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Biomedical subjects

I Diamond

Publications and source records attributed to I Diamond.

At least 127 records · Page 7Linked to original sources
PubMed1979

Inhibition of the evoked release of acetylcholine by the porphyrin precursor delta-aminolevulinic acid.

The effect of delta-aminolevulinic acid (ALA) on neuromuscular transmission were studied. High concentrations (0.6 to 18 mM) of ALA caused significant reductions in the amplitudes of curarized end-plate potentials (epps). Changing the ratio of calcium to magnesium in the bathing solution allowed the quantal content of the epps to be directly measured. Under these conditions, ALA reduced the quantal content of epps without affecting the depolarization produced by a single quantum of acetylcholine. It was concluded that ALA, in high concentrations, inhibits the release of acetylcholine evoked by a nerve impulse but is unlikely to be the cause of the neurological defects of acute porphyria.

Acetylcholine↗
PubMed1979

Phosphorylation of the membrane-bound acetylcholine receptor: inhibition by diphenylhydantoin.

Purified postsynaptic membranes can be used as a model system to study the regulation of synaptic membrane proteins. These membranes contain protein kinase activity that phosphorylates the acetylcholine receptor (AChR). We find that diphenylhydantoin (DPH) interacts with these membranes to inhibit phosphorylation of the membrane-bound AChR. DPH appears to alter the availability of postsynaptic membrane proteins for phosphorylation by a synaptic membrane protein kinase. The concentration of DPH that produces half-maximal inhibition of AChR phosphorylation is about 5 x 10(-5) M. This suggests that one of the specific effects of DPH in the nervous system may be related to inhibition of phosphorylation of postsynaptic membrane proteins.

Animals↗
PubMed1979

Successful therapy of crystalcryoglobulinemia: a case report.

Successful therapy for a case of multiple myeloma with a spontaneously crystallizing cryoglobulin of the IgG2-kappa light chain variety was achieved, using both continuous-flow cell centrifugation plasmapheresis to rapidly lower the M component and combination chemotherapy with phenylalanine mustard, prednisone, procarbazine, and vincristine to control the myeloma process. This resulted in resolution of incapacitating large and small necrotic cutaneous ulcerations of the extremities. Physicochemical studies of the crystalcryoprotein demonstrated that cryoprecipitation was rapid and accompanied by the formation of needle-shaped crystals, yet was completely reversible at 37 degrees C. Cryocrit determinations varied depending upon relative centrifugal forces and temperature and did not always relate linearly to the amount of abnormal protein, thus making these alone unreliable in assessing response to therapy.

Antineoplastic Agents↗
PubMed1978

Glycolysis of quiescent cultures of 3T3 cells. Addition of serum, epidermal growth factor, and insulin increases the activity of phosphofructokinase in a protein synthesis-independent manner.

Addition of serum to quiescent cultures of 3T3 cells markedly enhances the specific activity of phosphofructokinase assayed in centrifuged homogenates. The effect depends on both serum concentration and the time of exposure to serum. Mixing experiments, mearsurements of the enzyme at different pH values and persistence of the activation after Sephadex chromatography render unlikely the possibility that activators or inhibitors play a significant role in the stimulation of phosphofructokinase by serum. In addition to serum, epidermal growth factor and insulin also enhance the activity of phosphofructokinase. The activation occurs in the presence of 30 microgram/ml of cycloheximide. It is not the result of a high glycolytic flux because drugs (dinitrophenol and oligomycin) that interfere with ATP synthesis and are potent stimulators of glycolysis in intact cells fail to increase phosphofructokinase activity and because the growth-promoting factors increase the enzyme activity in glucose-free medium. Thus, the activation of phosphofructokinase activity appears specifically related to the action of growth-promoting factors and it may offer an experimental system to investigate the chemical signals or cellular conditions, or both, that lead to rapid cell proliferation.

Blood↗
PubMed1978

Glycolysis in quiescent cultures of 3T3 cells. Stimulation by serum, epidermal growth factor, and insulin in intact cells and persistence of the stimulation after cell homogenization.

Addition of serum to quiescent cultures of 3T3 cells rapidly increases lactic acid formation and subsequently stimulates cell division. The stimulation of lactic acid production is seen at high, saturating concentrations of extra-cellular glucose. It is dependent on the time of exposure and on the dose of serum and is not blocked by the addition of cycloheximide, puromycin, or actinomycin D. In contrast, serum only marginally affects glycolysis by rapidly growing 3T6 or SV40-3T3 cells. In addition to serum, epidermal growth factor (0.1 to 10 ng/ml) and insulin (10 to 500 ng/ml) cause a striking stimulation of glycolysis in quiescent 3T3 cells. Neither exogenous cyclic nucleotides nor ouabain effect the glycolytic response, but the presence of Ca2+ markedly influences the activation of glycolysis by epidermal growth factor and by insulin. A novel finding in this study is that homogenates prepared from quiescent cells treated with serum, epidermal growth factor, or insulin show increased glycolysis as compared with homogenates from nonstimulated cultures. This finding will allow further experimental analysis of the cause of increased glycolysis in rapidly proliferating cells.

Blood↗
PubMed1978

Ultrastructure of fallopian tube carcinoma.

Fallopian tube carcinoma is one of the rarest of primary gynecologic malignancies. Normal tubal epithelium is composed of secretory, ciliated, and intercalary cells. To determine the cellular composition and ultrastructural details of this rare neoplasm, a moderately well-differentiated tubal carcinoma was studied with the electron microscope. A prominent feature was the formation of numerous ultramicro alveolar spaces lined by cell surface microvilli. The nuclei of the neoplastic cells demonstrated a variety of fine structural abnormalities. Based on cell size and shape criteria, a possible dual tumor cell population was suggested. However, no cilia were seen in any of the tumor cells and almost all were devoid of secretory granules. These latter observations suggest that this tumor was primarily a proliferation of intercalary cells.

Aged↗
PubMed1977

Ultrastructure of myeloma cells in a case with crystalcryoglobulinemia.

The bone marrow of a patient with multiple myeloma of the IgG2 Kappa type with spontaneously crystallizing cryoglobulin was studied by electron microscopy. The ultrastructure of the myeloma cells disclosed the presence of a crystalline material in the cytoplasm within the rough endoplasmic reticulum (RER) as well as in extracisternal sites. The crystalline material was also seen extracellulary with a distinctly unique subunit structure. The tubular units measured 200 +/- A (SEM) externally with an internal diameter of 100 +/- A (SEM). The intracellular distribution did not indicate a characteristic organelle association usually observed in protein synthesizing cells. It is suggested, based on the present observations and the findings of others, that the crystalline material may represent polymerized protein synthesized by free ribosomes mostly in extracisternal locations, a pattern often seen in neoplastic plasma cells. Diffusion to extracisternal sites of precrystalline material through the membranes of the RER is a possible alternative mechanism.

Bone Marrow↗