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Biomedical subjects

J G Jones

Publications and source records attributed to J G Jones.

At least 163 records · Page 9Linked to original sources
PubMed1991

In vitro microleakage associated with posterior composite restorations used with different base/bonding system combinations.

The study aimed to determine the base/restoration combination which allowed the least microleakage in Class II cavities. One hundred premolar teeth were prepared with a standardized, minimal two-surface cavity and randomly ascribed to ten equal groups. The cavities were restored by use of one of ten different material/technique combinations. Restored teeth were sealed to within 1 mm of the restoration margins with nail varnish prior to the immersion of the crowns in 5% (buffered) eosin for 48 h. The teeth were then hemisected longitudinally, in a mesio-distal plane, through the midline of the restoration by means of a diamond disc with water coolant, and one half of each tooth was then photographed. The transparencies were examined by image analysis programmed to facilitate calculation of the percentage of the tooth/restoration interface and of the crown dentin exhibiting dye penetration. Light- and chemically-cured glass-ionomer-based restorations showed similar amounts of leakage when expressed as a percentage area of crown dentin. This was significantly (p less than 0.05) less than that shown by cavities both etched and bonded. Cavities restored without enamel etching or involving the use of a bonding system exhibited significantly (p less than 0.05) greatest leakage.

Acid Etching, Dental↗
PubMed1991

Clinical features of giant cell arteritis.

The clinical features of GCA can be classified into: (1) the systemic manifestations of malaise, weight loss, fever, night sweats and depression; (2) the proximal muscle pain and stiffness of polymyalgia rheumatica; (3) arteritic manifestations of pain or tenderness due to local inflammation; and (4) arteritic manifestations of ischaemia due to narrowing or occlusion of vessels. These may occur singly or in any combination and may come and go with the passage of time. Thus GCA can result in many different clinical signs and symptoms. The feared ocular and cerebrovascular complications of the condition can be prevented by the early institution of corticosteroid treatment. Early diagnosis is therefore vital. This is a simple matter when GCA presents in the classical textbook manner, but in atypical cases diagnosis can be exceedingly difficult. The absence of a reliable way of excluding the disease means that diagnosis is often a clinical exercise. A sound knowledge of the many and varied clinical manifestations of GCA is therefore required if the physician is going to prevent the ocular and cerebrovascular complications of GCA by early diagnosis and treatment.

Diagnosis, Differential↗
PubMed1991

The physiological cost of wearing a disposable respirator.

In order to gain an understanding of the physiological stresses imposed by the wearing of a single-use disposable respirator, a series of experiments was done to measure the cardiopulmonary effects of wearing the respirator (heart rate, respiratory rate, and blood pressure); resistance to breathing while wearing a respirator; and heat stress imposed by the use of a respirator (changes in inspired and expired air temperature). Ten men, ages 24 to 35, of varying fitness levels, served as volunteers in the studies. All the men exercised on a treadmill both with and without 3M Model 8715 disposable respirators. Workloads corresponding to light, moderate, and heavy levels were calculated for each volunteer based on his maximal oxygen uptake. As work intensity increased, an increase in breathing resistance was found. Peak resistances were in the range of +/- 2 cm water. Work-intensity level increases in respiratory rates were found with and without the respirators, but the respirator use trial had a significantly increased respiratory rate. Heart rate also showed a dose-related increase as work intensity increased and was significantly greater in the respirator trials at heavy levels of work and during recovery. Systolic blood pressure showed a biphasic response to respirator use, being significantly lower at rest and higher at high levels of work. Diastolic blood pressure changes were less dramatic but were elevated in the respirator trials. Clinically important increases in blood pressure were found in two volunteers when respirators were worn. Air temperatures immediately anterior to the face were, on average, 7.5 degrees C higher in the respirator trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Nitrous oxide sedation causes post-hyperventilation apnoea.

We have studied, in six normal subjects, the effect of nitrous oxide sedation on the ventilatory pattern and oxygen saturation using pulse oximetry (SpO2) after hyperventilation to an end-tidal carbon dioxide partial pressure (PE'CO2) of 3 kPa. This value of PE'CO2 was shown to be less than the apnoeic threshold of all these subjects when their ventilation vs PE'CO2 response curves were plotted. All subjects became apnoeic when told to relax following hyperventilation while breathing 75% nitrous oxide for 90 s. Apnoea was defined as cessation of breathing for 20 s or more. The mean duration of apnoea was 78 s (range 29-130 s). All subjects demonstrated arterial desaturation (mean SpO2 75%, range 44-87%). In contrast, following hyperventilation with air, no apnoea was seen in any subject, although there was some evidence of desaturation (mean SpO2 92.5%, range 88-98%). It was concluded that subjects who are sedated with nitrous oxide behave similarly to those who are anaesthetized rather than to those who were fully conscious, in that they become apnoeic below the apnoeic threshold point. The reduction in SpO2 after hyperventilation was explained almost entirely by apnoea and may explain abnormalities of respiratory control and hypoxaemia in patients recovering from general anaesthesia or sedation accompanied by hypocapnia. This mechanism may be of importance in obstetric patients after breathing Entonox, when apnoea and hypoxaemia may reduce oxygen delivery to the fetus.

Adult↗
PubMed1991

Changes in amplitude and latency of the P300 component of the auditory evoked potential with sedative and anaesthetic concentrations of nitrous oxide.

The P300 component of the auditory evoked response was recorded from six subjects whilst they listened via headphones to a series of clicks which were interrupted unpredictably by a tone burst. They were instructed to press a button as quickly as possible after hearing the tone whilst breathing first air and then a series of increasing concentrations of nitrous oxide. Both the amplitude and the latency of the P300 changed in a dose-dependent manner with nitrous oxide, as did minimum reaction time. At nitrous oxide concentrations which prevented recall of any events that occurred whilst breathing the gas, four subjects continued to respond to the tone by pressing the button. In three subjects, the P300 wave was still detectable with a nitrous oxide concentration at which the task was no longer performed. These results show that there is retention of the ability to perform a reaction time task when there is a complete loss of recall of the task. There may be some recognition of an auditory stimulus, as manifest by a P300 wave, albeit reduced greatly in amplitude, in the absence of a motor response to it. The P300, therefore, merits investigation as a tool for studying conscious awareness under anaesthesia.

Anesthesia Recovery Period↗
PubMed1991

Patterns of oxygenation after thoracotomy.

We have studied patterns of oxygen saturation (SpO2) before and after thoracotomy in 20 patients monitored nightly from the preoperative night to the fourth postoperative night. After operation, 10 patients received paravertebral bupivacaine (PVB) infusion and 10 received paravertebral saline (PVS) infusion. Papaveretum was given as required. Before operation the SpO2 profiles formed two groups: stable with SpO2 greater than 94% and stable with a median SpO2 less than 94% (hypoxaemia). During the first night after operation SpO2 profiles formed four groups: stable, not hypoxaemic (2/20); stable, hypoxaemic but improving (8/20); stable and constant hypoxaemia (5/20); unstable, hypoxaemic and deteriorating (5/20). Eleven patients remained hypoxaemic as late as the fourth night after operation. All patients who were hypoxaemic before operation were hypoxaemic after operation. Postoperative hypoxaemia was predicted in only 50% of cases. Papaveretum requirement was reduced in the PVB group, but regional analgesia did not affect the proportion of patients showing each SpO2 profile. Papaveretum caused a decrease in SpO2 in both analgesic groups.

Adult↗
PubMed1991

Driving and arthritis.

In a 3-year period, 94 patients with driving difficulties due to a variety of musculoskeletal disorders were assessed by the occupational therapy department of a rheumatology unit. The individual's ability to carry out each part of the driving process was recorded and the patients were classified into six broad categories. While some parts of the driving process often proved difficult, patterns of disability were found with different musculoskeletal disorders. Almost all of these difficulties could be overcome by simple modifications to vehicle or driving technique. Only one severely disabled individual required referral to a specialized mobility unit, while two individuals were found to be unsafe. Thus, almost all arthritic individuals are able to continue driving with the help of simple modifications. By providing an unsophisticated driving assessment service, a rheumatology unit can enable patients to continue driving and so maintain independence.

Arthritis↗
PubMed1991

Methylamine metabolism in Hansenula polymorpha: an in vivo 13C and 31P nuclear magnetic resonance study.

Methylamine uptake, oxidation, and assimilation were studied in Hansenula polymorpha, a methylotrophic yeast. The constitutive ammonia transport system was shown to be effective at accumulating methylamine within cells cultured with methylamine or ammonia as a nitrogen source. [13C]methylamine oxidation rates were measured in vivo in methylamine-adapted cells by 13C nuclear magnetic resonance and were found to be lower than its uptake rate into the cells. The 13C label of methylamine was found exclusively in trehalose and glycerol, and [13C]formaldehyde was also extensively assimilated, indicating the presence of an assimilation pathway for the methylamine carbon. In vivo 31P nuclear magnetic resonance analysis showed major differences in the endogenous polyphosphate levels and mean chain length during adaptation of the cells from ammonia to methylamine, indicating that methylamine accumulated in the vacuole in the same manner as basic amino acids and purines. [13C]glucose metabolism was drastically altered during adaptation of the cells from ammonia to methylamine as a nitrogen source. The total rate of glucose utilization and the rate of ethanol production fell. Direct trehalose synthesis from glucose increased, indicating a switch from carbon utilization for growth to that for storage. The rate of methylamine oxidation was sufficient to support a much higher flow of carbon into central biosynthetic pathways. These results suggest that this reduction in biosynthetic carbon flow, rather than nitrogen availability, was the main factor responsible for reducing the growth rate of the yeast when ammonia was replaced by methylamine as the nitrogen source.

Ammonia↗
PubMed1991

Direct detection of free radical generation in an in vivo model of acute lung injury.

Electron spin resonance (ESR) spectroscopy has been used to provide direct evidence that free radical production occurs in an in vivo model of acute lung injury. Two experimental groups of rabbits were given the spin trap alpha-phenyl N-tert.-butyl nitrone (PBN), together with endotoxin in the test group, and saline in the control group. Both groups were subsequently briefly ventilated with air containing cigarette smoke. Plasma samples from the endotoxin pretreated group showed a sudden burst of radical formation, detected as PBN spin adduct, which peaked in the first ten minutes after smoke exposure. No signals were detected in the control group. Permeability of the alveolar capillary barrier of the lung, measured by the clearance of 99mTc-DTPA, demonstrated significantly greater damage following smoke in the endotoxin primed animals than in the controls. Temporal studies suggest that this increase in permeability occurred after a burst of radical production. These studies provide supportive evidence for the hypothesis that endotoxin promotes the accumulation of a population of primed white cells within the lung, which when triggered by cigarette smoke, are able to generate a burst of free radicals which produce tissue damage and acute lung injury.

Animals↗
PubMed1991

Ulnar tunnel syndrome.

The ulnar tunnel syndrome is a relatively uncommon condition resulting from compression of the ulnar nerve as it passes through the loge de Guyon, or ulnar tunnel, in the wrist. The syndrome may cause weakness and atrophy of the intrinsic hand muscles and loss of sensation in the ulnar nerve distribution of the hand. The most common cause of ulnar tunnel syndrome is chronic occupational trauma, either from pressure exerted over the hypothenar eminence by a tool or from the use of the heel of the hand as a hammer. Nonoccupational etiologies include congenital, inflammatory, neoplastic, vascular, metabolic, degenerative and traumatic disorders. Diagnosis often requires neurophysiologic evaluation, in addition to a careful history and physical examination. Conservative treatment aimed at protecting the ulnar tunnel from trauma frequently is effective. Occasionally, surgical decompression of the ulnar tunnel is required.

Clinical Protocols↗
PubMed1990

Measurements of pulmonary mechanics prior to the elective extubation of neonates.

We measured total respiratory system compliance (CRS) and resistance (RRS) by the passive expiratory flow technique prior to the elective extubation of 61 neonates with a history of respiratory distress syndrome. Successful trials of extubation were characterized by a higher mean value of CRS when compared to trials that led to reintubation (1.52 vs. 1.10 mL/cm H2O, P = 0.004). Low values of CRS (0.9 mL/cm H2O or less) were invariably associated with extubation failure, whereas high values of CRS (1.3 mL/cm H2O or greater) were associated with extubation success in 94% of patients. A higher mean value of RRS was recorded in the group of infants who failed extubation when compared to those who were successful (0.22 vs. 0.17 cm H2O/mL/s, P = 0.042). We propose that measurements of pulmonary mechanics, particularly CRS, may be useful in identifying infants who will be at risk for extubation failure.

Airway Resistance↗
PubMed1990

Heterogeneity in hormone receptor status in primary and metastatic endometrial cancer.

The rationale for endocrine therapy in patients with advanced endometrial carcinoma may be based on the presence of estrogen or progesterone receptors in the primary tumor. A study was designed to evaluate tumor cell heterogeneity of steroid hormone receptors in the primary and metastatic sites in endometrial cancer. Primary endometrial cancer tissue samples from 10 patients and 16 metastatic tumor sites were simultaneously analyzed for estrogen and progesterone receptors, using a radioligand biochemical assay. The primary tumor was estrogen receptor (ER) and progesterone receptor (PR) positive in 70 and 60% of the patients, respectively. The metastatic sites were ER positive in 63% and PR positive in 25%. The primary tumor tissue and the metastatic disease showed an identical ER and PR status in only 25 and 19%, respectively. Four patients had multiple metastatic sites analyzed. In two of four patients the PR values, and in three of four patients the ER values, in these metastatic sites were discordant. These data support the concept of tumor cell heterogeneity for steroid hormone receptors in endometrial cancer. To optimize treatment planning, it may be important to biopsy primary, metastatic, and recurrent tumor sites for individual analysis of receptor activity.

Adenocarcinoma↗
PubMed1990

Virulence of papillary endometrial carcinoma.

While uterine papillary serous carcinoma (UPSC) has been well described as a virulent subtype of endometrial adenocarcinoma (AC), with behavior similar to that of papillary serous ovarian carcinoma, the papillary endometrial (PE) variant has not been well characterized. We studied 117 patients with endometrial carcinoma identified by our tumor registry, pathology files, and practice records from March 1981 to February 1989: 76 with AC, 26 with PE, and 15 with UPSC. Age and demographic data were similar for all three groups. All of the AC patients, 84% of PE patients, and 87% of UPSC patients had early-stage disease by clinical exam; however, 10% of AC patients, 23% of PE patients, and 87% of UPSC patients had extrauterine disease at surgery (P less than 0.05). Deep myometrial invasion occurred in 29% of AC patients, 36% of PE patients, and 60% of UPSC patients (P less than 0.05). Comparative analysis of the PE and UPSC groups revealed more marked nuclear anaplasia (P less than 0.05) and more frequent vascular space involvement (nonsignificant) in the UPSC group. At 3 years, 75% of the AC group was alive without disease. In contrast, the median progression-free interval for the PE group was 33 months, and for the UPSC group, 9 months (P less than 0.05). These data suggest a transition of increasing virulence corresponding with increasing papillary features, from AC to PE to UPSC. The papillary feature may be a new, significant risk factor in endometrial carcinoma.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1990

Ovarian conservation in placental site trophoblastic tumor.

While isolated reports on the management and natural biology of placental site trophoblastic tumor (PSTT) continue to accumulate, little attention has been given to ovarian conservation in the surgical management of this disease. Review of the literature reveals ovarian involvement by this tumor to be infrequent and, when present, grossly apparent at laparotomy. In the reported cases, grossly normal ovaries did not contain pathologic evidence of tumor. This study reports two additional cases in which at least one ovary was preserved. Until more reliable criteria are available for predicting which cases of PSTT will pursue a malignant course, the option of ovarian conservation should be available to young patients requiring abdominal surgery, if the disease remains confined to the uterus.

Adult↗