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Biomedical subjects

R A Norton

Publications and source records attributed to R A Norton.

At least 37 records · Page 2Linked to original sources
PubMed1990

Sterol phylogenesis and algal evolution.

The stereochemistry of several sterol precursors and end products synthesized by two fungal-like micro-organisms Prototheca wickerhamii (I) and Dictyostelium discoideum (II) have been determined by chromatographic (TLC, GLC, and HPLC) and spectral (UV, MS, and 1H NMR) methods. From I and II the following sterols were isolated from the cells: cycloartenol, cyclolaudenol, 24(28)-methylenecycloartanol, ergosterol, protothecasterol, 4alpha-methylergostanol, 4alpha-methylclionastanol, clionastanol, 24beta-ethylcholesta-8,22-enol, and dictyosterol. In addition, the mechanism of C-24 methylation was investigated in both organisms by feeding to I [2-3H]lanosterol, [2-3H]cycloartenol, [24-3H]lanosterol, and [methyl-2H3]methionine and by feeding to II [methyl-2H3]methionine. The results demonstrate that the 24beta configuration is formed by different alkylation routes in I and II. The Delta25(27) route operates in I while the Delta24(28) route operates in II. Based on what is known in the literature regarding sterol distribution and phylogenesis together with our findings that the stereochemical outcome of squalene oxide cyclization leads to the production of cycloartenol rather than lanosterol (characteristic of the fungal genealogy) and the chirality of the C-24 alkyl group is similar in the two nonphotosynthetic microbes (beta oriented), we conclude that Prototheca is an apoplastic Chlorella (i.e., an alga) and that Dictyostelium as well as the other soil amoebae that synthesize cycloartenol evolved from algal rather than fungal ancestors.

Journal Article↗
PubMed1988

Comparison of the chromatographic properties of sterols, select additional steroids and triterpenoids: gravity-flow column liquid chromatography, thin-layer chromatography, gas-liquid chromatography and high-performance liquid chromatography.

The chromatographic properties of approximately 100 sterols, select steroids of plant origin (sapogenins and steroidal alkaloids) and triterpenoids has been evaluated in this laboratory by monitoring their elution characteristics in adsorption (gravity column and thin-layer methods with and without the addition of silver nitrates), gas and reversed-phase high-performance liquid chromatography. The utility of each methodology to act in one or another chromatographic mode-separation, radio-chemical purification, quantitation and structural elucidation, is discussed. The importance of the tilt of the -OH group at C-3 as well as the polarity, size, an shape of the rest of the molecule as it effects the hydrogen-bonding ability of the -OH group is demonstrated through changes in chromatographic behavior that result from the step-wise introduction of double bonds, methyl, bromo, oxygen, nitrogen and cyclopropyl groups into 5 alpha-cholestanol. An independent aid in the structure identification and quantitation of the compounds was use of a multiple-wavelength diode array detector in which different wavelengths of the UV spectrum (200-400 nm) were simultaneously monitored following passage of the sample through a reversed-phase C18 column.

Chromatography, Gas↗
PubMed1986

Zinc oxide to induce molt in layers.

The effects of the addition of Zn as ZnO to diets to induce molt were evaluated against a fasted control. Experiment 1 involved 315 Leghorn hens, 15 months old, randomly distributed among five treatments, each replicated seven times with 9 hens per replicate. Hens fasted for 10 days were compared with hens fed diets to which ZnO was added at 10,000, 5,000, or 2,500 ppm for 7, 14, or 21 days. No significant differences were observed among treatments for days to return to 50% production, hen-day and hen-housed production, egg weight, grams egg per hen-day, grams of feed per gram egg, mortality, or Haugh units during the 22-week experimental period. Experiment 2 involved 420 Leghorn hens, 18 months old, randomly distributed among five treatments, each replicated seven times with 12 hens per replicate. Treatments involved fasting for 10 days or feeding diets with 10,000, 5,000, or 2,500 ppm ZnO fed for 7, 14, or 21 days. Hens fasted and hens fed diets with 10,000 ppm ZnO at the start of the experiment ceased production in significantly less time (4.6 to 6 days) than hens fed 5,000 ppm ZnO (14.3 to 14.9 days); however, days to return to 50% production from the start of the experiment did not differ among treatments. Feed consumption and feed cost per hen day during molt were lowest (P less than .05) in the fasted hens.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1978

International comparison of prevalence of resistance to antibiotics.

Prevalence of bacterial resistance to antibiotics was found to be substantially different in two separate regions of the world. The average percent resistant to individual antibiotics was nearly three times greater, and the percent of isolates resistant to six or more antibiotics 14 times greater among isolates at the Hôpital St Joseph in Paris than among those at the Peter Bent Brigham Hospital in Boston or at any of six US hospitals. Differences were not due to culture sampling or susceptibility testing methods used in the hospitals. Differences were nearly as great between isolates from patients recently admitted to the two hospitals, suggesting differences in the bacterial flora of their communities. Similar systematic comparisons of resistance prevalence in different parts of the world might help to define optimal antibiotic usage practices.

Anti-Bacterial Agents↗
PubMed1977

Linear and rod-shaped peptic ulcers.

Experience with the routine use of the pharmacologically aided, double-contrast examination to demonstrate various primary and healing ulcers over a six month period is assessed. Thirteen linear or rod-shaped ulcerations were diagnosed. It appears that gastric relaxation and the demonstration of fine mucosal relief are necessary to detect ulcers of linear or rod form.

Contrast Media↗
PubMed1976

Streptozocin-treated Verner-Morrison Syndrome: plasma vasoactive intestinal peptide and tumor responses.

A patient with watery diarrhea, hypokalemia, hypochlorhydria, and a non-beta islet cell carcinoma of the pancreas (Verner-Morrison syndrome) was found to have an elevated vasoactive intestinal peptide (VIP) concentration in the plasma as well as in the tumor. Treatment with streptozocin resulted in a dramatic subjective and objective tumor response in this patient. Plasma VIP concentration fell into the normal range after four courses of treatment, diarrhea ceased after the third course of therapy, and measurable tumor mass markedly decreased during that same period of time. The patient remains in clinical remission with no evidence of tumor regrowth 18 months after the beginning of treatment. In this patient, plasma VIP measurements were an excellent marker of tumor activity and correlated well with objective disease measurements and clinical response.

Adenoma, Islet Cell↗
PubMed1975

Pharmacology and clinical use of antacids.

The pharmacology of antacids, with particular reference to their clinical use in treating acid-peptic disease, is discussed. Liquid antacid suspension should be given at least as often as one hour after each meal and at bedtime. Inthe treatment of the acute phase of acid-peptic disease, hourly antacid is recommended. The dose should be planned in terms of milliequivalents of acid neutralizing capacity and should be adjusted according to the type of disease under treatment. All antacids have side effects, the most serious of which are metabolic. In clinical terms, the harmful sustemicside effects of calcium carbonate and sodium bicarbonate outweigh their benefit as neutralizing agents; they should rarely be employed in the treatment of acid-peptic disease. The more common antacid side effects of diarrhea (magnesium hydroxide) and constipation (aluminum hydroxide) are best managed by appropriately alternating the agents or by using one of the various antacid mixtures.

Antacids↗