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Biomedical subjects

R Walden

Publications and source records attributed to R Walden.

At least 19 recordsLinked to original sources
PubMed1992

Activation of a plant gene by T-DNA tagging: auxin-independent growth in vitro.

A transferred DNA (T-DNA) tagging vector with the potential to produce dominant mutations was used with cocultured Agrobacterium tumefaciens and protoplasts to tag genes involved in the action of the plant growth substance auxin. Transgenic calli were selected for their ability to grow in the absence of auxin in the culture media. From one experiment, 12 calli that displayed this phenotype were recovered, of which 11 were able to regenerate into plants. In one plant studied in detail, protoplast division in the absence of auxin genetically cosegregated with a single T-DNA insert. A messenger RNA encoded by a 6.4-kilobase sequence of plant genomic DNA rescued from the mutant is overexpressed relative to untransformed plants. The genomic DNA, as well as a cognate complementary DNA, once transfected into protoplasts promote growth and cell division in vitro in the absence of exogenously added auxin.

Agrobacterium tumefaciens↗
PubMed1992

Laser Doppler flowmetry in lower extremity ischemia: application and interpretation.

The present study was undertaken in order to develop numerical criteria for the parameters of laser Doppler flowmetry-skin blood flow velocity and pulse wave amplitude in the evaluation of lower extremity ischemia. Fifty limbs of young healthy volunteers were examined in order to obtain baseline normal values. Patient population was divided into moderately ischemic (52 limbs) and severely ischemic (22 limbs), based on patients' complaints, physical examination, ankle-brachial indices, pulse volume recordings and arteriographies. Univariate comparison between the three groups of skin blood flow velocity and pulse wave amplitude at each time point were done by analysis of variance. Power of discrimination between degrees of ischemia was evaluated by computing sensitivity and specificity, based on skin blood flow velocity and pulse wave amplitude values at time points best for predicting the severity of disease by multiple regression analysis. Using cutoff points of < 31 for skin blood flow velocity and < 9 for pulse wave amplitude, a 96% sensitivity and 96% specificity were obtained in separating normal from ischemic limbs. Cutoff points of < 9 for skin blood flow velocity and < 4 for pulse wave amplitude discriminated with a 100% sensitivity and specificity between the moderately and severely ischemic limbs. We propose the use of laser Doppler flowmetry with local heating and reactive hyperemia, and the cutoff points stated above as an additional tool to evaluate lower extremity ischemia through assessment of cutaneous microcirculation.

Adult↗
PubMed1978

Ischemia of toes as a presenting symptom in primary thrombosis: a case report.

Although thrombotic occlusion of small vessels in thrombocytosis is allegedly well recognized, it has been reported only rarely. We treated 4 patients with primary thrombocytosis in whom ischemic toe lesions with normal peripheral pulses were the presenting and only symptoms. The symptoms preceded diagnosis by 5 years, 3 years, 1 year, and 1 month respectively. Treatment of the hematologic disorder resulted in disappearance of the toe lesions. Thrombocytosis should be routinely searched for in patients with ischemic toes and normal peripheral pulses.

Aged↗
PubMed1978

Congenital membranous obstruction of the inferior vena cava.

Congenital membranous obstruction of the inferior vena cava is a rare phenomenon resulting from failure of anastomosis between the right subcardinal vein and the liver. A case is reported in which the presenting symtpom was bleeding from esophageal varices. Cirrhosis was present and other signs of vena caval obstruction were minimal. The diagnosis was made only after an ineffective mesenterico-caval shunt had been performed. Venacavography or pressure measurements in the inferior vena cava are mandatory before attempting a porta-systemic shunt operation.

Budd-Chiari Syndrome↗
PubMed1977

Gangrene of toes with normal peripheral pulses.

Ten patients with pregangrenous and gangrenous changes of the toes in the presence of normal peripheral pulses are described. In the absence of diabetes this is an uncommon condition and is only rarely reported upon in the literature. Four patients had non occlusive arteriosclerotic changes in large arteries; three suffered from thrombocytosis and one from polycythemia vera; one patient had a monoclonal gamopathy and one was exposed to cold three months before the onset of gangrene. None of these patients smoked regularly. Severe pain usually preceded the gangrene. The process did not progress proximally in any patients, and in those who underwent toe amputations the healing was uneventful. Vasodilators and low-molecular dextran were not effective. Lumbar sympathectomy was performed in three patients, also with no effect on the course of the disease. Treatment of hematological disorders gave relief in three patients. Proximal arteriosclerotic changes should be corrected if possible to eliminate a source of emboli. In two patients anti-platelet aggregation agents provided relief. Toe amputation should be conservative and performed when definite demarcation appears between necrotic and viable tissue. This condition has a benign prognosis.

Adult↗
PubMed1977

Phantom sweating.

Phantom sweating is a sensation in which the patient feels that sweat is about to burst out of skin pores, but in which sweating never actually occurs. In a series of 100 patients undergoing bilateral upper dorsal sympathectomy for palmar hyperihidrosis, 82 patients were specifically questioned and 48 (59%) reported phantom sweating. Phantom sweating started soon after the operation, was triggered by the same stimuli that caused hyperhidrosis preoperatively, lasted for a few seconds, and tended to diminish with time. In an average follow-up of 18 months, the phenomenon disappeared in 11 patients (23%). Phantom sweating is probably a symptom of residual sympathetic activity.

Follow-Up Studies↗
PubMed1976

Bioavailability of tolamolol.

Bioavailability of capsule and tablet formulations of tolamolol were compared by measuring plasma concentration of tolamolol and reduction in maximum exercise heart rate over a period of twelve hours in eight healthy subjects in a two-way cross-over study. Tolamolol was absorbed more rapidly from capsules than from tablets; this did not result in any significant difference in the reduction in maximum exercise heart rate between the two formulations. There was no significant difference between area under curve of reduction in exercise tachycardia and area under-curve of plasma concentration of tolamolol for the two formulations. Reduction in maximum exercise heart rate was related to logarithm of plasma concentration of tolamolol between two and twelve hours after both formulations.

Adult↗
PubMed1975

Pharmacokinetic and pharmacological studies with tolamolol in man.

Pharmacokinetic and physiological variables were measured in six healthy subjects after intravenous and oral administration of tolamolol. 2. After intravenous injection of tolamolol (20 mg), there was a biphasic decline both in plasma concentration and attenuation of maximum exercise tachycardia. First and second phase half-lives of plasma concentration were 7 min and 2.5 h respectively. WReduction of maximum exercise tachycardia declined from 32 beats/min at 2 h to 19 beats/min at 8 hours. Clearance of tolamolol from blood ranged from 0.8-1.41 min-1. 3. After the oral administration of tolamolol (100 mg), the average volume of distribution was 220.1 and plasma concentration half-life 1.8 hours. After ten eight-hourly doses of 100 mg there was no accumulation of tolamolol and the half-life of plasma clearance was unchanged. 4. Hydroxytolamolol was detected in plasma in two of six subjects after oral tolamolol. 5. There was a significant positive correlation between reduction in maximum exercise heart rate and logarithm of plasma concentration of tolamolol after both oral and intravenous administration.

Adult↗
PubMedDate not supplied

Processes of transport and absorption in the developing infant intestine.

An understanding of changes in the processes of absorption, detoxification, and intoxication in the intestine of infants, especially during the perinatal period, may aid in reaching an understanding of why the syndrome of infant botulism is restricted to the first six months of life. Some of the important metabolic changes associated with both the perinatal and the postnatal period of development are emphasized in these studies. A more complete understanding of the processes by which substances are absorbed into the intestine and then reexposed via the enterohepatic circulation may provide clues about why infant botulism occurs.

Adenosine Triphosphate↗