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Biomedical subjects

M M Smith

Publications and source records attributed to M M Smith.

At least 127 records · Page 7Linked to original sources
PubMed1992

Furcation anatomy of the first mandibular molar in dogs.

Tooth surface and interradicular area (furcation) measurements were taken of 20 first mandibular molar teeth obtained randomly from canine cadavers. The lingual furcation entrance had a mean width of 1.2 +/- 0.3 mm. The buccal furcation entrance had a mean width of 1.3 +/- 0.4 mm. There was no significant difference between mean furcation entrance measurements. The horizontal attachment area between the cementoenamel junction and the coronal roof of the lingual furcation was 1.1 +/- 0.4 mm. The horizontal attachment area between the cementoenamel junction and the coronal roof of the buccal furcation (0.5 +/- 0.3 mm) was significantly different from the lingual horizontal attachment area. Distal root length and mesial root length were 16.0 +/- 1.5 mm and 16.1 +/- 1.6 mm, respectively. The mean coefficient of variation for variables measured was 14.0%. Tooth size did not have a significant effect on furcation entrance measurement. All teeth had a concavity coronal to the furcation area, which extended apically for a mean distance of 65.6% of the distal root length and 83.8% of the mesial root length. Furcation anatomy of the first mandibular molar is complex and may be a contributing factor in periodontal disease involving the interradicular area.

Animals↗
PubMed1992

Potential attachment area of the first mandibular molar in dogs.

Tooth root and root trunk surface area measurements were taken from 20 first mandibular molar (M1) teeth obtained randomly from canine cadaver specimens. The mean root surface area for all teeth was 497.1 +/- 116.2 mm2. The cumulative surface areas of the mesial (MR) and distal (DR) roots were 251.4 +/- 70.2 mm2 and 211.7 +/- 51.9 mm2, respectively. The root trunk surface area was 34.0 +/- 21.4 mm2. Surface area measurements for individual roots and the root trunk were significantly different. Cumulative individual root surface area (MR + DR) was 93.2% of total root surface area. The MR surface area contributed most to total root surface area (50.6%) and cumulative individual root surface area (54.3%). The mean distance from the beginning of the root trunk to the furcation was 2.1 mm. On the basis of the linear variation of the percentage of root surface area of the M1, 44.6% of the total root surface area was 3 to 7 mm apical to the most coronal aspect of the cementoenamel junction. The MR was heart-shaped, compared with the more cylindrical shape of the DR.

Animals↗
PubMed1991

T-plate for middle carpal and carpometacarpal arthrodesis in a dog.

Partial arthrodesis was performed for carpal hyperextension injury in a dog. T-plate application for middle carpal and carpometacarpal arthrodesis was associated with low patient morbidity and allowed normal pet activity without clinical lameness. Radiography revealed bony healing of arthrodesed joints, reactive bone formation over the dorsal aspect of the plate, and periarticular osteophyte formation. A guarded prognosis is advised for degenerative joint disease that may lead to decreased range of motion of the antebrachiocarpal joint.

Animals↗
PubMed1991

Nucleosome fractionation by mercury affinity chromatography. Contrasting distribution of transcriptionally active DNA sequences and acetylated histones in nucleosome fractions of wild-type yeast cells and cells expressing a histone H3 gene altered to encode a cysteine 110 residue.

A technique for the separation of transcriptionally active and inactive nucleosomes by mercury affinity chromatography has been applied to study the nucleosomal distribution of DNA sequences from the GAL1, ACT1, HIS4, MAT alpha, and HMRa genes of yeast. In mammalian cells, the method has been shown to separate active from inactive nucleosomes and to fractionate the active nucleosomes into two classes, one retained on the mercury column because of salt-labile associations with certain thiol-reactive non-histone proteins, and the other bound by covalent linkage of the cysteine 110 thiol groups of histone H3 molecules to the mercurated support. The first class of nucleosomes is elutable in 0.5 M NaCl; the second is displaced by 10 mM dithiothreitol (DTT) (Walker, J., Chen, T. A., Sterner, R., Berger, M., Winston, F., and Allfrey, V.G. (1990) J. Biol. Chem. 265, 5736-5746). We show that, in wild-type yeast cells, in which histone H3 lacks cysteinyl residues, very little DNA and a negligible complement of nucleosomes appear in the DTT-eluate, confirming the requirement for the H3-thiols in the mercury-binding reaction. Moreover, the DTT-eluted fraction is seriously deficient in the actively transcribed GAL1, ACT1, HIS4, and MAT alpha DNA sequences. Site-directed mutagenesis was employed to create an H3 gene containing a cysteine codon in place of the alanine codon at position 110 of the yeast H3 amino acid sequence. A strain was constructed containing the mutant histone H3 gene instead of the normal H3 gene. Subsequent fractionations of the mutant nucleosomes by mercury-affinity chromatography revealed a characteristic nucleosome peak in the DTT-eluted fraction. Its content of transcribed GAL1, ACT1, and HIS4 DNA sequences was 20- to 500-fold higher than that of the corresponding DTT-eluted fraction of wild-type yeast. Although this result is in accord with the finding that, in mammalian cells, the thiol groups of histone H3 become accessible when nucleosomes "unfold" during transcription, we find that nucleosomes containing the GAL1 DNA sequences of the yeast H3-mutant also bind to the mercury column when that gene is not being expressed. We conclude that many yeast nucleosomes are maintained in a "primed," potentially active state, possibly due to the very high constitutive levels of acetylation of the core histones. However, the nucleosomes of the HMRa gene, which is not expressed in a MAT alpha yeast strain, are virtually absent from the DTT-eluted nucleosome fractions of the H3-mutant cells, indicating that prolonged silencing of the gene is accompanied by compaction and loss of H3-thiol reactivity of its nucleosomes.

Acetylation↗
PubMed1991

Intraoperative gamma detection probe with presurgical antibody imaging in colon cancer.

In this study, presurgical gamma camera imaging and an intraoperative gamma detection probe were used in 12 consecutive patients 6 to 22 days after infusion with indium 111-labeled anticarcinoembryonic antigen monoclonal antibody (111In-MoAb). In three of 11 patients who underwent laparotomy, clinical management was affected by the probe findings: localization of occult retroperitoneal disease, identification of an occult cecal lesion, and localization of residual disease at a site of local recurrence. Of all intra-abdominal lesions seen using any method, the probe identified 18 (86%) of 21, compared with 14 (67%) of 21 with the 111In-MoAb scan, 10 (48%) of 21 by computed tomographic scan, and 16 (76%) of 21 after surgical exploration. Uptake of 111In-MoAb in the portal (n = 3) and mediastinal (n = 3) lymph nodes was not associated with histologic findings of malignant neoplasms. For all pathologically confirmed extrahepatic and nonportal sites of cancer, the probe localized nine of nine, compared with five of nine by 111In-MoAb scan, two of nine by computed tomographic scan, and six of nine by surgical exploration. Important clinical uses of the intraoperative probe included occult lesion identification, localization of areas with 111In uptake shown with MoAb scanning, and verification of complete resection of areas with 111In-MoAb uptake.

Abdominal Neoplasms↗
PubMed1991

Hepatitis E virus (HEV): molecular cloning and sequencing of the full-length viral genome.

We have recently described the cloning of a portion of the hepatitis E virus (HEV) and confirmed its etiologic association with enterically transmitted (waterborne, epidemic) non-A, non-B hepatitis. The virus consists of a single-stranded, positive-sense RNA genome of approximately 7.5 kb, with a polyadenylated 3' end. We now report on the cloning and nucleotide sequencing of an overlapping, contiguous set of cDNA clones representing the entire genome of the HEV Burma strain [HEV(B)]. The largest open reading frame extends approximately 5 kb from the 5' end and contains the RNA-directed RNA polymerase and nucleoside triphosphate binding motifs. The second major open reading frame (ORF2) begins 37 bp downstream of the first and extends approximately 2 kb to the termination codon present 65 bp from the 3' terminal stretch of poly(A) residues. ORF2 contains a consensus signal peptide sequence at its amino terminus and a capsid-like region with a high content of basic amino acids similar to that seen with other virus capsid proteins. A third open reading frame partially overlaps the first and second and encompasses only 369 bp. In addition to the 7.5-kb full-length genomic transcript, two subgenomic polyadenylated messages of approximately 3.7 and 2.0 kb were detected in infected liver using a probe from the 3' third of the genome. The genomic organization of the virus is consistent with the 5' end encoding nonstructural and the 3' end encoding the viral structural gene(s). The expression strategy of the virus involves the use of three different open reading frames and at least three different transcripts. HEV was previously determined to be a nonenveloped particle with a diameter of 27-34 nm. These findings on the genetic organization and expression strategy of HEV suggest that it is the prototype human pathogen for a new class of RNA virus or perhaps a separate genus within the Caliciviridae family.

Amino Acid Sequence↗
PubMed1991

Histone structure and function.

The past year has seen major advances in our understanding of histone and nucleosome structure and function. Direct DNA mapping and thermodynamic experiments have finally provided conclusive evidence that the histones impose an altered helical pitch on the DNA as it is wrapped on the surface of the core histone octamer. Further, it is now clear that lysine acetylation in the amino-terminal domains of histones H3 and H4 can alter the topology of the DNA in chromatin and probably influence its higher-order folding. Genetic experiments reported in the past year have provided a wealth of new information on histone structure and function, including the identification of the peptide domain of histone H4 that is necessary for permanent gene repression, the confirmation that nucleosome structure is critical for centromere function, and evidence that histone acetylation plays a significant role in chromosome dynamics.

Amino Acid Sequence↗
PubMed1991

Nutritional dwarfing: a growth abnormality associated with reduced erythrocyte Na+,K(+)-ATPase activity.

To assess whether nonorganic nutritional dwarfing (ND) is accompanied by a biochemical adaptation to reduced nutrient intake, Na+,K(+)-ATPase activity of erythrocytes was examined. The study included 27 children with ND who demonstrated deteriorating linear growth and poor weight gain (caused by self-imposed dietary restrictions), 20 patients who initially exhibited ND growth patterns and subsequently experienced catch-up weight gain and growth after nutritional rehabilitation (NDR), and 32 normally growing children who had familial short stature and/or constitutional growth delay (F/CSS). Na+,K(+)-ATPase activity in erythrocytes was significantly lower in ND patients than in the NDR and F/CSS groups. Furthermore, Na+,K(+)-ATPase activity was positively correlated with incremental body weight gain. Na+,K(+)-ATPase concentrations did not differ significantly with regard to sex, chronological age, bone age, or pubertal status. These data suggest that the growth retardation of ND patients is associated with decreased erythrocyte Na+,K(+)-ATPase activity without other biochemical evidence of malnutrition.

Adolescent↗
PubMed1991

The chromatin structure of Saccharomyces cerevisiae autonomously replicating sequences changes during the cell division cycle.

The chromatin structures of two well-characterized autonomously replicating sequence (ARS) elements were examined at their chromosomal sites during the cell division cycle in Saccharomyces cerevisiae. The H4 ARS is located near one of the duplicate nonallelic histone H4 genes, while ARS1 is present near the TRP1 gene. Cells blocked in G1 either by alpha-factor arrest or by nitrogen starvation had two DNase I-hypersensitive sites of about equal intensity in the ARS element. This pattern of DNase I-hypersensitive sites was altered in synchronous cultures allowed to proceed into S phase. In addition to a general increase in DNase I sensitivity around the core consensus sequence, the DNase I-hypersensitive site closest to the core consensus became more nuclease sensitive than the distal site. This change in chromatin structure was restricted to the ARS region and depended on replication since cdc7 cells blocked near the time of replication initiation did not undergo the transition. Subsequent release of arrested cdc7 cells restored entry into S phase and was accompanied by the characteristic change in ARS chromatin structure.

Cell Cycle↗
PubMed1991

The highly conserved N-terminal domains of histones H3 and H4 are required for normal cell cycle progression.

The N-terminal domains of the histones H3 and H4 are highly conserved throughout evolution. Mutant alleles deleted for these N-terminal domains were constructed in vitro and examined for function in vivo in Saccharomyces cerevisiae. Cells containing a single deletion allele of either histone H3 or histone H4 were viable. Deletion of the N-terminal domain of histone H4 caused cells to become sterile and temperature sensitive for growth. The normal cell cycle progression of these cells was also altered, as revealed by a major delay in progression through the G2 + M periods. Deletion of the N-terminal domain of histone H3 had only minor effects on mating and the temperature-sensitive growth of mutant cells. However, like the H4 mutant, the H3 mutants had a significant delay in completing the G2 + M periods of the division cycle. Double mutants containing N-terminal domain deletions of both histone H3 and histone H4 were inviable. The phenotypes of cells subject to this synthetic lethality suggest that the N-terminal domains are required for functions essential throughout the cell division cycle and provide genetic evidence that histones are randomly distributed during chromosome replication.

Alleles↗
PubMed1991

Effects of hydrogen peroxide on the metabolism of human rheumatoid and osteoarthritic synovial fibroblasts in vitro.

The effects of hydrogen peroxide (H2O2) on the metabolism of cultured human synovial fibroblasts derived from joints of four patients with rheumatoid arthritis and three with osteoarthritis have been investigated. The exposure of rheumatoid cell cultures to this oxygen derived species at sublethal concentrations (1-100 mumol/l) induced a dose related inhibition of both hyaluronic acid (HA) and DNA synthesis. In contrast, in osteoarthritic cell lines a biphasic response was shown. At low concentrations of H2O2 (less than 10 mumol/l) a stimulatory effect on HA synthesis was noted, whereas in the presence of higher concentrations (greater than 10 mumol/l) a significant inhibition of synthesis occurred. These deleterious effects of H2O2 were partially reduced by the addition of catalase to the culture media. The finding that both HA and DNA synthesis were inhibited at concentrations of H2O2 less than those which caused loss of cell integrity (greater than 200 mumol/l) suggests oxidation of intracellular components, such as glyceraldehyde-3-phosphate dehydrogenase, and subsequent depletion of ATP concentrations.

Arthritis, Rheumatoid↗
PubMed1991

Lung function abnormalities and decline of spirometry in scleroderma: an overrated danger?

To document the prevalence and progression of pulmonary involvement in scleroderma (systemic sclerosis including the CREST syndrome), the clinical notes and lung function records of 113 cases were reviewed. Lung function was normal in 39 cases, isolated impairment of DLCO was found in 38 patients, a restrictive defect was present in 27 cases and there was evidence of airflow obstruction in 9 cases. The median duration of symptoms was 10 years. Dyspnoea and an interstitial pattern on chest X-ray were associated with impaired lung function. Death during the period of review was significantly related to initial impairment of the DLCO. Sixty-six patients (53 women and 13 men) underwent repeat spirometry at least 1 year after initial testing. The rates of change in VC and FEV1 were no more rapid than would be expected for normal subjects. There was no significant difference in rates of change between men and women or between dyspnoeic patients and those who were asymptomatic. The extent of skin involvement and the presence of interstitial fibrosis on chest X-ray were unrelated to the rate of loss of lung function. It is concluded that most scleroderma patients in this study had abnormal lung function when first tested, but overall significant worsening of spirometry was not found.

Adolescent↗
PubMed1991

Salivary mucoceles.

The overall incidence of salivary gland disease in dogs and cats is low. Salivary mucocele is the most frequently diagnosed disease of salivary glands. Mucoceles consist of collections of saliva in subcutaneous, sublingual, pharyngeal, or periorbital locations. Definitive therapy of salivary mucoceles consists of excision of the affected salivary gland and mucocele drainage.

Animals↗
PubMed1991

Axial pattern flap based on the caudal auricular artery in dogs.

An axial pattern flap that was based on the sternocleidomastoideus branches of the caudal auricular artery and vein was developed. Control flaps, which included ligation and division of the caudal auricular artery and vein, were similarly developed on the contralateral aspect of the neck. Mean survival of caudal auricular artery axial pattern flaps (85.2%), compared with control flaps (63.9%), was significantly different (P less than 0.05). On the basis of results of this study, an axial pattern flap based on the sternocleidomastoideus branches of the caudal auricular artery and vein may be a source of skin for reconstructive procedures of the head and neck.

Animals↗
PubMed1991

Nutritional dwarfing: is it a consequence of disturbed psychosocial functioning?

Nutritional dwarfing refers to a condition in which maladaptive eating patterns play a primary role in poor linear growth and delayed pubertal development. The present controlled study assesses whether nutritionally dwarfed children and adolescents differ in their psychosocial adjustment from healthy children and adolescents of comparable height in ways that might account for their undernutrition. Children with nutritional dwarfing (n = 16) were compared by standardized questionnaires with a short-stature (ie, heights below the fifth percentile) control group composed of children and adolescents with constitutional growth delay and/or familial short stature (n = 31). Scores on a self-report screening questionnaire for eating disorders did not differentiate the groups. Moreover, the vast majority of nutritionally dwarfed patients expressed a desire to have a heavier physical appearance. Whereas the groups were generally similar in self-perceptions of domain-specific competencies and positive psychosocial adjustment, the parents of nutritionally dwarfed children reported that their children showed significantly fewer externalized behavior problems. These findings suggest the existence of an eating disturbance that compromises growth in childhood and/or adolescence which, unlike anorexia nervosa, is not associated with evidence of psychopathology.

Adolescent↗
PubMed1991

Potential attachment area of the fourth maxillary premolar in dogs.

Tooth root and root trunk surface area measurements were made on 20 permanent fourth maxillary premolar (P4) teeth randomly harvested from canine cadaver specimens. Mean root surface area for all 20 teeth was 562.8 +/- 124.9 mm2. Cumulative surface areas of the mesiopalatal, mesiobuccal, and distal roots were 113.8 +/- 29.0 mm2, 138.5 +/- 34.6 mm2, and 180.8 +/- 39.9 mm2, respectively. The mesial root trunk and distal root trunk surface areas were 60.0 +/- 17.5 mm2 and 72.1 +/- 33.2 mm2, respectively. There was not a significant difference between the root surface area of the mesial root trunk and distal root trunk; however, all other root surface area measurements were significantly different (P less than 0.01). Cumulative individual root surface area (distal root + mesiobuccal root + mesiopalatal root) was 76% of total root surface area. The distal root surface area contributed most to total root surface area (32.1%) and cumulative individual root surface area (41.7%). Observation of the linear variation of percentage of root surface area revealed 40.8% of the total root surface area to be in the portion located between 5 and 9 mm apical to the most coronal aspect of the cementoenamel junction. The mesiobuccal root and distal root were cylindrical compared with the flattened, concave shape of the mesiopalatal root.

Animals↗
PubMed1991

Coronary heart disease knowledge test: developing a valid and reliable tool.

This study tested the validity and reliability of a written test designed to assess knowledge of coronary heart disease (CHD) and its risk factors. The subjects were 93 males diagnosed with CHD. Subjects were classified into a treatment group (n = 48) or a control group (n = 45) based on whether or not they participated in a cardiac rehabilitation program (CRP). An additional 38 subjects were used to pilot test the original form of the knowledge test, which consisted of 80 multiple-choice questions. Content validity was established by a five-member jury of cardiac rehabilitation experts. Each question was rated using a Likert-type scale. Questions that did not receive an average rating of at least four were eliminated. The revised form was pilot tested for validity and internal consistency with the discrimination index (point biserial correlation coefficient) and the Kuder-Richardson formula 20 (KR-20). Questions with a discrimination index of less than 0.14 were eliminated; thus, the final form of the test consisted of 40 questions. Validation of this test yielded difficulty ratings (DRs) between 0 percent and 98 percent, with an average DR of 63 percent. Construct validation indicated that the average test score of subjects participating in a CRP was significantly higher than that of non-participants (t = 3.51, df = 91, p less than or equal to 0.01). The internal-consistency reliability of the test was 0.84. The results indicate that this test is a valid and reliable tool for assessing patients' knowledge of CHD and its risk factors.

Adult↗