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At least 703 records · Page 39Linked to original sources
PubMed2006

Potential role of a new hand-held miniature gamma camera in performing minimally invasive parathyroidectomy.

PURPOSE: Sestamibi scans have increased the use of minimally invasive parathyroidectomy (MIP) to treat primary hyperparathyroidism (PHPT) when caused by a parathyroid single adenoma. The greatest concern for surgeons remains the proper identification of pathological glands in a limited surgical field. We have studied the usefulness of a new hand-held miniature gamma camera (MGC) when used intraoperatively to locate parathyroid adenomas. To our knowledge this is the first report published on this subject in the scientific literature. METHODS: Five patients with PHPT secondary to a single adenoma, positively diagnosed by preoperative sestamibi scans, underwent a MIP. A gamma probe for radioguided surgery and the new hand-held MGC were used consecutively to locate the pathological glands. This new MGC has a module composed of a high-resolution interchangeable collimator and a CsI(Na) scintillating crystal. It has dimensions of around 15 cmx8 cmx9 cm and weighs 1 kg. The intraoperative assay of PTH (ioPTH) was used to confirm the complete resection of pathological tissue. RESULTS: All cases were operated on successfully by a MIP. The ioPTH confirmed the excision of all pathological tissues. The MGC proved its usefulness in all patients, even in a difficult case in which the first attempt with the gamma probe failed. In all cases it offered real-time accurate intraoperative images. CONCLUSION: The hand-held MGC is a useful instrument in MIP for PHPT. It may be used to complement the standard tools used to date, or may even replace them, at least in selected cases of single adenomas.

Adenoma↗
PubMed2001

Insulin responsiveness of sheep, ponies, miniature pigs and camels: results of hyperinsulinemic clamps using porcine insulin.

It had been suggested that marked species differences in glucose tolerance tests were due to differences in insulin resistance. To compare insulin responsiveness, euglycemic hyperinsulinemic clamps were carried out in sheep, ponies, miniature pigs and camels. Porcine insulin was infused as primed-continuous infusions for 2 h (6 mU x kg(-1) x min(-1)). The steady state glucose infusion rates in the pigs, sheep, ponies and camels were 96.0, 18.6, 7.1 and 6.1 micromol x kg(-1) x min(-1), respectively. The maximal plasma insulin concentrations during the insulin infusions were 2,700 microU x ml(-1) in the camels, 1,400 microU x ml(-1) in the sheep and ponies and 600 microU x ml(-1) in the pigs. The rate of insulin removal from plasma was lowest in the camels as compared to the sheep, ponies and pigs (0.019, 0.038, 0.035 and 0.070 min(-1), respectively). In all species the concentrations of plasma non-esterified fatty acids dropped significantly 10-30 min after the start of the insulin infusion. However, the rates of non-esterified fatty acid reduction were higher in the pigs and sheep than in the camels and ponies. Results confirm a considerably higher insulin responsiveness in the pigs as compared to the sheep. The ponies and camels were found to be even more insulin-resistant than the sheep.

Adaptation, Physiological↗
PubMed2004

Miniaturized heme proteins: crystal structure of Co(III)-mimochrome IV.

Protein design provides an attractive approach to test the essential features required for folding and function. Previously, we described the design and structural characterization in solution of mimochromes, a series of miniaturized metalloproteins, patterned after the F-helix of the hemoglobin beta-chain. Mimochromes consist of two medium-sized helical peptides, covalently linked to the deuteroporphyrin. CD and NMR characterization of the prototype, mimochrome I, revealed that the overall structure conforms well to the design. However, formation of Delta and Lambda diastereomers was observed. To overcome the problem of diastereomer formation, we re-designed mimochrome I, by engineering intramolecular, interchain interactions. The resulting model was mimochrome IV: the solution structural characterization showed the presence of the Lambda isomer as a unique form. To examine the extent to which the stereochemical stability and uniqueness of mimochrome IV was retained in the solid state, the crystal structure of Co(III)-mimochrome IV was solved by X-ray diffraction, and compared to the solution structure of the same derivative. Co(III)-mimochrome IV structures, both in solution and in the solid state, are characterized by the following common features: a bis-His axial coordination, a Lambda configuration around the metal ion, and a predominant helical conformation of the peptide chains. However, in the crystal structure, intrachain Glu1-Arg9 ion pairs are preferred over the designed, and experimentally found in solution, interchain interactions. This ion pairing switch may be related to strong packing interactions.

Arginine↗
PubMed1985

Coronary artery spasm induced in miniature swine: angiographic evidence and relation to coronary atherosclerosis.

In a swine model of coronary artery spasm, the pathogenetic role of coronary atherosclerosis was examined. Following endothelial balloon denudation of the left circumflex coronary artery (LCX), male miniature swine were fed a laboratory chow diet containing 2% cholesterol. Although there was no difference in the extent of coronary vasoconstrictive response to histamine, serotonin, and ergonovine between the left anterior descending coronary artery (LAD) and the LCX before the denudation, a constrictive response was significantly augmented along the denuded portion of the LCX 1 and 3 months after the denudation. Augmented vasoconstrictive responses to phenylephrine were never evidenced. Histamine was the most potent vasoactive agent, and coronary artery spasm was provoked repeatedly by intracoronary or intravenous administration of histamine in the presence or absence of cimetidine. The spasm was provoked only in the denuded portion of the LCX, the same area which was angiographically normal before the occurrence of the spasm. Histologically, atherosclerotic changes were predominant along the denuded portion of the LCX. Topologic correlation was suggested between the site of the spasm and the site of coronary atherosclerosis. It is concluded that in this swine model of coronary artery spasm, atherosclerotic changes may be an important causative factor, in terms of an activation of multiple receptor-operated calcium channels in the coronary artery.

Animals↗
PubMed1991

Miniaturization of three carbohydrate analyses using a microsample plate reader.

Three carbohydrate analyses (reducing value by copper-bicinchoninate, total carbohydrate by phenol-sulfuric acid, and D-glucose by glucose oxidase) have been miniaturized using a microsample plate reader. The use of the reducing-value procedure to measure the hydrolysis of starch by alpha-amylase and the use of the glucose oxidase method to measure the hydrolysis of lactose by lactase are illustrated.

Carbohydrates↗
PubMed1993

Alterations of muscle activities and jaw movements after blocking individual jaw-closing muscles in the miniature pig.

Although the inactivation or removal of motoneurones and muscles are known to affect development and growth of the craniofacial skeleton and masticatory muscles, the effect of these on functional activity patterns is not clear. The goal of this study was to evaluate the immediate responses of masticatory muscle activities to temporary nerve blocks of individual jaw-closing muscles. Nineteen experiments were made with four miniature pigs (Sus scrofa). Electromyograms of the masticatory muscles and jaw movements were recorded during natural chewing. Then, the function of individual jaw-closing muscles was removed unilaterally by local anaesthesia, and the recording repeated. The results showed a general increase in the activities of the other jaw-closing muscles, particularly those that were synergistic with the blocked muscle in producing lateral movements. Furthermore, the lateral pterygoid showed stronger activity, and accordingly the lateral movement was increased. Digastric muscle activity and the magnitude of jaw opening also tended to increase. Thus, the response to loss of a muscle is a strong, immediate compensation by synergists.

Animals↗
PubMed1995

Latency of the jaw-opening reflex in the premature, preweaning and adolescent pig (hanford strain miniature pig, Sus scrofa).

The jaw-opening (digastric) reflex was elicited by electrical stimulation of oral mucosa in miniature pigs (Sus scrofa) varying in age from 5 days premature to 101 days post-term. The latency of reflex electromyographic activity varied between 12-14 ms in the most immature animals and 9-11 ms in the oldest animals. The very long-latency digastric responses found in the immature young of nesting mammals were not seen in the relatively precocious young of this species.

Aging↗
PubMed1983

Effects of a new antianginal agent, nicorandil, on normoxic and anoxic contractions in isolated miniature pig coronary arteries exposed to 5-hydroxytryptamine and norepinephrine: comparison with nitroglycerin and diltiazem.

Nicorandil, nitroglycerin and diltiazem effects on normoxic and anoxic contractile responses to 5-hydroxytryptamine (5-HT) and norepinephrine (NE) were compared in isolated miniature pig coronary artery strips. Anoxia augmented contractile responses of the strips to 5-HT and NE. Nicorandil and nitroglycerin inhibited the normoxic contractile responses to 5-HT and NE and the further contraction induced by subsequently imposed anoxia. Diltiazem inhibited only the responses to 5-HT and to subsequently imposed anoxia. Whereas nicorandil and nitroglycerin produced relaxation of both potassium- and lanthanum-induced contractions, diltiazem was an effective relaxant of the potassium-induced contraction. The present experiments demonstrate that anoxia can augment the contractions of isolated large coronary arteries to 5-HT and NE. Nicorandil as well as nitroglycerin attenuate normoxic and anoxic contractions to 5-HT and NE. This is probably accomplished by inhibition of intracellular Ca2+ mobilization.

Animals↗
PubMed1984

Cardiac morphologic alterations in acute minoxidil cardiotoxicity in miniature swine.

Minoxidil, a vasodilating antihypertensive drug, was given orally at 10 mg/kg daily for 2 days to twelve 25- to 35-kg miniature pigs. Twelve control pigs were also studied. Minoxidil-treated pigs had tachycardia and hypotension and were killed 24 hr after the second dose. Gross examination showed diffuse hemorrhage in left atrial epicardium in all pigs, and also in ventricular epicardium (2 of 12 pigs) and endocardium (3 of 12 pigs). Pale areas of necrosis were observed on incision of the left ventricular papillary muscles in 3 pigs. Light and electron microscopic studies showed acute vascular damage with hemorrhage in the left atrial epicardium. Affected arterioles had endothelial cell swelling and transmural and perivascular accumulations of leukocytes, edema fluid, fibrin clumps, and erythrocytes. The swollen endothelial cells had large, irregularly shaped nuclei with abundant euchromatin; mitotic figures were frequent. The cytoplasm contained numerous polysomes and cisterns of rough endoplasmic reticulum. Fibroblasts adjacent to damaged vessels had edematous cytoplasm and increased amounts of rough endoplasmic reticulum. In the affected left ventricular papillary muscles, necrotic myocytes showed contraction bands, mitochondrial matrical densities, lipid accumulation, initial lysis of I bands, and pyknotic nuclei. The lesions were judged to result from two mechanisms: (1) hemorrhagic lesions from drug-induced vascular injury centered on epicardial and subepicardial arterioles and (2) papillary muscle necrosis from ischemic injury from hypoperfusion during minoxidil-induced tachycardia and hypotension.

Animals↗
PubMed1992

Morphologic and clinical study of the retinal circulation in the miniature pig. A: Morphology of the retinal microvasculature.

The microvasculature of the retina was studied in 20 miniature pigs by means of vascular corrosion casts and semithin histological sections. These techniques provided information useful for a better understanding of retinal fluoangiography. Various characteristics of the porcine retinal vessels, which are similar in the human retinal vasculature, were demonstrated in this study: the holangiotic retina, the trilaminar organization of the retinal capillaries and the presence of particular avascular zones, radial peridiscal capillaries and initial annular constrictions of certain arteriolar side-branches. The intrinsic retinal vasculature also shows some dissimilarities between both species. The major retinal blood vessels of the pig lie very superficially in the nerve fibre layer, in contrast to their deeper location in man. The streak-shaped macular area of the pig contains no major vessels but, unlike the central fovea in the human eye, it is not completely avascular. Another interesting finding is the presence of a large anterior border venule in the porcine retina.

Animals↗
PubMed1988

Effects of changes in infusion rate versus glucose concentration on absorption in infant miniature pig small intestine.

The effect of changes in the rate of infusion versus glucose concentration on glucose, water, and sodium absorption was studied in 20 infant miniature pigs using the single-pass small intestinal perfusion technique. During infusions of glucose loads of up to 75.0 mumol/min, glucose absorption increased similarly whether rate of infusion or glucose concentration was increased. Beyond 75.0 mumol/min, glucose absorption was not altered by changes in infusion rate, but was enhanced by increases in glucose concentration (slope of rate vs. concentration, p less than 0.0001). Net water and sodium absorption were similar in the two groups except for a decrease at the highest glucose concentration (rate vs. concentration at 187.5 mumol/min, p less than 0.05). A glucose concentration of 112.5 mM resulted in maximal glucose, water, and sodium absorption.

Animals↗
PubMed1988

Effect of different total parenteral nutrition fuel mixes on small intestinal growth and differentiation in the infant miniature pig.

Insulin has been proposed as an important factor in the regulation of growth and differentiation of the small intestine. In the newborn miniature pig, we induced significant physiologic increases in serum insulin and the insulin/glucagon ratio without altering serum glucose, beta-hydroxybutyrate, glucagon, cortisol, T3, and T4 using glucose-based total parenteral nutrition (TPN) in one group (group G) compared with a combination of glucose and fat in another group (group G/F). Control animals were sham-operated and fed a pelleted diet (group OC). Duodenal villus surface area and mucosal height were significantly greater in group G/F compared with group G. No other differences between the TPN groups were found in small intestinal growth, mucosal protein, deoxyribonucleic acid and ribonucleic acid content, and disaccharidase activities. As anticipated, group OC demonstrated increased intestinal length, weight, and villous surface area compared with the TPN groups. Ileal sucrase and jejunal and ileal maltase activities were greater in the TPN groups compared with those in group OC. Physiologic changes in serum insulin and the insulin/glucagon ratio induced by the TPN fuel mix do not appear to have altered small intestinal growth, composition, and differentiation in the healthy small intestine.

Age Factors↗
PubMed1985

Influence of age and sex on composition and lipid fluidity in miniature swine plasma lipoproteins.

Age- and sex-related differences were observed in the plasma cholesterol level, the plasma concentrations of certain lipoprotein components, and the HDL lipid phase fluidity in miniature swine from post-weaning (6 weeks) through puberty (6 months), maturity (2-6 years), and old age (10-12 years). Age effects were more dominant in the males, with VLDL protein; LDL protein, triacylglycerol, and phospholipid; and HDL triacylglycerol, phospholipid, cholesterol, and polyunsaturated fatty acids showing statistically significant negative correlations with age. These effects were not observed in females. HDL cholesterol was positively correlated with age in females. Total plasma cholesterol decreased with age in males only, but plasma triacylglycerol was not influenced by age in either sex. Higher concentrations of all lipoprotein lipids were observed in the female minipigs regardless of age. HDL lipids became less fluid with age in the males alone suggesting a physical chemical basis for the lower incidence of heart disease among females. The more fluid HDL circulating in the female may be more capable of mobilizing peripheral tissue cholesterol for catabolism thus protecting her from developing atherosclerotic lesions.

Age Factors↗
PubMed1992

A miniature piezoelectric polymer transducer for in vitro measurement of the dynamic contact stress distribution.

Previous studies of contact pressure measurement between articular surfaces have been mostly limited to static techniques. The purpose of our study was to develop a new dynamic technique for a direct measurement of the local contact stresses, and to apply the new method to an in vitro cadaver study of the patellofemoral joint pressures. The miniature transducer consists of a 2 mm diameter and 28 microns thick piece of piezoelectric polymer film sandwiched between two stainless steel electrodes of similar diameter. A water-resistant capsule consisting of Teflon film and Hysol epoxy was applied around the transducer. The transducer was 3 mm in diameter and 0.7 mm in thickness. A 3 mm well was made at six locations in the patella, corresponding to superior, middle, and inferior regions of both facets. Six transducers were cemented within each well, flush with the articular cartilage. The transducers were calibrated in situ before and after the experiment. The femur was rigidly fixed to the loading apparatus and the tibia was allowed to flex and extend through a 90 degrees range of motion using an Instron and a pulley system connected to the quadriceps tendon. Q angles of 0, 5, 10 and 15 degrees were established by adjusting the direction of the quadriceps tendon. Stresses ranging from 0.1-1.3 MPa were recorded at various locations. These values varied in flexion and extension. An overall decrease in these stresses was noted after tuberosity elevation up to 1.5 cm, following which increased values up to 1.8 MPa were recorded mostly in the superior section.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗
PubMed1995

Unified enantioselective capillary chromatography on a Chirasil-DEX stationary phase. Advantages of column miniaturization.

Immobilized Chirasil-DEX (mono-6-O-octamethylenepermethyl-beta-cyclodextrin chemically linked to dimethylpolysiloxane) can be employed as a versatile chiral stationary phase in chromatography. The chiral polymer has a long lifetime and is configurationally and thermally stable. The concept of unified enantioselective chromatography has been demonstrated for the enantiomer separation of hexobarbital by gas chromatography, supercritical fluid chromatography, liquid chromatography and capillary electrochromatography on a single open-tubular column (1 m x 50 microns I.D.) coated with Chirasil-DEX. The advantages of miniaturization in contemporary chromatographic enantiomer separation are demonstrated. Chirasil-DEX coated on porous silica is also useful for enantiomer separation in high-performance liquid chromatography.

Carbohydrate Sequence↗
PubMed1982

A rapid miniaturized solid-phase radioimmunoassay technique for secreted immunoglobulins, employing microtiter plates, antibody bound to polyacrylamide beads, and filter strip harvesting.

We have developed a solid-phase radioimmunoassay technique, which allows a large number of samples to be assayed, while minimizing amounts of reagents and technician time. The assay is run in microtiter plates, which results in improved organization, shorter assay set-up time and advantageous miniaturization. On the first day only 3 reagents are required: sample or standard, a 125I-labeled antigen, and an antibody attached to a polyacrylamide bead. After on overnight incubation period, the assay is harvested using a commercial microharvesting apparatus (24 samples/2 min) and placed directly into a gamma counter for counting. In the present study, we have developed the assay to measure secreted IgG, IgM and IgA, and we have compared our results with those of a standard radioimmunoassay technique. This rapid, simple, economical approach should be applicable to the radioimmunoassay of other substances as well.

Acrylic Resins↗
PubMed1982

Miniaturization of beta-galactosidase immunoassays using chromogenic and fluorogenic substrates.

Enzyme immunoassay techniques are widely use to quantify various antigens and antibodies. The final step of these techniques (i.e. enzyme reaction) may be carried out in several ways (e.g. chromogenic, fluorogenic, or radioactive substrate and thermometric measurement). This paper compares the effectiveness of the chromogenic and the fluorogenic substrates in the beta-galactosidase immunoassay. Using microtitration plates (150 microliter samples) coated with anti-human IgE, and anti-human IgE labeled with E. coli beta-galactosidase, the lowest concentrations of IgE that one could detect employing either the chromogenic (o-nitrophenyl-beta-D-galactopyranoside) or the fluorogenic (4-methyl-umbelliferyl-beta-D-galactopyranoside) substrate were determined. It was found that both substrates were almost equally effective in measuring the lowest concentration of IgE (0.075-0.13 IU/ml) under the optimal conditions. But, using fluorogenic substrate and suitable apparatuses the enzyme immunoassay can be miniaturized. Thus by using decreasing volumes of reagents, progressively smaller amounts of antigen were quantified: as the sample volumes were reduced from 150 to 10 microliter and finally to 0.3 microliter a progressive decrease from 7 x 107 molecules of IgE to 2.9 x 107 molecules and to 1.5 x 106 molecules was observed. The corresponding lowest detection limits were 0.075 IU/ml, 0.46 IU/ml and 0.8 IU/ml.

Animals↗