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Biomedical subjects

P Altman

Publications and source records attributed to P Altman.

17 recordsLinked to original sources
PubMed2001

Evaluation of the percutaneous intramyocardial injection for local myocardial treatment.

Therapeutic angiogenesis requires the induction of new blood vessel formation for the treatment of peripheral vascular and coronary artery disease. Efficacious application of this new therapy requires optimizing multiple factors, including the therapeutic agent, dosing, frequency of administration, and delivery modality. In this study, a helical needle drug infusion catheter was applied for optimal application of percutaneous intramyocardial delivery (PIMD). (125)Iodine-labeled albumin was injected by PIMD into the left ventricle myocardium in eight swine. After 1 hr, PIMD resulted in a high concentration of radiolabel at the treatment site; 16.4% +/- 2.1% of delivered and 81.4% +/- 2.6% of the total cardiac activity was concentrated at the site of delivery. The depth of needle penetration correlated with the myocardial retention of delivered protein. The myocardial retention of radiolabel in animals with shallow injections was 10.1% +/- 0.8%, compared to 18.9% +/- 3.3% retention after deep injections. The specific activity at the treatment site (radioactive counts per gram of tissue) was 115 +/- 36, 226 +/- 55, and 47 +/- 10 times higher compared to liver, lung, and kidney, respectively. Continuous coronary sinus and aortic blood sampling indicates that within 15 min following intramyocardial injection, a significant amount of nonretained protein is found within the coronary sinus. This study defines some of the parameters that can affect optimal application of PIMD and demonstrates that PIMD is a safe and efficient method for local drug delivery.

Animals↗
PubMed1997

Stresses from flexure in composite helical implantable leads.

This study presents a theoretical model of the general stress state found in helical implantable leads in bending. The model accurately predicts stress in large filarity coils made from clad wire. The stress is predicted using flexural rigidity of the coil and is developed to include the effects of coil pitch and the relative amounts and composition of the coil materials. The results is verified using finite element models of coils made from MP35N wire and MP35N clad silver wire. The resulting model will be especially useful for the fatigue analysis and engineering design of implantable leads which are built in this manner.

Computer Simulation↗
PubMed1995

Change of intradisc pressure versus volume change.

To gain further insight into the biomechanics of the intervertebral disc and determine a potential mechanism for causation and relief of symptoms related to a herniated disc, the pressure-volume relationship was determined within the nucleus pulposus (NP). In 17 intact human cadaver lumbar discs, pressure was measured continuously within the NP by means of a miniature strain gauge at the tip of a size 4 French (1.3 mm) catheter inserted into the NP. The volume of the NP was increased at the slow, continuous rate of 0.034 ml/min by the pump-regulated infusion of saline colored with methylene blue. In 12 unloaded discs, NP pressure rose in a linear fashion (linear r2 = 0.96) from an initial mean pressure of 174 +/- 81 kPa. The mean rate of pressure rise was 327 +/- 109 kPa/ml of volume increase. The peak pressure reached was limited to 550 kPa by the capacity of the strain gauge. Similar linear relationships were obtained during saline infusion into 5 vertically loaded discs. The data define the pressure-volume relationship within the disc and show that the NP, surrounded by the relatively inelastic annulus and the solid vertebral end-plates, has the properties of a tight hydraulic space in which a large pressure rise will regularly result from a small increase in volume. Presumably, the opposite is also true. The data may provide a biomechanical basis for variation in symptoms related to physiological changes in disc volume, and for any benefit obtained from interventions designed to remove disc tissue.

Biomechanical Phenomena↗
PubMed1995

Fall of intradiscal pressure with laser ablation.

In an experimental system where intradiscal pressure could be measured before and after laser ablation, we found that there was a significant fall of intradiscal pressure after 1000 J of Nd:YAG laser energy was delivered to fresh cadaver discs. That this was not due to fenestration was demonstrated by control experiments using an identical system, but without turning on the laser. Here, there was no significant fall of intradiscal pressure.

Humans↗
PubMed1995

Efficiency of disc ablation with lasers of various wavelengths.

In testing the CO2 lasers in CW and pulse mode, the erbium:YAG, the Nd:YAG 1318 microns and 1064 microns, the argon, the holmium:YAG, and the excimer, we found the greatest efficiency in the CO2 CW and pulse mode, and the lowest efficiency in the argon. Data with the holmium:YAG were unreliable because of the early generation laser tested. The Nd:YAG was second only to the CO2 laser, and because the latter has no waveguide, we deemed the Nd:YAG the laser of choice for PLDD.

Animals↗
PubMed1992

Percutaneous laser disc decompression. A new therapeutic modality.

The authors present a new advance in the treatment of herniated disc disease using percutaneous Nd:YAG laser to vaporize a small portion of nucleus pulposus, thereby decompressing the disc. In vitro and in vivo animal data are presented. Three hundred seventy-seven magnetic resonance imaging or computed tomography scan-documented, herniated, nonsequestered lumbar intervertebral discs with corresponding clinical findings in 333 patients were so treated in an outpatient setting. The longest follow-up was 62 months, with a mean of 26 months. According to the Macnab criteria, there was a good to fair response in 261 patients (78.4%), and a poor response in 72 (21.6%); 166 patients experienced relief of pain during the procedure. One-third of repeat magnetic resonance imaging scans at 4-6 months postlaser treatment showed modest to moderate decrease of disc herniation.

Adult↗
PubMed1992

Strip extensiometry for comparison of the mechanical response of bovine, rabbit, and human corneas.

Specimens of bovine, rabbit, and human corneas were systematically tested in uniaxial tension to experimentally determine their effective nonlinear stress-strain relations, and hysteresis. Cyclic tensile tests were performed over the physiologic load range of the cornea, up to a maximum of 10 percent strain beyond slack strain. Dimensional changes to corneal test specimens, due to varying laboratory environmental conditions, were also assessed. The measured stress-strain data was found to closely fit exponential power function relations typical of collagenous tissues when appropriate account was taken of specimen slack strain. These constitutive relations are very similar for rabbit, human and bovine corneas; there was no significant difference between the species after preconditioning by one cycle. The uniaxial stress strain curves for all species behave similarly in that their tangent moduli increase at high loads and decrease at low loads as a function of cycling. In the bovine and rabbit data, there is a general trend towards more elastic behavior from the first to second cycles, but there is little variation in these parameters from the second to third cycles. In comparison, the human data demonstrates relatively little change between cycles. Increases in width of corneal test specimens, up to a maximum of 2 percent were found to occur under 95 percent relative humidity test conditions over 10 minutes elapsed time test periods, while specimens which were exposed to normal laboratory conditions (45 percent RH) were found to shrink in width up to a maximum of 9.5 percent over the same elapsed time period. The thickness of the test specimens were observed to decrease by 3 percent in 95 percent relative humidity and by 12 percent in 45 percent relative humidity over the same elapsed time period.

Aged↗
PubMed1977

Evaluation of the new Gravigard IUCD inserter.

Incorporation of a flexible plastic rod into the new Gravigard plastic inserter assembly has, in our opinion, allowed for easier insertion and positioning of the device in the uterus compared with the previously available metal rod.

Aluminum↗
PubMed1976

Aneurysm of the aorta treated by wiring: case report of a 38-year survival.

A patient with a syphilitic aneurysm of the aorta treated by the insertion of wire is presented. The patient remained well for almost 40 years, but finally succumbed after rupture. The autopsy findings are discussed. To our knowledge, this represents the longest reported survival after treatment of an aortic aneurysm by wiring.

Aged↗
PubMedDate not supplied

Arteriohepatic dysplasia. II. Hepatobiliary morphology.

Five children were noted to have arteriohepatic dysplasia (Alagille's syndrome) between 3 and 7 months of age. Prior to diagnosis, four underwent Kasai procedures after intraoperative cholangiograms failed to demonstrate patency of the extrahepatic bile ducts. In three patients, a focal proximal hypoplasia of the common hepatic duct was demonstrated with fibrosis and increased vascularity. Hypoplasia of the gallbladder occurred in two patients. Changes were observed in the porta hepatis. Eighty of 208 micrometers bile ducts were associated with peripherally located gland-like structures. These changes are indistinguishable from those in fibrous remnants of extrahepatic biliary atresia. Hepatic features of sequential liver biopsies obtained in the five patients were divided into early and late changes. From birth to 3 months of age, the pathology consisted of cholestasis and bile duct destruction. After 3 months of age, there was persistent cholestasis, paucity of interlobular bile ducts, and portal fibrosis. Ductular proliferation was not an intrinsic change. When present, it was related to a recent episode of cholangitis.

Bile Ducts↗