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Biomedical subjects

J A Martin

Publications and source records attributed to J A Martin.

At least 37 records · Page 2Linked to original sources
PubMed2001

Incidence rates for complete cusp fracture.

OBJECTIVES: Although complete cusp fracture is acknowledged to occur frequently, incidence rates have been reported rarely. This study determined incidence rates for complete coronal cusp fracture per person and per tooth type. METHODS: All fractures presenting among enrollees in a dental health maintenance organization using two geographically isolated clinics were noted for 105 days. For a sample of these enrollees, likelihood of attending the clinic in the event of a fracture was assessed through a telephone survey, and the at-risk status of all teeth was determined through a record survey. Incidence rates were calculated for persons, and for individual tooth types for all complete fractures and for non-carious complete fractures. In addition, for posterior teeth the distribution of fractured cusps, and the severity of fractures were examined. RESULTS: Per-person incidence rates for complete coronal fractures for all teeth were 89.0 and 72.7 per 1000 person years, respectively, for all fractures and for non-carious fractures. The rates for all anterior and all posterior teeth were 10.2 and 69.9, respectively, for all non-carious fractures. In mandibular posterior teeth, lingual cusps fractured twice as frequently as facial cusps, while the opposite was true for maxillary premolars. Among maxillary molars, the mesiofacial and distolingual cusps fractured most frequently. The large majority of fractures exposed dentin (95%), while pulpal exposure occurred infrequently (3%). A minority of fractures extended below the gingival crest (24%) or the DEJ (25%). CONCLUSIONS: This is the first report of fracture incidence rates for enumerated persons and teeth at risk and as such helps define the magnitude of the problem for dentists and their patients.

Adolescent↗
PubMed2001

Training general practitioners in flexible sigmoidoscopy to screen for colorectal cancer.

BACKGROUND: A screening programme to detect polyps or early carcinoma would significantly reduce the mortality and morbidity of colorectal cancer (CRC). The aims of the present study were to evaluate: (i) the feasibility of training general practitioners in flexible sigmoidoscopy (FS) for CRC screening; (ii) the acceptability of screening by faecal occult blood testing (FOBT) and FS in asymptomatic standard risk Australians aged over 50 years; and (iii) the yield of such screening. METHODS: Subjects were recruited by general practitioner (GP) referral, newspaper advertisement or by a direct approach to retirement villages. Participants were mailed a FOBT kit and a prescreening questionnaire. Flexible sigmoidoscopy was performed by a GP supervised by an experienced endoscopist. Subjects then completed a second questionnaire. General practitioners were assessed after 50 unassisted procedures. RESULTS: A total of 264 individuals contacted the study coordinator; 169 were screened. Screening was accepted well by the participants. Fifteen per cent of subjects had polyps and 4% had a positive FOBT. Training in FS was adversely affected by the availability of resources. Three GPs completed 50 unassisted procedures over a 15-month period, but none were able to reliably assess the distal bowel. CONCLUSIONS: Although the three trainees and their supervisors did not consider that the GPs were adequately trained after 50 unassisted procedures, training was adversely affected by limited resources within the Victorian public hospital system. Screening by FOBT and FS was considered to be acceptable by the patients undergoing these procedures. Existing facilities are not adequate if GPs are to be trained in FS as part of a national CRC screening program.

Aged↗
PubMed2001

Telomere erosion and senescence in human articular cartilage chondrocytes.

Aging and the degeneration of articular cartilage in osteoarthritis are distinct processes, but a strong association exists between age and the incidence and prevalence of osteoarthritis. We hypothesized that this association is due to in vivo replicative senescence, which causes age-related declines in the ability of chondrocytes to maintain articular cartilage. For this hypothesis to be tested, senescence-associated markers were measured in human articular chondrocytes from donors ranging in age from 1 to 87 years. These measures included in situ staining for senescence-associated beta-galactosidase activity, (3)H-thymidine incorporation assays for mitotic activity, and Southern blots for telomere length determinations. We found that senescence-associated beta-galactosidase activity increased with age, whereas both mitotic activity and mean telomere length declined. These findings indicate that chondrocyte replicative senescence occurs in vivo and support the hypothesis that the association between osteoarthritis and aging is due in part to replicative senescence. The data also imply that transplantation procedures performed to restore damaged articular surfaces could be limited by the inability of older chondrocytes to form new cartilage after transplantation.

Adolescent↗
PubMed2001

Social cognition and subclinical paranoid ideation.

OBJECTIVE: A number of cognitive biases have been identified relevant to persecutory thought (e.g. exaggerated self-serving bias). Moreover, findings of increased depressed mood in conjunction with high levels of self-esteem have contributed to theories of persecutory ideation (e.g. Bentall, Kinderman, Kaney, 1994). Using a nonclinical sample, the present study sought to expand upon previous research by examining the linear relationship between persecutory ideation and multiple clinical and social cognitive variables. DESIGN: A cross-sectional design was used. Correlational and multiple regression analyses were conducted. METHOD: One hundred and ninety-three undergraduate students were administered a battery of questionnaires which assessed the following domains: Paranoid ideation, depression, social anxiety, self-monitoring, attributional style and self-esteem. RESULTS: Higher levels of paranoid ideation were significantly associated with greater depressed mood, social anxiety and avoidance, evaluation apprehension, self-monitoring and lower self-esteem. There were no significant associations between paranoid ideation and attributional biases. CONCLUSIONS: These findings suggest that mood, anxiety and perceptions of the self are related to paranoid ideation in a nonclinical sample. These findings are tempered, however, by studying a nonclinical sample and the self-report measures of paranoid ideation that might be assessing multiple aspects of paranoid thought (e.g. ideas of reference).

Adolescent↗
PubMed2001

On the duration of spatial fluency measures.

Various measures of spatial fluency have been developed and have been shown to be sensitive to right frontal lobe dysfunction. Patients with diffuse cerebral injuries (traumatic brain injury) also show impaired performance. Administration times for these tests range from three to five minutes. It is well known that longer tests provide more reliable data. In the present study, the base rates of unique designs and perseverative errors on the Five-Point Test were examined minute-by-minute for ten minutes, in a sample of healthy young adults (n=80). Contrasts between each minute showed significant decreases in number of unique designs to the ninth minute (significant at p<.001). Contrasts between each minute revealed significant increases (significant at p<.00l) in percentage of perseverative errors to the eighth minute. Data demonstrating the progressive decrease of unique designs and progressive increase of perseverative errors as a function of time have important implications for clinical practice. Optimal administration time is considered in the context of clinicians' objectives.

Adult↗
PubMed2001

The prevalence and correlates of psychological distress following physical and sexual assault in a young adult cohort.

Among a birth cohort of New Zealand's 21-year-olds, 41% experienced physical or sexual assault in the previous 12 months. The level of psychological distress experienced by the 374 victims was determined in interviews assessing for symptoms indicative of posttraumatic stress disorder and ratings of impairment in activities of daily living. Of the 141 women victims, 32.6% were identified as experiencing psychological distress as were 9.9% of the 233 men. For men, bivariate analyses showed psychological distress was significantly associated with factors indicative of increased assault severity, and for women an increased likelihood of distress was associated with the location of assault and the relationship to the assailant. Positive indicators of social support were not significantly associated with less adverse psychological outcomes. However, for both men and women, resisting the assailant was associated with a reduced likelihood of psychological distress. Multivariate analyses revealed that for both women and men, unemployment uniquely predicted variance in distress, over and above that accounted for by characteristics of the assault.

Adult↗
PubMed2001

Roles of articular cartilage aging and chondrocyte senescence in the pathogenesis of osteoarthritis.

Osteoarthritis (OA), the disease characterized by joint pain and loss of joint form and function due to articular cartilage degeneration, is not an inevitable consequence of aging, but a strong association exists between age and increasing evidence of OA. Aging changes in articular cartilage that increase the risk of articular cartilage degeneration include fibrillation of the articular surface, decrease in the size and aggregation of proteoglycan aggrecans, increased collagen cross-linking and loss of tensile strength and stiffness. These alterations are most likely primarily the result of aging changes in chondrocyte function that decrease the ability of the cells to maintain the tissue including decreased synthetic activity, synthesis of smaller less uniform aggrecans and less functional link proteins and decreased responsiveness to anabolic growth factors. Our recent work suggests that the cause of the age-related loss of chondrocyte function may be progressive senescence of articular cartilage chondrocytes marked by a decline in mitotic activity, increased expression of the senescence-associated enzyme beta-galactosidase and erosion of telomere length. New efforts to prevent the development or progression of OA might include strategies that delay the onset of chondrocyte senescence or replace senescent cells.

Aggrecans↗
PubMed2000

Births: preliminary data for 1999.

OBJECTIVES: This report presents preliminary data for 1999 on births in the United States. U.S. data on births are shown by age, race, and Hispanic origin of mother. Data on marital status, prenatal care, cesarean delivery, and low birthweight are also presented. METHODS: Data in this report are based on more than a 97-percent sample of births for 1999. The records are weighted to independent control counts of births received in State vital statistics offices in 1999. Comparisons are made with 1998 final data. RESULTS: The crude birth rate in 1999 was 14.5 per 1,000 population, a slight decline from 1998 (14.6), returning to the level observed in 1997. However, the fertility rate, which is limited to women aged 15-44 years, was 65.8 in 1999, a slight increase over the rate for 1998 (65.6). The birth rate for teenagers continued to decline for 1998-99, dropping 3 percent to 49.6 births per 1,000 females aged 15-19 years. The 1999 rate for teenagers is 20 percent lower than the recent high point in 1991. The rate for young teenagers 15-17 years fell 6 percent, and the rate for teenagers 18-19 years declined 2 percent. Since 1991, rates have fallen 26 percent for teenagers 15-17 years, and 15 percent for teenagers 18-19 years. Birth rates for women aged 20-24 years declined slightly between 1998 and 1999 whereas the rate for women aged 25-29 years rose 2 percent. Birth rates for women in their thirties and forties continued their long increase. Rates for women in their thirties increased 2 to 3 percent and were the highest in three decades. The birth rate for women aged 40-44 years was the highest level reported since 1970. The birth rate for unmarried women in 1999 was 43.9 per 1,000, 1 percent lower than in 1998 and 6 percent lower than the peak level reported for 1994 (46.9). However, the number of births to unmarried women was up about 1 percent due to the continued increase in the number of unmarried women of childbearing age. The rate of prenatal care utilization continued to improve. The total cesarean rate increased 4 percent between 1998 and 1999 and continued a 3-year rise. The low birthweight rate remained unchanged at 7.6 percent.

Adolescent↗
PubMed2000

Trends in twin birth outcomes and prenatal care utilization in the United States, 1981-1997.

CONTEXT: Multiple births account for an increasing percentage of all low-birth-weight infants, preterm births, and infant mortality in the United States. Since 1981, the percentage of women with multiple births who received intensive prenatal care (defined as a high number of visits, exceeding the recommendation of the American College of Obstetricians and Gynecologists by approximately 1 SD beyond the mean number of visits for women initiating care within each trimester) has increased significantly. OBJECTIVES: To explore the hypothesis that more aggressive management of twin-birth pregnancies may be associated with changes in birth outcomes in this population. DESIGN, SETTING, AND SUBJECTS: Cross-sectional and trend analysis of data from the National Center for Health Statistics' birth and infant death records for all twin births occurring in the United States between 1981 and 1997, excluding those with missing or inconsistent data. MAIN OUTCOME MEASURES: Trends in preterm birth, low birth weight, preterm and term small-for-gestational-age (SGA) births, and infant mortality, by level of prenatal care utilization. RESULTS: The preterm birth rate for twins increased from 40.9% in 1981 to 55.0% in 1997. The percentage of low-birth-weight infants increased from 51.0% to 54.0%. The preterm SGA rate also increased from 11.9% to 14.1%, while the term SGA rate decreased from 30.7% to 20.5%. For women with intensive prenatal care utilization, the preterm birth rate increased from 35.1% to 55.8%, compared with an increase from 50.6% to 59.2% among women with only adequate use. Twin preterm deliveries involving either induction or first cesarean delivery also increased from 21.9% to 27.3% between 1989-1991 and 1995-1997. The twin infant mortality rate for women with intensive prenatal care use declined between 1983 and 1996 and remained lower than the overall twin infant mortality rate. CONCLUSIONS: An apparent increase in medical interventions in the management of twins may result in the seeming incongruity of more prenatal care and more preterm births; however, these data suggest that women with intensive prenatal care utilization also have a lower infant mortality rate. JAMA. 2000;283:335-341

Cross-Sectional Studies↗
PubMed2000

Reversible suppression of in vitro biomineralization by activation of protein kinase A.

Parathyroid hormone (PTH-(1-34)) potently suppresses apatite deposition in osteoblastic cultures. These inhibitory effects are mediated through signaling events following PTH receptor binding. Using both selective inhibitors and activators of protein kinase A (PKA), this study shows that a transient activation of PKA is sufficient to account for PTH's inhibition of apatite deposition. This inhibition is not a result of reduced cell proliferation, reduced alkaline phosphatase activity, increased collagenase production, or lowering medium pH. Rather, data suggest a functional relationship between matrix assembly and apatite deposition in vitro. Bone sialoprotein (BSP) and apatite co-localize in the extracellular matrix of mineralizing cultures, with matrix deposition of BSP temporally preceding that of apatite. Transient activation of PKA by either PTH-(1-34) or short term cAMP analog treatment blocks the deposition of BSP in the extracellular matrix without a significant reduction in the total amount of BSP synthesized and secreted. This effect is reversible after allowing the cultures to recover in the absence of PKA activators for several days. Thus, a transient activation of PKA may suppress mineral deposition in vitro as a consequence of altering the assembly of an extracellular matrix permissive for apatite formation.

Alkaline Phosphatase↗
PubMed2000

Births: final data for 1998.

OBJECTIVES: This report presents 1998 data on U.S. births according to a wide variety of characteristics. Data are presented for maternal demographic characteristics including age, live-birth order, race, Hispanic origin, marital status, and educational attainment; maternal lifestyle and health characteristics (medical risk factors, weight gain, and tobacco and alcohol use); medical care utilization by pregnant women (prenatal care, obstetric procedures, complications of labor and/or delivery, attendant at birth, and method of delivery); and infant health characteristics (period of gestation, birthweight, Apgar score, abnormal conditions, congenital anomalies, and multiple births). Also presented are birth and fertility rates by age, live-birth order, race, Hispanic origin, and marital status. Selected data by mother's State of residence are shown including teenage birth rates and total fertility rates, as well as data on month and day of birth, sex ratio, and age of father. Trends in fertility patterns and maternal and infant characteristics are described and interpreted. METHODS: Descriptive tabulations of data reported on the birth certificates of the 3.94 million births that occurred in 1998 are presented. RESULTS: Birth and fertility rates increased in 1998 by about 1 percent, the first increase since 1990. Birth rates for teenagers fell 2-5 percent. Rates for women in their twenties increased 1-2 percent each, whereas rates for women in their thirties rose 2-4 percent. All measures of childbearing by unmarried women increased in 1998; the number of births rose 3 percent, the birth rate increased about 1 percent while the percent of births that were to unmarried women rose to 32.8 percent. Smoking by pregnant women overall dropped again in 1998, but continued to increase among teenagers. Improvements in prenatal care utilization continued. The cesarean delivery rate increased for the second year after declining for 7 consecutive years. The proportion of multiple births continued to rise; higher order multiple births (e.g., triplets, quadruplets) rose by 13 percent in 1998, following a 14 percent rise from 1996 to 1997. Key measures of birth outcome--the percents of low birthweight and preterm births--increased. These changes are in large part the result of increases in multiple births.

Adolescent↗
PubMed2000

Tenascin-C in tendon regions subjected to compression.

Tendon regions subjected almost exclusively to tension differ from regions subjected to high levels of compression as well as tension. Regions not exposed to compression consist primarily of spindle-shaped fibroblasts surrounded by densely packed longitudinally oriented collagen fibrils formed principally from type-I collagen. In contrast, regions subjected to compression have a fibrocartilagenous structure and composition: they consist of spherical cells surrounded by a matrix containing hyaline cartilage proteoglycans (aggrecan) and type-II collagen as well as type-I collagen. Reducing their adhesion to the matrix may help cells in the latter regions establish and maintain a spherical shape and minimize their deformation when the tissue is subjected to mechanical stress. We hypothesized that expression of tenascin-C, an anti-adhesive protein, is part of the adaptation of tendon cells to compression that helps establish and maintain fibrocartilagenous regions. To test this hypothesis, we compared segments of bovine flexor tendons subjected to repetitive compression (distal) with segments that are not subjected to compression (proximal) to determine whether they differed in tenascin-C content and expression. RNA and protein analyses showed that tenascin-C expression was elevated in the distal tendon. Tendon cells from the distal segment expressed more tenascin-C mRNA than did cells from the proximal segments for as long as 4 days in cell culture, indicating that increased tenascin-C expression is a relatively stable feature of the distal cells. Moreover, purified tenascin-C inhibited the attachment of cultured tendon cells to fibronectin. These observations support the hypothesis that tenascin-C expression is a cellular adaptation to compression that helps establish and maintain fibrocartilagenous regions of tendons by decreasing cell-matrix adhesion.

Animals↗
PubMed2000

Paracetamol (acetaminophen) hypersensitivity.

BACKGROUND: Acetaminophen (paracetamol) is an analgesic antipyretic drug with no antiinflammatory effects and is widely used worldwide. Earlier clinical studies reported IgE-mediated adverse reactions to acetaminophen, but in vivo and in vitro tests have been inconclusive. OBJECTIVE: We propose to demonstrate an IgE-mediated mechanism in four patients with adverse reactions to acetaminophen (paracetamol). Tolerance to aspirin and other nonsteroidal antiinflammatory drugs are present in all patients. METHODS: We studied four patients with anaphylactic reactions to acetaminophen who tolerated aspirin and other nonsteroidal antiinflammatory drugs. Skin tests, oral challenges and immunoassay for allergen-specific IgE antibodies with acetaminophen were performed in all patients. RESULTS: All patients tolerated the aspirin oral challenge without adverse effects. In contrast, the oral challenge with acetaminophen produced adverse effects in all patients. Skin tests with acetaminophen were positive in two patients (3-mm wheal and flare) and IgE antibodies acetaminophen were detected in serum from two patients. CONCLUSION: We describe four patients with adverse reactions to acetaminophen but with tolerance to aspirin and other nonsteroidal antiinflammatory drugs. Skin tests, oral challenges, and serum IgE results with acetaminophen suggest that an IgE-mediated mechanism is responsible for these reactions.

Acetaminophen↗
PubMed2000

An internal histidine residue from the bacterial surface protein, PAM, mediates its binding to the kringle-2 domain of human plasminogen.

The determinants of binding of a peptide lacking C-termini-exposed lysine residues to a kringle domain were investigated using an up-regulated lysine binding kringle (K2Pg[C4G/E56D/K72Y]) of plasminogen and a peptide (a1-PAM) with a sequence derived from a surface-exposed M-like streptococcal protein. Significant kringle-induced chemical shifts in a His side-chain of a1-PAM were revealed by two-dimensional NMR. Further studies using isothermal titration calorimetry (ITC) provided support for the involvement of His12 in the peptide/ protein complex. In an effort to screen a1-PAM-derived truncation peptides, a combinatorial mixture, a1deltaa2-PAM[H12X] (where X=Pro, Arg, His, Trp, Lys, Ala, Phe, Asp and Gly), was analyzed using the surface-enhanced laser desorption ionization time-of-flight mass spectrometry (SELDI) platform. The major peptide that remained bound to the surface of the K2Pg[C4G/ E56D/K72Y]-containing chip was that containing His12, corresponding to the wild-type sequence. Minor peaks, representing binding, were obtained for Lys12-, Arg12- and Trp12-containing peptides. Individual peptides containing these amino acids were then examined using ITC and the binding constants obtained correlated with the relative strengths of binding estimated from the SELDI-based screen.

Bacterial Proteins↗
PubMed2000

Identification of adult populations at high risk for dental caries using a computerized database and patient records: a pilot project.

OBJECTIVES: The purpose of this study is to test the usefulness of dental insurance claims history, supplemented with radiographic caries diagnoses, as a means of identifying caries-active and caries-inactive working adults, as determined by bacterial levels. Computerized identification of at-risk groups may facilitate subject selection for clinical trials designed to test caries-preventive strategies. METHODS: Two groups of subjects were initially selected from an insurance database based upon their dental service utilization during a one-year period: a "low restorative" group of individuals defined as persons who had received no restorative treatment, and a "high restorative" group comprised of individuals who had received at least three multisurfaced restorations. A chart review confirmed a diagnosis of caries in the high restorative group and an absence of caries in the low restorative group. Subjects were then approached for saliva collection. The low and high restorative groups were compared for salivary mutans streptococci and lactobacilli levels, stimulated flow rate, and buffer capacity (n = 48). RESULTS: The high and low restorative groups differed in mutans streptococci levels, but not on other measures. CONCLUSIONS: A group of subjects who had recently received multisurfaced restorations that were placed for reasons of caries had significantly higher levels of mutans streptococci and potential for continued caries activity when compared to a group of subjects who had received no restorations and were caries free.

Adult↗