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Biomedical subjects

R J Lewis

Publications and source records attributed to R J Lewis.

At least 217 records · Page 12Linked to original sources
PubMed1992

Imaged thoracoscopic lung biopsy.

Imaged thoracoscopic surgery is a technique utilized to operate on the intrathoracic organs without making a formal thoracotomy incision. Eleven patients underwent lung biopsy with this procedure and each had markedly reduced postoperative pain. Each patient resumed preoperative activity levels within one week of discharge from the hospital. Besides thoracotomy and thoracoscopy, imaged thoracoscopic surgery provides another option for approaching the intrathoracic organs.

Adult↗
PubMed1992

Are inaccuracies in self-reported weight motivated distortions?

The accuracy of self-reported weight and the motivation of distorted reporting were studied among 169 female and 101 male college students. Although subjects were moderately accurate in their weight estimates, errors reflected women's underreporting, men's overreporting, and heavier persons' underreporting. With body mass controlled, most motivational variables had little explanatory value.

Adult↗
PubMed1992

Socioeconomic impacts and management ciguatera in the Pacific.

The inshore fisheries resource is important to the health and culture of many of the inhabitants of Pacific Island countries (PIC). Ciguateric fishes (mainly demersal reef fishes) cause a range of distressing and often debilitating gastrointestinal neurological and cardiovascular disturbances. Consequently, ciguatera limits the utilisation of this otherwise over-exploited resource. For many victims, the symptoms suffered during the chronic phase of ciguatera (lasting weeks, months and occasionally years) are exacerbated upon consumption of certain foods, particularly non-toxic fishes. After each outbreak, victims and members of their social-network experience a transient increase in perception of the risk of eating reef fish. The impact of ciguatera is greatest in atoll island countries where fish is the primary source of protein (it also has a major impact and to facilitate the management of ciguatera in PIC, regular information is required that quantifies: (i) the true incidence of ciguatera; (ii) the extent and way in which different communities avoid ciguatera; and (iii) the adverse impact ciguatera has on health, the workforce, trade and tourism. Over the last 15 years (based on SPEHIS data to 1990), some countries recorded a decrease in the ciguatera problem (New Caledonia, Marshall Is.), other countries an increase (Kirbati, Tuvalu, French Polynesia), while still other countries recorded an increase followed by a decrease in ciguatera (Tokelau, American Samoa, Western Samoa, Fiji and Vanuatu). There may also be seasonal trends in the incidence of ciguatera in some countries e.g. Fiji. Management options presently implementable in PIC include: (i) treatment with i.v. mannitol; (ii) provision of timely advise on the location and status of ciguatera "hot spots" in each country that would allow affected communities to react objectively to the risk posed by ciguatera; and (iii) modification of human behaviour and aspirations to reduce the impact of increasing population, pollution and development (e.g. causeways) pressures.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Liquid chromatographic mass spectrometric methods for the determination of marine polyether toxins.

Experiments with novel nitrogenous coumarin-based reagents yielded moderately fluorescent derivatives of brevetoxin-3 and ciguatoxin-1. The diethylaminocoumarin-carbamic acid esters of brevetoxin-3 were resolved by high performance liquid chromatography into two derivative peaks that correspond to substitutions at the C-37 and C-41 hydroxyls. The derivatives produced intense molecular ions under fast atom bombardment ionization conditions, confirming derivative identity. Ciguatoxin-1 was also successfully derivatized, resolved, and identified by HPLC-fluorometry with an estimated lower limit of detection of 0.5 to 1.0 ng.

Chromatography, High Pressure Liquid↗
PubMed1992

Video-assisted thoracic surgical resection of malignant lung tumors.

Forty patients with malignant pulmonary disease underwent evaluation, staging, and a biopsy or resection by means of video-assisted thoracic surgery. There were 20 men and 20 women whose ages ranged from 27 to 82 years. Eight patients had a wedge resection for metastatic carcinoma, three a lobectomy for primary carcinoma, six exploration of the thorax, five biopsy of the aortopulmonary window, and eighteen a sublobar resection for primary carcinoma of the lung. There was no mortality. Three patients had air leaks that lasted an average of 8 days. Video-assisted thoracic surgery seems to be useful for more precise staging of carcinoma of the lung, and, in some patients, resectional operations can be performed.

Adult↗
PubMed1992

Tracheostomies. Indications, timing, and complications.

Although tracheostomy is performed most commonly for ventilator-dependent patients who have had prolonged periods of endotracheal intubation, it is still necessary and used for other airway problems. Patient management as it relates to indications, timing, various surgical techniques, types of tubes, and complications of tracheostomy and other forms of airway maintenance and control are discussed and evaluated.

Airway Obstruction↗
PubMed1992

Inferred characteristics of successful suicides as function of gender and context.

This paper examines college students' attributions about suicide as a function of gender and context (athletic vs. relationship failure). Results indicated that male athletes who suicided were considered more emotionally well-adjusted compared to males who suicided because of a relationship failure and all females. Male and female athletes who suicided were seen as more competent and less distressed compared to those who suffered a failed relationship. Females were also seen as more distressed compared to males. These results are discussed in terms of a positive bias toward athletes in our society as well as gender stereotypes. Implications of these findings as well as methodological limitations are discussed.

Adolescent↗
PubMed1991

Strain dependent production of ciguatoxin precursors (gambiertoxins) by Gambierdiscus toxicus (Dinophyceae) in culture.

Thirteen strains of Gambierdiscus toxicus isolated from Queensland (Australia), Hawaii, French Polynesia and the Virgin Islands were mass cultured and extracted for ciguatoxin. A biodetrital sample containing wild G. toxicus collected from the Republic of Kiribati was also extracted for ciguatoxin. Ciguatoxin, as characterized from moray eels, was not detected in any of the strains examined. Two Queensland strains and the wild G. toxicus produced putative ciguatoxin precursors named gambiertoxins. These gambiertoxins were less polar than ciguatoxin but produced bioassay signs in mice and in-vitro responses in isolated guinea pig atria and vas deferens which were similar (but not identical) to those produced by ciguatoxin. The gambiertoxins from cultured cells were also shown to competitively inhibit the binding of [3H]brevetoxin-3 to rat brain membranes in a dose-dependent manner. The gambiertoxins were more potent than ciguatoxin (on a per mouse unit basis) at stimulating neural elements of guinea pig atria. The two culture strains produced similar amounts of gambiertoxins, even when grown in nutrient media made from different seawater containing different concentrations of nutrients. Changes in nutrient media did not induce the other strains of G. toxicus to produce gambiertoxins. The production of these ciguatoxin precursors appears to be limited to only certain genetic strains of G. toxicus, with the majority of strains not producing these toxins. We propose that ciguatera occurs when blooms of G. toxicus strains genetically capable of producing these ciguatoxin precursors enter the marine food chain. These toxins could then become oxidatively metabolized in fishes to the major polar ciguatoxin. Wild cells produced approximately 100-fold greater quantities of gambiertoxins per cell than did the two culture strains indicating that there is considerable potential for increased production of these ciguatoxin precursors from G. toxicus in culture.

Animals↗
PubMed1991

Purification and characterization of ciguatoxins from moray eel (Lycodontis javanicus, Muraenidae).

Viscera (48.3 kg) from moray eels (Lycodontis javanicus) collected in a ciguatera endemic area were extracted and the ciguatoxins characterized. Three major ciguatoxins, CTX-1, CTX-2 and CTX-3, were isolated and purified to homogeneity on reverse phase high performance liquid chromatography. Several minor toxins were also detected. CTX-1 (490 micrograms) was comparable by both 1H nuclear magnetic resonance (1H NMR) and mass spectroscopy (MH+ m/z = 1111) to ciguatoxin isolated previously from moray eels. CTX-2 (280 micrograms) and CTX-3 (100 micrograms) were less polar ciguatoxins not previously characterized. CTX-2 and CTX-3 differed from CTX-1 by 16 mass units, suggesting that they were less oxygenated analogues. 1H NMR revealed that the hydroxyl at C54 in CTX-1 was absent in CTX-2 and CTX-3. An additional change in the chemistry of CTX-2 compared to CTX-1 and CTX-3 was also suggested on the basis of 1H NMR, indicating that CTX-2 may arise from a different precursor to CTX-1. CTX-3 is likely to be an intermediate in the oxidation of a gambiertoxin (sodium channel toxins from Gambierdiscus toxicus) to CTX-1. The i.p. LD50 values for CTX-1, CTX-2 and CTX-3 were 0.25, 2.3 and 0.9 micrograms/kg, respectively. The signs induced in mice by the ciguatoxins were similar, except that CTX-2 and CTX-3 induced hind-limb paralysis that was absent with CTX-1. Each ciguatoxin was potent orally. CTX-1, CTX-2 and CTX-3 competitively inhibited the binding of [3H]brevetoxin-3 to voltage-dependent sodium channels with relative potencies qualitatively (but not quantitatively) comparable to mouse lethality. This study reveals that the relatively small chemical differences between CTX-1, CTX-2 and CTX-3 give rise to significant structure-activity and pharmacokinetic differences.

Animals↗
PubMed1991

Dioxin contamination and growth and development in great blue heron embryos.

A great blue heron colony located near a pulp mill in British Columbia failed to fledge young in 1987, with a concurrent sharp increase in polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) levels in their eggs. In 1988 we tested the hypothesis that the PCDD and PCDF contamination caused reproductive failure by increasing mortality of the heron embryos in ovo. Pairs of great blue heron eggs were collected from three British Columbia colonies with low, intermediate, and high levels of dioxin contamination: Nicomekl, Vancouver, and Crofton, respectively. One egg of each pair was incubated under laboratory conditions at the University of British Columbia (UBC) while the other egg was analyzed for PCDDs and PCDFs. All incubated eggs were fertile. All eggs from the Nicomekl colony hatched, while 13 of 14 eggs from Vancouver and 12 of 13 eggs from Crofton hatched. Subcutaneous edema was observed in 4 of 12 chicks from Crofton and 2 of 13 chicks from Vancouver. No edema was seen in the chicks from Nicomekl. There was a small, but significant, negative regression of plasma calcium concentration, yolk-free body weight, tibia length, wet, dry, and ash weight, beak length, and kidney and stomach weight of the hatched chicks on the tetrachlorodibenzo-p-dioxin (TCDD) level of the paired eggs. Fewer down follicles were present on the heads of TCDD-contaminated chicks. Hence while dioxins did not cause mortality of the heron embryos in ovo, the depression of growth and the presence of edema are suggestive that dioxins at the levels found in the environment have an adverse effect on the development of great blue heron embryos.

Animals↗
PubMed1991

MMPI correlates of Exner's Egocentricity Index in an adolescent psychiatric population.

This research examined the relationship between Exner's Egocentricity Index (EI) and Minnesota Multiphasic Personality Inventory (MMPI) Scales 2, 4, and 9 in an adolescent psychiatric population. Subjects with a low EI had significantly higher MMPI Depression (D) scale elevations compared to those with a high EI. Furthermore, of the adolescents who had Scale 2 scores in the clinical range, 68% also had an EI in the bottom half of the distribution. There was no relationship between the EI and MMPI scales 4 and 9. These findings are discussed in light of the generally poor correlations between MMPI and Rorschach variables.

Adult↗
PubMed1991

Special report: video-endoscopic thoracic surgery.

Since the advent of video optics, with the projection of images on a screen, a new option has been added to the armamentarium of the thoracic surgeon: video-endoscopic thoracic surgery. A case report of a 33-year-old woman demonstrates the successful new procedure.

Adult↗
PubMed1991

A safe method for sedating and monitoring patients for upper and lower gastrointestinal endoscopy.

Although the incidence of significant complications occurring during endoscopic procedures that require sedation are low, it has been demonstrated that they are usually related to cardiovascular system dysfunction. Such complications are a manifestation of cardiac hypoxia and are a function of the arterial oxygen desaturation. A practical method of monitoring such patients includes continuous oxygen saturation measurements and EKG monitoring. From October, 1987 to July, 1989, a total of 730 endoscopic examinations were performed using a combination of meperidine and midazolam as an intravenous (IV) bolus for sedation. Supplemental nasal oxygen was routinely given at 2 L per minute and real-time monitoring was performed with electrocardiograph and continuous pulse oximeter. There were no deaths and only four untoward events related to medication that altered the course of the examination. Transient hypoxemia that responds to gentle stimulation and bradycardia resolving with cessation of endoscope advancement are viewed as physiologic responses and not complications. All occurrences were immediately identified and corrected appropriately, and no morbidity resulted. With proper monitoring of oxygen saturation, pulse, and cardiac rhythm in a patient with nasal oxygen, IV bolus administration of meperidine and midazolam is a safe and adequate sedation even in the elderly and debilitated patient.

Procedural Sedation↗
PubMed1990

Toxicity of Australian and French polynesian strains of Gambierdiscus toxicus (Dinophyceae) grown in culture: characterization of a new type of maitotoxin.

Gambierdiscus toxicus strains isolated from Australia and French Polynesia were grown in modified f2 and f10 nutrient media and the cells extracted for ciguatoxin and maitotoxin. The high nutrient enrichment of f2 media induced aberrant cell morphology in both strains whereas the majority of cells grown in f10 media had the typical lenticular shape of wild G. toxicus cells. The Australian strain grew faster and produced greater cell densities than the French Polynesian strain. Different chromatographic types of maitotoxin were extracted from the two G. toxicus strains and purified to homogeneity using reverse-phase high-performance liquid chromatography. The toxins elicited similar bioassay signs in mice, but produced different death-time vs dose relationships. The maitotoxin extracted from the Australian strain eluted later on both straight-phase and reverse-phase chromatographic columns than did the maitotoxin extracted from the French Polynesian strain. The maitotoxin extracted from the French Polynesian strain was chromatographically identical to reference maitotoxin. For each strain no differences were found between maitotoxins extracted from cells grown in f2 or f10 media. Only one toxin was produced by each strain of G. toxicus. Ciguatoxin was not produced by either strain.

Animals↗