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Biomedical subjects

H Cohen

Publications and source records attributed to H Cohen.

672 records · Page 38Linked to original sources
PubMedDate not supplied

Determination of aflatoxin M1 in milk by liquid chromatography with fluorescence detection.

A liquid chromatographic (LC) method is proposed for the determination of aflatoxin M1 in milk. The method was successfully applied to both liquid whole and skim milk and also whole and skim milk powder. The samples are initially extracted with acetonitrile-water followed by purification using a silica gel cartridge and a C18 cartridge. Final analysis by LC was achieved using a radial compression module equipped with a 5 micron C18 column and a fluorescence detector. The method was successfully applied to samples at levels of 10 to 0.08 ppb added aflatoxin M1 with recoveries in the range of 70-98%.

Aflatoxin M1↗
PubMedDate not supplied

Capillary gas chromatographic determination of T-2 toxin, HT-2 toxin, and diacetoxyscirpenol in cereal grains.

A capillary gas chromatographic (GC) method using an electron capture detector is described for determining T-2 and HT-2 toxins and diacetoxyscirpenol (DAS) in cereal grains at levels as low as 100 ppb for T-2 and DAS and 50 ppb for HT-2. Samples are extracted with methanol-water according to the Scott method, and further purified on a silica gel cartridge and a cyano column. Heptafluorobutyrylimidazole (HFBI) is added to form the esters of the analytes. Ester(s) of T-2, HT-2 and DAS are separated on a 30 m X 0.32 mm DB-5 fused silica column and measured with a 63Ni electron capture detector. Samples were confirmed by gas chromatography/mass spectrometry using electron impact ionization and single ion monitoring at the molecular mass of 501.11 m/z for T-2, 665.08 m/z for HT-2, and 502.12 m/z for DAS at 10 000 resolving power. The method was applied to wheat, oats, and barley. Average recoveries ranged from a low of 65% for T-2 in barley to a high of 99% for DAS in oats.

Chromatography, Gas↗
PubMedDate not supplied

The ineffectiveness of tobramycin combination therapy in Streptococcus faecium endocarditis.

A patient required mitral valve replacement following ineffective antibiotic treatment of enterococcal endocarditis caused by Streptococcus faecium. Endocarditis had relapsed despite therapy with ampicillin and tobramycin for six weeks. A second relapse had occurred following treatment with penicillin and gentamicin. Initial failure of antibiotic therapy may be related to the known lack of in vitro and in vivo synergy between penicillin and tobramycin against S. faecium. Effective therapy of enterococcal endocarditis requires considerations of bacterial speciation, determination of high-level aminoglycoside resistance, and preferably adequate antibiotic synergy studies to assure effective therapy.

Ampicillin↗
PubMedDate not supplied

Failure strength of four veneered primary stainless steel crowns.

The purpose of this study was to determine the amount of shear force required to fracture or dislodge the veneered facings of four commercially available veneered primary incisor stainless steel crowns (SSC) and to characterize the veneer failures. Forty Unitek SSCs (#4 left central incisor) were shaped to fit a master die and then 10 each were mailed to four commercial dental laboratories that produce veneered SSCs. The resulting four types of crowns tested were: Cheng Crowns (CC), [Peter Cheng Orthodontic Laboratory]; Kinder Krowns (KK) [Mayclin Dental Studio, Inc]; NuSmile Primary Crowns (NC), [Orthodontic Technologies, Inc]; and Whiter Biter Crown II (WB), [White Bite Inc]. Each crown was cemented onto a standardized die and then thermocycled at 4 degrees C and 55 degrees C for 500 1-min cycles. Each die was then placed into a custom holder on the Instron (Model 4204) testing machine. A force was applied at the incisal edge of the veneer at 148 degrees, (the primary inter-incisal angle), with a crosshead speed of 1 mm/min until the veneer fractured or was dislodged. The mean force (N) required +/- SD to produce failure was, respectively: KK (397.2 +/- 53.0); NC (447.2 +/- 78.5); CC (511.9 +/- 83.4); WB (686.5 +/- 181.4). Analysis of variance (ANOVA) indicated significance at P < 0.0001. A Scheffe's post hoc comparison demonstrated that the Whiter Biter (WB) group required significantly (alpha = 0.05) more force for failure than the other three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMedDate not supplied

Vertigo after sailing a nineteenth century ship.

Few papers describe illusions of motion after sailing for which subjects do not seek medical assistance. After sailing on a square-rigged ship for five-hour periods subjects were surveyed about the incidence, intensity, and quality of such illusions. Even on a calm day, 20% to 41% of the crew experienced post-sailing vertigo, but it only occurred among the nonprofessional sailors. This phenomenon is characterized by extinction with repeated exposure, a lag time to onset of about two hours, brief duration, and occurrence in enclosed visual surrounds. These data are similar to vestibular habituation and suggest that some central vestibular mechanisms may be involved.

Adult↗