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Biomedical subjects

R A Lewis

Publications and source records attributed to R A Lewis.

At least 217 records · Page 12Linked to original sources
PubMed1988

Aminozolamide suspension: the role of the vehicle in a topical carbonic anhydrase inhibitor.

Aminozolamide (6-amino-2-benzothiazolesulfonamide) is a carbonic anhydrase inhibitor derived from ethoxzolamide that has been shown in gel formulation to lower IOP in rabbits, primates and humans. This study was designed to determine whether aminozolamide in suspension was also effective in lowering IOP. In separate single dose and multiple dose studies, patients with ocular hypertension were tested over 24 hours. No statistically significant drop in intraocular pressure was noted between the treated and control eye. In addition, conjunctival injection was noted in three of eleven subjects after multiple dosing. These studies suggest that retention of aminozolamide at the active site is inadequate when delivered in a suspension vehicle. In the past 10 years, efforts to develop an effective topical carbonic anhydrase inhibitor have been vigorously pursued. This has been aided by advancements in drug delivery and chemical synthesis involving molecular modification of existing carbonic anhydrase inhibitors. Various compounds have been developed that retain carbonic anhydrase inhibitory activity, penetrate the cornea and optimize the other important pharmacokinetic properties to lower intraocular pressure. One such compound, aminozolamide (6-amino-2-benzothiazolesulfonamide) is derived from ethoxzolamide. In suspension, it has been shown to lower IOP in rabbits and primates. It also has been shown to lower IOP in patients with ocular hypertension when delivered in a gel vehicle. The carbomer gel vehicle, a drug delivery system also used with pilocarpine (Pilopine HS), is used to prolong ocular contact and enhance penetration. The importance of the role of the vehicle in a topical carbonic anhydrase inhibitor has not been assessed.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗
PubMed1988

Analgesic and mechanistic evaluation of spiradoline, a potent kappa opioid.

Spiradoline (a congener of the kappa opioid agonist, U-50488H) was evaluated for analgesic and related activities in rodents. In nine antinociceptive assays utilizing various thermal, pressure and chemical and physical irritants, the potency of spiradoline ranges from 4.7 to 23 (mean = 13) times that of U-50488H. Naloxone blocks the analgesic effect of spiradoline. The in vivo naloxone pA2 for this antagonism is much lower than that for the antagonism of morphine and approximates that of U-50488H. The analgesic potency of spiradoline is greatly reduced in mice made tolerant to U-50488H but not in those made tolerant to morphine. Repeated treatment with spiradoline does not induce physical dependence as evidenced by a lack of naloxone-precipitated jumping and withdrawal-induced hyperalgesia. In sum, these observations suggest that spiradoline is a potent kappa agonist analgesic. However, further evaluation of spiradoline revealed differences between this compound and U-50488H. We have previously shown that the analgesic effect of the latter compound, but not that of morphine, is profoundly antagonized by reserpine or p-chlorophenylalanine. In contrast, spiradoline is only marginally antagonized by these serotonin-depleting treatments. Evaluation of the enantiomers of spiradoline revealed that the (-)-enantiomer is more than 30 times as potent as the (+)-enantiomer in analgesic tests. The (-)-enantiomer is similar to U-50488H with regard to antagonism by p-chlorophenylalanine, lack of physical dependence-inducing properties and cross-tolerance. In contrast the (+)-enantiomer induces physical dependence and displays marked cross-tolerance in morphine-tolerant mice.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1988

Tightly linked flanking markers for the Lowe oculocerebrorenal syndrome, with application to carrier assessment.

The Lowe oculocerebrorenal syndrome (OCRL) is characterized by congenital cataract, mental retardation, and defective renal tubular function. A map assignment of OCRL to Xq24-q26 has been made previously by linkage analysis with DXS42 at Xq24-q26 (theta = 0, z = 5.09) and with DXS10 at Xq26 (theta = 0, z = 6.45). Two additional families were studied and three additional polymorphisms were identified at DXS42 by using a 35-kb sequence isolated with the probe detecting the original polymorphism at DXS42. With additional OCRL families made informative for DXS42, theta remained 0 with z = 6.63; and for DXS10 theta = 0.03 and z = 7.07. Evidence for placing OCRL at Xq25 also comes from a female with Lowe syndrome and an X;3 translocation. We have used the Xq25 breakpoint in this patient to determine the position of OCRL relative to the two linked markers. Each derivative chromosome was isolated away from its normal counterpart in somatic cell hybrids. DXS42 was mapped to the derivative chromosome X containing Xpterq25, and DXS10 was mapped to the derivative chromosome 3 containing Xq25-qter. The markers DXS10 and DXS42 therefore show tight linkage with OCRL in six families and flank the Xq25 breakpoint in a female patient with an X;3 translocation. Linkage analysis with flanking markers was used to assess OCRL carrier status in women at risk. Results, when compared with carrier determination by ophthalmologic examination, indicated that the slit-lamp exam can be a sensitive and specific method of carrier determination in many cases.

Animals↗
PubMed1988

Penetrance of von Recklinghausen neurofibromatosis: a distinction between predecessors and descendants.

This paper reviews the concepts of penetrance and expressivity and examines their application to the specific disorder von Recklinghausen neurofibromatosis. The data suggest that assessments of penetrance among predecessors to probands yield results different from those of assessments of penetrance among descendants to probands. For descendants at risk, penetrance is very close to 100%. For predecessors at risk, extremely variable expressivity may confound estimates of penetrance; as a specific example, a family is described in which two brothers have bona fide von Recklinghausen neurofibromatosis and their mother manifests the neurofibromatosis mutation only as iris Lisch nodules.

Female↗
PubMed1988

6-amino-2-benzothiazole-sulfonamide. The effect of a topical carbonic anhydrase inhibitor on aqueous humor formation in the normal human eye.

The carbonic anhydrase inhibitor, 6-amino-2-benzothiazolesulfonamide, formulated as a 3% suspension in a gel vehicle was instilled in one eye of 21 human subjects in a single dose study to determine its effect on aqueous dynamics. A small but statistically significant effect on aqueous humor flow was observed 2 to 7 hours after application. By 8 hours, the effect had disappeared, and intraocular pressure (IOP) measured 8 hours after application of a single dose was unchanged in these normal volunteers. The drug and its vehicle caused local side effects including irritation, hyperemia, and blurred vision. The authors wondered if multiple doses would produce a greater effect. Four subjects received up to four doses of the drug over 2 days and were restudied. Marked bulbar injection and follicular conjunctivitis, attributable to either the drug or the vehicle, developed in two of the subjects, both contact lens wearers. A milder form of bulbar injection and follicular conjunctivitis developed in a third subject, who received three doses of the drug and was not a contact lens wearer. These side effects precluded additional multiple-dose testing of this formulation of the drug, and no conclusions about the effect of the drug on aqueous flow can be drawn from this portion of the study.

Adult↗
PubMed1988

A genetic study of Gardner syndrome and congenital hypertrophy of the retinal pigment epithelium.

Gardner Syndrome (GS) is an autosomal dominant variant of colorectal polyposis with essentially complete penetrance. It is distinguished from the other polyposis syndromes by its delayed age at onset, the number of polyps, and its extracolonic manifestations. The presence of epidermal cysts, bony osteomata, desmoid tumors, and dental anomalies are distinguishing features of this syndrome. Recently, multiple and bilateral patches of congenital hypertrophy of the retinal pigment epithelium (CHRPE) have been described in three families with classical GS. Tight linkage of the GS and CHRPE phenotypes (Z = 9.752; theta = 0) suggested that CHRPE is a pleiotropic effect of the Gardner mutation within the families in which the ophthalmic trait occurs and is thus a useful marker for the early detection of GS gene carriers. We have analyzed six new families segregating for classic GS and CHRPE. Linkage was tested between GS and CHRPE and between these two phenotypes and a battery of 22 informative biochemical and serological markers. We have extended the linkage analysis on two GS-CHRPE families originally reported elsewhere. Linkage between GS and CHRPE at theta = 0 was observed in all families, a result supporting our original suggestion that CHRPE is a congenital manifestation of the GS mutation. Exclusionary linkage data presented confirm that, for linkage analysis in these families, the CHRPE phenotype is a more powerful marker than other phenotypic features of GS.

Adolescent↗
PubMed1987

The effects of N-3 polyunsaturated fatty acids on the generation of platelet-activating factor-acether by human monocytes.

Human leukocytes generate platelet-activating factor (PAF-acether), a lipid mediator of inflammation, from membrane alkyl phospholipids through the release of arachidonic acid or other fatty acids at the 2-position and subsequent acetylation. Because it was previously demonstrated that fish oil fatty acids suppress human leukocyte arachidonic acid release and metabolism, separate experiments were conducted to investigate the effects of dietary fish oil supplementation and in vitro incubation with fish oil fatty acids on calcium ionophore-stimulated PAF-acether generation in human monocytes. In subjects on their regular diets, a 4-hr incubation of monocyte monolayers with an optimally effective concentration of arachidonic acid of 1 micrograms/ml resulted in a 64% increase of calcium ionophore-induced net PAF-acether generation from 7.75 +/- 0.78 ng/10(6) cells for untreated monolayers to 12.70 +/- 1.21 ng/10(6) cells (mean +/- SEM). Treatment of monolayers with eicosapentaenoic acid (EPA) at the optimal concentration of 1 micrograms/ml decreased net PAF-acether generation by 28%. However, treatment of monocyte monolayers with docosahexaenoic acid did not appreciably affect net PAF-acether generation. The changes in PAF-acether release with each fatty acid added in vitro paralleled those in total PAF-acether generation; the percentage PAF-acether release remained unaffected. Three weeks of dietary supplementation with 18 g MaxEPA daily, providing 3.2 g EPA did not affect the PAF-acether generation of calcium ionophore-stimulated human monocyte monolayers. However, 6 weeks of dietary supplementation resulted in a 47% decrease of net total PAF-acether generation and a concomitant 59% decline in net PAF-acether release; the percentage release of PAF-acether was not affected. Thus, whether added to the diet or introduced in vitro, fish oil-derived fatty acids suppress PAF-acether generation by human monocyte monolayers.

Adult↗
PubMed1987

The metabolism of deoxyguanosine in mitochondria: a characterization of the phosphorylation process which occurs in intact mitochondria.

Isolated, intact mitochondria were evaluated for their ability to phosphorylate deoxyguanosine. This activity was stimulated by exogenous ATP, substrates for oxidative phosphorylation or added inorganic phosphate. Inhibitors of oxidative phosphorylation lowered the levels of deoxyguanosine phosphorylation. From a Hanes plot, an apparent Km of 0.83 microM deoxyguanosine was calculated for the phosphorylation activity in intact mitochondria. In the presence of a 20-fold excess of added deoxynucleosides, none of those tested were strongly inhibitory. However, added UDP and dTDP were stimulatory and dGTP and dGDP were inhibitory to the phosphorylation of deoxyguanosine. These data show that mitochondria phosphorylate deoxyguanosine and that the process is regulated by other events which take place within the organelle.

Adenosine Diphosphate↗
PubMed1987

Synthesis and release of leukotriene C4 by human eosinophils.

When human peripheral blood eosinophils isolated to 92.5% +/- 6.9 purity were stimulated with either the calcium ionophore A23187 or N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP), immunoreactive leukotriene C4 (LTC4) was initially localized intracellularly and was subsequently released to the external medium in kinetically distinguishable steps. Eosinophils were stimulated with 2.5 microM A23187 in the presence of 20 mM L-serine, a hypochlorous acid scavenger that prevents the oxidative metabolism of sulfidopeptide leukotrienes. Total production of immunoreactive LTC4, the sum of intra- and extracellular LTC4, was complete within 5 to 10 min. At 5, 10, and 30 min, 65.9% +/- 15.2, 42.3% +/- 24.3, and 5.5% +/- 3.9, respectively, of the total amount of LTC4 measured remained intracellular as detected after the media and cells were separated and the latter was extracted with methanol. The time course for the intracellular synthesis and extracellular release of immunoreactive LTC4 from eosinophils pretreated with 5 micrograms/ml cytochalasin B and stimulated with 0.5 microM FMLP was like that obtained with ionophore, although the total LTC4 production was only approximately 10%. The identity of the intracellular LTC4 was confirmed by elution with reverse-phase high pressure liquid chromatography followed by scanning UV spectroscopy, radioimmunoassay, and bioassay. Eosinophils that were stimulated with A23187 in the absence of L-serine metabolized newly synthesized LTC4 to 6-trans-LTB4 diastereoisomers and subclass-specific diastereoisomeric sulfoxides that were identified only in the extracellular medium. Thus the response of purified eosinophils to two different stimuli demonstrates a transient intracellular accumulation of biologically active LTC4, the distinct extracellular release, and the apparent limitation of oxidative metabolism to the extracellular location.

Arachidonic Acids↗
PubMed1987

Mapping X-linked ophthalmic diseases. III. Provisional assignment of the locus for blue cone monochromacy to Xq28.

Blue cone monochromacy (BCM) is an infrequent X-linked retinal disorder typified by poor central visual acuity and color discrimination, early onset of nystagmus, variable degrees of myopia and astigmatism, and a nearly normal retinal appearance. The physiologic functions of rods and blue cones are preserved. The regional location of the genetic mutation causing BCM has been unknown. We have applied the modern molecular techniques of analysis of restriction fragment length polymorphisms to three multigenerational kindreds in which BCM is segregating. Significant linkage is established to two DNA markers, DXS15 and DXS52, each of which maps to the vicinity of Xq28. Regional localization of the locus for BCM has the potential to improve carrier detection and to provide antenatal diagnosis in families at risk for the disease.

Chromosome Mapping↗
PubMed1987

Biochemical and functional interactions of a selective kappa opioid agonist with calcium.

The discovery of the selective kappa opioid receptor agonist, U-50488H, has provided a tool for the study of the mechanisms and function of the kappa receptor-effector. We have investigated the interactions of this compound with calcium in several biochemical and functional studies to assess the involvement of calcium mechanisms in the kappa receptor-linked effector. In rat brain synaptosomes, U-50488H attenuated the uptake of 45Ca++ induced by K+ (40 mM) depolarization. This effect was concentration-related (U-50488H 10(-5) to 10(-7) M), was apparent in short (8-second) but not longer (1-minute) term incubations, and did not occur in the presence of a non-polarizing concentration (5.6 mM) of K+. Naloxone (10(-7) M) did not block this effect of U-50488H (10(-6) M), and higher concentrations (10(-5) M) alone blocked calcium uptake. We have found that the binding of the depolarizing amino acid analog, kainic acid, is enhanced by CaCl2. U-50488H (10(-4) to 10(-6) M) blocks this enhancement of 3H-kainic acid binding in vitro and also blocks the in vivo effects of kainic acid. In mice, intravenous injection of kainic acid causes scratching, convulsions, and death, depending on the dose administered. U-50488H blocks all of these effects (ED50 = 4.5 mg/kg for antagonism of convulsions induced by 27.5 mg/kg kainic acid). The convulsions induced by intracerebroventricularly administered kainic acid are also blocked by U-50488H as are those induced by similarly administered Bay K 8644, a calcium channel activator. All of these anticonvulsant effects of U-50488H were antagonized by naltrexone. Together these data indicate that the kappa agonist U-50488H has functionally relevant interactions with depolarization-related Ca++ mechanisms in the central nervous system.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1987

Phosphorylation of deoxyguanosine in intact and fractured mitochondria.

The phosphorylation of deoxyguanosine was measured in fractured and intact mitochondria and an apparent Km of 16 microM for deoxyguanosine was calculated using fractured mitochondria. The effects of various deoxynucleotides on the phosphorylating activity in fractured organelles was tested at both a high and low ratio of NXP/ATP and at two pH values, 7.0 and 5.5. Exogenous dGTP, dGDP or dITP were inhibitory under all conditions tested. With a NXP/ATP ratio of 0.08 at pH 7.0, TTP, TDP, dADP, ADP, UTP and UDP were stimulatory, but at pH 5.5 only TTP elicited that response. When the NXP/ATP ratio was 10 at pH 5.5, TTP and UTP increased the activity more than 10-fold, whereas, at pH 7.0 TTP, TDP, dADP, ADP, UTP, UDP caused stimulation, but to a much lesser extent. When exogenous Mg2+, Mn2+ or Ca2+ were added to intact mitochondria, the rates of phosphorylation were lowered. In fractured mitochondria in the absence of exogenous ATP, little phosphorylation occurs, hence these metal ions caused little change. ATP-Mg, ATP-Mn and ATP-Ca, each at 0.05 mM caused a small inhibition with intact mitochondria, whereas, these compounds supported phosphorylation with fractured organelles. ATP-Mn (10 mM) or ATP-Ca (10 mM) stimulated phosphorylation in both intact and fractured mitochondria. Intact mitochondria synthesized dGMP, dGDP and dGTP when metal ion or ATP-Me concentrations were low (0.05 mM) or when Mg2+ concentration was high (10 mM). Additions of ATP-Ca, ATP-Mn, ATP-Mg, Mn2+ or Ca2+ at 10 mM cause the loss of dGDP and dGTP formation and, in most cases, an increase in the synthesis of dGMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The metabolism of deoxyguanosine in mitochondria. Characterization of the uptake process.

The uptake of deoxyguanosine by rat liver mitochondria was characterized. The process required an intact mitochondrial membrane and exhibited a dependence on added phosphate. Deoxyguanosine uptake was minimally influenced by Mg2+ or Mn2+, but Ca2+ at concentrations above 0.5 mM were detrimental. Of the deoxynucleosides tested, only deoxyinosine inhibited the uptake of deoxyguanosine. The ribonucleoside guanosine was not observed to compete with its deoxynucleoside analog. Known inhibitors of nucleoside transport, cytochalasin B and NBMPR, did not block deoxyguanosine uptake, but the sulfhydryl reagents NEM and pCMB were both inhibitory. The uptake of deoxyguanosine was shown to be a saturable process and an apparent Km of 0.64 microM was calculated from a Hanes plot.

Animals↗
PubMed1987

The metabolism of deoxyguanosine in mitochondria: relationship of the uptake of deoxyguanosine to the electron transport chain and adenosine triphosphate.

That deoxyguanosine is taken up by isolated rat liver mitochondria has been shown. This report describes the relationship between that uptake and oxidative phosphorylation. By measuring this process in the presence of standard inhibitors of oxidative phosphorylation it was determined that a functional electron transport chain, but not the phosphorylation of ADP, was essential for uptake. ATP analogs adenyl(beta,gamma-methylene)diphosphate and adenylimidodiphosphate blocked uptake, indicating that ATP hydrolysis was required. ADP also proved to be an inhibitor. Exogenous UTP slightly stimulated deoxyguanosine uptake, as did added ATP, but several other nucleotides (dGTP, dATP, UDP, dGDP) were inhibitory. A sulfhydryl group was important for deoxyguanosine uptake and inhibition of uptake by N-ethylmaleimide was protected by both deoxyguanosine and ATP. These data show that deoxyguanosine uptake by mitochondria is a process which is coordinated and, perhaps, regulated by other events which take place in the organelle.

Adenosine Diphosphate↗
PubMed1987

Critical considerations in the development of an assay for sulfidopeptide leukotrienes in plasma.

A sensitive and specific assay has been developed for measurement of total sulfidopeptide leukotrienes (LT) in plasma. LTC4 and LTD4 in plasma are converted to LTE4 which is then extracted by C18 Sep-Pak binding and elution. Total LTE4 is resolved by reverse phase high performance liquid chromatography (RP-HPLC) and quantitated by radioimmunoassay (RIA). A [3H]LTE4 internal standard is added to the starting plasma sample to allow overall recovery to be calculated and to define the fractions from RP-HPLC to be assayed for LTE4-like immunoreactivity. The correlation between the measured increase in LTE4 concentration after addition of incremental amounts of LTC4 and LTE4 to plasma was 0.989 and 0.978, respectively, with slopes of 1.05 and 1.11. Addition of 51 pg/ml LTE4 to 5 ml plasma was detectable; the measured increase was 48 +/- 12 pg/ml (mean +/- SE, n = 7). The intra-assay coefficient of variation for 341 pg/ml of added LTC4 was 3.2% (n = 6). Sulfidopeptide leukotrienes could not be detected in blood samples taken from 12 normal volunteers in whom the theoretical detection limit, calculated from the sensitivity of the RIA, the overall recovery of LTE4, and the volume of plasma extracted, was 83 +/- 4 pg LTE4/ml plasma (0.19 +/- 0.01 pmol sulfidopeptide leukotriene/ml plasma; mean +/- SE).

Adult↗
PubMed1987

LTB4 mediated hypoxemia in guinea pigs: relationship to pulmonary and cardiovascular pathophysiology.

LTB4 is released in the presence of lung injury and may therefore play a role in the pathophysiology of the lung damage. We therefore, administered LTB4 as an I.V. bolus or as an aerosol to guinea pigs and assessed the physiologic response and the lung histology. After 2 ug of I.V. LTB4 airway pressure (AP) rose transiently by 5 +/- 1 mmHg and at five min was back to baseline while PaO2 fell from 96 +/- 5 mmHg to 78 +/- 3 mmHg and remained low at least 45 min. Static compliance (Cstat) was unchanged. Right ventricular systolic pressure (RVSP) and mean aortic pressure (MAP) rose from 9 +/- 1 to 16 +/- 1 mmHg and 43 +/- 4 to 62 +/- 5 mmHg respectively while cardiac index (C.I.) fell from 266 to 208 ml/kg/min but all values were baseline again by 10 min. Aerosolized LTB4 raised AP by 4.6 +/- 0.2 mmHg while PaO2 fell from 90 +/- 7 to 52 +/- 5 mmHg. AP recovered by 20 min but PaO2 remained low at least for 1 hour. MAP, RVSP and CI and Cstat were unaffected. Both I.V. and inhaled LTB4 increased neutrophil infiltrate in the lung although the water aerosol control did too, preventing us from showing a significant effect with LTB4 aerosol. Indomethacin blocked the airway effects and the hypoxemia after I.V. or aerosolized LTB4 but not the neutrophil infiltrate or the rise in RVSP. It actually enhanced (p less than .05) the rise in MAP after I.V. LTB4. Thus cyclooxygenase released products likely mediated the rise in airway pressure and the prolonged fall in PaO2 after LTB4 in guinea pigs but not the pulmonary and systemic vasoconstriction.

Administration, Inhalation↗