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Biomedical subjects

T J Lynch

Publications and source records attributed to T J Lynch.

At least 109 records · Page 6Linked to original sources
PubMed1986

Bleomycin inhibition of angiotensin-converting enzyme activity from serum, lungs, and cultured pulmonary artery endothelial cells.

The interaction between bleomycin (BLM) and angiotensin-converting enzyme (ACE) from bovine lungs, serum, and cultured pulmonary artery endothelial cells was examined. ACE activity from all sources was inhibited by metal-free BLM but not by metal-complexed BLM. The metal-free deamide metabolite of BLM, which is nontoxic, also inhibited ACE activity from bovine endothelial cell homogenates and serum. Incubation of intact cultured pulmonary artery endothelial cells for 1 h with metal-free BLM produced a concentration-dependent inhibition of cellular ACE activity, which was persistent, lasting at least 24 h after drug removal. In addition, the enzyme activity released into the culture medium was decreased. The inhibition of cellular ACE activity occurred in the absence of (1) cell death as measured by dye exclusion, (2) inhibition of total protein synthesis as measured by [3H]leucine incorporation, and (3) decreased cellular enzyme content as assayed using a monoclonal antibody against the enzyme. These results indicate that a brief exposure of intact cultured pulmonary endothelial cells to BLM can produce direct and prolonged inhibition of ACE activity. The inhibition of ACE activity does not relate directly to cell death but rather appears to result from metal chelation by BLM.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1986

Coronavirus antibody detection in cats by computer-assisted kinetics-based enzyme-linked immunosorbent assay (KELA): field studies.

A total of 2238 feline serum samples submitted to the New York State Diagnostic Laboratory over a 1-year period were tested for the presence of coronavirus antibodies, using the computer-assisted, kinetics-based enzyme-linked immunosorbent assay (KELA). Cats from which sera were obtained were categorized by sex, age, breed, and disease status, and variations in mean antibody titers for different sub-classifications within each category were analyzed by computerized statistical analysis. As expected, higher mean antibody titers were recorded for cats with feline infectious peritonitis, and for cats with a recent history of possible coronavirus exposure. However, an unexpected inverse relationship between coronavirus antibody titer and age was also found. Certain cattery-oriented pure breeds appeared to have higher mean antibody titers, because their sample populations contained a higher percentage of younger cats and cats of unknown age-groups which, over-all, had higher mean titers. Taken together, the data substantiated the efficacy of the computer-assisted KELA for routine detection of serum coronavirus antibodies in cats.

Animals↗
PubMed1985

Carbon tetrachloride-induced eicosanoid synthesis and enzyme release from rat peritoneal leucocytes.

When rat peritoneal leucocytes were incubated with carbon tetrachloride, a PLA2 was activated, eicosanoids were generated and lysosomal and cytoplasmic enzymes were released. The predominant eicosanoid generated was TXB2 with lesser amounts of PGE2, 6-keto PGF1 alpha and LTB4. Preincubation of the cells with two structurally unrelated thromboxane synthetase inhibitors reduced PLA2 activity and enzyme release and also reduced the total amounts of eicosanoids liberated. An anti-PGI2 antibody partially reversed the effects of thromboxane synthetase inhibitors indicating a role for endogenous PGI2 generation in the cytoprotective effects of these agents in this system. Exogenous PGI2 was also cytoprotective but the timing of its administration was critical. The cytoprotective effect of PGI2 was potentiated by a phosphodiesterase inhibitor, indicating a possible pivotal role of cAMP in cell protection.

Animals↗
PubMed1985

A model for signal transmission in an ear having hair cells with free-standing stereocilia. II. Macromechanical stage.

A model of the signal-processing properties of the macromechanical system of the alligator-lizard middle and inner ear is developed. The model is based on measurements (as a function of tone frequency) of ossicular and basilar-membrane motion and of acoustic input-admittance at the tympanic membrane before and after alterations of middle-ear and inner-ear structures. From the structure of the ear, we formulate an equivalent electric network consisting of six admittance blocks and two transformers. The admittance blocks represent the mechanical properties of particular structures, e.g. the tympanic membrane (TM), the ossicle, the TM-ossicular joint, the vestibule, the basilar membrane and the helicotrema. The transformers represent the conversions from acoustical to mechanical variables performed by the TM-ossicular system and by the columella footplate. The block admittances and transformer ratios are inferred from the measurements, and each admittance is approximated by a network with a few simple elements. The resulting model fits the experimental results satisfactorily, allows correlations between specific structures and response behavior, and predicts the macromechanical transfer function. This transfer function acts as the first stage of a model of the alligator-lizard auditory periphery (Weiss et al., Weiss and Leong, 1985, Hearing Res. 20, 131-138, 157-174, 175-195). In the model the frequency dependence of basilar-membrane motion (1) is determined primarily by the tympanic membrane and extracolumella in the middle frequencies and (2) is affected by the helicotrema at low frequencies and the TM-ossicular joint at high frequencies.

Acoustics↗
PubMed1985

Morphine-induced pupillary fluctuations in the rat: correlations with EEG and respiratory changes.

Pupil area in rats was continuously monitored by infrared pupillometry during morphine-induced (30 mg/kg i.p.) mydriasis and pupillary fluctuations. EEG records from all visual system areas as well as frontal cortex, amygdala and mesencephalic reticular formation show intermittent electrographic bursting to be simultaneous with miosis during the period of fluctuations. Mydriasis occurs at the cessation of each burst, but both of these events occur 1-3 seconds after an effect on respiration composed of a slight change in tidal volume and a 10% decrease in minute respiratory rate. The reason for the essential synchrony of the respiratory change, the cessation of global bursting and the change in parasympathetic input to the pupil is unknown.

Animals↗
PubMed1984

Acoustic input-admittance of the alligator-lizard ear: nonlinear features.

The acoustic input-admittance at the alligator lizard's tympanic membrane varies with stimulus level; the magnitude of the variation can be as much as a factor of three. At 1.6 kHz, the frequency of maximum admittance magnitude, the admittance varies when the stimulus level exceeds 65 dB SPL. At frequencies above or below 1.6 kHz, larger SPLs are needed to produce admittance changes. With stimulus frequencies below 0.3 kHz or above 4.0 kHz the admittance is virtually constant for stimulus levels up to at least 100 dB SPL. The nonlinear behavior (a) is greatly reduced when the cochlear partition is destroyed, (b) does not return when the mechanical load of the partition is replaced, (c) is decreased by the introduction of proteolytic enzymes into the inner ear, and (d) is not affected by some manipulations that greatly reduce cochlear potentials. The results suggest that the mechanical properties of the cochlear partition are the source of the nonlinear admittance. Parallels between this phenomenon and two-tone distortion products in the ear canal (Rosowski et al. (1984): Hearing Res. 13, 141-158) suggest that the same nonlinear mechanical source that generates the level-dependent admittance also produces two-tone distortion products in the lizard ear canal. Published demonstrations of level-dependent admittance in mammalian ears, although rather different from these results, do not rule out the presence of a similar mechanism in the mammalian cochlea.

Acoustic Impedance Tests↗
PubMed1984

Bleomycin hydrolase activity in pulmonary cells.

The metabolism of bleomycin (BLM) A2 by BLM hydrolase in the 105,000 X g supernatant fraction of homogenates obtained from freshly isolated and cultured pulmonary cells was assayed by high-pressure liquid chromatography. BLM A2 was converted solely to the less toxic desamido metabolite by the cytosol from isolated rabbit and bovine alveolar and interstitial macrophages, cultured rabbit and bovine pulmonary fibroblasts and cultured rabbit pulmonary artery endothelial cells. The BLM hydrolase activity in the cytosol from cultured rabbit fibroblasts had an apparent Km of 700 microM and Vmax of 33 nmol/hr/mg protein. The rate of BLM dA2 formation found with the cytosol of cultured rabbit pulmonary artery endothelial cells and pulmonary fibroblasts was 3 to 5 times greater per cell than that from the cytosol of rabbit alveolar and interstitial macrophages. Freshly isolated rabbit type II pneumocytes and bovine pulmonary artery endothelial cells grown in culture had undetectable levels of this inactivating enzyme activity. The expression of BLM hydrolase activity in rabbit pulmonary fibroblasts was stable for at least five passages in culture and was not significantly different over wide cell densities in culture. These data suggest that heterogeneity in the cellular distribution of BLM hydrolase activity exists in lungs. High levels of BLM hydrolase activity in the pulmonary endothelium or fibroblasts of some species may have an important role in determining the toxicity of BLM to the lungs.

Animals↗
PubMed1983

Evaluation of a computer-assisted, kinetics-based enzyme-linked immunosorbent assay for detection of coronavirus antibodies in cats.

A computer-assisted, kinetics-based enzyme-linked immunosorbent assay was adapted for the detection of coronavirus antibodies in feline serum. An alkaline antigen diluent (carbonate-bicarbonate buffer, pH 9.6) used in initial experiments produced diffuse, nonspecific color reactions in both viral and control antigen cuvettes which were correlated, paradoxically, with coronavirus antibody levels in test sera. These interfering reactions were minimized by use of lower-pH antigen diluents such as water and phosphate-buffered saline. Background kinetics-based enzyme-linked immunosorbent assay reactivity directed against a noncoronaviral component of antigen tissue culture fluids could then detected in numerous sera, particularly in samples with lower titers. Much of this reactivity was shown to be associated with bovine gamma globulins in cell culture fluid. It was not serum lot or species specific, since a variety of bovine serum lots as well as individual lots of serum from other mammalian and avian species reacted. Reactivity was markedly reduced when cells for antigen preparation were grown in gamma globulin-free bovine serum. Generation of corrected slope values from the kinetics-based enzyme-linked immunosorbent assay made it possible to correct for residual background reactivity in individual test sera and thus eliminate a potentially major source of false-positive reactions. Collectively, these studies indicated that the control of nonspecific reactivity in feline coronavirus serology is absolutely essential to obtain useful estimates of specific antibody responses.

Animals↗
PubMed1982

Computer-assisted enzyme immunoassays and simplified immunofluorescence assays: applications for the diagnostic laboratory and the veterinarian's office.

A computer-assisted enzyme-linked immunosorbent assay (ELISA) system, based on kinetics of the reaction between substrate and enzyme molecules, was developed for testing large numbers of sera in laboratory applications. Systematic and random errors associated with conventional ELISA technique were identified leading to results formulated on a statistically validated, objective, and standardized basis. In a parallel development, an inexpensive system for field and veterinary office applications contained many of the qualities of the computer-assisted ELISA. This system uses a fluorogenic indicator (rather than the enzyme-substrate interaction) in a rapid test (15 to 20 minutes' duration) which promises broad application in serodiagnosis.

Animal Diseases↗
PubMed1982

Induction of melanized cells from a goldfish erythrophoroma: isolation of pigment translocation variants.

Melanization was induced in some cells of a goldfish tumor cell line (GEM-81) by cultivating the cells in autologous serum. The melanized cells continued to proliferate in vitro and several clones were isolated that differed with respect to cell morphology and intracellular distribution of pigment. Some of the clones consisted of cells able to translocate their melanosomes in response to epinephrine, melatonin, or adenosine 3', 5'-monophosphate.

Animals↗
PubMed1982

Isolation of xanthophores from the goldfish (Carassius auratus L.).

A method is described for the isolation of milligram quantities of viable, hormone-responsive xanthophores from goldfish scales. The preparations are typically 70 to 90% pure and are useful for biochemical analyses or for establishing primary cultures.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1982

Input impedance of the cochlea in cat.

Tones were delivered directly to the stapes in anesthetized cats after removal of the tympanic membrane, malleus, and incus. Measurements were made of the complex amplitudes of the sound pressure on the stapes PS, stapes velocity VS, and sound pressure in the vestibule PV. From these data, acoustic impedance of the stapes and cochlea ZSC delta equal to PS/US, and of the cochlea alone ZC delta equal PV/US were computed (US delta equal to volume velocity of the stapes = VS X area of the stapes footplate). Some measurements were made on modified preparations in which (1) holes were drilled into the vestibule and scala tympani, (2) the basal end of the basilar membrane was destroyed, (3) cochlear fluid was removed, or (4) static pressure was applied to the stapes. For frequencies between 0.5 and 5 kHz, ZSC approximately equal to ZC; this impedance is primarily resistive ([ZC] approximately equal to 1.2 X 10(6) dyn-s/cm5) and is determined by the basilar membrane and cochlear fluids. For frequencies below 0.3 kHz, [ZSC] greater than [ZC] and ZSC is primarily determined by the stiffness of the annular ligament; drying of the ligament or changes in the static pressure difference across the footplate can produce large changes in [ZSC]. For frequencies below 30 Hz, ZC is apparently controlled by the stiffness of the round-window membrane. All of the results can be represented by an network of eight lumped elements in which some of the elements can be associated with specific anatomical structures. Computations indicate that for the cat the sound pressure at the input to the cochlea at behavioral threshold is constant between 1 and 8 kHz, but increases as frequency is decreased below 1 kHz. Apparently, mechanisms within the chochlea (or more centrally) have an important influence on the frequency dependence of behavioral threshold at low frequencies.

Acoustic Impedance Tests↗
PubMed1981

cAMP renders Ca2+-dependent phosphodiesterase refractory to inhibition by a calmodulin-binding protein (calcineurin).

Calmodulin is a ubiquitous, multifunctional, Ca2+-dependent regulatory protein, controlling a wide variety of Ca2+-mediated reactions. The versatility of calmodulin raises the question of how it exerts specificity at the molecular level. Cyclic nucleotide phosphodiesterase consists of multiple forms, one of which requires calmodulin for full activity. Calcineurin, a calmodulin-binding protein, inhibits the calmodulin-stimulated phosphodiesterase activity by competing with the enzyme for calmodulin. In this report, we present experiments which indicate that, although calcineurin potentially inhibits calmodulin-supported enzyme activity, its effectiveness as an inhibitor depends on the level of cAMP. In the presence of elevated levels of cAMP, the affinity of calmodulin for phosphodiesterase increased markedly, but that for calcineurin was not altered. Thus, the enzyme became relatively refractory to inhibition by calcineurin. This finding suggests that an increase of cellular cAMP could lead to a condition favorable to its own hydrolysis and that this phenomenon might represent an example of molecular specificity in calmodulin-regulated reactions.

Animals↗
PubMed1979

Purification and characterization of an inhibitor protein of brain adenylate cyclase and cyclic nucleotide phosphodiesterase.

A heat-labile inhibitor protein of adenylate cyclase (EC 4.6.1.1) and phosphodiesterase (EC 3.1.4.17) has been purified to apparent homogeneity from bovine brain cerebrum by a simple two-column procedure. The inhibitor exerts its effect on adenylate cyclase or phosphodiesterase by forming a complex with the Ca2+-dependent activator protein, thereby competing with the apoenzyme for the activator. The protein was estimated to have a molecular weight of 80,000 and a Stokes radius of 39 A by gel filtration. The inhibitor was resolved in a sodium dodecyl sulfate-polyacrylamide gel into two equal molar subunits, with molecular weights of 60,000 and 18,500. In the presence of the activator and Ca2+, the thermal stability of the inhibitor was increased, indicative of a new conformation. The effectiveness of the inhibitor varied considerably, depending on its sequence of addition to the reaction mixture relative to phosphodiesterase and the activator protein, presumably because the activator appeared to have a greater affinity for the inhibitor than for phosphodiesterase.

Adenylyl Cyclase Inhibitors↗
PubMed1979

Leukopenia due to penicillin and cephalosporin homologues.

Leukopenia is an infrequently recognized complication of penicillin-related antibiotic and cephalosporin therapy. We describe our experience with nine individuals and reviewed reports of 11 cases from the literature. Seventy-six percent of cases occurred in individuals receiving 150 mg/kg/day or more of the various penicillin and cephalosporin homologues; 67% received these high doses for two or more weeks before the onset of leukopenia. Leukopenia was unusual within the first week of antibiotic treatment. Standard medical texts often recommend blind administration with 12 to 23 g/day of these antibiotics regardless of weight. It is suggested that these antibiotics be administered according to a maximum milligram per kilogram per day dosage as is done in children. Beyond the first week of administration, careful monitoring of the blood cell count should be conducted for those receiving high doses of these antibiotics.

Adolescent↗