Biomedical subjects

S J Graham

Publications and source records attributed to S J Graham.

42 records · Page 3Linked to original sources

PubMed1989

Validation of a method for the assay of related compounds in famotidine raw materials and formulations.

A high-performance liquid chromatographic (HPLC) method has been developed for the determination of famotidine and related compounds in drug raw materials and formulations. The minimum detectable amount of the available related compounds is less than 0.02% and the minimum quantifiable amount is less than 0.1%. Famotidine impurity levels were between 0.5 and 2.5% in raw materials. 0.44% in one tablet sample and about 3% in an IV solution, allowing for stabilizers.

Chromatography, High Pressure Liquid↗

PubMed1982

Choroidal neovascular membranes and senile macular choroidal degeneration: their association in disciform macular degeneration.

Senile macular choroidal degeneration (SMCD) is responsible for the majority of cases of new central vision loss in the over-fifty population. It is also the single largest cause of legal blindness in the United States. Choroidal neovascular membranes are frequently associated with SMCD and initiate a disciform process that may lead to profound central vision loss. Clinically, it is very difficult to visualize actual new vessel membranes without the aid of rapid sequence fluorescein angiography; various clinical signs, however, are indicative of their presence. Recognition of choroidal neovascular membranes is important; certain membranes lend themselves to photocoagulation by the retinal specialist. This treatment may be successful in preventing further severe and permanent visual loss in some individuals. The purpose of this paper is to discuss the mechanisms of disciform macular degeneration, as well as the clinical signs important to the recognition of choroidal neovascular membranes.

Choroid↗

PubMed1981

Inorganic carbon limitation and chemical composition of two freshwater green microalgae.

Two freshwater chlorophytes, Chlorella vulgaris and Scenedesmus obliquus, were grown in inorganic carbon-limited continuous cultures in which HCO(3) was the sole source of inorganic carbon. The response of the steady-state growth rate to the external total inorganic carbon concentration was reasonably well described by the Monod equation; however, the response to the internal nutrient concentration was only moderately well represented by the Droop equation when the internal carbon concentration was defined on a cellular basis. The Droop equation was totally inapplicable when total biomass (dry weight) was used to define internal carbon because the ratio of carbon to dry weight did not vary over the entire growth rate spectrum. In batch cultures, maximum growth rates were achieved at the CO(2) levels present in atmospheric air and at HCO(3) concentrations of 3 mM. No growth was observed at 100% CO(2). Both nitrogen uptake and chlorophyll synthesis were tightly coupled to carbon assimilation, as indicated by the constant C/N and C/chlorophyll ratios found at all growth rates. The main influence of inorganic carbon limitation appears to be not on the chemical structure of the biomass, but rather on cell size; higher steady-state growth rates lead to bigger cells.

Journal Article↗

PubMed1980

Sickle cell retinopathy.

Ten percent of North American blacks have one of four forms of sickle cell disease. Eight to nine percent have sickle cell trait (AS disease); One-half to one percent have SThal disease; Four-tenths percent have SS disease; One-tenth to three-tenths percent have SC disease. The SC and SThal forms present with the most frequent and severe ocular manifestations, including proliferative and non-proliferative retinopathies. Approximately 1% of the black population is at risk for serious ocular complications. The purpose of this paper is to familiarize the reader with the retinal signs, transmissibility, and pathophysiology of a high incidence disease. Early recognition and referral results in prolonged visual function if proper therapy is undertaken. A brief overview of ocular therapies is included.

Adult↗

PubMedDate not supplied

Changes in fibroglandular volume and water content of breast tissue during the menstrual cycle observed by MR imaging at 1.5 T.

MR imaging at 1.5 T was used to investigate variations in breast parenchyma during the menstrual cycle. Seven subjects were examined twice weekly over at least one menstrual cycle. A three-point Dixon technique (TE = 19 msec, TR = 2000 msec) provided images of fat, water, and static magnetic field (Bo), from which two quantitative whole breast parameters were calculated: the mean relative volumetric water content, , and the mean volumetric fibroglandular fraction, . Four of seven subjects showed unequivocal cyclic variations in and consistent with expected histologic changes; and values were elevated during menses and reduced in mid-cycle. The maximum deviation measured for each of the four subjects was < or = 10% in and units. These variations probably do not influence significantly the clinical interpretation of unenhanced MR breast images. Quantitative measurements of breast parenchyma, however, should recognize these effects.

Adipose Tissue↗

PubMedDate not supplied

Understanding pulsed magnetization transfer.

Using a two-pool exchange model of magnetization transfer (MT), numeric simulations were developed to predict the time dependence of longitudinal magnetization in both semisolid and liquid pools for arbitrary pulsed radiofrequency (RF) irradiation. Whereas RF excitation of the liquid pool was modeled using the time-dependent Bloch equations, RF saturation of the semisolid pool was described by a time-dependent rate proportional to both the absorption lineshape of the semisolid pool and the square of the RF pulse amplitude. Simulations show good agreement with experimental results for a 4% agar gel aqueous system in which the two-pool kinetics have been well studied previously. These simulations provide a method for interpreting pulsed MT effects, are easily extended to biologic tissues, and provide a basis for optimizing clinical imaging applications that exploit MT contrast.

Computer Simulation↗