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Biomedical subjects

C Cameron

Publications and source records attributed to C Cameron.

At least 55 records · Page 3Linked to original sources
PubMed1991

Absence of allelic loss on chromosome 5q by RFLP analysis in preleukemia.

Thirty-eight patients with various forms of myelodysplastic syndrome (MDS) were studied for the loss of restriction fragment length polymorphism (RFLP) heterozygosity on chromosome 5q as inferential support for the presence of a growth regulatory locus in this area of the genome. Conventional chromosomal analysis was performed in addition to RFLP studies of constitutive and granulocyte DNA using five polymorphisms from chromosome 5. Allelic loss in granulocyte DNA was identified in only one patient in whom monosomy 5 had already been defined cytogenetically. These results suggest that DNA sequence loss from chromosome 5q other than that observed cytogenetically is a rare event in MDS. Thus the potential involvement of a growth regulatory gene(s), from this area of the genome, in the leukemogenic process most likely involves a more subtle genetic change.

Alleles↗
PubMed1991

Extended continuous infusion low-dose recombinant interleukin-2 in advanced cancer: prolonged immunomodulation without significant toxicity.

In previous clinical trials, recombinant interleukin-2 (rIL-2) has been infused at high doses over short periods of time to generate lymphokine-activated killer (LAK) cells in vivo. These trials have been limited by severe toxicities, and the immunologic effects of rIL-2 have been transient. The present study was designed to assess the toxicity and immunologic effects of prolonged administration of low doses of rIL-2. In this phase I study, patients with advanced cancer were scheduled to receive intravenous (IV) infusion of rIL-2 without interruption for 3 months in an outpatient setting. Twenty-one patients received rIL-2 at doses ranging from 0.5 x 10(5) to 6.0 x 10(5) U/m2/d. Treatment was extremely well tolerated, and no patient experienced grade 3 or grade 4 toxicity. The lowest dose level (0.5 x 10(5) U/m2/d) did not have demonstrable immunologic activity. At doses of 1.5 x 10(5) and 4.5 x 10(5) U/m2/d, rIL-2 infusion resulted in the specific expansion of natural-killer (NK) cells (sixfold and ninefold increases, respectively, at these two dose levels) without any changes in B cells, T cells, neutrophils, or monocytes. Grade 2 toxicity was observed at the dose of 6.0 x 10(5) U/m2/d, as three patients required interruption of therapy and two patients who completed therapy developed transient hypothyroidism. In patients with increased NK cells, enhancement of non-major histocompatibility complex (MHC)-restricted cytotoxicity and increased generation of LAK cells in vitro were also demonstrated. Therapy with low-dose rIL-2 can be given safely in an uninterrupted fashion for prolonged periods of time in an outpatient setting. This results in selective expansion of NK cells in vivo with minimal toxicity. Further investigation of this schedule for immunomodulation in vivo should be pursued in phase II studies of both malignant and immunodeficient disease states.

Adult↗
PubMed1990

The ethnographic approach: characteristics and uses in gerontological nursing.

Ethnography presents the researcher with a methodology for studying meaning carefully; a process for going beyond what is seen or heard to infer what people know by careful listening and observation of behavior, environment, and context. Ethnography describes and explains both regularities and variations in human behavior; the method accommodates the careful description of irregularities in a complex society that may not be or cannot be explained in traditional theory. Ethnography can strengthen traditional methods of theory development generally and gerontological nursing specifically. The descriptive value of ethnography as a qualitative research method to generate concepts, theories, and hypotheses in substantive knowledge areas within gerontological nursing is recognized.

Aged↗
PubMed1988

Transvenous closure of acquired ventricular septal defects.

Post infarction ventricular septal defect is an uncommon but frequently fatal complication of myocardial infarction. In this report a method for creating experimental ventricular septal defects is described and the use of a transvenous balloon catheter for closure of septal perforations reported. Ventricular septal defects were created with a specially designed punch in 25 adult mongrel dogs. Severe hemodynamic compromise occurred immediately following septal perforation in 15 animals which failed to permit sufficient time to pass the transvenous balloon catheter. However, passage of the catheter and occlusion of the ventricular septal defect was accomplished in the remaining 10 animals. Perforation of the ventricular septum resulted in a marked left-to-right shunt as indicated by changes in interventricular pressure and a step-up in the right ventricular PO2 saturations. Passage of the double balloon catheter and inflation of the balloons prevented left-to-right shunting and completely occluded the ventricular septal defect. Further refinements of this experimental catheter may result in the development of a balloon catheter that may be used to stabilize patients after spontaneous ventricular perforation, thus allowing them to recover from their infarction and undergo delayed repair of the ventricular septal defect.

Animals↗
PubMed1988

Effect of various low-dose concentrations of verapamil cardioplegia on small-amplitude electrical activity during cardioplegic arrest.

The effect of verapamil cardioplegia on atrioventricular conduction was examined in 19 dogs. During 90 minutes of ischemic arrest, five dogs received multidose potassium cardioplegia, containing 1.2 mg/L of verapamil (group 1), five received potassium cardioplegia containing 600 micrograms/L of verapamil (group 2) and nine animals received cardioplegia containing 300 micrograms/L of verapamil (group 3). Atrioventricular conduction was measured in all groups before bypass, after 90 minutes of ischemia and after 45 minutes of reperfusion. Specially designed plunge electrodes were used to monitor the electrical status of the heart during arrest in group 3 and, in addition, left ventricular function and concentration of high-energy phosphates were determined before and after ischemic arrest. Conduction was prolonged in four group 1 dogs and in two group 2. Atrioventricular conduction was measured in six group 3 dogs; five had prolonged conduction and one experienced second-degree heart block. Small-amplitude electrical potentials were recorded from the myocardium in two of nine dogs in group 3. Persistent electrical activity was associated with continued use of high-energy phosphates and resulted in decreased left ventricular function after 90 minutes of ischemic arrest. Our data indicate that small doses of verapamil will delay atrioventricular conduction and will not prevent small-amplitude electrical activity.

Animals↗
PubMed1987

Prevention of myocardial electrical activity during ischemic arrest with verapamil cardioplegia.

The effect of potassium cardioplegia and potassium cardioplegia containing verapamil hydrochloride on myocardial preservation and electrical activity during prolonged aortic occlusion was examined in 40 adult mongrel dogs. Twenty-four animals (Group 1) received potassium cardioplegia, and 16 animals (Group 2) received potassium verapamil cardioplegia. Potassium or potassium verapamil cardioplegia, 10 ml per kilogram of body weight, was administered after application of the aortic cross-clamp and at 30-minute intervals during the 90-minute arrest. Myocardial temperature was maintained within a range of 8 degrees to 10 degrees C with topical ice saline solution, and electrical activity was monitored with specially designed plunge electrodes. Plunge electrode activity was recorded from the myocardium during arrest in 16 of the 24 animals in Group 1; no electrical activity was present in the animals in Group 2 (p less than .001). The addition of verapamil to potassium cardioplegia increased the tolerance of the myocardium to prolonged ischemia and resulted in less depletion of high-energy phosphate stores and better preservation of mitochondrial ultrastructure and left ventricular function. These data suggest that verapamil augments the preservation provided by potassium cardioplegia by initiating and maintaining a more complete electrical arrest.

Animals↗
PubMed1986

Comparison of cod-liver oil and aspirin-dipyridamole for the prevention of intimal hyperplasia in autologous vein grafts.

The combination of aspirin and dipyridamole is currently used to prevent intimal hyperplasia and to improve long-term vein graft patency following myocardial revascularization. Preliminary studies indicate that cod-liver oil, rich in eicosapentaenoic acid, an unsaturated fatty acid, may also be effective in the prevention of intimal hyperplasia. Twenty-four mongrel dogs were used to compare the effectiveness of aspirin-dipyridamole and cod-liver oil on vein graft intimal hyperplasia following arterial bypass. Forty-eight segments of undistended autologous external jugular vein were interposed between bilaterally divided femoral arteries. All animals received a 2% cholesterol diet for 1 week before and 6 weeks after operation. Eight controls received the diet alone. Eight other animals received dipyridamole (2.5 mg per kilogram of body weight) two days before operation and dipyridamole (2.5 mg/kg) and aspirin (30 mg/kg) daily for 6 weeks after operation. Another 8 animals received cod-liver oil containing 1.8 gm of eicosapentaenoic acid daily 1 week before and for 6 weeks following operation. Serum cholesterol increased similarly in all groups; it rose from 4.5 +/- 0.2 mm/L to 8.3 +/- 0.8 mm/L in the controls, to 7.2 +/- 0.5 mm/L in the aspirin-dipyridamole group, and to 7.1 +/- 0.5 mm/L in the cod-liver oil group (p less than 0.01). Prothrombin time, partial thromoboplastin time, total platelet counts, and bleeding times were unchanged. Intimal hyperplasia was measured at 6 weeks with a Zeiss computerized microscope; 376 +/- 25 measurements were made from each graft. The intima increased from 4.5 +/- 0.2 to 83 +/- 10 micron in the control dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Effect of small-amplitude electrical activity on myocardial preservation in the cold potassium-arrested heart.

Recent reports indicate that small-amplitude electrical activity may be present in the cold potassium-arrested heart. Twenty-four mongrel dogs were placed on cardiopulmonary bypass and cooled to a rectal temperature of 26 degrees C. Myocardial preservation was provided with a combination of systemic hypothermia 26 degrees C. potassium (20 mEq/L) crystalloid cardioplegic solution (10 ml/kg) infused initially and every 30 minutes during 90 minutes of ischemic arrest, and topical hypothermia. Myocardial temperature was maintained between 8 degrees and 10 degrees C. Electrical activity and transmural myocardial temperature were monitored with specially designed plunge electrodes. Left ventricular stroke work index, cardiac index, and maximum rate of rise of left ventricular pressure were measured before bypass and 45 minutes after ischemic arrest. Biopsy specimens were taken before bypass and at 15 and 45 minutes after ischemic arrest. The specimens were used to measure adenosine triphosphate and to analyze electron microscopic ultrastructure. Small-amplitude electrical activity was present in 16 of 24 animals during cardioplegic arrest. Cardiac index decreased 18 ml/min/kg (not significant), left ventricular stroke work index fell by 0.28 +/- 0.1 gm-m/beat/kg (p less than 0.007), and maximum rate of rise of left ventricular pressure decreased 409 mm Hg/sec (p less than 0.01) in the eight animals without small-amplitude electrical activity. Adenosine triphosphate concentration was unchanged and electron microscopic ultrastructure was well preserved. In contrast, small-amplitude electrical activity (16 animals) resulted in a decrease in cardiac index of 67 ml/min/kg (p less than 0.001), a decrease in left ventricular stroke work index of 0.79 +/- 0.8 gm-m/beat/kg (p less than 0.001), and a fall in maximum rate of rise of left ventricular pressure of 775 mm Hg/sec (p less than 0.001). Adenosine triphosphate concentration decreased from 25 to 21 mumol/gm (p less than 0.04) and electron microscopic ultrastructure was poorly preserved (p less than 0.001). This study demonstrates that small-amplitude electrical activity in the cardioplegia-arrested heart at 10 degrees C impairs myocardial preservation.

Adenosine Triphosphate↗
PubMed1985

Cod-liver oil in the prevention of intimal hyperplasia in autogenous vein grafts used for arterial bypass.

Cod-liver oil, rich in eicosapentaenoic acid, an unsaturated fatty acid, was administered to 14 mongrel dogs to determine if this acid would prevent platelet-mediated intimal hyperplasia. Twenty-eight 1 cm segments of undistended jugular vein were interposed between bilaterally divided femoral arteries. Seven control animals were fed a 2% cholesterol diet 1 week before and for 6 weeks after the operation. A further seven animals received cod-liver oil capsules containing 1.8 gm of eicosapentaenoic acid daily 1 week before and for 6 weeks after autogenous vein implantation, in addition to the lipid-supplemented diet. Baseline serum cholesterol was 4.6 +/- 0.4 mmol/L. The rise in serum cholesterol was similar in the two groups and increased to 7.4 +/- 0.6 mmol/L (control group) and to 6.8 +/- 0.2 mmol/L (eicosapentaenoic acid group) (p less than 0.001). Prothrombin time, partial thromboplastin time, bleeding time, and platelet counts were unchanged in the two groups. Vein grafts, harvested at 6 weeks, were fixed in formaldehyde. Mean intimal thickness was measured from multiple vein graft cross sections with a Zeiss computerized interactive image analyzing system. A mean of 140 +/- 11 measurements were computed from each graft. Marked intimal hyperplasia occurred in the control group and increased from 4.3 +/- 0.3 to 86.4 +/- 14 micron. In contrast, a high eicosapentaenoic acid diet inhibited intimal hyperplasia, with intimal thickness only increasing from 4.0 +/- 0.4 to 24.8 +/- 2.7 micron (p less than 0.001). These data indicate that eicosapentaenoic acid inhibits platelet-mediated intimal hyperplasia and suggest that cod-liver oil could be used to prevent intimal hyperplasia in vein grafts used for myocardial revascularization.

Animals↗
PubMed1969

Histamine-sensitizing factor, mouse-protective antigens, and other antigens of some members of the genus Bordetella.

The three species of the genus Bordetella-B. pertussis, B. parapertussis, and B. bronchiseptica-have many antigens in common. Studies on representative strains of these species have shown that there are only a few specific antigens in each species. Whole-cell vaccines and extracts from B. pertussis contained specific mouse-protective antigen and a histamine-sensitizing factor. In addition, whole-cell vaccines and some saline extracts protected mice against intracranial challenge with B. bronchiseptica. Cells and a saline extract of B. parapertussis also protected against B. bronchiseptica but not against B. pertussis. Whole cells of B. bronchiseptica protected against B. bronchiseptica, but only one of three saline extracts protected against this challenge. Neither whole cells nor saline extracts from B. bronchiseptica protected against B. pertussis. The antigen in B. pertussis responsible for cross-protection against B. bronchiseptica was less resistant to heat than the protective antigen in B. bronchiseptica. Since histamine-sensitizing factor was not detected in B. bronchiseptica or B. parapertussis cells or extracts, this factor is not required to protect mice against B. bronchiseptica challenge. Whether B. pertussis vaccines protected against B. bronchiseptica by a nonspecific mechanism was not established, but it is clear that the specific antigen responsible for protection against B. pertussis was found only in B. pertussis and not in B. bronchiseptica or B. parapertussis.

Animals↗