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Biomedical subjects

J Meister

Publications and source records attributed to J Meister.

At least 19 recordsLinked to original sources
PubMed2002

Calcium solubility of dental enamel following sub-ablative Er:YAG and Er:YSGG laser irradiation in vitro.

BACKGROUND AND OBJECTIVE: The objective of the present study was to investigate the effect of sub-ablative Er:YAG (lambda = 2.94 microm) and Er:YSGG (lambda = 2.79 microm) laser radiation on the acid solubility of dental enamel. The influence of fluoride application prior to laser irradiation was additionally evaluated. STUDY DESIGN/MATERIALS AND METHODS: To this end, 294 enamel specimens were prepared from bovine teeth and divided into 14 groups of 21 specimens each. The enamel samples were irradiated in their groups with the Er:YAG and the Er:YSGG laser, using energy densities of 4, 6, and 8 J/cm(2) in each case. Irradiation was additionally repeated in the same way on specimens, which had previously been immersed in 1% sodium fluoride solution for 15 minutes. One group was left untreated and served as a control group. A further group was not irradiated, but only immersed in the 1% fluoride solution for 15 minutes. The enamel specimens were demineralised for 24 hours in an acetate buffer solution. The calcium content in the demineralisation solution was subsequently determined with the aid of atomic absorption spectrometry. RESULTS: The results indicate a decline in calcium solubility after laser irradiation. Compared to the control group, a 20% lower calcium content was detected in the demineralisation solution after irradiation with the Er:YSGG laser at 8 J/cm(2). The difference between the laser-irradiated groups and the untreated control group was, however, not statistically significant. A significantly lower calcium content was found in the demineralisation solution after fluoridation of the specimens. Additional laser radiation had no further effect on this result. CONCLUSIONS: In summary, it can be stated that, although the erbium laser wavelengths apparently have the potential to increase acid resistance, their application solely for caries prevention would not appear to be sensible under the prevailing conditions.

Analysis of Variance↗
PubMed2002

The ablation threshold of Er:YAG and Er:YSGG laser radiation in dental enamel.

The scientific investigation of fundamental problems plays a decisive role in understanding the mode of action and the consequences of the use of lasers on biological material. One of these fundamental aspects is the investigation of the ablation threshold of various laser wavelengths in dental enamel. Knowledge of the relationships and influencing factors in the laser ablation of hard tooth tissue constitutes the basis for use in patients and the introduction of new indications. The present paper examines the ablation threshold of an Er:YAG laser (lambda=2.94 micro m) and an Er:YSGG laser (lambda=2.79 micro m) in human dental enamel. To this end, 130 enamel samples were taken from wisdom teeth and treated with increasing energy densities of 2-40 J/cm(2). The sample material was mounted and irradiated on an automated linear micropositioner. Treatment was performed with a pulse duration of tau(P(FWHM)) approximately 150 micro s and a pulse repetition rate of 5 Hz for both wavelengths. The repetition rate of the laser and the feed rate of the micropositioner resulted in overlapping of the single pulses. The surface changes were assessed by means of reflected light and scanning electron microscopy. On the basis of the results, it was possible to identify an energy density range as the ablation threshold for both the Er:YAG and the Er:YSGG laser. With the Er:YAG laser, the transition was found in an energy density range of 9-11 J/cm(2). The range for the Er:YSGG laser was slightly higher at 10-14 J/cm(2).

Dental Enamel↗
PubMed2002

Influence of the pulse duration of an Er:YAG laser system on the ablation threshold of dental enamel.

The present study examines the dependence of the ablation threshold on the duration of the applied laser pulses in the dental enamel of human wisdom teeth. To this end, 600 treatments with the Er:YAG laser (lambda=2940 nm) were carried out on a total of 50 extracted teeth. The laser light was coupled into a fluoride glass light guide for this purpose, in order to ensure almost gaussian distribution of the light in a radially symmetrical beam. The beam diameter on the specimen was 610 micro m. The radiant exposure on the tooth surface was varied between 2 and 20 J/cm(2), while the duration of the pulses applied was changed in four steps from 100 micro s to 700 micro s. The irradiated tooth surfaces were examined for visible signs of ablation under a reflected-light microscope. The experiments revealed that, when pulses of shorter duration are used, the limit at which ablation sets in is reduced by up to approx. 3 J/cm(2). This expands the ablation threshold range of Er:YAG laser radiation to between 6 and 10 J/cm(2). In this context, both the pulse duration and the radiant exposure have a statistically significant influence on the ablation threshold (logistic regression, p<0.0001). Although the ablation threshold of the dental enamel can be changed by varying the pulse duration of the Er:YAG laser, no clinical consequences can be expected, as the shift is only slight.

Dental Enamel↗
PubMed2000

Stroke: a case review.

Stroke is indicated by an abrupt manifestation of neurologic deficits secondary to an ischemic or hemorrhagic insult to a region of the brain. Stroke is ranked as the third leading cause of death in the United States, affects more than 730,000 individuals per year, and accounts for 160,000 deaths annually. Approximately $40 billion is spent annually for health care treating stroke victims. This case report shows that despite the use of antithrombotic and/or antiplatelet aggregating drugs, the key to stroke management is primary prevention.

Aged↗
PubMed2000

Community-acquired pneumonia: a case study.

Community-acquired pneumonia (CAP) is an infectious disease commonly seen in the primary care environment. CAP is ranked as the sixth leading cause of death in the United States. It affects more than 10 million individuals per year and accounts for 500,000-1,000,000 hospital admissions. Precise diagnosis of CAP continues to be complex. Despite enormous advances in serologic analysis and antimicrobial development, at least 50% of causative pathogens are not identified. This article presents a case report of a white female in her seventies diagnosed with CAP and emphasizes the need for early detection, immunization, and prompt interventions to reduce morbidity and mortality rates. This case brings to light the dilemma practitioners can face when treating high-risk populations on an outpatient basis.

Aged↗
PubMed1999

Acute upper gastrointestinal bleed: a case study.

Upper gastrointestinal (UGI) bleeding on a presenting symptom is of major significance for nurse practitioners in any clinical setting. Bleeding in the upper gastric tract is a symptom of a disease process rather than a disease in itself. UGI bleeding accounts for 300,000 hospitalizations annually. An astute knowledge of the pathophysiology and clinical presentations of UGI bleeding enables swift intervention and a reduction in morbidity and mortality rates. This article presents a case report of a white male in his fifties diagnosed with metastatic colon cancer and acute UGI bleeding and emphasizes the need for early screening and detection, disease education, and prompt interventions to minimize associated complications.

Acute Disease↗
PubMed1999

Human babesiosis: a case study.

Babesiosis is an intraerythrocytic parasitic infection caused by protozoa of the genus Babesia and transmitted by the Ixodes dammini tick, which also transmits Lyme disease. Babesiosis is emerging as an illness of public health significance in the United States. Occurrences of Babesiosis infections have been reported during spring, summer, and fall in coastal areas in the northeastern United States. Asymptomatic patients may need only supportive care, whereas asplenic, elderly, and immunocompromised patients are at greatest risk for severe disease. However, overall mortality rates for symptomatic cases are less than 10%. This article presents a case report on a white male in his 70s diagnosed with human Babesiosis and emphasizes the need for early detection and prompt interventions to minimize the sequelae related to this tick-borne disease.

Aged↗
PubMed1998

Faecal progesterone metabolite analysis for non-invasive monitoring of reproductive function in the white rhinoceros (Ceratotherium simum).

The two subspecies of white rhinoceros, southern (Ceratotherium simum simum) and northern (Ceratotherium simum cottoni), breed poorly in captivity, and estimates of oestrous cycle length vary considerably (range, 25-90 days). To characterise reproductive patterns, faecal samples were collected 2-3 times/week for up to 56 months from non-pregnant animals (n=21) of both subspecies. Immununoreactive pregnanes containing a 20-oxo-group (20-oxo-P) were analysed in a group-specific enzyme immunoassay using an antibody against 5alpha-pregnane-3beta-ol-20-one 3HS:BSA. Reproductive patterns were highly variable among and within individual animals. However, rhinoceroses could be classified into four major categories on the basis of oestrous cycle length and luteal phase 20-oxo-P concentrations: (1) regular oestrous cycles of 10 weeks duration and > 800 ng/g (n=2 animals); (2) oestrous cycles between 4-10 weeks and 250-750 ng/g (n=6); (3) no apparent cycle regularity, but luteal activity indicated by 20-oxo-P concentrations of 100-200 ng/g (n=6); (4) no apparent luteal activity as indicated by 20-oxo-P of < 100 ng/g (n=7). In two attempts to induce ovarian activity, chlormadinone acetate was fed daily to one animal for 35 and 45 days, respectively. Each treatment was followed by a subsequent hCG injection which resulted in luteal phases of 17 and 18 days, respectively, beginning about 10 days after hCG. Concentration of faecal 20-oxo-P in one pregnant animal during the 4th and 5th month of gestation were markedly higher than those observed during the luteal phase of the cycle. In conclusion, two thirds of white rhinoceroses in this study had erratic or missing luteal activity, whereas variable cycles of 4-10 weeks in length were evident in six females, and regular oestrous cycles of 10 weeks in length were found in two animals.

Animals↗
PubMed1998

Lavage administration of dilute surfactants after acute lung injury in neonatal piglets.

Exogenous surfactant therapy is not standard in the acute respiratory distress syndrome (ARDS) because of a lack of proven benefit. Nonuniform surfactant distribution after either bolus or aerosol administration may be an important factor limiting response. In a previous study of acute lung injury, we demonstrated that lavage administration of Exosurf (13.5 mg phospholipid/ml) was both effective and distributed uniformly in the lungs. Since the endogenous surfactant pool is much smaller than the typical dose of exogenous surfactant administered, we hypothesized that dilute surfactant preparations (4-4.5 mg phospholipid/ml) administered by lung lavage would be equally effective in reversing pulmonary dysfunction in a piglet model of acute lung injury. We compared three dilute surfactants: Infasurf (n = 5), KL4-Surfactant (n = 6), and Exosurf (n = 5) with controls (n = 6) and undiluted Exosurf (13. 5 mg phospholipid/ml; n = 6). All dilute surfactant preparations were effective in improving oxygenation and other parameters of pulmonary function. Surfactant administered by lavage resulted in uniform lung distribution. We conclude that dilute surfactants administered by lung lavage are effective in reversing pulmonary dysfunction after acute lung injury. We speculate that doses in the range of 20-40 mg phospholipid/kg may be adequate to improve lung function in ARDS when exogenously administered surfactant is uniformly distributed in the lung.

Animals↗
PubMed1998

Predictors of cervical cancer screening in Mexican American women of reproductive age.

Several barriers impede cancer prevention in the Mexican American population. This study identified sociocultural factors that could be used to increase screening rates for cervical cancer in women of reproductive age. A survey was conducted in 1991 of 366 Mexican American women ages 18 to 40 in Tucson, Arizona, to assess current compliance with cervical cancer screening guidelines and several psychological, social, and cultural variables. Women who had never been screened (13 percent of the sample) had a knowledge deficit, no gynecological care, and no sexual activity. Women not screened annually (16 percent) lacked preventive care, imperfectly understood the Pap test, had lower self-efficacy expectations for understanding physicians, experienced higher emotional stress about the test, and were older and less acculturated. Women who have never been screened require basic education on cancer and cancer screening and policy changes increasing access to care. For women with less routine screening, preventive care, supportive attitudes, and health care skills must be encouraged.

Adolescent↗
PubMed1997

Promoting meconium clearance from the lungs of the neonatal piglet with asymmetric high frequency oscillation.

To investigate the role of high frequency oscillation (HFO) in promoting meconium clearance from the airway, we used a commercially available ventilator configured with maximal expiratory flow exceeding inspiratory flow (asymmetric HFO or AHFO). We hypothesized that AHFO would move meconium in an expiratory direction (toward the ventilator). We first tested our hypothesis in vitro and, later, in vivo using the neonatal piglet. In vitro experiments using a Plexiglas airway confirmed meconium movement in an expiratory direction when bias ratio was > or = 2. For in vivo experiments, each piglet received a 3 mL/kg intratracheal bolus of a 44 g/100 mL meconium mixture followed by 45 min of mechanical ventilation. Then, in part 1, the piglet was placed in a 15 degree head down tilt position and randomized to either AHFO [ratio of inspiratory time/expiratory time (I:E) of 70:30] or HFO (I:E ratio of 30:70). After 30 min of either AHFO or HFO, the piglet was crossed over to the alternate strategy for an additional 30 min. For part 2, we maintained the piglet on either AHFO or HFO continuously for 4 h. Results demonstrate that, although there was a tendency for larger volumes of meconium to be aspirated from the airway during AHFO in part 1 experiments, there was no difference found in part 2. We also found no significant differences in blood gases or hemodynamic measurements between AHFO and HFO during the prolonged observation period in part 2 of our study. We conclude that AHFO is of no benefit in the treatment of meconium aspiration syndrome.

Animals↗
PubMed1995

Cancer in Hispanics: issues of concern.

Hispanics are among the fastest growing minorities in the United States, after Asian-Americans and Pacific-Islanders. Hispanics, Latinos, Chicanos, Mexican-Americans, Puerto Ricans, Cuban-Americans, etc. are all designations used to describe this large, heterogeneous population with different cultural, ethnic, geographic, and social backgrounds. There is still no clear definition of the term "Hispanic." The data available regarding the incidence, morbidity, and mortality from cancer in Hispanics are scarce, scattered, outdated, and often incomplete. From the studies looking at the accessibility and availability of medical care for this population, few have examined in detail the variability within the entire Hispanic population. The aggregation of culturally distinct subgroups, which have resided in the United States for different periods of time, into a more inclusive Hispanic category assumes that all persons of Mexican, Cuban, and Puerto Rican extraction have similar needs and experience similar barriers in using health services. There is, however, no clear evidence for this assumption. On the contrary, there is evidence that each group has specific characteristics that make it different and independent from another, despite the fact that they also share some commonalities. Because of the lower overall prevalence of cancer in this population, potential protective factors need to be explored. Hispanics, however, appear to have a less favorable stage of disease at presentation and have overall lower death rates from cancer than non-Hispanic whites, but lower overall survival in certain cancers. Demographic and epidemiologic data collection need to be updated and improved.(ABSTRACT TRUNCATED AT 250 WORDS)

Attitude to Health↗
PubMed1994

The Escherichia coli prr region encodes a functional type IC DNA restriction system closely integrated with an anticodon nuclease gene.

The prr locus was originally described as coding a ribonuclease that is activated after phage T4 infection to cut within the anticodon of a specific tRNA, inactivating protein synthesis and thus blocking phage development. Wild-type T4 phage has two genes coding the enzymes polynucleotide kinase and RNA ligase, whose only function seems to be to repair the damage done by the anticodon nuclease. As the only apparent function of the prr ribonuclease is to combat phage infection, it can be considered as an RNA-based restriction enzyme. In non-infected cells, the prr enzyme is kept inactive in a complex with three other proteins which were predicted on the basis of DNA homologies to be the subunits of a type IC DNA restriction and modification system. Unlike other type IC systems so far characterized, prr is chromosomally rather than plasmid coded. However, sequences upstream from prr also have homology with sequences from the plasmid R124 and the prophage P1. We have now investigated the prr system and shown that it is indeed a bona fide type IC system which we call EcoprrI, and which is active both in vivo and in vitro. The system is fully functional even in the absence of the anticodon nuclease and seems to be a typical type I enzyme. EcoprrI recognizes the sequence CCA(N7)RTGC. One peculiarity is that, with low efficiency, EcoprrI will recognize and methylate variants of its recognition sequence such as CCT(N7)ATGC, which is methylated in one strand of the DNA only.

Amino Acid Sequence↗
PubMed1993

Macroevolution by transposition: drastic modification of DNA recognition by a type I restriction enzyme following Tn5 transposition.

We have characterized a novel mutant of EcoDXXI, a type IC DNA restriction and modification (R-M) system, in which the specificity has been altered due to a Tn5 insertion into the middle of hsdS, the gene which encodes the polypeptide that confers DNA sequence specificity to both the restriction and the modification reactions. Like other type I enzymes, the wild type EcoDXXI recognizes a sequence composed of two asymmetrical half sites separated by a spacer region: TCA(N7)RTTC. Purification of the EcoDXXI mutant methylase and subsequent in vitro DNA methylation assays identified the mutant recognition sequence as an interrupted palindrome, TCA(N8)TGA, in which the 5' half site of the wild type site is repeated in inverse orientation. The additional base pair in the non-specific spacer of the mutant recognition sequence maintains the proper spacing between the two methylatable adenine groups. Sequencing of both the wild type and mutant EcoDXXI hsdS genes showed that the Tn5 insertion occurred at nucleotide 673 of the 1221 bp gene. This effectively deletes the entire carboxyl-terminal DNA binding domain which recognizes the 3' half of the EcoDXXI binding site. The truncated hsdS gene still encodes both the amino-terminal DNA binding domain and the conserved repeated sequence that defines the length of the recognition site spacer region. We propose that the EcoDXXI mutant methylase utilizes two truncated hsdS subunits to recognize its binding site. The implications of this finding in terms of subunit interactions and the malleability of the type I R-M systems will be discussed.

Base Sequence↗
PubMed1984

Nadolol in hypertensive patients maintained on long-term hemodialysis.

The pharmacokinetics, efficacy, and safety of nadolol were evaluated in hypertensive patients maintained on long-term hemodialysis. In nine patients the plasma elimination half-life of unchanged nadolol averaged 26 hours following a single 40 mg oral dose during the interdialytic period. Nineteen patients received nadolol once after each dialysis session. In addition, 12 of the 19 patients also received hydralazine and/or furosemide daily. Predialysis blood pressures and heart rates were significantly lower with nadolol than with combination or single therapy with conventional antihypertensive drugs, including other beta blockers. Nadolol administered only after each dialysis session (i.e., two or three times a week), in conjunction with hydralazine and/or furosemide, is an effective antihypertensive agent in hypertensive patients receiving long-term hemodialysis.

Adrenergic beta-Antagonists↗
PubMed1984

The sensitivity and specificity of nutrition-related variables in relationship to the duration of hospital stay and the rate of complications.

We assessed the nutritional status at the time of hospital admission of 74 patients who were admitted for elective gynecologic or urologic operations. Nutritional assessment included measurement of serum albumin, thyroxine-binding prealbumin, retinol-binding protein, weight-change history, estimate of daily protein and total calorie intake, and a global estimate of nutritional risk. The sensitivity, specificity, false-positive rate, likelihood ratio, and positive predictive value of these nutrition-related variables were analyzed in patients who stayed in the hospital for longer than 10 days and in those patients with recognized complications. In the analysis of patients who remained in the hospital longer than 10 days, the finding of a low serum protein concentration or a low protein intake was most sensitive, and a low serum albumin concentration was the most specific. A receiver-operating-characteristic diagram that depicts the sensitivity and false-positive rates for the single variables and the combinations of variables is probably the most clinically useful summary of our study. Using the information in such a diagram, a clinician might choose variables that are more sensitive to identify hospitalized patients who should receive special nutritional attention in comparison with another clinician who might need fewer false-positive results for a prospective study of nutritional intervention.

Adult↗