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Biomedical subjects

G Johnson

Publications and source records attributed to G Johnson.

At least 325 records · Page 18Linked to original sources
PubMed1991

Interference with phage lambda development by the small subunit of the phage 21 terminase, gp1.

Bacteriophage lambda development is blocked in cells carrying a plasmid that expresses the terminase genes of phage 21. The interference is caused by the small subunit of phage 21 terminase, gp1. Mutants of lambda able to form plaques in the presence of gp1 include sti mutants. One such mutation, sti30, is an A. T-to-G.C transition mutation at base pair 184 on the lambda chromosome. The sti30 mutation extends the length of the ribosome-binding sequence of the Nul gene that is complementary to the 3' end of the 16S rRNA from GGA to GGAG. The sti30 mutation causes a approximately 50-fold increase in the level of expression of a Nul-lacZ reporter gene, indicating that the sti30 mutation overcomes the gp1 inhibition by increasing the level of expression of gpNul. Although the Nul and A genes of lambda overlap, the sti30 mutation has little effect on the level of gpA expression, indicating that translational coupling does not occur.

Bacteriophage lambda↗
PubMed1991

Electrode system influence on biphasic waveform defibrillation efficacy in humans.

BACKGROUND: Several clinical studies have demonstrated a general superiority of biphasic waveform defibrillation compared with monophasic waveform defibrillation using epicardial lead systems. To test the breadth of utility of biphasic waveforms in humans, a prospective, randomized evaluation of defibrillation efficacy of monophasic and single capacitor biphasic waveform pulses was performed for two distinct nonthoracotomy lead systems as well as for an epicardial electrode system in 51 cardiac arrest survivors undergoing automatic defibrillator implantation. METHODS AND RESULTS: The configurations tested consisted of a right ventricular-left ventricular (RV-LV) epicardial patch-patch system, an RV catheter-chest patch (CP) nonthoracotomy system, and a coronary sinus (CS) catheter-RV catheter nonthoracotomy system. For each configuration, the defibrillation current and voltage waveforms were recorded via a digital oscilloscope to measure defibrillation threshold voltage, current, resistance, and stored energy. Biphasic waveform defibrillation proved more efficient than monophasic waveform defibrillation for the epicardial RV-LV system (4.8 +/- 4.1 versus 6.7 +/- 4.9 J, p = 0.047) and the nonthoracotomy RV-CP system (23.4 +/- 11.1 versus 34.3 +/- 10.4 J, p = 0.0042). Biphasic waveform defibrillation thresholds were not significantly lower than monophasic waveform defibrillation thresholds for the CS-RV nonthoracotomy system (15.6 +/- 7.2 versus 20.0 +/- 11.5 J, p = 0.11). Biphasic waveform defibrillation proved more efficacious than monophasic waveform defibrillation in 13 of 20 patients (65%) with RV-LV epicardial patches, 10 of 15 patients (67%) with an RV-CP nonthoracotomy system, and nine of 16 patients (56%) with an RV-CS nonthoracotomy system. CONCLUSIONS: Biphasic pulsing was useful with nonthoracotomy lead systems as well as with epicardial lead systems. However, the degree of biphasic waveform defibrillation superiority appeared to be electrode system dependent. Furthermore, for a few individuals, biphasic waveform defibrillation proved less efficient than monophasic waveform defibrillation, regardless of the lead system used.

Adult↗
PubMed1991

Non-nursing duties in theatre. Part 1.

In this article Gillian Johnson explains the research methods used in a survey looking at non-nursing duties carried out in the operating theatre. She also makes recommendation about her findings in a second article to be published next month.

Humans↗
PubMed1991

Non-nursing duties in theatre. Part 2.

In part 1 the author described the methodology for identifying theatre nurse perceptions of the theatre nursing role and of non-nursing duties. This article moves on to describe stage 2, a non-participant observational study of what the nurses were actually doing.

Humans↗
PubMed1991

Surgery for chronic vein insufficiency.

1. Although varicose veins are the most prevalent form of venous insufficiency, obstruction or valvular incompetence of the deep system produces the most severe forms of lower extremity venous insufficiency and is responsible for most cases of leg ulceration of venous etiology. 2. With careful patient selection, surgery for varicose veins can be successful. Deep venous surgery, however, has limited indications and still carries a high failure rate; it should only be indicated in selected patients after conservative therapy has failed. 3. The main causes for failure of deep venous surgery are the low pressure and low velocity flow characteristics of the venous system that favor thrombosis.

Chronic Disease↗
PubMed1991

Intermittent claudication.

The natural history of intermittent claudication is generally benign. Clear indications for revascularization in patients with intermittent claudication are rest pain and necrotic tissue. Disabling claudication in patients who are at low operative risk is another acceptable indication for surgical treatment. Young patients with intermittent claudication from aortoiliac occlusion constitute a subset of patients in whom a more aggressive approach is justified. Nevertheless, in most patients, the management of intermittent claudication should be conservative.

Female↗
PubMed1991

Effects of prostacyclin and taprostene in splanchnic artery occlusion shock.

Prostacyclin (PGI2) and taprostene (CG-4203) were studied in a highly lethal model of splanchnic artery occlusion (SAO) shock in pentobarbital anesthetized rats. Total occlusion of the superior mesenteric and celiac arteries for 40 min resulted in a severe shock state often resulting in a fatal outcome within 2 h following release of the occlusion. PGI2 or taprostene was infused at a rate of 100 ng/kg/min commencing at occlusion of the celiac and superior mesenteric arteries. Taprostene significantly improved survival time and taprostene treated animals maintained post-reperfusion mean arterial blood pressure (MABP) at significantly higher values compared to rats receiving taprostene vehicle (final MABP 96 +/- 3 vs 45 +/- 3.5 mmHg, p less than 0.001, respectively). In addition, taprostene significantly (p less than 0.05) attenuated the rise in hematocrit in SAO shock and the activity of plasma cathepsin D (p less than 0.005 from SAO vehicle). Taprostene also tended to decrease the accumulation of free amino-nitrogen compounds, but not significantly. In contrast, PGI2 neither improved survival time and the maintenance of post-reperfusion MABP, nor attenuated the rise in hematocrit, the plasma accumulation of free amino-nitrogen compounds, or plasma cathepsin D activity. These findings suggest that taprostene may possess greater cytoprotective properties than PGI2.

Animals↗
PubMed1990

Comparative analysis of hematopoietic growth factors released by stromal cells from normal donors or transplanted patients.

We compared the erythroid burst-promoting activity (BPA) and colony-stimulating activity (CSA) released under serum-deprived conditions by stromal cells derived from nine normal subjects and from nine patients after bone marrow transplantation. BPA and CSA were defined according to the capacity of the conditioned media (CM) to stimulate formation of erythroid bursts and granulocyte/macrophage (GM) colonies in serum-deprived cultures of nonadherent marrow cells. Six patients (group A) failed to establish or maintain successful allografts during the study. The remaining three (group B) did not experience problems with engraftment. CM from all stromal cell cultures contained detectable levels of BPA. Preincubation of the CM with an anti-GM colony-stimulating factor (GM-CSF) monoclonal antibody (MoAb), but not with a rabbit anti-interleukin-3 (IL-3) serum, reduced BPA by an average of 94%. CM from normal and group B stromal cell cultures contained detectable CSA, and the levels correlated with the amounts of granulocyte-CSF (G-CSF) detected by a specific bioassay. G-CSF was not detectable in medium conditioned by stromal cells from transplanted patients with poor marrow function. These results indicate that CM from stromal cells from normal subjects and transplanted patients with good marrow function contain both GM-CSF and G-CSF, while CM from stromal cells from transplanted patients with poor marrow function contain detectable levels of GM-CSF only. The reduced capacity of these stromal cells to produce G-CSF is associated with a reduced capacity of the CM to sustain GM colony formation and may be associated with the inability of these patients to sustain their neutrophil counts in vivo.

Biological Assay↗
PubMed1990

Objective measurement of limb perfusion by dermal fluorometry. A criterion for healing of below-knee amputation.

Quantitative fluorometry has been recommended as an accurate adjunct to clinical judgment in the preoperative assessment of lower-extremity amputation level. In this prospective study of 56 patients who had below-knee amputation, clinical judgment was used as the sole criterion for site selection. Quantitative fluorometry was compared with clinical judgment in a prospective, blinded study. All patients were studied before amputation with administration of intravenous fluorescein. Fifteen minutes after injection, objective measurement of dye fluorescence was performed at multiple sites with a quantitative fluorometer, and a dye fluorescence index was derived. All limbs undergoing amputation were ischemic, manifested by rest pain, nonhealing ulcers, or gangrene. Five patients (8.7%) failed to heal at the below-knee level. The mean dye fluorescence index for the group that healed was 81 +/- 51 (range, 13 to 259) and for the group that failed to heal, 110 +/- 49 (range, 70 to 195). Objective measurement of fluorescein perfusion did not correlate with amputation healing at the below-knee level in our patient population.

Adult↗
PubMed1990

Endothelial cell thromboxane production and its inhibition by a calcium-channel blocker.

Vascular endothelium has been established as a major source of prostacyclin production. Whether endothelial cells are also capable of synthesizing thromboxane A2 remains controversial. Suppression of such endothelial thromboxane synthesis would be beneficial for short-term patency of vascular grafts. This study examined the production of thromboxane A2 by endothelial cells and its modulation by the calcium-channel blocker nifedipine in vitro. The results indicate that (1) endothelial cells spontaneously secrete thromboxane A2, (2) this production can be enhanced severalfold in the presence of arachidonic acid, and (3) the calcium-channel blocker nifedipine significantly inhibits thromboxane production without demonstrable toxicity to the endothelial cells.

Animals↗
PubMed1990

Endothelial cell response to polyvinyl chloride-packaged GORETEX: effect of surface contamination.

A Fourier transform infrared spectroscopic study of polyvinyl chloride packaged GORETEX vascular prostheses indicated that their internal and external surfaces were coated with an additive layer presumed to be derived from the polyvinyl chloride packaging. This layer was not removed by washing in phosphate buffered saline but was soluble in trimethyl pentane and hexane. Some other treatments of GORETEX and the packaging were shown to remove the contaminant from the surface and this correlated with an inferior in vitro aortic endothelial cell response. Analyses of materials extracted from both the polyvinyl chloride and the GORETEX surface indicated that the major surface component was a long chain aliphatic ester, either a plasticizer or a lubricant constituent.

Animals↗
PubMed1990

Synergism between superoxide dismutase and sodium nitrite in cardioprotection following ischemia and reperfusion.

The effects of acidified sodium nitrite (NaNO2), a releaser of nitric oxide (NO), combined with human superoxide dismutase (hSOD), were investigated in a 6-hour model of myocardial ischemia (MI) with reperfusion in open-chest, anesthetized cats. Acidified NaNO2 (12.5 mmol/kg/hr) was infused intravenously in cats starting 0.5 hour after occlusion of the left anterior descending (LAD) coronary artery, which was reperfused 1.5 hour following occlusion. Significantly lower plasma creatine phosphokinase activities were observed at all times beyond 3 hours for MI cats given NaNO2 + hSOD when compared with the other MI groups. The areas-at-risk expressed as percentages of the total left ventricular weights were not significantly different among any of the MI groups. However, the necrotic area expressed as a percentage of the myocardial area-at-risk was significantly lower in the MI + NaNO2 + hSOD-treated cats compared with all other MI groups. The NaNO2-treated group also produced a significant decrease in the necrotic area relative to the area-at-risk. Cardiac myeloperoxidase (MPO) activities indicated no significant difference in number of neutrophils attracted to the ischemic zone in the NaNO2 + hSOD-treated MI cats when compared with the other MI groups. Acidified NaNO2 + hSOD together exert significant protection on the myocardium subjected to ischemia and reperfusion injury. NaNO2 may act synergistically with hSOD to prolong the action of NO by scavenging free radicals that inactivate NO.

Animals↗
PubMed1990

Profile of patients with human immunodeficiency virus infection presenting to an inner-city emergency department: preliminary report.

Increasing numbers of patients with diagnosed HIV infection are presenting to inner-city emergency departments. Unfortunately, there is little information available on the characteristics and emergency clinical problems of HIV-infected patients to guide physicians in patient care and strategies for resource use. Preliminary data from an on-going investigation revealed that there were 254 emergency visits (1.8% of total) by 164 patients with known HIV infection during the four-month period of March to June 1988. Only 171 visits (62%) were likely related to patients' underlying HIV infection. Nine percent of IV drug users (IVDUs) carried a diagnosis of AIDS before presentation compared with 68% of patients who were homosexual or bisexual. Fifty-five patients (21.7%) presented with their first known complication of HIV. Among the 140 risks from patients previously considered asymptomatic, those with homosexual or bisexual risk were 3.6-fold more likely to present with a first-time complication of HIV than were IVDUs. HIV-infected patients were twice as likely to have inadequate insurance compared with a sample of ED seronegative controls. Of the 130 risks by IVDUs, 85% were without adequate insurance coverage compared with 56% of the 91 patient risks from homosexual or bisexuals (P less than .05). Generally, patient presentations did not imply an obvious diagnosis; vague constitutional complaints were the most common (42%). Preliminary interpretation of the data is that IVDUs use emergency services as a routine source of care. Because IVDUs probably represent those with more recent infection and HIV infection continues to spread unabated in this risk group, we can expect increasing numbers of patients to present to EDs with symptomatic HIV infection in the future.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1990

An effective and adaptable transvenous defibrillation system using the coronary sinus in humans.

With use of a coronary sinus catheter electrode, a right ventricular catheter electrode and a chest wall patch electrode system, defibrillation threshold voltage, current and energy were measured with four distinct transvenous defibrillation techniques delivered in random sequence in each of 12 survivors of cardiac arrest immediately before implantation of a standard epicardial patch defibrillation system. The four transvenous defibrillation techniques were 1) single pathway monophasic pulsing, 2) single pathway biphasic pulsing, 3) dual pathway sequential pulsing, and 4) dual pathway simultaneous pulsing. A transvenous defibrillation method was considered to be potentially useful only if the defibrillation threshold was less than or equal to 500 V (less than or equal to 15 J delivered energy). The 500 V value would allow a 2:1 defibrillation safety margin for a device with a maximal output of 30 J. No single transvenous pulsing technique was uniformly superior in efficacy. However, by choosing the best pulsing technique for each patient, it was possible to obtain an average defibrillation threshold of 410 +/- 135 V leading edge voltage, 7.2 +/- 2.5 A leading edge current and 11.3 +/- 7.4 J delivered energy for the group of 12 patients. With the ability to vary defibrillation technique, transvenous antiarrhythmic device implantation would have been possible in 10 (83%) of the 12 patients at or below a 15 J defibrillation threshold cutoff point. In contrast, if only one transvenous defibrillation method had been used, as few as 5 and at most 8 of the 12 patients would have been candidates for a transvenous defibrillation system given a 15 J defibrillation threshold cutoff point for insertion.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

New and versatile approaches to the synthesis of CPP-related competitive NMDA antagonists. Preliminary structure-activity relationships and pharmacological evaluation.

Fourteen new CPP analogues have been prepared with methyl 1-(phenylmethyl) (+/-)-1,2-piperazinedicarboxylate 3 as a versatile synthetic intermediate. Derivatives were evaluated as NMDA ligands by their ability to displace [3H]CPP from rat cortical membranes. The binding affinity of various chain lengths at the N4-position of the CPP analogues, 5a, 5b, and 9a mimics the binding affinity observed for the acyclic derivatives AP6, AP8, and AP5. Analogue 9a, with a single methylene group in its phosphonate side chain, exhibited diminished affinity for the NMDA receptor when compared to the structurally similar piperidine compound CGS 19755. Replacement of the phosphonic acid moiety with monoionizable acidic groups such as a carboxylate or a phosphinate resulted in a reduction of binding affinity. An aryl spacer between the N4-nitrogen and the distal acidic group was detrimental to binding as was alkylation at the N1-position. Steric bulk, however, was better tolerated when a phenyl group was positioned alpha to the phosphonate, as seen with analogues 21 and 22.

Animals↗