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Biomedical subjects

K D Smith

Publications and source records attributed to K D Smith.

At least 199 records · Page 11Linked to original sources
PubMed1968

Assay systems for the study of gene function. 2 assay systems, the syntheses of RNA and protein, are described; their virtues and drawbacks are discussed.

The study of genetic regulatory mechanisms operating in plants and animals is of paramount importance in contemporary biology. A precise understanding of the mechanisms that underlie normal cellular differentiation is a prerequisite for understanding neoplastic transformation and genetic disease. At present, we are not aware of a single assay system that can give answers to all questions we are already able to pose. Studies of RNA synthesis are valuable because they provide a direct measurement of transcriptional activity. But these studies remain incomplete until we succeed in unraveling the metabolic roles of the molecules whose synthesis we study. In this respect, the study of enzyme synthesis represents a better defined assay system, although the interpretation of observed fluctuations in synthetic rates is made difficult by the many steps that intervene between the genes and their finished protein products. We propose that a combination of protein biosynthetic and cytogenetic analysis is a promising assay system for further investigation.

Alcohol Oxidoreductases↗
PubMedDate not supplied

Modulation of sialyl Lewis X dependent binding to E-selectin by glycoforms of alpha-1-acid glycoprotein expressed in rheumatoid arthritis.

Alpha-1-acid glycoprotein (AGP) is an extensively glycosylated acute phase protein of imprecisely defined physiological function. Nonetheless it is known that the oligosaccharide component comprising 42% of the 41 kDa molecular weight is critical to the previously described multifarious immunomodulatory functions of AGP in vitro. Complex oligosaccharides were enzymically released from AGP purified from the blood of rheumatoid arthritis sufferers by our oligosaccharide protective method. Oligosaccharide profiling was by means of high pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Monosaccharide composition analysis revealed increased fucosylation of inflammatory AGP oligosaccharide chains, suggesting the potential for expression of the tetrasaccharide antigen and E-Selectin ligand, sialyl Lewis X (sLeX). The hypothesis that AGP may function to inhibit blood cell binding to activated endothelium at E-Selectin was tested in a microtitre cell-protein binding assay. In this system we have shown that the oligosaccharide moiety of AGP, as expressed in inflammatory disease, can inhibit the sLeX/E-Selectin interaction. Thus we have identified a correlation between the abnormal glycosylation of AGP in rheumatoid arthritis and suppression of sLeX dependent cell adhesion through inhibition of E-selectin binding which could be the basis of a novel, site specific, anti-inflammatory agent.

Animals↗
PubMedDate not supplied

Chromatographic investigation of the glycosylation pattern of alpha-1-acid glycoprotein secreted by the HepG2 cell line; a putative model for inflammation?

In certain pathophysiological conditions, such as rheumatoid arthritis, there are alterations in the glycosylation pattern of the acute phase protein, alpha-1-acid glycoprotein (AGP). These changes are likely to be functionally significant, however, verification of the latter role requires a system which reflects in vivo glycosylation changes in AGP and also produces sufficient quantities of the protein for further study. The human hepatoma cell line HepG2 is documented as displaying a shift in the glycosylation pattern of glycoproteins from normal state to acute phase after stimulation with inflammatory mediators. We have isolated AGP from the culture medium of HepG2 cells both before and after stimulation with a cytokine preparation and analysed the glycosylation pattern of each preparation, after enzymatic release, by high pH anion-exchange chromatography. Before stimulation, the glycosylated population was similar to a profile of AGP isolated from normal plasma; however, cytokine stimulation resulted in a shift to a profile which was consistent with that of AGP from a rheumatoid arthritis sufferer. Thus a HepG2 cell culture system is capable of being a crude model of the changes in glycosylation of acute phase proteins although it has a tendency to produce oligosaccharide chains which are not fully sialylated.

Animals↗
PubMedDate not supplied

Relationship between the results of sperm analysis and GIFT.

In vitro fertilization (IVF) and GIFT have been proposed as therapeutic approaches in infertile couples where a significant male factor is present. To date, few published data are available relating the success rate of GIFT to the severity of the male factor. In this report the results of the first 172 GIFT cases were analyzed. The overall pregnancy rate was 18.0%. The relationship between the occurrence of pregnancy and sperm count (millions/ml), total sperm count (millions/ejaculate), % motility, motile sperm count (millions/ml) and total motile sperm count (millions/ejaculate) were examined. Significant direct correlations were observed between the clinical pregnancy rate and sperm count, total sperm count, motile sperm count and total motile sperm count. Motile sperm count and total motile sperm count had the best correlations with clinical pregnancy rates, which were over 24.0% in groups with motile sperm counts exceeding 40 X 10(6) cells/ml or total motile sperm counts greater than 100 X 10(6)/ejaculate. The clinical pregnancy rates were 12.5% and 7.7%, respectively, for groups with motile sperm counts under 10 X 10(6)/ml and total motile sperm counts below 25 X 10(6)/ejaculate. No correlation was found between percent motile cells and pregnancy rate. Results of the sperm penetration assay using zona-free hamster eggs were available in a subpopulation of 27 patients. No significant correlation between this sperm penetration assay and pregnancy rate could be demonstrated. The incidence of chemical pregnancy showed a significant negative correlation with the total motile sperm count, indicating a higher incidence of early pregnancy wastage in cases of oligozoospermia.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMedDate not supplied

Evaluation of pharmacological induction of fatty acid beta-oxidation in X-linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy (X-ALD) is an inherited neurometabolic disorder associated with elevated levels of saturated unbranched very-long-chain fatty acids (VLCFA; C > 22:0) in plasma and tissues, and reduced VLCFA beta-oxidation in fibroblasts, white blood cells, and amniocytes from X-ALD patients. The X-ALD gene (ABCD1) at Xq28 encodes the adrenoleukodystrophy protein (ALDP) that is related to the peroxisomal ATP-binding cassette (ABCD) transmembrane half-transporter proteins. The function of ALDP is unknown and its role in VLCFA accumulation unresolved. Previously, our laboratory has shown that sodium 4-phenylbutyrate (4PBA) treatment of X-ALD fibroblasts results in increased peroxisomal VLCFA beta-oxidation activity and increased expression of the X-ALD-related protein, ALDRP, encoded by the ABCD2 gene. In this study, the effect of various pharmacological agents on VLCFA beta-oxidation in ALD mouse fibroblasts is tested. 4PBA, styrylacetate and benzyloxyacetate (structurally related to 4PBA), and trichostatin A (functionally related to 4PBA) increase both VLCFA (peroxisomal) and long-chain fatty acid [LCFA (peroxisomal and mitochondrial)] beta-oxidation. Isobutyrate, zaprinast, hydroxyurea, and 5-azacytidine had no effect on VLCFA or LCFA beta-oxidation. Lovastatin had no effect on fatty acid beta-oxidation under normal tissue culture conditions but did result in an increase in both VLCFA and LCFA beta-oxidation when ALD mouse fibroblasts were cultured in the absence of cholesterol. The effect of trichostatin A on peroxisomal VLCFA beta-oxidation is shown to be independent of an increase in ALDRP expression, suggesting that correction of the biochemical abnormality in X-ALD is not dependent on pharmacological induction of a redundant gene (ABCD2). These studies contribute to a better understanding of the role of ALDP in VLCFA accumulation and may lead to the development of more effective pharmacological therapies.

Adrenoleukodystrophy↗
PubMedDate not supplied

The durability of the Semmes-Weinstein 5.07 monofilament.

Peripheral neuropathy is a risk factor that predisposes diabetic patients to plantar foot ulcerations and lower extremity amputations. Clinicians have searched for a reliable, cost-effective, and simple method in the identification of diabetic patients who are at increased risk of developing plantar foot ulcers. Currently, many diabetic foot clinics utilize the Semmes-Weinstein 5.07/10 g monofilament in this identification process. Ten 5.07 monofilaments were placed in an Instron Dynamic Testing Instrument and their respective filament forces were measured utilizing a Mettler scale after being subjected to repetitive applications. After 500 cycles were performed, there was an average filament force reduction of 1.2 g. After 1,500 cycles, there was still an average reduction of 1.2 g. F-testing and the Duncan test identified a significant difference between filament forces at 0, 500, 1,000, and 1,500 cycles. These data lead to a conclusion that continual utilization of the nylon filaments may lead to a reduced ability to accurately detect peripheral neuropathy and identify those who are at risk for the development of plantar foot ulcerations.

Diabetic Foot↗
PubMedDate not supplied

Strategies for cell engineering in tissue repair.

Cellular and tissue engineering are new areas of research, currently attracting considerable interest because of the remarkable potential they have for clinical application. Some claims have indeed been dramatic, including the possibility of growing complete, artificial organs, such as the liver. However, amid such long-term aspirations there is the very real possibility that small tissues (artificial grafts) may be fabricated in the near future for use in reconstructive surgery. Logically, we should focus on how it is possible to produce modest, engineered tissues for tissue repair. It is evident that strategies to date either depend on innate information within implanted cells, to reform the target tissue or aim to provide appropriate environmental cues or guidance to direct cell behavior. It is argued here that present knowledge of tissue repair biology points us toward the latter approach, providing external cues which will direct how cells should organize the new tissue. This will be particularly true where we need to reproduce microscopic and ultrastructural features of the original tissue architecture. A number of such cues have been identified, and methods are already available, including substrate chemistry, substrate contact guidance, mechanical loading, and biochemical mediators to provide these cues. Examples of these are already being used with some success to control the formation of tissue structures.

Journal Article↗
PubMedDate not supplied

Development of a totally implantable artificial heart.

The first generation of an integrated, totally implantable electrohydraulic total artificial heart was designed for long-term cardiac replacement. The system consists of an elliptical blood pump with an interatrial shunt, Medtronic-Hall 27 mm and 25 mm inflow and outflow valves, respectively, an energy converter consisting of an axial-flow, hydraulic pump driven by a brushless DC motor, and an electronics system with transcutaneous energy transmission and telemetry. Energy is supplied by internal nickel-cadmium rechargeable batteries that supply power for 20 min and external silver-zinc batteries that are designed to supply energy to run the system for 5 hr. The blood pump consists of a single layer diaphragm cast from Biolon, with joined right and left ventricles sharing a common base. The dynamic stroke volume is 84 ml, and maximum cardiac output is 9.2 L/min at a heart rate of 110 beats/min on the mock circulation. A 4.3 mm diameter interatrial shunt is used to balance the volumetrically coupled ventricles. The energy converter pumps hydraulic fluid alternately between ventricles, with controlled, active filling in one ventricle during the systolic phase of the other ventricle. Internal or external controllers adjust the heart rate and motor speed to maintain normal atrial filling pressures and full stroke. Electromagnetic induction is used to transfer energy through the skin and a bidirectional infrared data link incorporated within the transcutaneous energy transmission coils is used to transmit information. The entire system is being assembled and refined for long-term animal implant studies.

Algorithms↗