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Biomedical subjects

D Hoffman

Publications and source records attributed to D Hoffman.

At least 19 recordsLinked to original sources
PubMed1992

Massive intraoperative pulmonary embolism.

Intraoperative massive pulmonary embolism is extremely rare. We describe such a case in a patient treated for a prolonged period preoperatively with intravenous heparin after an acute myocardial infarction and unsuccessful attempt at angioplasty, emphasizing that the problem should be borne in mind to facilitate expeditious and appropriate management. A clue to the diagnosis is interruption of venous return that is not due to a kink in the cannulae.

Aged↗
PubMed1992

Spontaneous host endothelial growth on bioprostheses. Influence of fixation.

BACKGROUND: Neither homografts nor bioprostheses have previously been seen to acquire a host endothelium. We previously reported a direct relation between aldehyde tanning and bioprosthesis calcification and the absence of calcification in the absence of aldehyde. METHODS AND RESULTS: Bovine pericardium was 1) treated with 0.625% glutaraldehyde and stored in 4% formaldehyde, 2) treated with 99.5% glycerol, and 3) treated with 99.5% glycerol and stored in formaldehyde (0.25-4%). The treated pericardium was used to construct stentless mitral valve prostheses (of a single pattern) that were implanted in weanling sheep. After the animals were killed, a strip of anterior cusp from annulus to papillary muscle was processed and examined by scanning electron microscopy for the presence of host endothelial growth. Avoidance of aldehyde allowed host endothelial growth in all cases (six of six), and pure aldehyde treatment inhibited growth in five of six animals. Exposure to aldehyde after glycerol treatment interfered with endothelialization significantly; after longer periods of implantation, however, endothelial growth occurred almost invariably in this group (12 of 13 implanted longer than 200 days). For this group, there was a statistically significant difference for duration of implantation between the valves that grew endothelium and those that did not (218.4 +/- 61.9 versus 128.5 +/- 65.4 days). CONCLUSIONS: Aldehyde treatment inhibits endothelial growth. With glycerol treatment, growth is uniformly present. Limited exposure to aldehydes after glycerol treatment inhibits endothelial growth, but this effect was ameliorated by prolonged implantation. The possibility of host endothelium-covered, noncalcifying bioprostheses is now real.

Animals↗
PubMed1991

Pulsed ultrasound and the hyperbarically exposed mouse fetus.

To enhance the likelihood of cavitation, pregnant mice were subjected to hyperbaric conditions and quickly returned to atmospheric pressure. Following this treatment, they were exposed to spatial average, pulse average intensities of 100 W/cm2 (2.2-MHz, 20-microseconds pulses with a duty cycle of 1/1000 or a temporal average spatial average intensity of 0.1 W/cm2). Fetal weights, deaths and malformations were scored. No statistically significant effects were observed in the offspring.

Animals↗
PubMed1991

Surgical correction of posttraumatic VSD via the right atrium.

We report the cases of four patients seen with ventricular septal defects (VSDs) resulting from penetrating chest trauma; initial surgical management was via left thoracotomy and comprised relief of tamponade and suture of the surface cardiac wound. A VSD was suspected in all four patients postoperatively on the basis of a holosystolic murmur as confirmed with two-dimensional echo and angiography. Elective surgical repair was undertaken on cardiopulmonary bypass with bicaval cannulation and cardioplegic arrest. The interventricular septum was approached through the right atrium (no attempt was made to free the anterior surface of the right ventricle from adhesions). Three defects were closed directly and one was closed with a pericardial patch. The surgical correction of posttraumatic VSD from a penetrating injury can be safely and effectively achieved via a right atrial approach.

Echocardiography↗
PubMed1991

Temporomandibular joint surgery.

This article reviews the spectrum of temporomandibular joint surgery. Indications for surgical treatment are discussed. Techniques are presented in an orderly fashion, from simple to complex. Preoperative and postoperative care are reviewed.

Arthroplasty↗
PubMed1990

NGF released from a polymer matrix prevents loss of ChAT expression in basal forebrain neurons following a fimbria-fornix lesion.

Following a unilateral fimbria-fornix lesion, the delivery of nerve growth factor (NGF) to the ipsilateral lateral ventricle of the rat can prevent the lesion-induced loss of choline acetyltransferase (ChAT) expression in the ipsilateral medial septum and vertical diagonal band region. In the present study, the ability of polymer rods to deliver NGF and to prevent a decrease in basal forebrain ChAT expression following a fimbria-fornix lesion was assessed. NGF was loaded into an ethylene vinyl acetate copolymer (EVAc) rod, fabricated by a melt-extrusion process. NGF release was established by the ability of the rods to induce neurite extension from PC12 cells and chick E12 dorsal root ganglia. Unilateral aspirative lesions of the fimbria-fornix were performed in adult rats, followed by implantation of a polymer rod into the ipsilateral lateral ventricle. Five animals received EVAc rods containing only the carrier molecule bovine serum albumin (BSA), and six received EVAc rods containing both BSA and NGF. After 2 weeks, ChAT-positive cells were counted in the medial septum and vertical diagonal band regions. Rats with NGF-releasing rods displayed ChAT(+) cell counts ipsilateral to the lesion equal to 88% of those on the contralateral side. In contrast, ChAT(+) cell numbers were 42% in animals with rods releasing BSA only (P less than 0.001). No undue reaction to implanted rods was noted. Following a fimbria-fornix lesion, NGF released from polymer matrices effectively prevents a lesion-induced reduction in ChAT expression in basal forebrain neurons.

Animals↗
PubMed1990

Killing of Drosophila larvae by the fields of an electrohydraulic lithotripter.

Drosophila larvae contain small gas bodies stabilized within their respiratory system. Because these bubbles are inhibited in their capacity to expand by the surrounding tissues, it is probable that they do not respond to acoustic fields in the manner described by classical cavitation theory that assumes a spherical bubble in an infinite fluid. However, just because of this inhibited expansion, they may serve as reasonable models for the gas bodies in mammalian tissues. Approximately one half of a population of Drosophila larvae is killed by exposure to 3 to 10 double lithotripter shocks with a positive pressure of 2-3 MPa. In contrast with the predictions of classical cavitation theory, adding a negative pressure to the exposure has little influence on the killing rate or its threshold pressure. The available evidence suggests that interaction of gas bodies in tissues with pressure fields and the resultant biological effects may be qualitatively different than predicted by classical cavitation theory and that positive rather than negative pressure may be a predictor of these effects.

Animals↗
PubMed1990

Electromyographic analysis of bow string release in highly skilled archers.

A predominant archery coaching tenet holds that the most effective means of releasing the bow string is by relaxation of the finger flexor muscles without activation of finger extensors. To evaluate the validity of this view, EMG patterns of the flexor digitorum superficialis and extensor digitorum muscles of the draw arm were examined using surface EMG electrodes in 15 highly skilled archers as each performed six shots. Each archer displayed consistent EMG patterns from shot-to-shot and two distinct flexor-extensor patterns were exhibited by the sample. The first, characterized by eight of the archers, supported the relaxation principle. For these archers, both flexor and extensor digitorum activity decreased markedly immediately prior to or at arrow release. The second pattern, characteristic of the remaining seven archers, contradicted the coaching tenet. While the flexor digitorum pattern was essentially the same as that described for the first pattern, the extensor digitorum displayed a marked increase in activity just prior to release, indicating that string release was facilitated by an active extension of the fingers. It was concluded that highly skilled archers do not predominantly reflect a release consistent with the coaching canon and that factors other than the string release mechanism discriminate the performances of skilled archers.

Adult↗
PubMed1989

Sister chromatid exchanges in Chinese hamster ovary cells exposed to high intensity pulsed ultrasound: inability to confirm previous positive results.

This study was undertaken in an attempt to determine a physical mechanism of action for a recently published report of a small but statistically significant increase in sister chromatid exchanges (SCEs) in Chinese hamster ovary cells exposed to high-intensity pulsed ultrasound. The "positive" report's protocol involved a sizeable chance of ultrasound beam impingement on the side wall of the cell exposure chamber. Ten experiments per regimen were conducted; the regimens included exposures of (a) chamber center, (b) chamber wall, (c) nine grid sites, 0.5 mm between sites, and (d) nine grid sites, 1.5 mm between sites. The last was an exact replication of the conditions previously reported to induce the small SCE effect. The results did not support the postulate of an increase in SCEs with the ultrasound exposures.

Animals↗
PubMed1989

A test of I2t as a dose parameter for fetal weight reduction from exposure to ultrasound.

It has been suggested that fetal weight reduction by ultrasound exposure is linearly related to the dose parameter I2t, where I is the intensity and t the exposure time. A direct test of the concept was conducted using CF-1 mice. No effect on fetal weight was found at values of the dose parameter large enough to produce measurable heating in the fetal and maternal tissues.

Animals↗