharmaceutical undergoing phase III trials in the United States. In a preliminary investigation of the efficacy and safety of mercaptoacetylglycine in 30 adult patients with suspected renal disease we used simultaneous imaging with orthoiodohippurate as the physiological "gold standard". Of these patients 11 had undergone renal transplantation. Factors, such as time to peak renal activity, clearance half-life and regional functional comparison, were similar by orthoiodohippurate and mercaptoacetylglycine imaging. Visual and quantitative analysis of angiograms and renograms was markedly facilitated with the use of mercaptoacetylglycine. Several morphological abnormalities were apparent only during mercaptoacetylglycine evaluation. No adverse effects, changes in vital signs or significant changes in clinical laboratory status were encountered. Since mercaptoacetylglycine combined an excellent technetium image with the pharmacokinetics of orthoiodohippurate, mercaptoacetylglycine may supplant all other agents for routine clinical use.

Adult↗
PubMed1989

Genetic interactions underlying flower color patterns in Antirrhinum majus.

Diverse spatial patterns of flower color in Antirrhinum can be produced by a series of alleles of pallida, a gene encoding an enzyme required for pigment biosynthesis. The alleles arose by imprecise excision of a transposable element, Tam3, and we show that they carry a series of deletions involving progressive removal of sequences adjacent to the excision site. This has enabled us to define three cis-acting upstream regions, A, B, and C, which differentially affect the level of pallida expression in distinct areas of the flower. We show further that an unlinked locus, delila, regulates the spatial distribution of pallida transcript. Deletion of regions ABC at the pallida locus uncouples pallida from regulation by delila, whereas deletion of A or AB brings pallida under regulation by delila in a new area of the flower. These results suggest that diverse patterns of pallida expression reflect the different ways in which alleles interact with a prepattern of both common and spatially specific genetic signals in the flower.

Alleles↗
PubMed1988

A semi-dominant allele, niv-525, acts in trans to inhibit expression of its wild-type homologue in Antirrhinum majus.

Niv-525 is a semi-dominant allele of the nivea locus, which encodes the enzyme chalcone synthase required for flower pigment biosynthesis in Antirrhinum majus. Plants heterozygous for niv-525 and wild-type (Niv+) allele, have flowers with a reduced intensity and novel spatial pattern of pigmentation compared with Niv+ homozygotes. In heterozygotes, niv-525 acts in trans to reduce the steady-state level of nivea transcript produced by its Niv+ homologue and hence the quantity of chalcone synthase protein. Niv-525 carries an inverted duplication of 207 bp in its promoter region which has arisen following excision of the transposable element Tam 3. This structure can be explained by a model of plant transposable element excision that involves resolution of two hairpin DNA molecules. Possible mechanisms for the trans-acting effect of niv-525 and its relationship to other examples of allelic interactions, such as transvection in Drosophila melanogaster, are discussed.

Acyltransferases↗
PubMed1988

Occlusal considerations for partially or completely edentulous skeletal Class II patients. Part II: Treatment concepts.

Four basic concepts must be considered when developing the prosthetic occlusion for skeletal class II patients: (1) Centric relation must be used as a reference position to relate the mandible to the maxillae; (2) the posterior denture teeth must be positioned close to their former positions; (3) freedom of movement must be created in eccentric movements; and (4) multiple occlusal contacts must be provided in centric and eccentric positions. We have described a method that incorporates these basic concepts and provides a harmonious occlusal arrangement for both edentulous and partially edentulous class II patients.

Dental Occlusion, Balanced↗
PubMed1988

Occlusal considerations for partially or completely edentulous skeletal class II patients. Part I: Background information.

Although approximately 15% of the population may be classified as having the skeletal class II relationship, this group of patients is far from homogeneous. Two prototypes were used to delineate various problems in the prosthodontic occlusion that dentists may encounter with these patients. A satisfactory occlusion is difficult to achieve because of skeletal discrepancies, limited space for occlusal contact, steep guidance factors, and the necessity for multiple eccentric occlusal contacts because of the significant range of mandibular motion.

Cephalometry↗
PubMed1987

Importance of cellular DNA content in pre-malignant breast disease and pre-invasive carcinoma of the female breast.

The risk of malignant change in pre-invasive breast disease such as proliferative atypia (PA) or the risk of invasive carcinoma arising from ductal carcinoma in situ (DCIS) remains uncertain in individual women because of the absence of any prognostic criteria. In order to clarify this, the cellular DNA content (ploidy) of 51 screen-detected lesions has been investigated. Cellular DNA measurements were made by static cytometry following Feulgen staining of disaggregated tissue sections and the resulting histograms classified as either diploid or aneuploid. Thirteen cases of PA and twelve of DCIS were compared with twenty-six biopsies showing DCIS with adjacent invasive carcinoma (DCIS + Ca). In the latter group, ploidy of the invasive carcinoma was compared with the associated DCIS in 16 cases. Aneuploid cells were found in approximately 30 per cent of PA and DCIS lesions but in 23 of 26 cases of DCIS + Ca. Of 16 assessable cases of co-existing DCIS and micro-invasive carcinoma both were aneuploid in 11, both diploid in 1, and in 4 cases the DCIS was aneuploid whereas the invasive carcinoma was diploid. These results suggest that aneuploidy may be of value in predicting the most biologically aggressive of these pre-invasive lesions.

Aged↗