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Biomedical subjects

M A Carroll

Publications and source records attributed to M A Carroll.

67 records · Page 4Linked to original sources
PubMed1977

Reverse phase high speed liquid chromatography of antibiotics. II. Use of high efficiency small particle columns.

Improved methods for the separation and quantitation of cephalosporins, penicillins, tetracyclines and several miscellaneous antibiotics by reverse phase high speed liquid chromatography are presented. The methods have been improved significantly by the substitution of high efficiency, small particle (approximately 10 micrometer reverse phase columns in place of the previously used medium efficiency, pellicular columns. The conditions and procedures described here illustrate that considerable improvements in separation and sensitivity of detection of antibiotics are achieved. Pure compounds, complex mixtures of antibiotics in a variety of dosage forms and fermentation broths are routinely analyzed by the described procedures.

Anti-Bacterial Agents↗
PubMed1975

Reverse phase high speed liquid chromatography of antibiotics.

Reverse phase high speed liquid chromatographic methods are presented for the separation and detection of cephalosporins, penicillins, tetracyclines and other miscellaneous antibiotics. The reverse phase approach is superior to ion-exchange liquid chromatography and spectrophotometric, chemical and microbiological procedures currently in use. In addition to being simple and easy to control, the technique is rapid, convenient and precise and provides the basis for the direct analysis of pure compounds, stability samples, complex mixtures and dosage forms of all types. Preparative chromatography has been used in our laboratory for the separation and isolation of up to 500 mg of antibiotics. Using this approach, we have separated and isolated small impurities as well as pure feference compounds. The methodology reported here can be extensively applied to the separation, quantitation and isolation of both naturally occurring and synthetically produced antibiotics in a variety of media including physiological fluids.

Anti-Bacterial Agents↗
PubMedDate not supplied

Exaggerated renal thromboxane and prostaglandin release by angiotensin II in suprarenal aortic coarctation hypertension.

The ability of angiotensin II and arachidonic acid to release immunoreactive prostaglandins into venous and ureteral effluents of rabbit isolated perfused kidneys was examined 7 days after suprarenal aortic coarctation (SRAC) or sham operation (SHAM). Renal vascular responses to angiotensin II were significantly enhanced in SRAC and accompanied by an enhanced venous efflux of bioassayable prostaglandins. Angiotension II-induced release of immunoreactive PGE2, PGF2 alpha, 6-keto PGF1 alpha and TxB2 into the venous effluent was exaggerated in SRAC. As angiotensin II did not stimulate TxB2 efflux in the SHAM group the induction of TxB2 release by SRAC is particularly noteworthy. These changes in eicosanoid release in response to angiotensin II were not mimicked by arachidonic acid administration. These results suggest that in renovascular hypertension angiotensin II-induced prostaglandin release is primarily augmented in the vascular compartment and is consistent with the sensitivity of renal function to cyclooxygenase inhibitors in renovascular hypertension.

Angiotensin II↗
PubMedDate not supplied

Renal cytochrome P450-related arachidonate metabolite inhibits (Na+ + K+)ATPase.

The function of the nephron, the anatomical unit of the kidney, is segmented; at least 12 segments have been identified that differ in their morphology, transport properties and hormonal responsiveness. The medullary portion of the thick ascending limb of the loop of Henle (mTALH) has one of the highest concentrations of (Na+ + K+)ATPase found in mammalian tissues, reflecting the importance of this nephron segment in the regulation of extracellular fluid volume, as active sodium transport is driven by (Na+ + K+)ATPase. Here, in cells derived primarily from the mTALH of the outer medulla of rabbit kidney, we have identified a cytochrome P450-dependent monooxygenase system which metabolizes arachidonic acid to two biologically active oxygenated products; one of the products inhibits (Na+ + K+)ATPase and the other relaxes blood vessels. We report that formation of these oxygenated arachidonate metabolites is stimulated by arginine vasopressin (AVP) and salmon calcitonin (SCT).

Animals↗
PubMedDate not supplied

Renal arachidonic acid metabolism. The third pathway.

Cells were isolated from the outer medulla of the rabbit kidney, primarily from the thick ascending limb of Henle's loop (mTALH). These mTALH cells are heavily invested with a cytochrome P450-linked monooxygenase that represents the third pathway by which arachidonic acid is metabolized. After cell separation, approximately 80% of the cells proved to be mTALH in origin, based on electron microscopic criteria and immunofluorescent localization of Tamm-Horsfall protein, a specific marker for mTALH cells. The specific activity of alkaline phosphatase, a marker for proximal tubular cells, decreased threefold after separation of mTALH cells from outer medullary cells, associated with a fourfold increase in the capacity of the separated mTALH cells to metabolize arachidonic acid. Incubation of mTALH cells with 14C-arachidonic acid resulted in formation of oxygenated metabolites, identified as two peaks (P1 and P2), which accounted for 30 to 40% of the recovered radioactivity. Formation of prostaglandin E2 and F2 alpha accounted for only 3 to 5%. The chromatographic retention times of P1 and P2 were different from products of lipoxygenases. An inhibitor of cytochrome P450-dependent enzymes, SKF-525A (50 microM), reduced product formation by mTALH cells by more than 70%, while induction of cytochrome P450 increased product formation. Formation of P1 and P2 by cell-free homogenates of mTALH was totally dependent on the presence of nicotinamide adenine dinucleotide phosphate, reduced form (NADPH), which suggests a NADPH-dependent cytochrome P450-linked monooxygenase pathway. Vasopressin and calcitonin (10(-10) M to 10(-7) M) stimulated release of arachidonic acid metabolites from mTALH cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMedDate not supplied

Regulation of preglomerular microvascular 20-hydroxyeicosatetraenoic acid levels by salt depletion.

BACKGROUND: 20-hydroxyeicosatetraenoic acid (20-HETE) is the preeminent renal eicosanoid. The protean properties of 20-HETE - vasoactivity, mitogenicity and modulation of transport in key nephron segments - serve as the basis for the essential roles of 20-HETE in the regulation of the renal circulation and electrolyte excretion and as a second messenger for endothelin-1 (ET-1) and a mediator of selective renal effects of angiotensin II (AII). Renal autoregulation and tubular glomerular feedback are mediated by 20-HETE through constriction of preglomerular microvessels, particularly afferent arterioles. METHODS AND RESULTS: We had reported that rat preglomerular microvessels (PGMV; afferent-interlobular-arcuate/interlobular) in response to angiotensin II (AII) generate primarily 20-HETE and lesser quantities of 19-HETE. We have now addressed a possible link between the renin-angiotensin-system (RAS) and induction of cyclooxygenase (COX-2). As Na+ deprivation induces COX-2 expression/activity in the renal cortex and AII stimulates release of 20-HETE from PGMV, we used a stimulus, low dietary salt, to activate the RAS and COX-2 and thereby explore potential interactions involving 20-HETE and COX-2. CONCLUSIONS: The capacity of COX to metabolize 20-HETE to prostaglandin analogs e.g., 20-OH PGF2a and 20-OH PGE2, may be critical to modifying the renal vascular and tubular actions of the eicosanoids.

Animals↗
PubMedDate not supplied

Cytochrome P-450 metabolites of arachidonic acid: implications for blood pressure regulation.

In the presence of NADPH cytochrome P-450-dependent monooxygenases oxidize arachidonic acid giving rise to four epoxyeicosatrienoic acids (EETs) which are hydrolyzed enzymatically to dihydroxyeicosatrienoic acids (DHETs). EETs generate vasodilators. Allylic oxidation forms hydroxyeicosatetraenoic acids, of which 12(R)HETE is an inhibitor of Na(+)-K(+)-ATPase and renin release. Finally, omega and omega-1 hydroxylation of arachidonic acid generates 20- and 19-HETEs which are involved in the development of hypertension in SHR rats.

Animals↗
PubMedDate not supplied

Rapid colorimetric determination of activity of subtilisin enzymes in cleaning products.

A new colorimetric method is described for the determination of enzymatic activity of subtilisin in cleaning products. The procedure is more rapid and precise than the casein digestion methods commonly used to assay protease activity. The principle of the colorimetric method depends on the determination rate of p-nitrophenol released on hydrolysis of N-CBZ-L-leucine-p-nitrophenyl ester at pH 8.0 by subtilisin, with correction for any nonenzymatic (spontaneous) hydrolysis of the substrate. Because of the broad range of hydrolytic activity of this enzyme, and the difficulties in predicting its proteolytic activity, this hydrolytic rate was chosen as a general indicator of subtilisin enzyme behavior. The slope for 7 replicate standard curves generated over a 6 week period exhibited a relative standard deviation of 7.5%, and 8.0% for 20 replicates with an enzyme cleaning product. Papain does not interfere with this assay.

Caseins↗