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Biomedical subjects

D Shaw

Publications and source records attributed to D Shaw.

At least 127 records · Page 7Linked to original sources
PubMed1995

Influence of gravity and body position on normal oropharyngeal swallowing.

The influence of gravity, if any, on pharyngeal bolus transport is unknown. The aim of the present study was to evaluate the effect of gravity and body position on the radiological and manometric events during the normal oropharyngeal swallow. In eight healthy male volunteers, we performed simultaneous videoradiography and manometry, using a manometry catheter incorporating a perfused sleeve measuring upper esophageal sphincter pressure and three solid-state transducers recording pharyngeal pressures. Swallows of 5 and 10 ml of barium were performed in three different body positions: upright, horizontal, and 30 degrees head down (inverted). Hypopharyngeal intrabolus pressure increased significantly in the horizontal and inverted positions compared with upright, P = 0.0001. This resulted in increased maximal sphincter diameters during bolus flow (P = 0.0001) and shorter duration of sphincter opening (P = 0.03). As a result, transsphincteric flow increased in the horizontal and inverted positions, P = 0.04. Total swallowing duration, oral and pharyngeal transit time, pharyngeal peristaltic amplitude and duration, the length of the bolus in the pharynx, and excursions of the hyoid and larynx were unaffected by body position. We conclude that intrabolus pressure is an important determinant of upper esophageal sphincter opening in the healthy oropharynx and that gravity does not influence pharyngeal bolus transport. The healthy upper esophageal sphincter has residual opening capacity that can be demonstrated by altering body posture.

Adult↗
PubMed1995

Influence of prenatal photoperiods on postnatal reproductive responses to daily infusions of melatonin in the Siberian hamster (Phodopus sungorus).

Prepubertal reproductive development in juvenile male Siberian hamsters can be strongly influenced by photoperiod information received during gestation. Information transmitted from the mother hamster to her fetuses appears to modify the photoperiodic mechanism of the developing hamsters so that they may respond differently to certain intermediate day lengths [i.e. 14 h of light and 10 h of darkness/day (14L)] experienced after birth depending on whether gestation occurred in longer or shorter day lengths. In adult and juvenile hamsters, the duration of the nocturnal elevation of pineal and serum melatonin (MEL) is an important component of the photoperiodic system coding for day length. In the present study, we investigated whether the photoperiod in effect during gestation could influence the responsiveness of developing male hamsters to daily MEL infusions of fixed durations administered after weaning. The results indicated that hamsters gestated under 16L or 10L did not differ from each other with respect to testicular growth in response to any of the fixed duration MEL infusions. Thus, target tissue responsiveness to fixed duration MEL infusions (over a range of 6-10 h) was the same regardless of the gestation photoperiod to which the animals had been exposed.

Animals↗
PubMed1995

Gender differences in influence of prenatal photoperiods on postnatal pineal melatonin rhythms and serum prolactin and follicle-stimulating hormone in the Siberian hamster (Phodopus sungorus).

In Siberian hamsters, the rate of testicular maturation during juvenile life can be influenced by both the prenatal photoperiod and the day length experienced postnatally. In this report, potential postnatal photoperiodic mechanisms modified by prenatal photoperiod were investigated in this species. The study examined the effect of prenatal photoperiodic history on the postnatal pineal melatonin (MEL) rhythm and on postnatal secretion of FSH and PRL. In the first study, the pineal MEL content of hamsters, gestated in either 16 h of light and 8 h of darkness/day (16L) or 10L and raised postnatally in 14L, was monitored at various times of the day and night at 18 days of age. We found that prenatal photoperiod did influence the postnatal pineal MEL rhythm in 18-day-old males, but a similar effect was not evident in females. For males, the durations of the nocturnal elevation of pineal MEL were 8.5 and 7 h in 16L and 10L gestated hamsters, respectively. However, MEL rhythms were similar to each other in the corresponding groups of females (8.5- and 9-h durations of elevated pineal MEL in 16L and 10L prenatal photoperiod groups, respectively). In a subsequent study using the same photoperiod paradigm, FSH and PRL concentrations were examined in both genders at 3- to 10-day intervals between 18-62 days of age. The serum PRL (day 22) and FSH (days 18 and 22) concentrations in males were significantly affected by prenatal photoperiod. Specifically, circulating serum PRL (on day 22) and FSH (on days 18 and 22) concentrations were increased substantially in 10L gestated, compared to 16L gestated, males raised in 14L after birth. In contrast, serum FSH concentrations in female hamsters were not different between 16L and 10L gestated groups at these times. In another study using the same experimental design, the pattern of testicular development was explored in males. Hamsters that had experienced a 10L photoperiod prenatally and were raised in 14L exhibited rapid testicular growth from 27-52 days of age compared to hamsters that had experienced a 16L prenatal photoperiod and were reared in 14L. These results support the hypothesis that in juvenile male hamsters exposed to 14L postnatally, endogenous MEL production and serum FSH concentrations are influenced by photoperiodic information received during fetal life. In addition, these findings help to explain why males gestated in 10L and raised in 14L exhibit accelerated testicular development in the first 2 months of life compared to males gestated in 16L and transferred to 14L after birth.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Experimental and theoretical study of the contact mechanics of five total knee joint replacements.

The tibio-femoral contact area in five current popular total knee joint replacements has been measured using pressure-sensitive film under a normal load of 2.5 kN and at several angles of flexion. The corresponding maximum contact pressure has been estimated from the measured contact areas and found to exceed the point at which plastic deformation is expected in the ultra-high molecular weight polyethylene (UHMWPE) component, particularly at flexion angles near 90 degrees. The measured contact area and the estimated maximum contact stress have been found to be similar in magnitude for all of the five knee joint replacements tested. A significant difference, however, has been found in maximum contact pressure predicted from linear elasticity analysis for the different knee joints. This indicates that varying amounts of plastic deformation occurred in the polyethylene component in the different knee designs. It is important to know the extent of damage as knees with large amounts of plastic deformation are more likely to suffer low cycle fatigue failure. It is therefore concluded that the measurement of contact areas alone can be misleading in the design of and deformation in total knee joint replacements. It is important to modify geometries to reduce the maximum contact stress as predicted from the linear elasticity analysis, to below the linear elastic limit of the plastic component.

Anthropometry↗
PubMed1995

Possible association of liver damage with the use of Chinese herbal medicine for skin disease.

From January 1991 to December 1993, we received reports of 11 cases of liver damage following the use of Chinese Herbal Medicine (CHM) for skin conditions. There was strong evidence of an etological association in 2 cases in which recovery after dechallenge and recurrence of hepatitis after rechallenge were observed. The time-course relationship, recovery after ceasing CHM, and absence of alternative causes of liver damage suggested an association in 2 further symptomatic cases following a single period of exposure. Herbal material was available for analysis in 7 cases. The plant mixtures varied so no single ingredient could account for liver injury in this case series. The mechanism of toxicity is unclear; effects do not appear dose-related and are probably idiosyncratic. Liver function should be monitored in patients who use CHM for skin disorders and its use discontinued if problems occur. The complexity of these cases illustrates the requirement for continuous surveillance of CHM including pharmacognostical investigation of ingredients.

Adult↗
PubMed1994

Iron-balance and dose-response studies of the oral iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) in iron-loaded patients with sickle cell disease.

Several life-threatening complications of the common disorder sickle cell disease require management with red blood cell transfusions and, hence, long-term iron-chelating therapy. The efficacy of the oral iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) has not previously been determined in patients with sickle cell disease. We compared the efficacy of L1 to that of standard-dose subcutaneous deferoxamine in four regularly transfused patients with homozygous sickle cell disease, who had evidence of severe iron overload and a history of poor compliance with deferoxamine. Determination of 24-hour urinary iron excretion conducted over 5 days immediately after transfusion showed that the mean daily urinary iron excretion induced by L1 at 75 mg/kg/d (0.48 +/- 0.23 mg/kg) was equivalent to that induced by deferoxamine at 50 mg/kg/d (0.39 +/- 0.06 mg/kg). In two of three patients studied, a significant (P < .025) increase in mean daily urinary iron excretion was achieved when the dose of L1 was increased to 100 mg/kg/d. Total iron balance studies, which quantitated both urinary and stool iron excretion on L1 and deferoxamine, determined that mean total daily iron excretion induced by deferoxamine (0.88 +/- 0.05 mg/kg) was significantly greater (P < .05) than that induced by L1 (0.53 +/- 0.17 mg/kg), attributable to the significantly greater stool iron excretion during deferoxamine treatment (0.50 +/- 0.16 mg/kg/d) compared with that measured during L1 treatment (0.12 +/- 0.08 mg/kg/d, P < .01). Stool iron excretion accounted for a significantly greater percentage of total iron excretion during deferoxamine treatment (59% +/- 20%) than during L1 treatment (23% +/- 14%, P < .01). These iron balance studies are the first to compare total iron excretion induced by L1 with that achieved by deferoxamine. They demonstrate that the mean total daily iron excretion during L1 treatment (0.53 +/- 0.17 mg/kg) is sufficient to maintain net negative iron balance in most regularly transfused patients with sickle cell disease. Because long-term compliance with L1 has been shown previously to be superior to that with deferoxamine in patients with homozygous beta-thalassemia, the use of L1 should increase the long-term effectiveness of iron chelation in patients with sickle cell disease.

Administration, Oral↗
PubMed1994

Ultrasound guided placement of transperineal prostatic afterloading catheters.

PURPOSE: A new method of performing temporary prostate brachytherapy which does not require an open laparotomy is described. METHODS AND MATERIALS: This procedure allows dynamic visualization of the placement of 13-gauge (I-125) or 17-gauge (Ir-192) afterloading catheters into the prostate gland via saggital ultrasound imaging. The image enables visualization of the entire path of the catheter as well as cephalad gland movement. The prostate gland, seminal vesicles, bladder neck, urethra, and rectum are easily identified and implanted, if desired, during the procedure. This procedure has been used in 34 patients as an interstitial boost for locally advanced (T2b, T3) prostatic carcinoma following external beam therapy as a means to safely deliver higher doses to the gland. Another eight patients have undergone this procedure as salvage following failure of prior radical prostatectomy or external beam therapy. RESULTS: Very customized dosimetry has been obtained using this technique as a result of the optimal catheter placement achieved under ultrasound guidance, particularly with I-125. Although it is too early to evaluate efficacy, the procedure has been well tolerated and is associated with minimal morbidity to date. CONCLUSION: This new procedure seems to be an excellent means of safe delivery of higher doses to the gland compared to conventional external beam therapy. Due to the ability to cover the seminal vesicles as well as the afterloading nature of this procedure, a more customized implant is obtained relative to most permanent techniques, and open laparotomy is not required.

Brachytherapy↗
PubMed1994

Case report 834: Chronic sclerosing osteomyelitis of the mandible with long bone periostitis.

We present the case of a patient with primary chronic osteomyelitis of the mandible, the radiological appearance of which is compatible with a diagnosis of chronic sclerosing osteomyelitis. The accompanying femoral and tibial periosteal reactive new bone formation and the benign clinical course suggest that this presentation may represent a form of chronic multifocal osteomyelitis.

Child↗
PubMed1994

Xanthogranulomatous pyelonephritis in childhood: ultrasound and CT diagnosis.

Four cases of diffuse xanthogranulomatous pyelonephritis (XPN) in young children are presented. In three patients the clinical picture was one of weight loss, anaemia and neutrophilia with a large renal mass. The fourth presented with haematuria. Ultrasound (US) and CT findings were almost identical in all four patients. US showed the affected kidney was massively enlarged but retained a reniform shape. Dilated fluid spaces containing calculi were present. CT confirmed the US findings and revealed peripheral enhancement without contrast excretion, with dilated calyceal spaces producing the "bear paw sign". Extrarenal extension into abdominal wall and psoas muscle is typical and was well demonstrated by CT. The affected kidneys were non-functioning and nephrectomy was required. Typical US and CT features allow a confident diagnosis of XPN and appropriate early treatment.

Child, Preschool↗
PubMed1994

Modelling diagnostic skills in the domain of skeletal dysplasias.

The diagnostic model used in the medical expert system Skeletal Dysplasias Diagnostician (SDD) is discussed. The model aims to capture the diagnostic skills of domain experts. Such skills represent high level strategies which apply across different medical domains and hence the presented model is relatively generic. Preliminary evaluation of an earlier version of the diagnostic model, which yielded promising results, has led to a considerably improved model. A sample consultation given in an appendix illustrates most aspects of the current model. The paper concludes by giving the authors' practical insights into the knowledge engineering of medical diagnostic systems.

Bone Diseases, Developmental↗
PubMed1994

A type-specific avian influenza virus subunit vaccine for turkeys: induction of protective immunity to challenge infection.

The fraction NP/HA (nucleoprotein/haemagglutinin) obtained from n-octyl-beta-D-glucopyranoside-treated influenza A H5N2 virus was highly enriched for NP with residual haemagglutinin. This preparation was incorporated in ISCOMs. This potent 'immunostimulating complex' induced the production of high antibody titres in turkeys. The NP/HA ISCOMs preparation was found to protect turkeys from both homologous and heterologous challenge infection as shown by reduced viral titres in the lung and trachea of vaccinated turkeys. Clearance of the virus from trachea and lungs was seen at late stages of infection. The vaccine also induced a cellular immune response as measured by T-cell proliferation and a delayed-type hypersensitivity response. The results reported in this study demonstrate that the NP/HA ISCOM vaccine is capable of inducing type-specific immunity and that it has potential utility as a vaccine in turkeys.

Animals↗
PubMed1994

Differences in the effects of NK1-receptor antagonists, (+/-)-CP 96,345 and CP 99,994, on agonist-induced responses in guinea-pig trachea.

1. The effects of the NK1-receptor antagonists, (+/-)-CP 96,345 and CP 99,994, on NK1-agonist evoked contractions were compared in isolated rings of guinea-pig tracheal smooth muscle. 2. (+/-)-CP 96,345 and CP 99,994 were similarly effective in antagonizing responses evoked by septide, whereas CP 99,994 was more effective than (+/-)-CP 96,345 in inhibiting responses evoked by [Sar9Met11(O2)] substance P. 3. These results suggest that responses to septide and [Sar9Met11(O2)] substance P may be operated via different populations of NK1-receptors.

Animals↗
PubMed1994

The paradoxical pulse in tamponade: mechanisms and echocardiographic correlates.

Pulsus paradoxus is an exaggerated fall in systolic blood pressure with inspiration (usually greater than 10 mm). Understanding the accuracy of pulsus paradoxus for a diagnosis of cardiac tamponade requires a consideration of the mechanisms underlying its genesis, and a knowledge of its presence in other conditions and its variable absence in cardiac tamponade with associated disease states. Echocardiography (M-mode, 2-D, and Doppler) has aided considerably our understanding of pulsus paradoxus. Inspiratory increases in right heart filling and output are widely accepted as necessary for pulsus paradoxus to occur; inspiration causes increases in right ventricular dimensions and pulmonic and tricuspid velocities, and decreases in left ventricular (LV) dimensions and aortic and mitral velocities and LV diastolic compliance. Doppler studies of pulmonary venous inflow confirm that an inspiratory fall in left atrial filling is necessary for pulsus paradoxus. Pulsus paradoxus is complex and multifactorial in origin; it may be absent in cardiac tamponade when certain conditions (e.g., LV dysfunction) coexist and may accompany disease states other than cardiac tamponade (e.g., obstructive airway disease). Thus, the significance of pulsus paradoxus (and its Doppler echo correlates) must be considered in the clinical context.

Animals↗
PubMed1994

Cytochrome P450 expression in oesophageal cancer.

The cytochrome P450 superfamily of enzymes play a central part in the metabolism of carcinogens and anti-cancer drugs. The expression, cellular localisation, and distribution of different forms of P450 and the functionally associated enzymes epoxide hydrolase and glutathione S-transferases have been investigated in oesophageal cancer and non-neoplastic oesophageal tissue using immunohistochemistry. Expression of the different enzymes was confined to epithelial cells in both non-neoplastic samples and tumour samples except the CYP3A was also identified in mast cells and glutathione S-transferase pi was present in chronic inflammatory cells. CYP1A was present in a small percentage of non-neoplastic samples but both CYP2C and CYP3A were absent. Epoxide hydrolase was present in half of the non-neoplastic samples and the different classes of glutathione S-transferase were present in a low number of samples. In carcinomas CYP1A, CYP3A, epoxide hydrolase, and glutathione S-transferase pi were expressed in at least 60% of samples. The expression of glutathione S-transferases alpha and mu were significantly less in adenocarcinoma compared with squamous carcinoma.

Adenocarcinoma↗
PubMed1994

An analysis of factors determining the need for ventriculoperitoneal shunts after posterior fossa tumor surgery in children.

The authors retrospectively reviewed 117 pediatric patients with posterior fossa tumors treated at The Children's Hospital and Medical Center, Seattle, Washington, between 1976 and 1990, in an attempt to determine what perioperative and intraoperative factors influenced the need for postoperative shunts. The ages of the patient population ranged from 4 months to 16 years 9 months. The factors evaluated included age at diagnosis, duration of symptoms, extent of hydrocephalus, tumor location, extent of tumor resection, presence and duration of an external ventricular drain, flow of cerebrospinal fluid (CSF) through the fourth ventricle after tumor resection, presence of hemostatic cavity linings, method of dural closure, tumor type, CSF infection, CSF leak, and pseudomeningocele formation. Of these variables, young age at diagnosis, tumors affecting midline structures, subtotal tumor resection as determined by immediate postoperative scans, prolonged requirement of an external ventricular drain, cadaveric dural grafts, pseudomeningocele formation, and CSF infections were statistically significant factors associated with the need for postoperative shunt placement, which was required in 36% of all patients. Therefore, considering the pertinent factors that may influence the need for postoperative shunt placement, a radical tumor resection should be done when possible, especially for midline lesions, and closure of the operative wound should be meticulous to avoid a CSF leak and subsequent infection. Foreign body dural substitutes as a cause of an inflammatory response in the CSF should also be avoided. Persistence of a pseudomeningocele despite serial taps and time will eventually require placement of a shunt after posterior fossa tumor surgery.

Adolescent↗
PubMed1994

Plain chest radiographic changes of the absent pulmonary valve syndrome.

The plain chest radiographs of 40 patients with the absent pulmonary valve syndrome in association with tetralogy of Fallot have been reviewed. The conventional frontal projection showed characteristic changes of massively dilated central pulmonary arteries with normal peripheral markings in all patients (100%). Lobar hyperinflation was present in a significant proportion of the infant group (38%) which in a smaller group can be a complication requiring surgery in addition to that for the cardiac malformation.

Cardiomegaly↗