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Biomedical subjects

J Ahmed

Publications and source records attributed to J Ahmed.

68 records · Page 4Linked to original sources
PubMed1984

Infrared spectroscopic studies of renal stones.

The chemical composition of 125 urinary stones was determined by means of an infrared spectrophotometric method using the potassium bromide pellet technique. Statistical combinations regarding the chemical composition of the stones are discussed and compared with the findings of other workers. Calcium oxalate was the commonest component of pure as well as mixed stones.

Apatites↗
PubMed1980

Radioimmunoassay of thyroxine-binding globulin: evaluation of a kit and diagnostic application.

Serum thyroxine-binding globulin (TBG) was measured by using a radioimmunoassay method. The within-batch coefficient of variation (CV) of the assay was 5% or less at different TBG concentrations with a between-batch variation of less than 10%. The mean TBG concentration in hypothyroidism (28.5 +/- 6.7 mg/l) was significantly higher, and that in hyperthyroidism (22.3 +/- 3.5 mg/l) was significantly lower, than the euthyroid mean (25.4 +/- 6.9 mg/l). Acutely ill patients suffering from various non-thyroidal illnesses were found to have significantly low mean TBG (13.8 +/- 4.3 mg/l). A group of women in late pregnancy had a higher mean value, as expected. Serum TBG level, however, was ineffective as a thyroid function test because of overlapping concentrations between groups. The derived index T4:TBG ratio was found to be superior to free thyroxine index (FTI) in many cases of acutely ill patients, pregnancy, and hereditary TBG abnormality. The 95% confidence limit for the ratio in euthyroids was 2.3 to 7.1. Serum TBG level with T4:TBG ratio is recommended as a replacement for the T3-uptake test and FTI.

Acute Disease↗
PubMedDate not supplied

Intracoronary radiation with gamma wire inhibits recurrent in-stent restenosis.

To study the safety and efficacy of intracoronary gamma radiation delivered via a new high-activity (192)Ir source wire for the treatment of in-stent restenosis. In-stent restenosis results from neointimal tissue proliferation especially in its diffused form and presents a therapeutic challenge. Gamma radiation has been shown to decrease neointima formation within stents in animal models and in initial clinical trials. A total of 26 patients with in-stent restenosis underwent successful intervention and was treated with open-label (192)Ir using a high-activity line source. The specific activity of the source wire was 372+/-51 mCi, and the dwell time was 10.8+/-1.9 min. Primary endpoints were freedom from death, myocardial infraction (MI), and repeat target lesion revascularization (TLR) at 6 months. Secondary endpoints included angiographic restenosis and intravascular ultrasound (IVUS) neointimal hyperplasia. Procedural success was high (96.2%), and in-hospital and 30-day complications were low with no deaths, MI, or requirement for repeat revascularization. At 6 months, event-free survival was 85%: one patient required repeat PTCA, one underwent bypass surgery, and two had an MI. Baseline lesion length measured 15.77 mm. Follow-up angiography was available in 21/25 (84%) patients. The binary restenosis rates were 19.0% (4/21) in-stent and 23.8% (5/21) in-lesion. Follow-up IVUS was available in 20/25 patients. There was no increase in intimal hyperplasia from postintervention to follow-up (3.11.8 vs. 3.41.8 mm(2); P=.32). Eight patients had a reduction of neointimal intimal tissue at follow-up. These results indicate that intracoronary gamma radiation with the Angiorad source wire is safe and effective in preventing in-stent restenosis.

Adult↗
PubMedDate not supplied

Effects of adaptation level and hypoglycemia on function of the cat retina during hypoxemia.

Acute hypoxemia (low PaO2) leads to changes in oxygen consumption and electrical responses of the outer retina of cats, but inner retinal ERG components and ganglion cell responses have been shown to be quite resistant to hypoxemia. The purpose of this study was to determine whether the resistance of the inner retina depends on (1) the stimulus conditions, specifically the degree of light adaptation; and (2) the ability of the photoreceptors to increase glycolysis during hypoxemia. To address these issues, recordings of single ganglion cell action potentials and of the b-wave and scotopic threshold response (STR) of the electroretinogram (ERG) were made from the eyes of anesthetized cats during hypoxemia alone and hypoxemia plus hypoglycemia. Ganglion cells appeared to be equally resistant to hypoxemia at high and low backgrounds (3.3 to 9.7 log equivalent quanta(555 nm)-deg-2(-s)-1), and the STR, recorded with dim stimuli during dark adaptation, when photoreceptor oxygen consumption is most susceptible to hypoxemia, was unchanged until PaO2 was below 30 mm Hg. The amplitude of the b-wave was similarly resistant to hypoxemia when the animal was normoglycemic. During hypoglycemia, however, both the b-wave and the STR became more sensitive to hypoxemia, beginning to change at PaO2s as high as 50 mm Hg when blood glucose was 40-50 mg/dl. It is argued that hypoglycemia limits or prevents the increased glycolytic ATP production that would ordinarily occur when the photoreceptor oxygen supply decreases, and that increased photoreceptor glycolysis is essential in the protection of the retina against mild hypoxemia.

Acute Disease↗
PubMedDate not supplied

Evidence for a ganglion cell contribution to the primate electroretinogram (ERG): effects of TTX on the multifocal ERG in macaque.

To assess the contribution of spiking inner retinal neurons to the multifocal electroretinogram (ERG), recordings were made from four monkeys (Macaca mulatta) before and after intravitreal injections of tetrodotoxin (TTX). TTX blocks all sodium-based action potentials and thus terminates spiking activity of amacrine and ganglion cells. TTX eliminated a large component from the control responses, and this TTX-sensitive component was present as early as 10 ms after the stimulus. Before injection with TTX, the 103 focal ERG responses varied in waveform across the retina. After TTX, the response waveforms were largely independent of retinal position, indicating that it was primarily the TTX-sensitive component of the control response that was dependent upon retinal location. Given that retinal ganglion cells compose a sizable proportion of the retinal elements that produce action potentials, it is likely that part of the TTX-sensitive component is due to the spiking activity of these cells. Further, the systematic change in waveform of the TTX-sensitive component with distance from the optic nerve head suggests that part of the TTX-sensitive component may originate from the activity of the ganglion cell axons. Based on these findings, there is reason to be optimistic that the multifocal technique can be employed to study the effects of glaucoma and other diseases that affect the inner retina.

Action Potentials↗
PubMedDate not supplied

Hyperkalemia in dialysis patients.

Serious hyperkalemia is common in patients with end-stage renal disease (ESRD) and accounts for considerable morbidity and death. Mechanisms of extrarenal disposal of potassium (gastrointestinal excretion and cellular uptake) play a crucial role in the defense against hyperkalemia in this population. In this article we review extrarenal potassium homeostasis and its alteration in patients with ESRD. We pay particular attention to the factors that influence the movement of potassium across cell membranes. With that background we discuss the emergency treatment of hyperkalemia in patients with ESRD. We conclude with a review of strategies to reduce the risk of hyperkalemia in this population of patients.

Acid-Base Equilibrium↗