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Biomedical subjects

J M Brady

Publications and source records attributed to J M Brady.

At least 19 recordsLinked to original sources
PubMed2000

Detecting the brain surface in sparse MRI using boundary models.

We introduce a framework for the detection of the brain boundary (arachnoid) within sparse MRI. We use the term sparse to describe volumetric images in which the sampling resolution within the imaging plane is far higher than that of the perpendicular direction. Generic boundary detection schemes do not provide good results for such data. In the scheme we propose, the boundary is extracted using a constrained mesh surface which iteratively approximates a 3D point set consisting of detected boundary points. Boundary detection is based on a database of piecewise constant models, which represent the idealised MR intensity profile of the underlying boundary anatomy. A non-linear matching scheme is introduced to estimate the location of the boundary points using only the intensity data within each image plane. Results are shown for a number of images and are discussed in detail.

Algorithms↗
PubMed1998

Estimation of compressed breast thickness during mammography.

To estimate radiation dose during mammography the breast thickness must be known. We present a new method for estimating the thickness of a compressed breast using only the breast image as projected onto a mammogram, calibration data such as the mAs value and image processing techniques. The method proves to be of high accuracy (+/- 0.2 cm for craniocaudal mammograms) and has the advantage over other methods of allowing retrospective estimation of thickness.

Breast↗
PubMed1997

Mammographic image analysis.

We describe our recent progress aimed at computer analysis of mammograms. The overall aim is to provide the clinician with reliable quantitative information. We summarise a representation we have developed of the 'interesting' (non-adipose) tissue in a breast, then put the representation to work in three ways: (i) to propose a new quantitative measure to aid in diagnosing masses; (ii) to explore the possibility of reducing by half the radiation dose required for a mammogram; and (iii) recalling some of the results that can be provided by differential compression mammography, in which mammograms are taken at two slightly different compressions.

Guidelines as Topic↗
PubMed1994

Detecting approximal dental caries with transillumination: a clinical evaluation.

Independent examinations of 300 patients were conducted to evaluate fiber optic transillumination's performance in caries detection. FOTI was used as an adjunct to clinical and radiographic examinations for caries, restoration or secondary caries of approximal surfaces in maxillary anterior permanent teeth. Clinical and radiographic examinations were significantly more effective.

Adolescent↗
PubMed1991

Evolution of the rat kallikrein gene family: gene conversion leads to functional diversity.

Kallikrein-like simple serine proteases are encoded by closely related members of a gene family in several mammalian species. Molecular cloning and genomic Southern blot analysis after conventional and pulsed-field gel electrophoresis indicate that the rat kallikrein gene family comprises 15-20 members, probably closely linked at a single locus. Determination of the nucleotide sequences of the rGK-3, -4, and -6 genes here completes sequence data for a total of nine rat kallikrein family members. Comparison of the rat gene sequences to each other and to those of human and mouse kallikrein family genes reveals patterns of relatedness indicative of concerted evolution. Analysis of nucleotide sequence variants in kallikrein family members shows that most sequence variants are shared by multiple family members; the patterns of shared variants are complex and indicate multiple short gene conversions between family members. Sequence exchanges between family members generate novel assortments of variants in amino acid coding regions that may affect substrate specificity and thereby contribute to the diversity of enzyme activity. Furthermore, small sequence exchanges also may play a role in generating the diverse patterns of tissue-specific expression of rat family members. These analyses indicate an important role for gene conversion in the evolution of the functional diversity of these duplicated genes.

Amino Acid Sequence↗
PubMed1990

The expression of two kallikrein gene family members in the rat kidney.

The mRNAs for two kallikrein gene family members expressed in the rat kidney have been characterized. One mRNA (PS) has previously been found in the pancreas and submaxillary gland and encodes true kallikrein. The second mRNA (K1) encodes a novel kallikrein-like enzyme expressed in the kidney and submaxillary gland that retains many of the key amino acid residues for the characteristic enzymatic cleavage specificity of kallikrein. Two oligonucleotide hybridization probes specific for the K1 mRNA demonstrate that the K1 mRNA is expressed in the kidney and submaxillary gland, but in none of the other eight tissues known to express one or more members of the rat kallikrein gene family. The K1 mRNA is the dominant kallikrein-related mRNA of the kidney, expressed at roughly 10 times the level of the true kallikrein (PS) mRNA. In the submaxillary gland the K1 mRNA is expressed at roughly one-fourth the level of true kallikrein mRNA.

Amino Acid Sequence↗
PubMed1989

Expression of two kallikrein gene family members in the rat prostate.

We have characterized two kallikrein gene family members expressed in the prostate and submaxillary glands of rats. One mRNA (S3) is identical with the previously characterized submaxillary gland S3 mRNA that encodes an enzyme closely related to tonin. The second mRNA (P1) encodes a novel kallikrein-like enzyme that retains key amino acid residues responsible for the characteristic enzymatic cleavage specificity of kallikrein. Two P1-specific oligonucleotide probes derived from the P1 mRNA sequence were used to demonstrate the presence of P1 mRNA in the prostate and submaxillary glands and its absence in eight other rat tissues known to express one or more members of the kallikrein family. The P1-coding gene (rGK-8) was identified among genomic clones containing kallikrein family members by hybridization with a P1-specific oligonucleotide probe. The identification of the P1 gene was verified by nucleotide sequencing; the exon sequences of rGK-8 match the P1 mRNA sequence. The upstream region of rGK-8, where transcriptional regulatory elements likely reside, is very similar to that of other rat kallikrein family genes which are expressed in distinct tissue-specific patterns.

Amino Acid Sequence↗
PubMed1989

Organization and expression of the rat kallikrein gene family.

We have cloned and characterized eight members of the kallikrein gene family from rat genomic DNA. Three of the cloned genes correspond to the previously characterized kallikrein family mRNAs PS, S2, and P1, which encode true kallikrein, tonin, and a novel kallikrein-like enzyme, respectively. In two cases, two kallikrein family genes are located on single genomic clones, suggesting close linkage of this family in the rat genome. Based on the total number of cloned genes and mRNAs, the minimum size of the rat family is 11 genes. Comparisons between the rat genes demonstrate a high degree of nucleotide sequence identity (greater than 80%) in exonic, intronic, and nearby flanking regions. This extensive sequence conservation not limited to clearly functional domains suggests that concerted evolution of this gene family has occurred. Despite the high overall sequence conservation among the rat family members, several discrete regions of high variability exist in the coding regions. We have defined the tissue-specific expression of the PS (true kallikrein), S2 (tonin), and S3 mRNAs with gene-specific oligonucleotide probes derived from these variant regions. PS is expressed in a wide range of tissues, while S2 mRNA is restricted to the submaxillary gland and S3 mRNA to the submaxillary and prostate glands. The high sequence conservation within the upstream flanking regions of these genes suggests that a small number of nucleotide differences determines the disparate transcriptional specificity of individual family members.

Amino Acid Sequence↗
PubMed1989

Scanning electron microscopy of submandibular sialoliths: a preliminary report.

This report compares the scanning electron microscopic appearances of the structures in two sialoliths, one surgically removed, the other naturally exfoliated. The first exhibited the typical structure of a lamellated outer layer with an amorphous core. The core contained a large number of structures resembling calcified filamentous organisms. The second consisted of a similar outer lamella but the core contained crystal-lined spaces, amorphous matrix and an heterogeneous array of crystal shapes: there were no structures resembling organisms.

Humans↗
PubMed1988

Androgen dependence of specific kallikrein gene family members expressed in rat prostate.

We have used oligonucleotide probes specific for members of the rat kallikrein/tonin gene family (PS, S1, S2, S3, K1, and P1) to establish which arginyl esteropeptidase (kallikrein-like) genes are expressed in the prostate. We have also compared the expression and androgen dependence of these genes in prostate, submaxillary gland (SMG) and kidney. Only S3 (tonin-like) and P1 (kallikrein-like) are expressed in the prostate, with S3 very much more abundant. Prostatic S3 mRNA disappears after 8 days castration and is restored to intact levels by dihydrotestosterone (DHT) but not estradiol benzoate (EB) for 8 days. Prostate P1 mRNA levels were similarly but not identically affected. All six genes are expressed in the SMG, with PS (true kallikrein) the most abundant. Levels of PS mRNA in SMG are unaffected by castration, DHT, or EB treatment, although mRNA levels of other kallikrein-like (S1, K1, and P1), tonin (S2), and tonin-like (S3) genes fall 40-60% after castration, and are unaffected or partially restored by DHT and/or EB administration. Only PS and K1 are expressed in the kidney, at much lower levels than in the SMG and unaffected by castration or steroids. These studies thus confirm and extend the concept of tissue specificity of arginyl esteropeptidase gene expression, and further demonstrate that the same gene(s) is differentially regulated by androgens in the rat prostate, SMG, and kidney.

Animals↗
PubMed1986

Considering the psychosocial aspects of AIDS.

People with AIDS have great needs--not only physical due to the effects of the disease on their bodies, but psychological as well. In addition, fear and repugnance of the disease and its victims has started another epidemic dubbed AFRAIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1982

Osteogenesis imperfecta lethal in infancy: case report and scanning electron microscopic studies of the deciduous teeth.

Radiologic evaluation of the skeleton and scanning electron microscopic studies of the teeth were performed on an infant boy with a lethal osteogenesis imperfecta (OI) syndrome who died at 10 mo of pneumonia. The skeletal findings included ribs that were focally expanded by fracture calluses, flat vertebral bodies, and wide limb bones. On fractured tooth surfaces, the enamel and dentin were normal as was the dentin calcification front. Although microscopic abnormalities have been noted in teeth from previously reported infants with lethal OI, a few studies also report infants with normal teeth. These differences in dental findings may indicate heterogeneity in OI lethal in infancy. Results of our study indicate that, until the primary biochemical defects in the OI syndromes are elucidated, examination of teeth from other infants with lethal OI and detailed evaluation of other clinical and skeletal features will aid in delineating heterogeneity and variation in expression in lethal OI.

Humans↗
PubMed1980

Scanning electron microscopy of teeth in dominant osteogenesis imperfecta: support for genetic heterogeneity.

Scanning electron microscopic studies were performed on 25 deciduous and permanent teeth from members of 7 kindreds with dominant nonlethal osteogenesis imperfects (OI). Two families had normal teeth on clinical and radiological examination; five families had blue or brown opalescent teeth with specific radiologic findings. Enamel surfaces and prism organization were normal on all teeth. On fractured surfaces, the dentin tubules of normal teeth from patients with OI were evenly distributed and coursed regularly to the dentin-enamel junction. Opalescent teeth had few tubules and those present were short, narrow, and tortuous. Dentin calcification fronts of normal teeth were composed of many nodules with regularly spaced openings on their surfaces. Calcification fronts of opalescent teeth were composed of irregularly spaced, small nodules, which varied greatly in size and the nodules lacked tubule openings on their surfaces. The results of this study support the concept that at least two dominant forms of OI exist--one in which all individuals with IO have normal teeth, and the other in which all with OI have blue or brown opalescent teeth with characteristic changes on SEM.

Dental Enamel↗
PubMed1980

Light microscopy, scanning electron microscopy, and microprobe analysis of bone response to zinc and nonzinc amalgam implants.

Freshly mixed, unset zinc-free and zinc-containing analgam was implanted in the right tibia of 32 rats. Half of the specimens were examined by the light microscope and the other half by the scanning electron microscope and x-ray microprobe analysis. It was found that amalgam is well tolerated by the rat osseous tissue, and there were no histologic reaction differences between zinc and zinc free amalgam. The surfaces of the implants were covered by an organic film at 3 weeks and with bone at later intervals. Very little corrosion products containing sulfur were observed on the amalgam surface at all intervals. Bone adjacent to the amalgam contained tin and sulfur irrespective of the presence of zinc in the alloy, indicating outward migration of specific components of the alloy.

Animals↗