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Biomedical subjects

R J Lewis

Publications and source records attributed to R J Lewis.

At least 19 recordsLinked to original sources
PubMed1992

One hundred consecutive patients undergoing video-assisted thoracic operations.

Video-assisted thoracic surgery is a new modality that allows visualization of and access to the intrathoracic organs without making a thoracotomy incision. One hundred consecutive patients underwent 113 thoracic procedures using this technique. Eight wedge resections for metastatic lesions, 6 pericardial windows, 1 bronchogenic cystectomy, 4 explorations of the aortopulmonary window, 1 decortication, 5 pleural scleroses, 8 bullous ablations, 25 lung biopsies, 19 wedge resections for carcinoma, 9 explorations of the thorax, 3 lobectomies, 1 esophageal cystectomy, 14 wedge resections for benign lesions, 4 pleurectomies, 1 excision of a neurogenic tumor, 3 mediastinal explorations, and 1 imaged axillary dissection were performed. There was no mortality. Ten patients had complications from which they recovered completely. Patients undergoing video-assisted thoracic operations seem to have reduced postoperative pain, shorter hospitalization, and quicker recovery times. Currently, this new modality appears to have beneficial value for patients; however, only further experience will determine its true merits.

Adolescent↗
PubMed1992

Imaged thoracic lobectomy: should it be done?

Imaged thoracic surgery is a new modality that is rapidly gaining acceptance from thoracic surgeons. Procedures that traditionally required a thoracotomy can now be done successfully using this technique in some patients. Three patients with primary carcinoma of the lung have undergone lobectomy using imaged thoracic surgery.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed1992

Imaged thoracoscopic surgery: a new thoracic technique for resection of mediastinal cysts.

Previously, intrathoracic organs have been approached by either thoracotomy or thoracoscopy. A technique, imaged thoracoscopic surgery, using video optics and projection of images on a screen provides another option for the thoracic surgeon. Two patients with mediastinal cysts, one bronchogenic and one esophageal, underwent surgical removal using imaged thoracoscopic surgery. Postoperative pain was markedly reduced, hospitalization shortened, and recovery accelerated. Numerous complex surgical procedures can be performed using imaged thoracoscopic surgery.

Adult↗
PubMed1992

Action of ciguatoxin on human atrial trabeculae.

This report describes the action of ciguatoxin-1, the major ciguatoxin present in fishes that cause ciguatera, on the contractile activity of human cardiac musculature. Ciguatoxin-1 caused a large, sustained and concentration-dependent positive inotropy in human atrial trabeculae that were obtained during coronary artery bypass surgery from otherwise healthy hearts. Atenolol (a beta 1-adrenoceptor selective antagonist without local anaesthetic-type activity) or low concentrations of tetrodotoxin abolished the positive inotropy caused by ciguatoxin-1, indicating that ciguatoxin-1 stimulated neural elements present in this tissue to release noradrenaline. The positive inotropic action of ciguatoxin-1 did not stem from a significant direct action on myocardial voltage-dependent sodium channels, nor did it stem from significant alpha 1- or beta 2-adrenoreceptor stimulation. Ciguatoxin-1 caused positive inotropy in preparations stimulated at between 0.02 and 2.0 Hz. Mannitol, currently the treatment of choice for ciguatera, did not significantly reverse the positive inotropy induced by ciguatoxin-1 in human atrial trabeculae.

Adult↗
PubMed1992

Multiple ciguatoxins in the flesh of fish.

Most cases of ciguatera (fish poisoning) result from consumption of the flesh of fishes contaminated with ciguatoxin(s); however, the relatively low toxicity of ciguateric fish flesh has hindered attempts to identify these ciguatoxin(s). Utilising high performance liquid chromatography, mass spectroscopy and mouse bioassay signs we have determined that ciguatoxin-1 (MH+ m/z = 1112), ciguatoxin-2 and ciguatoxin-3 are the major ciguatoxins present in the flesh of ciguateric fish. Ciguatoxin-1, -2 and -3 were present in yields of 0.19, 0.09 and 0.02 microgram/kg flesh, respectively, in Scomberomorus commersoni; 0.08, 0.09 and 0.07 microgram/kg flesh, respectively, in Plectropomus spp. and; 0.67, 0.61 and 0.06 microgram/kg flesh, respectively, in Pomadasys maculatus. Two minor toxins, which may be further oxidised analogues of ciguatoxin-1 and ciguatoxin-2, were also identified. The presence of multiple ciguatoxins in fish flesh has important consequences for the detection of ciguateric fish and may be a contributing factor to the observed variability in the symptoms of ciguatera.

Animals↗
PubMed1992

Ciguatoxins are potent ichthyotoxins.

The ciguatoxins are lipid soluble polyether compounds which have structural and biochemical features in common with the brevetoxins. Pure ciguatoxin-1, ciguatoxin-2 or brevetoxin-2 added to water containing Gambusia affinis induced similar signs, including pronounced opercular movement and uncoordinated swimming preceding death. The estimated LD50s (48 hr) to G. affinis for ciguatoxin-1, ciguatoxin-2 and brevetoxin-2 were 0.5, 2.1 and 10 nmoles/litre, respectively, indicating that the ciguatoxins were up to 20-fold more potent than the brevetoxins in this assay. Previous studies reveal that the ciguatoxins are more potent than the brevetoxins in both i.p. lethality to mammals and affinity for voltage-dependent sodium channels. However, relative to their affinity for the voltage-dependent sodium channel, brevetoxin-2 is 4-fold more potent to fish than the ciguatoxins, whereas the ciguatoxins are up to 11-fold more potent to mice than brevetoxin-2. This study found that only 3.4% of administered ciguatoxin-1 was accumulated by G. affinis. Ciguatoxin-1 may be biotransformed by G. affinis. The lethal effects of the ciguatoxins in fish may impose an upper limit on the levels of ciguatoxin carried by fish, which could contribute to the low incidence of human fatality associated with ciguatera.

Animals↗
PubMed1992

Treatment of prolonged ventricular fibrillation. Immediate countershock versus high-dose epinephrine and CPR preceding countershock.

BACKGROUND: Early countershock of ventricular fibrillation has been shown to improve immediate and long-term outcome of cardiac arrest. However, a number of investigations in the laboratory and in the clinical population indicate that immediate countershock of prolonged ventricular fibrillation most commonly is followed by asystole or a nonperfusing spontaneous cardiac rhythm, neither of which rarely respond to current therapy. The use of epinephrine in doses greater than those currently recommended has recently been shown to improve both cerebral and myocardial perfusion during cardiopulmonary resuscitation (CPR). The purpose of this study was to compare cardiac resuscitation outcome between immediate countershock of prolonged ventricular fibrillation with high-dose epinephrine therapy and conventional CPR before countershock of prolonged ventricular fibrillation in a canine model. METHODS AND RESULTS: After sedation, intubation, induction of anesthesia, and instrumentation, ventricular fibrillation was electrically induced in 28 dogs. After 7.5 minutes of ventricular fibrillation, animals were randomly allocated to two treatment groups: group 1, immediate countershock followed by recommended advanced cardiac life support (ACLS) interventions, or group 2, 0.08 mg/kg epinephrine and manual closed-chest CPR before countershock and ACLS. In both groups, ACLS was continued until a spontaneous perfusing rhythm was restored or for 20 minutes (total arrest time, 27.5 minutes). A spontaneous perfusing rhythm was restored in three of 14 group 1 animals and in nine of 14 group 2 animals (p = 0.014 by sequential analysis method of Whitehead). Coronary perfusion pressure (aortic minus right atrial pressure during CPR diastole) before countershock was significantly greater in group 2 (21 +/- 7 mm Hg) when compared with mean circulatory pressure in group 1 (9 +/- 8, p less than 0.01). CONCLUSIONS: The findings of this study suggest that a brief period of myocardial perfusion before countershock improves cardiac resuscitation outcome from prolonged ventricular fibrillation.

Animals↗
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↗