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J Lifka

Publications and source records attributed to J Lifka.

7 recordsLinked to original sources
PubMed2001

Ethers as pollutants in groundwater: the role of reaction parameters during the aquasonolysis.

Abstract Methyl tertiary butyl ether (MTBE) is one of the most used fuel oxygenates. Oxygenates improve combustion, thereby reducing CO and hydrocarbon emissions in motor vehicle exhaust. MTBE is highly soluble in water and poorly sorbed to carbon based substrates such as soil. An important property of MTBE is its poor biodegradability. The treatment of contaminated groundwater and wastewater by means of conventional biological, chemical and physical techniques turned out to be inefficient. As a matter of principle the degradation of organic compounds by ultrasound in water (aquasonolysis) is practicable as an advanced technology for remediation of waters contaminated with MTBE. The degradation reactions mainly occur in the cavitation bubbles as pyrolytical processes. Under the test conditions, the frequency range between 300 and 800 kHz leads to acceptable degradation values at a power density of 5 W/cm2. The degradation was not suppressed by radical scavenger (n-butanol). With concentrations above 25 mg/L MTBE in water, significantly influence of concentration on degradation could be observed.

Biodegradation, Environmental↗
PubMed1998

Device evaluation and coverage policy in workers' compensation: examples from Washington State.

Workers' compensation health benefits are broader than general health benefits and include payment for medical and rehabilitation costs, associated indemnity (lost time) costs, and vocational rehabilitation (return-to-work) costs. In addition, cost liability is for the life of the claim (injury), rather than for each plan year. We examined device evaluation and coverage policy in workers' compensation over a 10-year period in Washington State. Most requests for device coverage in workers' compensation relate to the diagnosis, prognosis, or treatment of chronic musculoskeletal conditions. A number of specific problems have been recognized in making device coverage decisions within workers' compensation: (1) invasive devices with a high adverse event profile and history of poor outcomes could significantly increase both indemnity and medical costs; (2) many noninvasive devices, while having a low adverse event profile, have not proved effective for managing chronic musculoskeletal conditions relevant to injured workers; (3) some devices are marketed and billed as surrogate diagnostic tests for generally accepted, and more clearly proven, standard tests; (4) quality oversight of technology use among physicians may be inadequate; and (5) insurers' access to efficacy data adequate to make timely and appropriate coverage decisions in workers' compensation is often lacking. Emerging technology may substantially increase the costs of workers' compensation without significant evidence of health benefit for injured workers. To prevent ever-rising costs, we need to increase provider education and patient education and consent, involve the state medical society in coverage policy, and collect relevant outcomes data from healthcare providers.

Cost Sharing↗
PubMed1987

Hormonal regulation of the synthesis and mRNA content of the regulatory subunit of cyclic AMP-dependent protein kinase type II in cultured rat ovarian granulosa cells.

These studies were undertaken to determine the molecular events by which estradiol and follicle-stimulating hormone (FSH) stimulate in ovarian granulosa cells the increase in the content of one of the regulatory subunits of cAMP-dependent protein kinase type II, RII51 (Mr = 51,000), and its electrophoretic variants RII51.5 (Mr = 51,500) and RII52 (Mr = 52,000). To analyze the de novo synthesis of RII51/52, granulosa cells were cultured (10(6) cells/ml) for 0, 12, 24, or 48 h with estradiol (10 nM) +/- FSH (12.5, 25, and 50 ng/ml), 8-bromo-cAMP (0.25-3 mM), or forskolin (0.5-100 microM) and then pulse-labeled with [35S]methionine (300 microCi/ml; 4 h). Labeled RII51, present either in urea extracts of total cellular protein or after partial purification from a soluble cell extract by cAMP-Sepharose chromatography, was quantitated by autoradiography of two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels and by excision of the silver-stained spots of the RII51 variants from the gels and counting. Synthesis of RII51 and its electrophoretic variants was low in cells cultured with estradiol alone for 48 h, whereas it was increased 4-5-fold in cells cultured with estradiol and FSH. Changes in the synthesis of actin were minor throughout the culture period regardless of hormone treatment. Pulse-chase experiments using [35S]methionine provided evidence that the isoelectric variants RII51.5 and RII52 may be derived from RII51 by post-translation modification, such as phosphorylation. Labelling with [32P]orthophosphate showed that RII52 contained more radioactivity than RII51.5 and RII51. Northern and filter hybridization assays demonstrated a 6-10-fold dose- and time-dependent increase in the amount of RII51 mRNA in granulosa cells exposed to estradiol and FSH or estradiol and forskolin compared to those cultured with estradiol alone. In vitro translation of poly(A)+ mRNA of granulosa cells from estradiol- and FSH-treated hypophysectomized rats also demonstrated an increase in the content of translatable RII51 mRNA. These studies indicate that in cultured rat granulosa cells the synthesis of RII51 and the content of its mRNA are selectively increased by estradiol and cAMP in a time- and dose-dependent manner. Based on these observations, RII51 appears to be a useful marker to determine the molecular (genomic?) sites of estradiol and FSH action in differentiating rat granulosa cells.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1987

Tissue distribution and hormonal regulation of messenger ribonucleic acid for regulatory and catalytic subunits of adenosine 3',5'-monophosphate-dependent protein kinases during ovarian follicular development and luteinization in the rat.

cDNA probes specific for the regulatory (R) subunits [RII51; (mol wt, 51,000) and RI (mol wt, 49,000)] and a catalytic (C alpha) subunit of cAMP-dependent protein kinases were used to analyze the hormonal regulation, tissue distribution, and content of mRNAs for these kinase subunits in the rat ovary. Filter hybridization assays demonstrated that mRNA specific for RII51 increased in both thecal and granulosa cells of preovulatory (PO) follicles, then declined precipitously (less than 10-fold) in both cell types within 7 h after an ovulatory (10-IU) dose of hCG and remained low in corpora lutea. Dose-response studies showed that doses of FSH greater than 2 micrograms were required to increase RII51 mRNA in granulosa cells of hypophysectomized (H) rats, whereas doses of 0.5-1.0 micrograms were effective in granulosa cells of H estradiol-treated (HE) rats. At all doses (0.5-50 micrograms) of FSH administered, RII51 mRNA was 4 times higher in granulosa cells of HE rats than in H rats. Solution hybridization assays demonstrated that the concentration of RII51 mRNA increased 6-fold from 20 molecules/granulosa cell in H rats to 120 molecules/cell in H rats treated with estradiol and FSH (HEF). Transcription assays using nuclei of granulosa cells demonstrated further that the 5- to 10-fold increases in RII51 mRNA content in estradiol-/FSH-induced granulosa cells was associated with increased transcription of the RII51 gene. In thecal cells of small antral (SA), PO, and luteinizing follicles, changes in the content of mRNA for RI and C alpha kinase subunits showed a pattern similar to that for RII51. However, in granulosa cells, mRNA specific for RI and C alpha was highest in SA follicles, declined in PO follicles, and remained unchanged during luteinization. The content of mRNA for RI (45-70 molecules/cell) and C alpha (10 molecules/cell) also changed less than 2-fold in granulosa cells of H, HE, and HEF rats. In summary, these results indicate that the content of RII51 mRNA is hormonally regulated in both thecal cells and granulosa cells during follicular development and luteinization. Low concentrations of gonadotropins increase RII51 mRNA, whereas an ovulatory dose of hCG causes mRNA for RII51 to decrease rapidly. In granulosa cells, induction of mRNA for RII51, but not that for RI and C alpha is induced by the actions of estradiol and FSH, and involves increased transcription of the RII51 gene.

Animals↗
PubMed1987

Cholesterol side-chain cleavage P450 messenger ribonucleic acid: evidence for hormonal regulation in rat ovarian follicles and constitutive expression in corpora lutea.

Using an affinity-purified antibody against cholesterol side-chain cleavage P450 (P450scc) and a human P450scc cDNA probe, 11 rat P450scc cDNA clones were identified and isolated from our rat granulosa cell lambda gt11 cDNA expression library. Two clones were plaque purified and subcloned into pBR322. One of these P450scc cDNA clones, approximately 1.2 kilobases (kb) in size, was used as a probe for Northern and filter hybridization assays to analyze the tissue distribution and hormonal regulation of P450scc mRNA in rat ovarian follicles and corpora lutea. Northern transfers revealed a single P450scc mRNA species about 2.0 kb in size. Filter hybridization assays showed that P450scc mRNA was low in granulosa cells and thecal cells of small antral follicles, was increased in both tissues of preovulatory follicles, and was rapidly (within 7 h) and maximally increased (30-fold) during hCG-induced luteinization. P450scc enzyme and mRNA were also elevated in corpora lutea isolated from pregnant rats (days 4-22 of gestation) and rats 1 day after parturition (day 23). The elevation of P450scc enzyme and mRNA was maintained despite the marked decline in serum progesterone concentrations between days 19-22, suggesting that once P450scc mRNA is induced in luteal tissue it may be constitutively expressed. Administering hormones to granulosa cells in culture and to hypophysectomized immature rats in vivo demonstrated that the induction of P450scc mRNA by FSH in granulosa cells was time, dose, and estradiol dependent. High doses of FSH acting on estradiol-primed cells gave the greatest response. The increase in P450scc mRNA in cultured granulosa cells was also stimulated by forskolin and was directly associated with increased synthesis of cAMP and progesterone accumulation. Thus, whereas the induction of P450scc mRNA in granulosa cells was dependent on hormones and cAMP, the maintenance of P450scc mRNA and P450scc protein in corpora lutea appears to involve constitutive expression of P450scc mRNA.

Animals↗
PubMedDate not supplied

Pituitary gonadotropin content in gonadectomized rats. Immunoassay measurements influenced by extraction solvent and testosterone replacement.

Increasing interest in events regulating gonadotropin synthesis and secretion led to the reexamination, by radioimmunoassay (RIA), of the pituitary content of luteinizing hormone (LH) and follicle stimulating hormone (FSH). In a preliminary experiment, the importance of the composition of the solvent used to homogenize pituitaries on the detection of LH and FSH was demonstrated by RIA. Experiment 1 demonstrated that a drop in pituitary FSH occurred acutely following gonadectomy in males, but not in females. Experiment 2 tested whether this decline resulted from loss of testosterone or inhibin. Males were castrated and treated daily with oil or testosterone propionate, porcine follicular fluid, porcine serum, or testosterone plus follicular fluid for 2 to 14 days. Castration lowered pituitary FSH at 2, 4, and 6 days. Follicular fluid suppressed serum FSH, but not LH, and did not prevent the fall in pituitary FSH. Testosterone blocked the rise of serum LH and FSH and prevented the decline in pituitary FSH.

Animals↗