Respiratory clearance of aerosolized radioactive solutes of varying molecular weight

To determine the influence of varying molecular weight (mol wt) on respiratory clearance of aerosolized solutes, we studied eight radiopharmaceuticals, each administered to four dogs: sodium 99mTc pertechnetate (TcO4), 99mTc glucoheptonate ([99mTc]GH), 51Cr-ethylenedinitrotetraacetate ([51Cr]EDTA), 99mTc diethylenetriaminepentaacetate ([99mTc] DTPA), 111In diethylenetriaminepentaacetate ([111In]DTPA), 67Ga desferoxaminemesylate ([67Ga]DFOM), 99mTc dextran ([99mTc]DX) and 111In transferrin ([111In]TF). After aerosolization (0.8 m MMD, 2.4 GSD), clearance was determined for 30 min and then corrected by intravenous injection for nonairspace radioactivity. In-TF clearance (0.11 +/- 0.10%/min) was lower than TcO4 (6.32 +/- 0.62%/min), [99mTc]GH (1.50 +/- 0.37%/min), [51Cr]EDTA (2.38 +/- 1.02%/min), [99mTc]DTPA (3.51 +/- 0.40%/min), [111In]DTPA (2.35 +/- 0.42%/min), [67Ga] DFOM (1.99 +/- 0.49%/min) and [99mTc]DX (1.81 +/- 0.75%/min) clearances (p less than 0.001). TcO4 clearance was higher than others (p less than 0.001). Technetium binding to DX was unsatisfactory; aerosolization caused unbinding from DTPA. We conclude that respiratory clearance of large mol wt solutes within 30 min is negligible and, that clearance of molecules between 347-5,099 daltons differs greatly, suggesting that binding and/or intrapulmonary retention affect transfer.     

Inhibition of dihydrofolate reductase from bacterial and vertebrate sources by folate, aminopterin, methotrexate and their 5-deaza analogues

The inhibition of dihydrofolate reductases from Escherichia coli and chicken liver by folate, methotrexate, aminopterin and their 5-deaza analogues was investigated to examine the importance of the N-5 nitrogen in slow-binding inhibition. Methotrexate, aminopterin and their 5-deaza analogues acted as slow, tight-binding inhibitors of both enzymes. Inhibition by methotrexate and 5-deazamethotrexate conformed to a mechanism in which there is an initial rapid formation of an enzyme-NADPH-inhibitor complex followed by a slow isomerization of this complex (Mechanism B). Aminopterin exhibited the same type of inhibition with the enzyme from E. coli. With the chicken-liver enzyme, however, the inhibition by aminopterin conformed to another type of slow-binding mechanism which involves only the slow interaction of the inhibitor with the enzyme to form an enzyme-NADPH-inhibitor complex (Mechanism A). The inhibition of both enzymes by 5-deazaaminopterin was also described by Mechanism A. Folate behaved as a classical, steady-state inhibitor of both enzymes, whereas 5-deazafolate exhibited slow-binding inhibition (Mechanism B) with the enzyme from E. coli and classical, steady-state inhibition with the enzyme from chicken liver. The substitution of a carbon for a nitrogen at the 5-position of methotrexate and aminopterin did not affect the tightness of binding of these compounds. By contrast, 5-deazafolate was bound about 4000 times more tightly than folate to the enzyme from E. coli and about 30 times more tightly than folate to the chicken-liver enzyme. Reasons for the differences in the binding of folate and 5-deazafolate are discussed.     

Aerosolized gadolinium-DTPA enhances the magnetic resonance signal of extravascular lung water

Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA), a contrast agent for magnetic resonance imaging, was administered by either aerosol or intravenous injection to rats. Proton relaxation times in excised lungs and kidneys were then measured. With increasing concentrations of aerosolized Gd-DTPA, the spin-lattice relaxation time (T1) of lungs decreased (enhanced) significantly (P less than .001), an effect that persisted for at least 80 minutes; there was no change in kidney T1. After intravenous injection of Gd-DTPA, lung T1 did not change, but kidney T1 decreased significantly (P less than .001), confirming previous observations of renal clearance. It is concluded that aerosolized Gd-DTPA is a more efficacious method of delivery of paramagnetic contrast agent to the lungs than intravenous injection, and that the lack of systemic effect after aerosolization indicates that enhancement was limited to the extravascular compartment.     

Lactation Duration: Influences of Human Milk Replacements and Formula Samples on Women Planning Postpartum Employment

Objective: To examine the influences of i hospital administration of breast milk replacement and receipt of formula samples on lactation duration among women planning postpartum employment.
Design: Prospective design.
Setting: Telephone interviews conducted prenatally and at 6 weeks, 3 months, and 6 months postpartum.
Participants: Sixty-nine participants entered the study; 53 completed all scheduled interviews.
Main Outcome Measures: Incidence and type. of in-hospital human milk replacement, incidence ar sources of formula samples, incidence of breastfeeding at 6 weeks postpartum, and duration of lactation.
Results: During hospitalization, 19% of in fants received formula; the incidence of breastfeeding at 6 weeks and duration of breastfeeding were significantly shorter in these infants compared with infants who were not fed formula. Fifty-nine percent of participants received formula samples from the hospital, 30% received samples from a physician's office, and 51% received samples by mail Receipt of formula samples by mail was associate with reduced incidence of breastfeeding at 6 weeks and shortened duration of lactation.
Conclusions: Early formula feeding and receipt of formula samples by mail may be barriers I lactation in women employed outside the home.     

The use of contact lenses by U.S. civilian pilots.

BACKGROUND: Since 1976, the use of contact lenses by civilian pilots has been permitted to correct distant vision for obtaining a Federal Aviation Administration (FAA) aeromedical certificate. This study examined the civil airman population's experience with contact lens use for a 30-year period (1967 to 1997). METHODS: Population totals for airmen who carried pathology codes 161 (contact lens) and 158 (orthokeratology) from January 1, 1967 through December 31, 1997 were used to calculate prevalence rates by class of medical certificate and age. The National Transportation Safety Board and FAA databases were queried to determine if contact lens use had contributed to aviation mishaps. RESULTS: The prevalence of contact lens use grew faster for first-class medical certificate holders and airmen > or = 40 years of age during the period. The frequency of airmen with orthokeratology increased by 23 times in a 10-year period. Reports from five aviation accidents and one incident suggested that contact lens use was a contributing factor in these mishaps. CONCLUSIONS: Professional pilots and older airmen were found to be more inclined to use contact lenses. The increasing use of contact lenses and the rapid changes in contact lens technology warrant continued monitoring to ensure aviation safety.     

Characterization of novel phorbol ester- and serum-responsive sequences of the rat ornithine decarboxylase gene promoter

Ornithine decarboxylase (a), the key regulatory enzyme in mammalian polyamine biosynthesis, is rapidly induced by mitogens and tumor promoters. We used transient expression assays and DNA-protein binding studies to examine the regulation of ODC promoter activity by phorbol esters and serum growth factors. A fragment of the ODC 5′ flanking region (nt -1156 to + 13) was sufficient to confer 12-O-tetradecanoylphorbol-13-acetate (a) -responsive expression to a luciferase reporter gene when transfected into H35 cells. However, induction by TPA was not observed in Rat2 fibroblasts, although refeeding of serum-starved Rat2 cells with fresh serum-containing medium rapidly induced a fivefold to sixfold increase in ODC promoter activity, maximal about 8 h after refeeding. Deletion analysis demonstrated that several sequences contributed to basal ODC promoter activity but that nt -92 to +13 was sufficient for induction by TPA or by serum. This sequence lacked canonical TPA-responsive elements, and an activator protein-1 (AP-1) consensus oligonucleotide failed to compete effectively for proteins binding to this region. Two of four protein complexes observed by gel-shift analysis of nt -92 to +13 were competitively inhibited by wild-type but not mutant oligonucleotides encompassing a variant cyclic AMP-response element (a) (ODC nt -50 to -42); however, a consensus CRE did not compete. Mutagenesis of this site demonstrated that it contributes to basal expression of the ODC promoter but not to TPA or serum responsiveness. Thus, we conclude that the proximal ODC promoter (nt -92 to +13) responds to TPA and serum stimulation in a cell-type-specific manner that is not mediated by canonical AP-1 elements. © 1995 Wiley- Liss, Inc.     

Over-Expression of AIF-1 in Liver Allografts and Peripheral Blood Correlates with Acute Rejection after Transplantation in Rats

Early and accurate detection of acute cellular rejection (ACR) is important in the management of liver allograft recipients. We hypothesized that expression of allograft inflammatory factor (AIF)-1 would be associated with liver allograft rejection as previous studies have shown that a relationship exists between kidney and heart transplantation. Indeed using rat orthotopic transplant models we found that the expression of allograft inflammatory factor-1 (AIF-1) can be detected in both allograft and peripheral blood leukocytes with peak levels detected 7 days following liver transplantation. Interestingly, AIF-1 expression increased 2-fold in acutely rejecting liver allografts compared to chronically accepted livers on days 5, 7 and 10 after transplantation. AIF-1 expression in peripheral blood leukocytes was also significantly greater in the rejection model than in the acceptance model. Flow cytometric analysis of peripheral blood leukocytes demonstrated that AIF-1 was expressed in ED2-positive cells, a marker for Kupffer cells. In vitro studies showed that AIF-1 expression in Kupffer cells was up-regulated by coculture with Th1 cytokines. However, neither LPS nor Escherichia coli (E. coli) administration had an affect on AIF-1 expression. These data indicate that high levels of AIF-1 expression reflect aggressive liver allograft rejection and suggest a role for monitoring AIF-1 in peripheral blood leukocytes as a monitor for increased immunosuppression.     

9-(2-Deoxy-2-fluoro-beta-D-arabinofuranosyl)guanine: a metabolically stable cytotoxic analogue of 2'-deoxyguanosine

The synthesis of 9-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)guanine (1b) from 1,3-di-O-acetyl-5-O-benzoyl-2-deoxy-2-fluoro-D-arabinofuranose (2a) and 2,6-dichloropurine in six steps using an enzymatic deamination as the last step is reported. The target compound was found to be stable to purine nucleoside phosphorylase cleavage and was cytotoxic in two cell lines, one a T-cell line. Incubation of L1210 cells with 1b results in an inhibition of DNA synthesis as judged by the reduced incorporation of labeled thymidine into DNA, while RNA and protein syntheses were unaffected.     

Axonal Growth into Tubes Implanted within Lesions in the Spinal Cords of Adult Rats

Cultured Schwann cells were implanted into the thoracic spinal cords of adult rats inside thin tubes made of polycarbonate film coated with poly- -lysine. Additional control tubes were implanted which did not contain cultured Schwann cells. Some of the control tubes were coated with poly- -lysine and others were not. One week to 2 months later the animals were perfused with fixatives and the tubes were prepared for light or electron microscopy. Immunocytochemical studies of the Schwann cell tubes reveal that they contain axons. Most of these axons are grouped in fascicles that run longitudinally through the tubes. The distribution of these axons matches precisely the distribution of basal lamina within the tubes as displayed by immunolabeling with an antibody to laminin. Surprisingly, the same patterns of labeling are seen in the control tubes, although they contain fewer axons. Control tubes lacking poly- -lysine contain the fewest. Electron microscopy verifies that the tubes, including control tubes, contain Schwann cells and axons of different diameters. Furthermore, the Schwann cells ensheathe and myelinate the axons. These results strengthen the hypothesis that Schwann cells can support axonal growth in the spinal cords of adult animals. They also demonstrate that these Schwann cells can be implanted or they can be derived from the host animal. This finding raises the possibility that therapies could be devised for bridging spinal cord lesions that are based on maximizing migration of endogenous host cells into the sites of lesions.     

Use of collagen tubes for implantation of hydroxylapatite: an experimental study

Collagen tubes were compared with routine injection for placement of hydroxylapatite in mandibular defects. It was found that the collagen film containers were effective in providing easier handling, more effective shaping, and less migration of particles.