Experimental investigation of mass efficiency curve for alpha radioactivity counting using a gas-proportional detector.

Gross alpha counting of evaporated water residues offers a simple method for screening alpha radioactivity in water for both public health and emergency purposes. The evaporation process for water has been improved by using a combination of roughening of the surface of counting planchettes, two-stage evaporation, and temperature-controlled block heating. The efficiency of the gas-proportional detector for alpha-particle detection in water residues was studied as a function of sample mass-thickness in the range between 0.1 and 13 mg cm(-2). The effect of alpha energy on the efficiency, as well as moisture absorption on the samples, were studied using (230)Th, (238)U, (239)Pu, (241)Am, and (244)Cm radionuclides. Also, alpha-to-beta crosstalk was investigated as a function of sample mass for (230)Th, (238)U, (239)Pu, (241)Am, and (244)Cm. The improved method can also be applied for gross alpha detection in biological fluids.

Transcription factor IIA mutations show activator-specific defects and reveal a IIA function distinct from stimulation of TBP-DNA binding.

The general transcription factor IIA (TFIIA) binds to the TATA binding protein (TBP) and mediates transcriptional activation by distinct classes of activators. To elucidate the function of TFIIA in transcriptional activation, point mutants were created in the human TFIIA-gamma subunit at positions conserved with the yeast homologue. We have identified a class of TFIIA mutants that stimulate TBP-DNA binding (T-A complex) but fail to support transcriptional activation by several different activators, suggesting that these mutants are defective in their ability to facilitate an activation step subsequent to TBP promoter binding. Point mutations of the hydrophobic core of conserved residues from 65 to 74 resulted in various activation-defective phenotypes. These residues were found to be important for TFIIA gamma-gamma interactions, suggesting that gamma-gamma interactions are critical for TFIIA function as a coactivator. A subset of these TFIIA-gamma mutations disrupted transcriptional activation by all activators tested, except for the Epstein-Barr virus-encoded Zta protein. The gamma Y65F, gamma W72A, and gamma W72F mutants mediate Zta activation, but not GAL4-AH, AP-1, GAL4-CTF, or GAL4-VP16 activation. The gamma W72A mutant failed to stimulate TFIID-DNA binding (D-A complex) but was able to form a complex with TFIID and DNA in the presence of Zta (Z-D-A complex). Thus, the ability of Zta to activate transcription with gamma W72A appears to result from a unique ability to form the stable Z-D-A complex with this mutant. Our results show that different activators utilize the general factor TFIIA in unique ways and that TFIIA contributes transcription activation functions in addition to the facilitation of TBP-DNA binding.

Differences in judgments of persuasive argument quality by three population groups in Iowa.

OBJECTIVES: This study describes a method for studying the perceived persuasiveness of rationales for adopting preventive health behaviors. METHODS: Using the Elaboration Likelihood Model, we surveyed 156 individuals as to the level of persuasiveness that each of several categories of reason presented in adopting target "prevention" behaviors such as eliminating the use of smokeless tobacco or seeking regular dental care. RESULTS: Significant differences between what the public reported as persuasive reasons and those selected by future dental practitioners were found. Patients saw potential cost savings, elimination of future pain, and being told by an authority person to adopt a behavior as highly persuasive reasons to adopt a target behavior. Nonwhite patients gave significantly higher scores than did white patients to arguments centering on social/aesthetic appeal. On the negative side, episodic care seekers felt significantly more strongly than regular care seekers that their practicing dental prevention activities (e.g., regular checkups, brushing, and flossing) benefited someone other than themselves (dental profession and dental manufacturers). CONCLUSIONS: Results of this study suggest that one way to improve persuasive public health preventive messages is to consider whether the fundamental arguments on which preventive health campaigns are built have broad patient appeal.

Considerations in establishing a dental program for the homeless.

The homeless are a diverse group who present the dental profession with a number of difficult challenges in the delivery of oral health services. Utilization of dental services by the homeless is low when provided in traditional settings and access is limited. The purpose of this case study is to review program planning issues focusing on the unique aspects of establishing dental programs for the shelter-based homeless. This paper is based on experiences in developing a dental program for homeless persons in Boston. The establishment of a portable dental program in 1988 for persons residing in shelters in the greater Boston area involved many administrative and clinical considerations. These factors included determination of needs and barriers to dental care, resource identification and development, program planning and implementation, evaluation, and the development of constituency support. The diversity of the homeless population in combination with the variation of space and medical resources at different shelter sites dictates flexibility in the development of programs to address the oral health needs of the homeless.

Dental caries in homeless adults in Boston.

OBJECTIVES: Information about the oral health status of the homeless is limited. The purpose of this study is to characterize the dental caries status among users of a dental treatment and referral program at homeless shelters in Boston, MA. METHODS: Persons attending the program during a one-year period were assessed for evidence of dental caries experience by a single examiner. DMFT counts were abstracted from patient records. RESULTS: The population examined (n = 73) was 66 percent male with a mean age of 36 years. The racial composition was 51 percent African-American, 34 percent Caucasian, and 14 percent Hispanic. The 70 dentate people examined had a mean DFT of 11.1 (SD = 6.1). The mean percent of DFT that was DT per person was 55.7 percent. Untreated caries was detected in 91.4 percent of those examined. CONCLUSIONS: These findings show evidence of previous dental services utilization by these homeless individuals, but demonstrate a high need for preventive and restorative dental therapy.

Molecular cloning of the small (gamma) subunit of human TFIIA reveals functions critical for activated transcription.

TFIIA is thought to play an important role in transcriptional regulation in higher eukaryotes, but its precise function is unclear. A human cDNA encoding a protein with 45% identity to the small subunit of yeast TFIIA has been isolated. TFIIA activity could be reconstituted by the mixing of recombinant large (alpha beta) and small (gamma) subunits. TFIIA-depleted HeLa nuclear extracts were used to demonstrate that TFIIA is essential for basal and activated transcription by several distinct classes of activators. Recombinant TFIIA functioned in transcriptional activation whether expressed as a dimer (alpha beta+gamma) or as a trimer (alpha+beta+gamma), which closely resembles the native form. Yeast TFIIA also functioned in transcriptional activation, and the human gamma subunit was functionally interchangeable with TOA2, its yeast homolog. Recombinant TFIIA mediated the stimulation of TFIID binding to the TATA region and downstream promoter sequences by the Zta transcriptional activator. Significantly, we found that TFIIA bound directly to Zta in an activation domain-dependent manner. One consequence of the TFIIA-mediated interaction between Zta and TFIID was the formation of a promoter-bound complex resistant to TATA oligonucleotide competition. These results demonstrate that TFIIA is an evolutionarily conserved general factor critical for activator-regulated transcription.

Perception of oral health needs by Southeast Iowa non-dental health care providers.

The purposes of this dental study were to identify, among non-dental health care providers and administrators, (1) those reasons assessed to be most persuasive in adopting selected dental preventive practices, (2) barriers perceived to be present for their clients to obtain dental services, and (3) practices which would make dental services more available to their clients. A nine-item dental care/attitude survey was completed by 82% (n = 68) of the health care and social services providers/administrators attending one of the United Way of East Central Iowa group meetings. The results of this survey indicated that, for these respondents, the most persuasive reasons for adopting preventive dental practice behaviors were based on susceptibility to disease and social and esthetic benefits. Further, the results of this survey showed that female respondents gave significantly higher scores than males to the importance of social benefits (self-worth and employment marketability), health benefits, and the importance that authority figures (dentists and physicians) placed on the behavior. Fifty-one percent of the respondents knew of patients who had problems obtaining dental services. The main reasons given for clients' access problems were the lack of money, the lack of insurance, and the lack of transportation.

Calcium channels in excitable cells: divergent genotypic and phenotypic expression of alpha 1-subunits.

The Ba2+ currents and mRNA levels of four members of the rat brain family of alpha 1-subunit Ca2+ channel genes were examined and compared in the rat cell lines GH3 and PC-12 and in the mouse lines NIE-115 and AtT-20. The RNA was measured with ribonuclease protection assays using probes derived from rat brain (rb) Ca2+ channel cDNAs (rbA, rbB, rbC, and rbD), and the Ba2+ currents were studied by whole cell patch-clamp recording. L-, N-, P-, and T-type currents were discriminated by the voltage dependence and pharmacological properties of Ba2+ currents. All cell lines expressed all four rat brain Ca2+ channel genes, except GH3 cells, which lacked rbB. The functional diversity of Ba2+ currents, however, was quite different among the cell lines. GH3 cells showed evidence of L- and T-type currents, undifferentiated PC-12 cells of L-type currents, AtT-20 cells of L-, N-, and P-type currents, and undifferentiated NIE-115 cells of a T-type current that was partially blocked by both nifedipine and BAY K 8644. Dimethyl sulfoxide-differentiated NIE-115 cells also had an L-type current. Differentiation of NIE-115 cells caused an increase in the levels of rbB, rbC, and rbD RNAs. Differentiation by nerve growth factor caused an increase in levels of all four genes in PC-12. Our data give further support for the assignment of rbA, rbB, and rbC/rbD gene products as components of P-, N-, and L-type Ca2+ channels, respectively.

Gains in dental care use not shared by minority elders.

Americans have steadily increased their reported use of dental services over the past 30 years. Persons aged 65 years and older have made the greatest gains, from 16 percent in 1957-58 to 43 percent in 1989. This article reviews national data on reported use of dental care over the past three decades, focusing on differences in rates of utilization on the basis of age, race, and national origin. In addition, differences in sample selection, definitions of race and national origin, and data collection methodology were reviewed to identify systematic sources of bias in comparing the data. Findings indicate that reported dental care use among minority elders has not increased parallel with elders of all races and national origins. In 1957-59, 17 percent of white elders versus 9 percent of nonwhite elders had seen a dentist within the past year. By 1989 percentages had improved to 45 percent of whites, but only 22 percent of blacks and 40 percent of Hispanics. In addition, reporting and recording race and national origin varied considerably during the three decades, hampering comparisons over time. Finally, published national data on usual correlates of dental care use (dentition status, insurance, age, income, and education) are inadequate to explain the causes of these discrepancies. More research is needed to identify barriers to use of dental care by all Americans, particularly those of African and Hispanic descent.(ABSTRACT TRUNCATED AT 250 WORDS)

A national survey on the use of glass-ionomer cements.

This study was conducted to determine why and how glass-ionomer cements are being used by general dentists. Data were collected by a mail survey sent to a random sample of approximately 1000 general dentists in the United States. The results showed that 94% of the respondents currently use or have used glass ionomers. The primary uses (in order of popularity) are: 1) as a base or liner, 2) as a luting cement, and 3) as a crown foundation. Eighty-two percent of the respondents who use glass-ionomer luting cements reported some postoperative tooth sensitivity, but a slightly larger proportion (85%) reported postoperative sensitivity with other cements.

Distinct promoters direct neuronal and nonneuronal expression of rat aromatic L-amino acid decarboxylase.

Aromatic L-amino acid decarboxylase (AADC, EC 4.1.1.28) catalyzes the decarboxylation of L-dopa to dopamine in catecholamine cells and 5-hydroxytryptophan to serotonin in serotonin-producing neurons. This enzyme is also expressed in relatively large quantities in nonneuronal tissues such as liver and kidney, where its function is unknown. Neuronal and nonneuronal tissues express AADC mRNAs with distinct 5' untranslated regions. To understand how this is accomplished at the genomic level, we have isolated rat genomic DNA encoding AADC. The organization of the AADC gene suggests that there are two separate promoters specific for the transcription of neuronal and nonneuronal forms of the AADC message. A small exon containing 68 bases of the neuronal-specific 5' end is located approximately 9.5 kilobases upstream of the translation start site, which is contained in the third exon. Approximately 7 kilobases upstream from the neuron-specific promoter is another small exon containing 71 bases of the 5' end of the nonneuronal AADC message. These data suggest that transcription initiating at distinct promoters, followed by alternative splicing, is responsible for the expression of the neuronal and nonneuronal forms of the AADC message.

Control of action potentials and Ca2+ influx by the Ca(2+)-dependent chloride current in mouse pituitary cells.

1. Perforated patch recording was used to examine the influence of the calcium-dependent chloride current (iCl(Ca)) on Ca2+ action potentials in AtT-20 pituitary cells. The calculated chloride equilibrium potential (ECl) was adjusted by changing either intracellular or extracellular [Cl-]. Action potential duration varied as a function of ECl. When ECl was set at -21 mV, both spontaneous and evoked action potentials displayed a long plateau phase between -20 and -25 mV, which typically lasted for several seconds. Setting ECl to more negative potentials resulted in briefer action potentials; at an ECl of -52 mV, no plateau phase was evident. Spontaneous depolarization and action potential firing still occurred when ECl was negative to firing threshold, which indicates that the slow depolarizing wave that precedes the firing of spontaneous action potentials does not require activation of ICl(Ca). 2. In voltage clamp experiments the magnitude of ICl(Ca) diminished slowly during a prolonged depolarization, over a time course that coincided with action potential termination. 3. Niflumic acid (100 microM) blocked ICl(Ca) by 90% but had no effect on either K+ or Ca2+ currents. This concentration of niflumic acid eliminated the plateau phase, but did not prevent the firing, of Ca2+ action potentials. 4. Internal [Ca2+] was measured photometrically after loading cells with the Ca2+ indicator dye, Fura-2. Under voltage clamp conditions, concentrations of niflumic acid (30-100 microM) that blocked depolarization-evoked ICl(Ca) had little or no effect on simultaneously recorded Ca2+ transients. Perforated patch recording from Fura-loaded cells showed that action potentials were temporally associated with transient increases in intracellular [Ca2+]. Niflumic acid (30-100 microM) disrupted the rhythmic firing of spontaneous action potentials and associated intracellular Ca2+ transients. 5. Fluorescent measurements of Ca2+ transients were also made in cells unperturbed by patch recording, and were used as a measure of action potential duration in the absence of experimental alteration of internal [Cl-]. Spontaneous Ca2+ transients were of long duration (approximately 2 s), which suggests that intracellular [Cl-] is relatively high (40-50 mM) in these cells. The spontaneous Ca2+ transients were inhibited by niflumic acid. 6. Niflumic acid up to 100 microM, had neglible effects on either basal or stimulated (by 2 microM-(+/-)-isoprenaline) hormone secretion, as shown by radioimmunoassay of adrenocortotrophic hormone release.(ABSTRACT TRUNCATED AT 400 WORDS)

Genomic sequencing of the 5'-flanking region of the mouse beta-globin major gene in expressing and nonexpressing mouse cells.

Genomic sequencing of two CG sites located in the 5'-flanking promoter region of the mouse beta-globin major gene shows these sites to be heavily methylated in the DNA from L929 mouse fibroblasts, a cell line that does not express the beta-globin gene. By contrast, the same CG sites in the DNA obtained from murine erythroleukemia cells, which can express the beta-globin gene, are unmethylated. The results suggest that either differentiation of progenitor cells to form the erythroid precursor murine erythroleukemia cell and/or transformation by the Friend virus group leads to demethylation of these CG sites. Final activation of the transcription process for the mouse beta-globin gene does not require demethylation in the 5'-promoter region of the DNA.

A comparative analysis of the influence of financing on Boston's neighborhood health center dental programs in 1979 and 1985.

This study determined whether or not income and other structural components of 15 Boston neighborhood health centers in 1979 and 1985 had a systematic influence on their dental productivity as measured by dental visits. Health center revenue sources, health center costs, dental program costs, dental and medical manpower, and type of facility license were analyzed in relation to dental visits using secondary data from multiple sources. Dental costs and dental manpower were substantial predictors of dental visits for both periods of time. Stepwise regression analyses suggest that in 1979, the type of license and the type of grants received also were associated with the number of dental visits. In 1985, however, none of the revenue variables showed an association with dental visits when controlling for dental manpower and dental costs.