Enamel solubility reduction by acidulated phosphate-fluoride (APF) treatment

The enamel solubility reducing (ESR) potential of acidulated phosphate-fluoride (APF) solutions containing varying amounts of F was studied. Commercial APF (1.23% F, pH 3.0) reduced solubility by about 80%. Fivefold dilutions of this APF were made with either phosphoric acid or water without significant effect on ESR potential. Further dilution to 0.12% F significantly decreased effectiveness. Commercially available APF products (1.23%) can be diluted several-fold with distilled water in the dental office without significant loss of ability to reduce the solubility of enamel.     

Several GABAA receptor subunits are expressed in LHRH neurons of juvenile female rats

Gamma aminobutyric acid (GABA), the dominant inhibitory neurotransmitter in brain, is involved in the developmental regulation of LHRH secretion. Morphological studies in rodents have demonstrated that LHRH neurons are innervated by GABA-containing processes, suggesting that LHRH secretion is under direct transsynaptic GABAergic control. While GABA acts through two different receptors, GABA_A and GABA_B, to exert its effects, it appears that GABA_A receptors are able to mediate both inhibitory and stimulatory effects of GABA on LHRH neurons. GABA_A receptors are heterooligomeric ligand-gated anion channels that exhibit a diverse array of functional and pharmacological properties. This diversity is determined by the structural heterogeneity of the receptors, which are assembled from the combination of different classes of subunits with multiple isoforms. Although several studies have described the effect of GABA_A receptor stimulation on LHRH and/or gonadotropin release in prepubertal animals, nothing is known about the receptor subunits that may be expressed in LHRH neurons at this phase in development. Double immunohistofluorescence followed by confocal laser microscopy revealed that subsets of prepubertal LHRH neurons are endowed with α₁, α₂, β_2/3, and γ₂ GABA_A receptor subunits. Combined immunohistochemistry for LHRH neurons and in situ hybridization for GABA_A subunit mRNAs confirmed that the genes encoding the α₁, α₂, β₃ and γ₂ subunits, but not the γ₁ subunit, are expressed in LHRH neurons. Notwithstanding the relative insensitivity of these methods, both the immunohistochemical and hybridization histochemical approaches employed indicate that only a fraction of LHRH neurons are endowed with GABA_A receptors. This arrangement suggests that those LHRH neurons bearing the appropriate GABA_A receptors are responsible for either the entire secretory response to direct GABAergic inputs or for its initiation.     

Determination of free thyroxin in serum by ultrafiltration: validation of a method and preliminary results

We describe the determination of concentrations of free thyroxin in serum by ultrafiltration based on the Amicon micropartition system. The assay is straightforward and requires about 4 h for 25 samples. Our results demonstrate a correlation coefficient of 0.81 compared with equilibrium dialysis, and of 0.88 compared with radioimmunoassay. For sera from 49 normal, 25 hyperthyroid, 24 hypothyroid, 50 euthyroid sick, and 13 pregnant subjects, the means (and SD) were respectively: 19.3 (4.9), 40.1 (13.6), 5.0 (2.9), 25.9 (10.5), and 16.1 (3.2) ng/L. The interassay CV was 9.9% and the intra-assay CV 7.2%. We conclude that this procedure is useful in the diagnosis of thyroid disease and offers advantages of simplicity, rapidity, and economy.     

Philadelphia chromosome (Ph1)-associated leukemias: A family study

In the present study we describe a family in which a mother and her son developed leukemia in close temporal proximity. The boy presented with a clinical picture consistent with acute lymphoblastic leukemia. His mother developed chronic myelogenous leukemia. Using Giemsa banding we demonstrated that both cases had an associated Philadelphia chromosome. Hematologic, cytogenetic, and HLA haplotyping studies were performed, but did not reveal a genetic basis for the high incidence of leukemia in this family.     

Selective suppression of granuloma formation and delayed hypersensitivity in rabbits

The relationship between dermal delayed hypersensitivity (DH) and granulomatous hypersensitivity was studied in rabbits sensitized with killed mycobacteria. Specific antigen challenge of sensitized animals resulted in extensive pulmonary granulomatous inflammation and induced suppression of both dermal DH and dermal granuloma formation. Whereas suppression of DH was concomitant with pulmonary granuloma formation, as is the case in a number of granulomatous diseases, a causal relationship between the two did not exist. Both DH and dermal granulomatous hypersensitivity were significantly suppressed whether or not the antigen challenge was of a granulomagenic (particulate) or nongranulomagenic (soluble) form. The data presented indicate that granulomatous hypersensitivity and DH are selectively suppressed with regard to different anatomical sites.     

Early detection of rifampin in human nerve tissue after an oral dose of 600 milligrams.

Rifampin in picogram quantities inhibited the ability of Mycobacterium bovis 44 BCG P3 to release 14CO2 from the oxidation of [14C]palmitic acid. By using these mycobacteria in a bioassay, samples of serum and posterior tibial nerve were assayed for inhibitory concentrations of rifampin. Within 8 to 12 h after ingestion of 600 mg of rifampin, the drug was detected in eight patients in concentrations ranging from 0.52 to 4.1 micrograms/ml in serum and in concentrations ranging from 0.6 to 6.3 ng/mg in posterior tibial nerve fiber tissue.     

Pyrazoloquinoline benzodiazepine receptor ligands: effects on schedule-controlled behavior in dogs

The effects of diazepam and the pyrazoloquinoline benzodiazepine receptor ligands CGS8216, CGS9896, and CGS9895 on schedule-controlled responding were studied in dogs. Responding was maintained under a multiple fixed-interval (FI) 5-min fixed-ratio (FR) 30 response schedule of food presentation. Diazepam (PO) produced dose-related decreases in response rates under FR component. Under the FI, rates first increased and then decreased with increasing doses of diazepam. Diazepam also produced a dose-related disruption of the temporal pattern of responding under the FI as measured by decreases in quarter-life values. CGS8216 IV produced dose-related decreases in response rates under both components. The highest oral dose of CGS8216 also decreased rates in both components. CGS8216 was approximately 100 times more potent by the IV route as compared to the oral route. CGS9896 IV had no significant effect on responding under either component of the multiple schedule. However, with increasing doses of CGS9896 PO, response rates under both components first decreased and then returned to control values. CGS9895 PO was without significant effect on responding. When CGS8216 was administered concomitantly with graded doses of diazepam, the former drug blocked the rate-decreasing effects of diazepam under the FR component, but not the rate-increasing effects of diazepam under the FI. The present results demonstrate that although these three pyrazoloquinolines are benzodiazepine receptor ligands, they do not exhibit diazepam-like effects on schedule-controlled behavior.     

Apparent monosomy 21 owing to a ring 21 chromosome: parental origin revealed by DNA analysis.

A three and a half year old mildly retarded boy is presented. Karyotyping showed monosomy 21 (45,XY,-21) in all 50 metaphase spreads examined from two lymphocyte cultures, and in 20% of cells examined from cultured fibroblasts; the remaining 80% of cells showed a ring 21 chromosome (46,XY,r(21)(p1q22]. Molecular studies using chromosome 21 specific DNA probes confirmed the monosomy in blood and showed that the ring 21 chromosome was paternal in origin. Parental karyotypes were normal.