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Biomedical subjects

S Wynchank

Publications and source records attributed to S Wynchank.

At least 37 records · Page 2Linked to original sources
PubMed1995

Transit through the distal quarter of the oesophagus in young children.

The transit time of 800 individual boluses through the distal quarter of the oesophagus was measured in 33 scintigraphic oesophageal studies which had been selected as typifying normal swallows in children. The results show that, in children, transit time through the distal quarter including the lower oesophageal sphincter is normally less than 2 seconds and that transit tends to be slower during the first 4 seconds after onset of swallowing.

Deglutition↗
PubMed1995

The "Fisherman's Waders" sign in a bone scan of inferior vena cava thrombosis associated with nephrotic syndrome.

This paper presents a 61-year-old male patient with nephrotic syndrome, hypercoagulability and IVC thrombosis. Increased soft tissue uptake below the level of the mid chest was seen in his bone scan. The term "Fisherman's Waders" sign is suggested for this finding, whose recognition may permit the identification of inferior vena cava obstruction in bone scans. The existence of a cavo-portal shunt was also confirmed by dynamic scintigraphy.

Blood Coagulation Disorders↗
PubMed1995

Lateral neck imaging for spatial localization of parathyroid tissue.

Two patients with an ectopic parathyroid adenoma are described. In both cases the lesions were clearly demonstrated in an anterior view on T1-201/Tc-99m scintigraphy, but were not identified during the first surgical exploration. Failure to identify the ectopic adenoma at surgery in the second patient led to oblique and lateral views being obtained. These views permitted correct depth localization. We, therefore, believe that lateral and oblique views can be of assistance in improving preoperative localization of an ectopic parathyroid adenoma.

Adenoma↗
PubMed1994

Analysis of motion of the head.

This study was undertaken to determine the geometric form of the surface on which a fixed point on the head moves as a result of neck motion. Motion of a retroreflective marker on the glabella of six normal subjects was stereoscopically recorded by two video cameras, during a variety of neck motions, performed on command. Near real-time computer analysis in three dimensions of the video images showed the marker moved on a surface that very closely approximated an elliptical paraboloid (with tendency to a hemisphere), after extraneous shoulder motion had been eliminated. Parameters defining the elliptical paraboloids were obtained. Using a reflex microscope, the shape of the articular facets on skull base and superior facets of C1 and C2 of 6 normal subjects were examined. The shapes of all these facets were calculated and also found to be elliptical paraboloids.

Adult↗
PubMed1994

Scintigraphic evaluation of esophageal transit and gastric emptying in familial dysautonomia.

Gastroesophageal dysfunction is a major cause of morbidity and mortality in patients with familial dysautonomia (FD). Most studies evaluating esophageal and gastric function in FD patients are either insensitive or invasive. Thus we have used a "milk" scan to quantitate abnormalities in esophageal transit and gastric emptying, while searching for gastroesophageal reflux and aspiration in these patients. The quantitative scintigraphic evaluation was performed in 35 patients with FD, 10 of whom were studied after fundoplication, pyloroplasty and gastrostomy. A prolonged esophageal transit time, ranging from 8 s to more than 60 s duration, was demonstrated in 11 patients. Gastroesophageal reflux was detected in 26 patients. In 16 patients delayed gastric emptying ranging from 63-94% was detected at 30 min, and in 13 patients delayed emptying ranging from 37-86% was observed at 120 min. Pulmonary aspiration was detected in 8 non-operated patients, four of whom had abnormal gastric emptying. The scintigraphic analysis of both esophageal transit and gastric emptying in familial dysautonomia is presented, and its role in evaluation and management of these patients discussed.

Adolescent↗
PubMed1993

Determining locations of intracerebral lesions for proton radiotherapy.

Using an external view of the head, the ability to direct a proton radiotherapy beam at an intracerebral lesion is described, using a biostereometric (BSM) technique. The positions of markers, recognizable on computed tomography (CT) or magnetic resonance (MR) images, at known locations on the skin of a patient's head are related to the site of the lesion seen on the images. The markers' positions are determined by a BSM device, incorporating six video cameras coupled to a computer. A transformation from a coordinate system, defined by the CT or MR images, to another coordinate system, that of the BSM device, allows the proton beam to be directed towards the lesion. Markers used in this work were solid steel spheres for CT and plastic spheres containing oil for MR images.

Biomarkers↗
PubMed1993

Effect of captopril on changes in rats' hearts induced by long-term irradiation.

The aim of this study was to test the efficacy of captopril, an angiotensin-converting enzyme inhibitor and a known suppressor of fibrosis, in preventing late radiation-induced cardiac pathology. Myocardial functional, histochemical and ultrastructural-morphometric studies were done on perfused hearts of rats isolated 3 and 6 months after 60Co gamma irradiation with 20 Gy and age-matched controls. At each time the animals were divided into the following groups: nonirradiated controls; irradiated once with 20 Gy; irradiated as above and given daily doses of captopril; daily doses of captopril without irradiation. The results showed that captopril, while ameliorating the decrease in the indices of capillary function, increase in mast cells, fibrosis, number of atrial granules, and changes in nerve terminals, failed to prevent the progressive functional deterioration of the hearts after irradiation. These findings suggest that an intramyofiber derangement may be involved in the long-term myocardial complications of irradiation.

Animals↗
PubMed1992

Modification of the effects of hyperthermia and neutron radiation on the activity of acid phosphatase in CaNT tumors.

Acid phosphatase activity was measured in implanted murine CaNT tumors of varying volumes. There is a clear monotonically increasing relation between acid phosphatase activity and tumor volume. Also the tumors were subjected to either induced artificial hypoxia or hyperthermia (41.0 degrees C) alone, or combined with neutron irradiation (3.8 Gy). Changes in the activity of this enzyme following radiation damage could reflect tissue damage associated with metabolic disturbances. The effect on enzyme activity after sequential hyperthermia and neutron irradiation is not synergistic, as is shown in the quantitative experimental data. This implies that the mechanisms of heat damage differ from that of neutron beam damage, as reflected by acid phosphatase activity. The CaNT tumor was also shown to be thermosensitive after administration of mitoxantrone. Finally, the role of exogenous ATP was shown to provide heat protection by modification of those thermal effects resulting in the activity of acid phosphatase. The augmentation of this hydrolytic enzyme probably represents initial metabolic damage in the tumor after different modalities of radiation alone, or combined with mitoxantrone and exogenous ATP.

Acid Phosphatase↗
PubMed1991

Mycotoxic peripheral myelinopathy, myopathy, and hepatitis caused by Diplodia maydis in vervet monkeys.

During recent historical times many Africans changed their diet to one based on maize. The grain is regularly contaminated by fungi which are toxigenic to domestic animals and birds. After one of the fungi, Diplodia maydis, in pure culture on maize, was added to the food of omnivorous primates there was demyelination of nerves, atrophy, degeneration and necrosis of muscle, and hepatitis. These preliminary results are applicable to veterinary and laboratory animal sciences. They may also be medically significant since neuromuscular syndromes of unknown cause are prevalent among Africans. Nerve conduction velocities and organ weights are defined for vervet monkeys.

Animals↗
PubMed1991

A critical comparison of three methods for measuring dental models.

A critical comparison of three methods for measuring distances between various fiducial points on orthodontic plaster casts is presented. The first method consisted of using a vernier caliper by which direct measurements (Dv) of the distances were recorded. The second method consisted of measuring the same casts using a reflex metrograph (Dm), where the co-ordinates of the points relative to two axes were recorded and the distances between various points were calculated. In the third method, reflection holograms of the casts were made, and the same distances were measured on the holographic images (Dh) using the reflex metrograph. The Wilcoxon sign rank test indicated no significant differences (p greater than 0.1) between measurements made by the various techniques. The means of the different distances scored varied within less than 0.5 mm (Dv-Dh), 0.5mm (Dv-Dm) and 0.2mm Dm-Dh). This study indicated that holograms can provide sufficiently accurate representations of orthodontic study models. Their retention as case records may solve the problem of the storage of orthodontic plaster casts.

Dental Records↗
PubMed1990

Gadolinium(III) complex equilibria: the implications for Gd(III) MRI contrast agents.

A computer model of blood plasma which has allowed the effect of Gd(III) contrast agents to be simulated has been developed. Initial binding of Gd(III) is to transferrin. At high concentration the metal ion binds to citrate and salicylate. At a concentrate of 10(-3) M, GdCl3 is predicted to effect a redistribution of the in vivo Zn(II), Ca(II), and Fe(II) complexes present in blood plasma. There is little effect on the Cu(II) distribution. At a concentration below 10(-5) M EDTA and DTPA have little effect on the free Gd(III) metal ion concentration. Above this concentration though, the metal ion is bound almost exclusively to the EDTA or DTPA. An attempt is made to relate the toxicity of GdCl3, [Gd(EDTA)]-, and [Gd(DTPA)]2- to the thermodynamic stability of these complexes. The effect of substitution kinetics is also discussed.

Computer Simulation↗
PubMed1990

Dosimetry of swallowed non absorbed 99mTc radiopharmaceuticals in pediatric patients.

A calculation is presented which derives the absorbed dose experienced by pediatric patients of different ages who swallow a non absorbable 99mTc compound. All previous models assume sudden movement of radionuclide from one compartment of the gastrointestinal tract to another. The present model is novel in considering continuous distal motion through the gut and so more closely approximates the physiologic situation. Published S values are used to derive absorbed doses. The resulting calculated absorbed doses are comparable to, or lower than, those previously published and these differences are most marked in the large gut, which remains the critical organ.

Child↗
PubMed1990

Theoretical and experimental considerations linking an environmental stress to expression of endogenous retroviruses in a mammalian tumour.

CBA mice, containing the transplantable CaNT adenocarcinoma were exposed to magnetic fields of 0.5T. Doubling times of the tumours were found to increase significantly from 71 to 123 hours. Electron microscopy of these tumours revealed that the numbers of intracisternal A-type viral-like particles increased from a total of 127 in control mice (counted in 97 fields from 4 different tumours), to 459 in mice exposed to magnetic fields (counted in 95 fields from 5 different tumours). Similarly, intra-cytoplasmic A-type particle numbers increased from 98 to 184. In contrast the number of budding and extracellular C-type virus particles did not differ significantly in mice exposed to the magnetic field. To our knowledge this is the first report linking an environmental stress (magnetic field) to the visible expression of endogenous retro-viral-like type-A particles. We therefore propose the hypothesis that environmental stress may be relevant to the expression of endogenous retroviruses in mammalian cells. Such a mechanism could be relevant in the mechanisms of carcinogenesis and in the rapid evolution of species.

Animals↗
PubMed1990

Cranio-facial trauma and cerebral SPECT studies using N-isopropyl-iodo-amphetamine (123I).

Cerebral SPECT studies with N-isopropyl-iodo-amphetamine (123I) (IMP) were performed in patients who had suffered cranio-facial trauma, with and without loss of consciousness (LOC). The results were compared with computed tomography (CT). Nine out of ten of those with LOC had normal CT scans and evident photopaenia in IMP studies. It is clear that IMP SPECT scans complement CT in the investigation of patients who have suffered cranio-facial trauma.

Adolescent↗
PubMed1989

Biodistribution of 131I-radiolabelled plasma low density lipoprotein in hyperlipidaemic vervet monkeys.

Low density lipoprotein (LDL) labelled with 131I has been administered to 6 Vervets 2 of which were high responders to an atherogenic Western diet in terms of plasma cholesterol, 2 were low responders and 2 were fed a high carbohydrate control diet. The ratio of hepatic to cardiac activity was recorded for up to 10 days after administration of the labelled LDL. Liver activity had a longer biological half life in the high-responders and this can be interpreted in terms of a variation of hepatic metabolism of LDL, with direct relevance to the human situation.

Animals↗