High-performance size-exclusion chromatographic procedure for the determination of fluoresceinyl isothiocyanate dextrans of various molecular masses in biological media

A high-performance size-exclusion chromatographic procedure, using Nucleosil Diol, for the quantitative analysis of fluoresceinyl isothiocyanate dextrans of various molecular masses (10,000-150,000) in biological media was developed. The influence of the molecular mass and the degree of substitution of the conjugates on the chromatographic behaviour are discussed. In addition to quantitation, the molecular mass of the conjugates with degree of substitution below 1.6 could be estimated from the chromatograms. Linear standard calibration curves were obtained at concentrations down to 0.050 micrograms ml-1 in rabbit plasma and urine and homogenates of rabbit liver, lymph node and muscle when the derivative (degree of substitution 0.85) was monitored by fluorescence detection (lambda ex = 493 nm, lambda em = 520 mm). The fluoresceinyl isothiocyanate dextrans were found to be stable for more than three days at 37 degrees in all biological media under investigation. A pH-rate profile for the alkaline hydrolysis of fluoresceinyl isothiocyanate dextrans was constructed. The applicability of the method to pharmacokinetic studies was demonstrated by recording the plasma concentration-time profile of a fluoresceinyl isothiocyanate dextran T-70 conjugate following intravenous injection to a rabbit. In relation to future pharmacokinetic investigations on dextran conjugates, the results reported indicate that labelling of the parent dextran with fluoresceinyl isothiocyanate and monitoring of the fluoresceinyl isothiocyanate dextran conjugate throughout the organism using the described method is a promising development.

Tetramine: occurrence in marine organisms and pharmacology

The occurrence of tetramethylammonium ion (TMA) in marine organisms is reviewed. The pharmacological action of TMA is also discussed, with special emphasis on the sign and symptoms experienced by oral poisonings. It is concluded that the major manifestations of TMA poisonings may be attributed to interactions with the autonomous nervous system. Fatal intoxications are due to neuromuscular blockade.

The toxin tetramine from the "edible" whelk Neptunea antiqua

The chemical nature of extracts of the marine gastropod Neptunea antiqua collected in the North Sea has been investigated. Amino acid analysis and spectroscopical studies (FAB MS, 1H NMR, 13C NMR and IR) on fractions purified by Biogel P-2 and Amberlite IR 120 column chromatography allowed the identification of 19 components. It was established that the water-soluble toxin responsible for poisonings, following ingestion of this snail, is tetramine (the tetramethylammonium ion present as an unknown salt). Contrary to what occurs in other Neptunea species (N. arthritica and N. intersculpta), tetramine was found not only in the salivary gland, but also in the remaining part of the animal, albeit in smaller concentration. In the isolated guinea-pig ileum assay, synergistic effects with other main components present (betaine, homarine) could not be demonstrated. Choline esters, believed to act synergistically in other Neptunea species, were not detected in Neptunea antiqua.

Multicystic transformation of the kidneys in dialysis patients

In a dialysis population patients who had been treated merely with haemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD) were examined with ultrasound. The occurrence of multicystic transformation of the kidney was 4/15 in HD patients and 8/25 in CAPD patients with no significant difference between the two groups. There was a significant association between the occurrence of multicystic transformation and the patient age while there was no significant association to the duration of dialysis or the duration of the uraemic state. No tumour or any other complication to cystic transformation was found. In 582 persons without renal disease examined as controls we found 44 with cystic change. This material does not support the recommendation of regular ultrasound examination of our dialysis patients. However, until these results can be confirmed by prospective studies we must recommend screening of all maintenance dialysis patients after a longer duration of dialysis.

Quantitative determination of dextran-naproxen ester pro-drugs with varying molecular weights and degrees of substitution in biological media by means of high-performance size exclusion chromatography with fluorescence detection

A high-performance size exclusion chromatographic procedure using a Nucleosil Diol column and fluorescence detection has been developed for the determination of dextran-naproxen ester pro-drugs with varying molecular weights and degrees of substitution in aqueous buffer solutions and biological media in the presence of the parent drug. The effect of several variables on the chromatographic behaviour of the compounds is discussed. Linear standard calibration curves were constructed for all the dextran derivatives incubated in whole blood and urine (human and rabbit), rabbit liver homogenate and human synovial fluid. In whole blood, the detection limit (lambda ex = 330 nm, lambda em = 360 nm) for a dextran T-70 pro-drug with a degree of substitution (DS) of 10.6 was found to be 2 micrograms ml-1 after applying a 20-micrograms sample to the column. The assay has been used in stability studies and determination of plasma concentration-time profiles after intravenous administration to rabbits of dextran-naproxen ester pro-drugs.

Diagnostic positive and negative ion fast atom bombardment mass spectrometry of low-molecular-weight ammonium compounds of marine origin

Five ammonium compounds--betaine, taurine, homarine, trigonelline and tetramethylammonium chloride--were investigated by positive and negative ion fast atom bombardment (FAB) mass spectrometry. Observation of the parent cation [M + H]+ together with series of clusters (e.g. [nM + H]+, n = 2-5) and fragmentation patterns in the positive FAB mode may be used diagnostically as a fingerprint of the compound. The shifts in mass and relative intensity by addition of trichloroacetic acid and metal salts offer corroborating information of the identity of a compound in a mixture. The FAB negative ion spectra were characterized by clusters incorporating the anion (e.g. [M + Cl]-) but are generally less informative than the spectra obtained in the positive mode.

Chlortetracycline and aflatoxin interaction in two lines of chicks

To determine if feed contaminants and feed additives interact, day-old chicks from lines bred for high and low antibody response to sheep erythrocytes were fed aflatoxin at a level of 3,000 ppb, chlortetracycline at a level of 550 ppm, or a combination of aflatoxin and chlortetracycline for a period of 6 wk. Weight gain in both lines of chicks was adversely affected by the aflatoxin treatment. There was a synergistic adverse effect in chicks of the low antibody response line when given chlortetracycline as well as aflatoxin, an effect not noted in chicks of the high antibody response line. Chlortetracycline alone had no effect on weight gain of low antibody response birds but increased the weight gain of chicks from the high antibody response line. Bursa to body weight ratios were adversely affected by aflatoxin in both lines of chicks, but chlortetracycline further adversely affected this parameter only in the low antibody response line. These results indicate that adverse effects of aflatoxin may be enhanced by addition of antibiotics to feed.

Interactions of aflatoxin and the antioxidant butylated hydroxytoluene in two-week-old chicks

Two-week dietary administration of 2500 ppb aflatoxin was sufficient to cause a decrease in bursal weights and a reduction in the number of splenic leukocytes in chicks. No significant effects on weight gain or feed efficiency were evident. The chicks also had elevated heterophil-to-lymphocyte ratios, suggesting a heightened reaction to stress. This effect could be blocked by dietary administration of the antioxidant butylated hydroxytoluene (BHT) at a concentration eight-fold over that normally present to preserve control feed. The BHT treatment increased the activities of the enzymes glutathione-S-transferase, aniline hydroxylase and O-demethylase, which metabolize aflatoxins in the liver.

Hypertrophic pyloric stenosis: determination of muscle dimensions by ultrasound

To evaluate the usefulness of ultrasound in hypertrophic pyloric stenosis (HPS) and to analyse the correlation between the dimensions of the pyloric muscle and the age and the weight of the child, 34 children with suspected HPS and 34 controls were examined. An overlap between the dimensions of the pyloric muscle in the HPS group and in the controls stresses the need to assess the muscle length, the muscle diameter, and the muscle wall thickness in establishing the sonographic diagnosis of HPS. We found the following criteria useful: muscle length greater than or equal to 19 mm, muscle diameter greater than or equal to 10 mm, and muscle wall thickness greater than or equal to 4 mm. The results did not confirm previous reports of increasing dimensions of the pyloric muscle with age and weight.

Pendred's syndrome. Acoustic, vestibular and radiological findings in 17 unrelated patients

Seventeen unrelated Danish patients with Pendred's syndrome, whose case stories have not been published previously, are presented. Acoustic and vestibular functions were examined and endocrinological screening was performed. There was a great variation in hearing ability as well as in thyroid function. Furthermore, in contrast to previous investigations, normal caloric function was demonstrated in the majority. In all patients a Mondini malformation was demonstrated. On the basis of this investigation it is concluded that: (1) the Mondini defect is part of Pendred's syndrome; (2) the inherited Mondini malformation is the underlying cause of the sensorineural hearing impairment; and (3) the hearing sensitivity varies greatly in these patients.

Macromolecular prodrugs. V. Simultaneous determination of high-molecular-weight dextran metronidazole monosuccinate ester prodrugs and the hydrolysis products metronidazole and the corresponding monosuccinate ester on nucleosil diol

A high-performance size-exclusion chromatography procedure using Nucleosil Diol has been developed which provides the simultaneous determination of macromolecular dextran metronidazole monosuccinate ester prodrugs and the hydrolysis products metronidazole and metronidazole monosuccinate. Various factors influencing the chromatographic behaviour of the compounds are discussed. Baseline separation of the three substances was achieved within 8 min by using a 0.05 M phosphate buffer pH 7.5 eluent at a flow-rate of 2 ml min-1. The detection limit at 320 nm for a conjugate with a degree of substitution of 4.61 was found to be 3.5 micrograms ml-1.

Influence of experimental rhinitis on the gonadotropin response to intranasal administration of buserelin

The influence of experimental rhinitis on the absorption of buserelin, measured as the serum luteinizing hormone (LH) response, has been investigated. A single dose of 200 micrograms buserelin was given to 24 healthy male volunteers after induction of experimental rhinitis with histamine and after use of a saline spray (placebo control). Except on one occasion, when the pump-spray apparently was incorrectly operated, serum LH concentration rose after buserelin. There was no difference in the LH response between histamine-induced rhinitis and saline controls. It was concluded that intranasal application of buserelin represents a reliable mode of application and that modification of the administration route or a change in the dosage schedule during naturally-occurring nasal inflammations, such as the common cold and allergic rhinitis, is unnecessary in patients undergoing chronic treatment with intranasal buserelin, e.g. for prostatic cancer, endometriosis, precocious puberty, and contraception.

Ability of ethoxyquin and butylated hydroxytoluene to counteract deleterious effects of dietary aflatoxin in chicks

The antioxidants ethoxyquin and butylated hydroxytoluene (BHT) were added to diets of chicks in concentrations three and eight times above that usually found in poultry feed beginning 15 days after hatch; the chicks had been placed on feed containing 1000 or 3000 ppb aflatoxin on the day of hatch. These diets were continued until chicks were 6 weeks of age. At that time, deleterious effects of aflatoxin on weight gain, feed efficiency, and organ weights (spleen, bursa) were evident. BHT alleviated these effects, but ethoxyquin did not. Pretreatment with ethoxyquin did not protect chicks either. Ethoxyquin was not able to induce the activities of chick liver enzymes that detoxify aflatoxin and other foreign compounds. Lack of effect of ethoxyquin on these enzymes may hinder ability of this antioxidant to protect chicks from aflatoxin.

Costs and benefits of medical student training to a health maintenance organization

As health maintenance organizations (HMOs) and managed health care systems expand, they represent an increasing potential as sites for medical student teaching. Considerable difference of opinion exists about the impact of medical training on these prepaid delivery systems. This study presents a methodology for estimating the subjective and objective costs and benefits of medical student training to an independent staff model HMO with a long-standing training program. Data are derived from a provider survey, a consumer survey, and patient visit logs. Principal subjective benefits include increased perceived quality of care, improved patient satisfaction, and enhanced provider education and joy of practice. Objective impacts include a decrease in productivity of 1.1 patient visits per half day and direct physician teaching labor of 46.8 minutes per half day. Applying this methodology to the specific program of ten courses gives rise to a figure of $180 000 ($16 900 per full-time equivalent student per year) for the "opportunity cost" of medical student training to the HMO. Rules of thumb are developed for application of this method prospectively to new programs in similar relationships between staff model HMOs and academic medical centers.

Pilocarpine prodrugs. II. Synthesis, stability, bioconversion, and physicochemical properties of sequentially labile pilocarpine acid diesters

Various novel diesters of pilocarpic acid were synthesized and evaluated as prodrug forms for pilocarpine with the aim of improving the ocular delivery characteristics of the drug. The pilocarpic acid monoesters previously studied cyclized spontaneously to pilocarpine in aqueous solution and although they showed enhanced corneal permeability when compared with pilocarpine these monoesters suffered from poor solution stability. The present study shows that this problem can be totally overcome by blocking the free hydroxyl group in the monoesters. Diesters of pilocarpic acid were obtained by esterification of this group. Such compounds were found to possess a high stability in aqueous solution (shelf lives of more than 5 years at 20 degrees C were estimated) but at the same time were readily converted to pilocarpine under conditions simulating those occurring in vivo through a sequential process involving enzymatic hydrolysis of the O-acyl bond followed by spontaneous lactonization of the intermediate pilocarpic acid monoester. Rate data are given for the conversion of the diesters in human plasma and in various rabbit eye homogenates. The pH-solubility profile was derived for a diester and lipophilicity parameters were determined for the compounds. All diesters were markedly more lipophilic than pilocarpine and the corresponding pilocarpic acid monoesters. The results suggest that pilocarpic acid diesters may be potentially useful pilocarpine prodrugs as they combine a high solution stability with an adequate rate of conversion to pilocarpine under in vivo conditions.

Fallopian tube patency demonstrated at ultrasonography

Fallopian tube patency was assessed in 24 infertile patients by hysterosalpingography (HSG) and ultrasonographic examination of the pouch of Douglas following transcervical injection of a sterile isotonic solution of NaCl. The presence of fluid in the pouch, after the injection, was taken to indicate tubal patency. The results of the HSG and the ultrasonographic diagnosis as to the presence of at least unilateral tubal patency were concordant in 21 patients. Pitfalls consisted of fluid accumulation in periadnexal adhesions, edema in the bowel wall, and spill of the injected saline into a large hydrosalpinx. Ultrasonography is advocated as the initial examination in assessing infertility in young women. If tubal patency is demonstrated, the patient should be recommended a six month trial period, to become pregnant, before invasive procedures are initiated.