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Biomedical subjects

R Walden

Publications and source records attributed to R Walden.

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

Geminivirus-based shuttle vectors capable of replication in Escherichia coli and monocotyledonous plant cells.

Shuttle vectors have been constructed that are able to replicate in either Escherichia coli or plant cells. They contain the ColE1 origin of replication and parts of the wheat dwarf virus genome, a geminivirus infecting a variety of species of monocotyledonous plants. Such plasmids are able to replicate in E. coli and wheat cells. The plasmids can be rescued in E. coli and show no changes during their passage through plant cells. Such an E. coli/plant cell shuttle vector system could be used for the amplification of foreign genes in plant cells, for studies on DNA rearrangement or the isolation of plant transposons.

Bacteriocin Plasmids↗
PubMed1991

[Surgery for thoraco-abdominal aortic aneurysm].

12 patients underwent resection of a thoraco-abdominal aortic aneurysm. There were 10 men and 2 women, ranging in age from 54-78 years (mean 65). Aortic arteriosclerosis was the primary etiology in 11, and Behcet's disease in the other 1. Most patients (7/12) presented with Type 3 aneurysm, extending from the distal descending thoracic aorta to the distal abdominal aorta; none had aortic dissection. 11 were operated on for symptoms related to the aneurysm: 3 of these had a contained rupture. The risk factors were chronic obstructive pulmonary disease in 10, hypertension (10), diffuse arteriosclerosis (8), ischemic heart disease (6), chronic renal failure (5) and cerebrovascular accident (1). The surgical technique in 11 was graft inclusion and visceral vessel reattachment. The main complication was acute renal failure, seen in 3 patients. None had spinal ischemia. Operative mortality was 33%. Of the 4 who died, 2 had myocardial infarction and 2 uncontrolled intraoperative bleeding. According to the literature the major complications are spinal cord ischemia and renal failure.

Acute Kidney Injury↗
PubMed1991

Vascular insufficiency quantitatively aggravates diabetic neuropathy.

The effect of lower-limb ischemia on the severity of neuropathy was examined in 48 diabetic patients with peripheral vascular disease. The severity of the vascular disease, as determined by medical history, physical findings, and laboratory data, was scored for each leg. Neuropathy was rated clinically and based on the results of nerve conduction studies of the common peroneal, posterior tibial, and sural nerves. A significant correlation was found between the vascular scores and neurologic variables of the two legs, most strikingly so in electrophysiologic data, with coefficients of .6 to .7. Nondiabetic control patients showed no evidence of neuropathy, regardless of the severity of ischemia, whereas diabetic controls without limb ischemia showed symmetrical neuropathy. These findings support the hypoxic theory in the pathogenesis of diabetic neuropathy.

Adult↗
PubMed1991

Pulse volume recording disturbances in paraplegic patients.

Spinal cord injuries may modify vascular reactivity in the denervated region. This study presents an original observation of altered vascular response in paraplegic patients. A group of 30 consecutive paraplegic otherwise normal individuals underwent a thorough vascular examination. There were 29 male and 1 female patient, 21 to 67 years old (average 41), all with traumatic spinal cord injury. Average time since injury was 17 years. All had good peripheral pulses and normal segmental Doppler pressure measurements. In 8 patients, plethysmography--pulse volume recording (PVR) was normal as expected. In 22 patients an unusual feature of the vascular examination was recorded, consisting of normal peripheral arterial pressures with PVR waveforms indicating poor pulsatility. This group was older than the group with normal studies: ages 44 +/- 13 vs 34 +/- 8 years (p = 0.05), and more time had elapsed since injury-20 +/- 12 vs 10 +/- 4 years (p = 0.015). The altered pulsatility demonstrated in most of those paraplegic patients may play a role in deficient wound healing frequently observed below the level of spinal neurological loss.

Adult↗
PubMed1991

Dehydroabietic acid, a major anionic contaminant of pulp mill effluent, reduces both active p-aminohippurate transport and passive membrane permeability in isolated renal membranes.

The renal organic anion transport system plays a pivotal role in elimination of potentially toxic anions. This system is driven by indirect coupling to the sodium gradient at the basolateral membrane, i.e., the organic anion enters the cell in exchange for internal alpha-ketoglutarate (alpha KG) and the in greater than out alpha KG gradient is regenerated by Na+/alpha KG cotransport. The resin acid, dehydroabietic acid (DHAA), is one of several anionic xenobiotics which enter the environment secondary to pulp and paper processing. Because it is largely ionized at neutral pH (pKa, 5.7), DHAA should share the organic anion system. Indeed, Na+/glutarate-coupled p-aminohippurate (PAH) uptake by renal basolateral membrane vesicles was inhibited competitively by DHAA (Ki congruent to 150 microM). Despite the reduced rate of PAH uptake, a substantial, but delayed, overshoot was observed, suggesting additional effects. Passive permeabilities to mannitol, PAH and sodium were all decreased by DHAA, consistent with a general tightening of the membrane. Decreased permeability extended the effective lifetime of imposed ion gradients. Thus, sodium driven glutarate uptake was stimulated by 200 microM DHAA, prolonging and more than doubling its overshoot. Because the immediate driving force for PAH uptake into basolateral membrane vesicles is the magnitude of the glutarate gradient, DHAA increased the driving force for PAH uptake and permitted a substantial overshoot despite the reduced rate of PAH uptake. These data indicate that DHAA has several distinctly different effects on the membrane.

Abietanes↗
PubMed1990

Techniques in plant molecular biology--progress and problems.

Progress in plant molecular biology has been dependent on efficient methods of introducing foreign DNA into plant cells. Gene transfer into plant cells can be achieved by either direct uptake of DNA or the natural process of gene transfer carried out by the soil bacterium Agrobacterium. Versatile gene-transfer vectors have been developed for use with Agrobacterium and more recently vectors based on the genomes of plant viruses have become available. Using this technology the expression of foreign DNA, the functional analysis of plant DNA sequences, the investigation of the mechanism of viral DNA replication and cell to cell spread, as well as the study of transposition, can be carried out. In addition, the versatility of the gene-transfer vectors is such that they may be used to isolate genes not amenable to isolation using conventional protocols. This review concentrates on these aspects of plant molecular biology and discusses the limitations of the experimental systems that are currently available.

Genetic Techniques↗
PubMed1990

[Gas gangrene].

A 66-year-old woman presented with left lower abdominal pain and paresthesias of the left thigh of 6 hours duration. 10 years previously she had undergone massive abdominal irradiation for retroperitoneal lymphoma. 3 days prior to admission she underwent rectal biopsy as part of a work-up for suspected inflammatory bowel disease. Within a few hours she developed fulminating gas gangrene of the left thigh and lower abdomen. In spite of aggressive surgical debridement she died 12 hours after admission. The incidence of gas gangrene is decreasing, but the mortality is still high. The diagnosis requires a high index of suspicion, especially in immunodepressed patients after invasive procedures or even minor trauma.

Abdominal Pain↗
PubMed1989

[Carotid endarterectomy].

Carotid endarterectomy was performed 77 times in 73 symptomatic patients. In 67 of them there had been 1 or more transient ischemic attacks (TIA), in 4 transient atypical symptoms, and in 2 mild persistent neurological deficits. After operation 1 died of a stroke and 1 had a nonfatal myocardial infarction. In 3.3% of 33 low-risk patients (Sundt's classes 1 and 2) there was mild postoperative neurological deficit. The rate of neurological complications was much higher in 40 high-risk patients (classes 2 and 3), including 5 with postoperative stroke. Followup averaged 21.5 months (longest 54 months), the 5-year survival (by extrapolation from a life table analysis curve) was 87%, and there was only 1 fatal stroke. Those who recovered from operation without complications had an 86% chance of having no further neurological problems.

Carotid Arteries↗
PubMed1989

Fatal disruption of a splenorenal shunt after multiple pregnancies.

A 39-year-old woman underwent a distal splenorenal shunt operation for bleeding esophageal varices due to liver cirrhosis. Following the operation she had 7 pregnancies at almost yearly intervals. At the term of the last pregnancy a disruption of the anastomotic site caused a fatal hemorrhage. The outcome of postshunt pregnancies as reviewed in the literature is usually favorable, but numerous pregnancies in these circumstances may carry a considerable risk.

Adult↗
PubMed1989

Errors and pitfalls in intraarterial thrombolytic therapy.

Sixty complications occurred during 138 courses of intraarterial thrombolytic therapy in 122 patients during a 5-year period. These complications were recorded and analyzed prospectively to identify underlying errors in management. There were 31 bleeding episodes, 15 vascular complications, and 14 other complications. Twelve of the bleeding episodes occurred at the puncture site, and 19 occurred at remote sites, accounting for six of the eight deaths in the series. Management errors were clearly identified in 27 of the 60 complications. The three following patterns of errors were recognized: (1) mismanagement of bleeding (12 instances), (2) wrong patient selection (nine instances), and (3) breach of the administration protocol (six instances). The group of 27 complications with underlying management errors included seven of the eight deaths in the present series. Efforts to prevent complications from thrombolytic therapy should concentrate on the specific patterns of management errors identified. This study indicates that low-dose intraarterial thrombolytic therapy is not a low-risk alternative to surgical intervention but should be viewed as a prelude or possible alternative to surgery in selected patients despite the risks involved.

Adolescent↗
PubMed1987

Simplified assessment of arterial graft patency using indium-labelled-platelet scintigraphy.

Arterial grafts were studied with indium-III-labelled platelets in 13 patients (18 graft limbs) in the early post-implication period. Platelet thrombogenic activity was graded into four grades by visual inspection of the images, and scintigraphic criteria of impending graft occlusion were defined. Dacron and polytetrafluoroethylene grafts had similar high thrombogenic activity in comparison with autologous veins. Nine graft studies showed patterns of radioactivity concentration that suggested threatening thrombosis and eight of these eventually occluded. In nine other studies absent to moderate radiolabelled platelet activity was observed and none occluded within a mean follow-up period of 24 months. Prediction of graft occlusion of scintigraphic evaluation using the present simple non-invasive technique is valuable since corrective measures may be instituted earlier and with greater success in the post-operative follow-up period.

Aged↗
PubMed1987

Clinical presentation of suspected carotid artery disease. Screening of candidates for arteriography with the assistance of the vascular laboratory.

The evaluation of suspected carotid artery disease was reviewed in a consecutive series of 292 patients referred by attending physicians in a university hospital. Twenty-three percent of the patients presented with classical transient ischemic attacks, and all those suitable for eventual surgery were recommended for arteriography. In 75% of the patients the presenting symptoms were nonlateralizing or equivocal. In this group the results of noninvasive vascular tests were decisive as to the recommendation for arteriography, which was positive in 79% of those performed. Among 100 surveyed patients who did not undergo arteriography, cerebrovascular accidents occurred in 3 patients: carotid disease was detected in 2 of them, in whom arteriography had been postponed for clinical reasons, while in the third a subsequent arteriography demonstrated no carotid lesion. Expert clinical assessment assisted by vascular studies prevented unnecessary arteriography in 62% and detected carotid pathology with atypical presentation in 13% of the patients.

Adolescent↗
PubMed1986

Effects of adenine and its isomer 4-aminopyrazolo-[3,4-d]-pyrimidine on 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced mortality in rats.

Adult male Fischer rats were given a single po dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equal to 2 times the LD50 to increase the serum and liver lipid concentrations and to induce mortality. In addition, animals were given 4-aminopyrazolo-[3,4-d]-pyrimidine (4APP), an agent that decreases serum lipids, or adenine (Ad), an agent that prevents the formation of fatty liver, to examine the relationship between changes in lipids and TCDD-induced mortality. The principal effect of 4APP on TCDD-induced mortality (325 micrograms TCDD/kg body wt) was that it shortened the mean time to death. In contrast, Ad stimulated feed consumption and decreased body weight loss, but the mean times to death were similar for TCDD and TCDD + Ad animals. Based on these mortality studies, 4APP, but not Ad, affects the TCDD-induced mortality in Fischer rats. The TCDD-induced sensitivity to 4APP, based on decreased mean time to death, implies that blocking the release and/or synthesis of triglyceride-rich lipoproteins by the liver, and the subsequent decrease in serum lipids, may play an important role in the TCDD-induced mortality. The increase in serum triglyceride associated with TCDD exposure appears to be essential in providing metabolic energy under circumstances where lipoprotein retrieval is reduced.

Adenine↗
PubMed1986

"Agroinfection," an alternative route for viral infection of plants by using the Ti plasmid.

Most plant viruses are transmitted by insect vectors. We present an alternative method for the introduction of infectious viral DNA that uses the ability of Agrobacterium to transfer DNA from bacterial cells to plants. Cauliflower mosaic virus was chosen to develop this method because it is the best characterized plant DNA virus and can be introduced into plants via aphids, virus particles, viral DNA, or suitably treated cloned DNA. We show that systemic infection of turnips results from wounding and inoculation with strains of Agrobacterium tumefaciens in which more than one genome of cauliflower mosaic virus have been placed tandemly in the T-DNA of the tumor-inducing plasmid. Thus such constructions allow escape of the viral genome from the T-DNA once inside the plants. The combined use of the tumor-inducing plasmid and viral DNA opens the way to molecular biological approaches that are not possible with either system alone.

Journal Article↗