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Biomedical subjects

R A Martin

Publications and source records attributed to R A Martin.

At least 127 records · Page 7Linked to original sources
PubMed1982

Liquid chromatographic determination of aflatoxins in artificially contaminated cocoa beans.

A high pressure liquid chromatographic method is described for the extraction and determination of aflatoxins in artificially contaminated cocoa beans. Aflatoxins were extracted by using a CB extraction, column cleanup, and chromatography on a reverse phase column with UV detection at 365 nm for aflatoxins B1 and G1 and fluorescence detection for aflatoxins B2 and G2 (365 nm excitation and 455 nm emission). Recoveries from artificially contaminated cocoa beans of various roast conditions ranged from 77.50 to 107.35%. CV values ranged from 4.87 for G1 to 7.66 for G2 (n = 8). The method can be used for cocoa beans ranging from no roast to a heavy roast (12 min at 400 degrees F).

Aflatoxins↗
PubMed1981

Effects of extracellular potassium and 4-aminopyridine on corticosteroid secretion.

Transient alteration in [K+]0 significantly influenced basal and stimulated corticosteroid secretory activity of superfused rat adrenal cortical tissue slices. A transient rise in [K%]0 resulted in an increase in basal steroid secretion. Removal of extracellular K+ from the superfusing medium significantly reduced basal as well as ACTh and cAMP-stimulated steroid production. Elevated [K+0] significantly potentiated cAMP's and to a much lesser extent increased ACTH's steroid stimulatory activity. The K+ flux inhibitor, 4-aminopyridine (4AP) (10 mM) elicited an initial decline in basal steroid secretory activity. A single 10-ml dose of 10 mM but not 1 mM 4AP significantly diminished, for many hours, ACTH's and cAMP's ability to stimulate adrenal steroid secretion. The combination of elevated [K+]0 and 4AP administration resulted in additional reduction of the ability of ACTH to stimulate steroid production. This combination of 4AP with [K+]0 elevations also blocked the potentiating effect of K+ on cAMP-stimulated steroid secretion. Together these findings demonstrated that some procedures which can alter the distribution of K+ across the adrenal cell membrane are capable of profoundly influencing the secretion of the predominant glucocorticoid from the rat adrenal gland under in vitro superfusion conditions. The data support the suggestion that a slight rise in intracellular K+ concentration would be stimulatory and that further increase of, or a decline in, this ion's intracellular level would be inhibitory to basal and stimulated steroid secretory activity.

Adrenal Cortex↗
PubMed1981

Hemolysis-induced gallstones in mice: increased unconjugated bilirubin in hepatic bile predisposes to gallstone formation.

We recently reported that nb/nb mice with hereditary hemolytic anemia spontaneously developed calcium bilirubinate gallstones. We undertook this study to determine whether the differences in gallbladder bile composition were due to altered gallbladder function or hepatic bile composition. Hepatic bile was obtained by cholecystostomy after common bile duct ligation. We found that (a) the hepatic bile of nb/nb mice with or without stones had higher concentrations of unconjugated (p less than 0.001) and total bilirubin (p less than 0.001) but lower concentrations of bile acids (p less than 0.05) than that of control mice; (b) the concentrations of total calcium and hydrogen ion were similar in all groups; (c) nb/nb mice with stones compared with nb/nb mice without stones had higher concentrations of unconjugated (p less than 0.05) and total bilirubin (p less than 0.05); (d) the outputs of unconjugated and total bilirubin of nb/nb mice with or without stones were higher than control mice (p less than 0.001) while bile acid, hydrogen ion, and calcium outputs were similar in all groups; (e) nb/nb mice with stones had higher outputs of unconjugated (p less than 0.005) and total bilirubin (p less than 0.05) than nb/nb mice without stones; (f) in nb/nb mice with stones, but not in those without stones or control mice, unconjugated bilirubin output was associated with bile acid output (p less than 0.001); and (g) unconjugated bilirubin and total bilirubin outputs were significantly correlated in all groups (p less than 0.001). Thus, an increased concentration and amount of unconjugated bilirubin in nb/nb hepatic bile is an essential factor in hemolysis-induced gallstone formation and modification of this abnormal nb/nb hepatic bile within the gallbladder promotes stone formation.

Animals↗
PubMed1981

Ion pairing high pressure liquid chromatographic determination of amaranth in licorice products.

A high pressure liquid chromatographic method is described for the determination of amaranth (FD&C Red No. 2; Red No. 2) in licorice products. The Red No. 2 is extracted with a basic buffer solution, cleaned up on a Sep-Pak column, Chromatographed on a reverse phase column in the ion pairing mode, and detected at 254 nm. The procedure is time-conservative with accurate and precise results. Recovery data ranged from 93 to 104%, and coefficients of variation were less than 4% for standards and samples.

Amaranth Dye↗
PubMed1980

High performance liquid chromatographic determination of carbohydrates in chocolate: collaborative study.

A collaborative study determining sucrose, glucose, fructose, maltose, and lactose in chocolate products was conducted using a previously published high performance liquid chromatographic (HPLC) method. Five samples (2 milk chocolates, 1 dark chocolate, 1 powdered mix, and 1 sirup) were analyzed in duplicate by 7 collaborators. The results indicate adequate method precision. In addition, the HPLC method allows for the simultaneous determination of 5 saccharides in chocolate products in 15 min. The method has been adopted as official first action.

Animals↗
PubMed1980

High pressure liquid chromatographic determination of theobromine and caffeine in cocoa and chocolate products: collaborative study.

Four duplicate samples of cocoa-containing materials, a practice sample, and standards were submitted to the collaborators for theobromine and caffeine analysis by HPLC. In the method the samples are defatted with petroleum ether, and dried. The fat-free residue is then extracted with water and an aliquot is injected into the chromatograph. Compounds are quantitated by comparison with internal or external standards, either by peak height or peak area. Results for all the analyses showed that few of the values were more than 2 standard deviations from the mean. The method has been adopted as official first action.

Cacao↗
PubMed1979

Facial myokymia with polyradiculoneuropathy.

Two patients had bilateral facial myokymia in association with polyradiculoneuropathy. Characteristic electromyographic findings allow polyradiculoneuropathy to be differentiated from other causes of facial movements, and support the possibility that extraaxial facial nerve involvement is another cause of facial myokymia.

Adult↗
PubMed1978

High pressure liquid chromatographic determination of theobromine and caffeine in cocoa and chocolate products.

A method was developed for determining theobromine and caeffine in cocoa and chocolate products by high pressure liquid chromatography. After a simple hot water extraction, both theobromine and caffeine were separated by using a reverse phase C18 column and a mobile phase of methanol-water-acetic acid (20 + 79 + 1). Theobromine and caffeine were quantitated at 280 nm; average recoveries were 98.7 and 95.0%; and coefficients of variation were 2.31 and 3.91%, respectively.

Beverages↗
PubMed1977

Spinal cord vascular malformations with symptoms during menstruation. Report of two cases.

Two patients had the initial complaint of fluctuating paraparesis, which was most evident at menstruation. One patient had a semimonthly fluctuating deficit. Spinal cord compression and ischemia, secondary to the vascular mass, were considered the most likely mechanisms. Blood levels of estrogen and progesterone during the menstrual cycle may have had a contributory effect. Fluctuating spinal cord deficits associated with a consistent portion of the menstrual cycle should alert the physician to the possibility of an arteriovenous malformation of the spinal cord.

Adult↗
PubMed1976

Effects of scopolamine on variable intertrial interval spatial alternation and memory in the rat.

A repeated measures procedure, variable intertrial interval (ITI) spatial alternation, was used to assess scopolamine effects on memory, and to compare effects of the drug on discrimination processes with effects on storage. Rats learned in two stages to press left and right levers in alternation on discrete trials separated by 5 different ITI's ranging from 2.5 to 40 s and presented in random order during the experimental session. In the first stage, alternating discrimination, alternation was controlled by a light on over the correct lever at the time of the trial; in the second stage, variable ITI spatial alternation, a centrally located panel light signalled all trials and alternation was controlled by stimuli from prior trials ('memory'). Alternation response occurrence declined moderately (but significantly) with increasing ITI duration in both the alternating discrimination and variable ITI spatial alternating discrimination and variable ITI spatial alternation stages; response occurrence was also significantly decreased by scopolamine treatment in both stages. Accuracy of alternating discrimination performance was not significantly altered by either ITI duration or scopolamine treatment. Accuracy of variable ITI spatial alternation performance on a trial varied inversely with the duration of the ITI that preceded the trial. Scopolamine treatment significantly reduced accuracy of lever pressing in variable ITI spatial alternation but did not alter the slope of the curves relating accuracy to ITI duration. These effects indicate that the drug impaired discrimination processes but did not alter memory storage.

Animals↗
PubMed1975

Cryptococcal meningoencephalitis.

A patient was admitted to hospital with an apparent psychiatric disturbance. When she became stuporous the cerebrospinal fluid was cultured but proved sterile. The latex test showed that serum was positive for cryptococcal antigens, and cryptococcal meningoencephalitis was diagnosed. Amphotericin B was given but when she developed a toxic reaction it was replaced by flucytosine. She responded well to flucytosine alone and no side effects appeared on continued treatment. Cryptococcal meningitis may present as a psychiatric disturbance, and serological tests are invaluable aids to diagnosis.

Adult↗