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Biomedical subjects

J C Allen

Publications and source records attributed to J C Allen.

At least 199 records · Page 11Linked to original sources
PubMed1983

Staphylococcus aureus bacteremia: a prospective study.

During a 22-month period, 47 patients with 49 consecutive episodes of Staphylococcus aureus bacteremia were identified and observed prospectively for the development of endocarditis and metastatic infection. Eighteen (37%) of the episodes were community-acquired and 31 (63%) were nosocomial. The mean patient age was 55 years, and all but nine patients had one or more underlying diseases. A primary focus was identified for 38 episodes (78%) most often an intravenous catheter, and 21 episodes (43%) were associated with a removable focus of infection. In this group, no patient had endocarditis after a mean duration of 20 days of therapy. Overall, two of 47 patients had endocarditis by clinical criteria; one was a drug abuser and one had no known heart disease. Forty-five of 49 episodes were treated with a single antimicrobial agent. There were 12 (24%) deaths in this series, seven (14.2%) directly due to staphylococcal infection. In this prospective study we found a low but definite risk of endocarditis associated with S aureus bacteremia. The mortality was similar to that in other recently published studies. All deaths occurred within two weeks of initiating therapy, indicating the potential importance of host factors in the outcome.

Adult↗
PubMed1983

Differences in K+-induced relaxation of canine femoral and renal arteries.

The extent and initial rate of potassium-induced relaxation of canine femoral and renal arteries were measured as a function of potassium concentration [K+]. Both parameters were greater in the renal artery at low [K+]; the dissociation constant for potassium of the femoral artery was greater than that of the renal artery. If potassium-induced relaxation reflects sodium pump activity, then these data indicate that the sodium pumps of the two arteries are different. When we repeated the above experiments in a lowered sodium medium, the rate and extent of potassium-induced relaxation and the apparent affinity for potassium increased in the femoral artery as predicted by kinetic models based on both isolated Na+-K+-ATPase and intact tissue. The same parameters in the renal artery, however, were unaffected by lowered sodium. These results and those presented in the companion paper [Am. J. Physiol. 245 (Heart Circ. Physiol. 14): H604-H609, 1983] can be interpreted to mean that potassium-induced relaxation does not accurately reflect sodium pump function in canine renal arteries.

Animals↗
PubMed1983

Ouabain binding, Na+-K+-ATPase activity, and 86Rb uptake of canine arteries.

In a previous report [Am. J. Physiol. 245 (Heart Circ. Physiol. 14): H598-H603, 1983] we measured potassium-induced relaxation of canine femoral and renal arteries as an index of sodium pump function and concluded that it may not be an accurate measure. In this report, the sodium pumps of femoral and renal arteries were examined using three separate approaches to compare sodium pump function more directly. The number of pump sites in subcellular fractions was measured using [3H]ouabain binding. No differences were observed (femoral artery 14.5 +/- 4.8 pmol/g wet wt; renal artery 17.4 +/- 6.5). Similarly, there was no difference in ouabain-inhibitable Na+-K+-ATPase activity in NaI-treated microsomal fractions of these arteries (femoral artery 3.10 +/- 0.65 mumol Pi X mg-1 X h-1; renal artery 3.42 +/- 0.23). Finally, sodium pump function was measured using the ouabain-inhibitable 86Rb uptake method. The rate of ouabain-inhibitable 86Rb uptake was found to be identical for the two arteries, as were the dissociation constants of the two arteries for rubidium. However, in the presence of 3.5 microM norepinephrine, the rate of 86Rb uptake in the renal artery was greater than that of the femoral artery. We conclude that, under resting conditions, the sodium pumps of femoral and renal arteries are identical, whereas in the presence of norepinephrine, the renal artery sodium pump is not rate limiting with respect to contractility. These data have significant implications with regard to the use of potassium-induced relaxation as an index of sodium pump activity.

Animals↗
PubMed1983

Polyamine-mediated inhibition of in-vitro cell proliferation is not due to acrolein.

The influence of acrolein or spermine on the viability and growth of phytohaemagglutinin-stimulated rat thymic lymphocytes in cultures supplemented with foetal calf serum have been investigated. Acrolein (greater than 20 microM) was cytotoxic; spermine had little effect on viability, but inhibited [3H]TdR incorporation at low concentrations (approximately 10 microM). Cells treated with greater than 8 microM acrolein 3 hr before stimulation exhibited irreversible inhibition of protein synthesis, whereas 50 microM spermine had no effect, even when cells were treated for 24 hr before stimulation. However, addition of 25 microM spermine after stimulation did inhibit both [3H]-uridine incorporation and protein synthesis: this was reversible if cells were freed of polyamine within 4 hr, but not if washed after 24 hr. These results show that, contrary to several previous reports, in-vitro inhibition of cell proliferation by spermine is not due to the formation and action of acrolein.

Acrolein↗
PubMed1983

Inhibition of cells in culture by polyamines does not depend on the presence of ruminant serum.

Using T-lymphocyte (T-LC) and granulocyte colony (GC) assays with truly proliferating cells, the inhibitory dose-response relationships of spermine and spermidine in the presence of selected sera have been examined. In contrast to previous studies which used [3H]thymidine uptake as an index of proliferation, in vitro inhibition by polyamines was shown to require neither foetal calf serum (FCS) nor the addition of any exogenous polyamine oxidase. Cells grown in the absence of FCS were between 5-50% as sensitive to polyamines as in its presence. By using specific inhibitors of polyamine oxidase, it was shown that polyamine-elicited mitotic inhibition in the absence of FCS was still dependent on a polyamine oxidase, and evidence is presented to show that the source of the enzyme is the cells themselves.

Animals↗
PubMed1983

Neuroblastoma, tuberous sclerosis, and subependymal giant cell astrocytoma.

A patient with Stage III paratesticular neuroblastoma diagnosed in infancy was treated with radiotherapy and chemotherapy. Typical depigmented "ash leaf" skin lesions of tuberous sclerosis appeared during early childhood. At 7 years of age he underwent craniotomy for a subependymal giant cell astrocytoma. The occurrence of neuroblastoma, tuberous sclerosis, and astrocytoma is unique, and supports the suggested relationship between neural crest tumors and hamartoma syndromes.

Brain Neoplasms↗
PubMed1983

Ionized calcium in human milk determined with a calcium-selective electrode.

We measured the concentration of ionized calcium in human milk with a Radiometer ionized calcium analyzer at 37 degrees C. This instrument is designed to use simultaneous outputs from a pH electrode and a calcium ion-selective electrode to obtain the true ionized calcium in blood plasma. Because both the ionic strength and the pH of human milk differ significantly from that of plasma, we used a calibration curve that corrected for these variables. No other substances in milk interfered with the electrode response to Ca2+. The Ca2+ concentration of milk decreased and the pH increased as CO2 was lost to the atmosphere. Samples collected in glass capillaries, which minimized CO2 loss, contained 2.84 (SD 0.56) mmol of Ca2+ per liter at pH 6.98. We emphasize the importance of maintaining physiological CO2 concentrations when Ca2+ is being measured in milk.

Calcium↗
PubMed1982

Intractable facial pain associated with a ganglioglioma of the cervicomedullary junction: report of a case.

A 6-year-old child with a brain stem tumor presented with the unusual complaint of intractable facial pain resembling trigeminal neuralgia in the absence of other symptoms or signs referable to the 5th cranial nerve. The radiological evaluation included a computed tomographic scan with intravenous contrast administration, which demonstrated an enhancing intramedullary lesion extending from the obex to C-4. After radiation and chemotherapy had failed to achieve symptomatic relief, the tumor, later proven to be a ganglioglioma, was radically removed with the ultrasonic aspirator. Postoperatively the patient experienced full pain relief.

Brain Neoplasms↗
PubMed1982

Imaging of brain tumors after administration of L-(N-13)glutamate: concise communication.

Cyclotron-produced L-(N-13)glutamate was used to visualize malignant intracranial tumors in 12 pediatric patients who had evidence of recurrent disease as documented by computed transaxial tomography (TCT). Imaging was performed using a rectilinear scanner, gamma camera, or a positron-emission tomograph (PET). The results indicate that N-13 is rapidly taken up by a majority of brain tumors following the administration of L-(N-13)glutamate, and that N-13 uptake is correlated with breakdown of the blood-brain barrier as demonstrated by contrast TCT or pertechnetate (Tc-99m) studies. The feasibility of using this agent in conjunction with PET is established.

Adolescent↗
PubMed1981

Dural sinus thrombosis in children with acute lymphoblastic leukemia.

Dural sinus thrombosis developed in two children with acute lymphoblastic leukemia during induction treatment with vincristine sulfate, prednisone, and asparaginase. Headache, nausea, emesis, and lethargy were the presenting signs. The diagnosis was confirmed by arteriography. The cause is presumed to be secondary to hypercoagulability due to asparaginase-induced antithrombin III deficiency. The patients received anticoagulation therapy and recovered completely. Only two of the six reported patients without heparinization survived.

Age Factors↗
PubMed1981

CT scans of long-term survivors of various childhood malignancies.

Forty-two children with various systemic malignancies in continuous remission for 1 to 3 years after the completion of chemotherapy had CT scans with normal ventricular dimensions, similar to a noncancer "control" population. Seventeen of these patients had acute lymphocytic leukemia (ALL) treated either with prophylactic cranial irradiation and intrathecal methotrexate [7] or intrathecal methotrexate alone [10] and the remaining 25 patients had soft tissue sarcomas. Sixteen other patients with sarcomatous meningitis had enlarged ventricles while on chemotherapy. Nine had ALL. Seven had soft tissue sarcomas, none of whom received any prior CNS irradiation or intrathecal chemotherapy. In this retrospective study no evidence of hydrocephalus or significant white matter hypodensity was detected in long-term survivors of childhood cancer, regardless of whether prophylactic intrathecal chemotherapy and/or cranial irradiation was given. Direct involvement of the CNS with meningeal cancer was the most important association with ventriculomegaly.

Adolescent↗
PubMed1981

Transfer of selenium from blood to milk in goats and noninterference of copper with selenium metabolism.

The mechanism of selenium secretion by the mammary gland and effects of dietary copper and selenium metabolism on selenium in milk were investigated. Radioactive sodium selective selenite was injected into the jugular vein of lactating goats fed concentrates containing 15 or 115 ppm copper. Blood and milk samples were collected hourly for 8 h and daily for 1 wk. Whole blood, plasma, whole milk, and casein, whey, and cream fractions of milk were counted for selenium-75. No significant differences due to dietary copper were seen. The selenium-75 was primarily associated with the casein in milk. The association of selenium with the whey fraction was greater for early periods than later and varied between animals. The specific activity based on protein content was greater in casein than in whey. Peak selenium-75 in whole milk occurred 2 h after the peak in plasma. On day 7 following selenium-75 dosing, kidney had the highest specific activity, and liver was slightly higher than mammary tissue. All subcellular organelle fractions of liver, kidney, and mammary tissue by homogenization and differential centrifugation contained significant selenium-75. Selenium normally is secreted from the mammary secretory cell in combination with protein through the secretory vesicles, metabolism of selenite prior to milk secretion is important, and copper does not interfere with normal metabolism of selenium.

Animals↗
PubMed1981

Chloride deficiency in Holstein calves from a low chloride diet and removal of abomasal contents.

Chloride deficiency signs were produced in young Holstein calves by a low chloride diet (.063% chlorine) and daily removal of chloride in abomasal contents. General clinical signs included anorexia, weights loss, lethargy, mild polydipsia, and mild polyuria. In latter stages of the deficiency, severe eye defects (scleral injection, sunken eyes, scaliness around eyes) and reduced respiration rate became evident. Feces contained varying amounts of blood and mucus. The chloride imbalance resulted in severe alkalosis and hypochloremia leading to secondary hypokalemia, hyponatremia, and azotemia. All deficient calves died after 24, 28, 38, and 46 days of treatment. Chloride concentrations of plasma in each of the calves just prior to death were similar at 31 to 35 meq/liter, which compares with normal 96 meq/liter. One additional calf made chloride deficient was recovered to normal health in 9 days following a single treatment with salt water and feeding of control diet containing .48% chlorine. Control calves fed a diet with .48% chlorine and which also had their abomasal contents removed daily grew normally and exhibited no deficiency signs. When dietary chloride was adequate, removal of abomasal contents (and chlorine) had no adverse effects on the animals.

Abomasum↗