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Biomedical subjects

C Perez

Publications and source records attributed to C Perez.

At least 145 records · Page 8Linked to original sources
PubMed1990

Bacteremias caused by Selenomonas artemidis and Selenomonas infelix.

We report two different cases of bacteremia caused by two recently described Selenomonas species, Selenomonas artemidis and Selenomonas infelix. Both species are normally found in human buccal flora. S. artemidis bacteremia appeared in a patient (number 1) who presented with an air-fluid pulmonary cavity and clinical conditions consistent with an anaerobic lung abscess. While the patient improved with antibiotic therapy, cultures of respiratory secretions yielded Mycobacterium tuberculosis. This case demonstrated a strong possibility of a coexisting lung abscess due to S. artemidis. S. infelix bacteremia appeared in a cancer patient (number 2) with heart disease during preterminal acute respiratory distress. It was more difficult in this case to assess the clinical impact of the Selenomonas organisms on the patient.

Adenocarcinoma↗
PubMed1990

Induction of Na(+)-K(+)-ATPase and its subunit mRNAs by serum in a rat liver cell line.

Addition of serum to confluent Clone 9 cells increased the protein, RNA, and DNA content per plate of cells; the increments became manifest within 3-6 h and were sustained for the 48-h duration of study. After the addition of serum, Na(+)-K(+)-ATPase activity was stimulated 1.25- and 1.45-fold at 6 and 12 h, respectively. In cells preincubated in the absence of serum for 24 h, addition of serum increased the abundances of Na(+)-K(+)-ATPase subunit mRNAs, mRNA alpha 1 and mRNA beta, coordinately by approximately 2- and 2.7-fold at 3 h, an effect that preceded the stimulation of Na(+)-K(+)-ATPase activity. The serum-induced increments in subunit mRNA abundances were further enhanced by the combined presence of serum and cycloheximide; mRNA alpha 1 and mRNA beta abundances were also augmented by cycloheximide alone (approximately 2.5- and 9.2-fold at 6 h, respectively). In cells incubated in the absence of serum, the half-lives of mRNA alpha 1 and mRNA beta, estimated from decrements in their abundances after the addition of actinomycin D, were 12 and 10 h, respectively. These data demonstrate that serum enhances Na(+)-K(+)-ATPase subunit mRNA abundance and enzyme activity in Clone 9 cells. Comparison of the estimated half-lives of Na(+)-K(+)-ATPase subunit mRNAs with the observed increments in their abundances at 3 h suggests that the serum-induced increases in mRNA alpha 1 and mRNA beta abundances are in large part due to enhanced synthesis of these mRNAs.

Animals↗
PubMed1990

The costs of low dose rate remote afterloading compared to manual afterloading brachytherapy.

A relatively recent development in the United States in brachytherapy technology is the use of equipment to remotely afterload radioactive sources into the patient applicators. This technique competes with past practices where the source was placed by hand. With remote afterloading, the sources are automatically removed from the patient and placed into a lead safe whenever healthcare personnel enter the patient's room. The primary benefit of remote afterloading brachytherapy is to reduce the radiation exposure to the patient's visitors and healthcare providers. By comparing the operating and maintenance costs for remote afterloading brachytherapy (RAL) and manual afterloading (MAL) for patients receiving conventional low dose rate brachytherapy from interstitial and intracavitary implants, estimates of the prospective cost of this increased safety can be offered.

Brachytherapy↗
PubMed1989

Increased arachidonic acid uptake by platelets from insulin-dependent diabetics and diabetic rats.

14C-Arachidonic acid uptake was measured in platelets obtained from 15 insulin-dependent diabetic and 17 control subjects and in 12 streptozotocin-diabetic and 21 control rats. The 14C-arachidonic acid uptake, expressed as pmol/10(8) platelets/min, mean +/- SEM, was significantly higher in platelets from diabetic subjects (2.80 +/- 0.23) and diabetic rats (1.73 +/- 0.20) than in the control subjects (2.29 +/- 0.15) and the control rats (1.35 +/- 0.08). No significant correlations were found between arachidonic acid uptake and glucose, total cholesterol or triglyceride plasma levels in either rats or humans. Arachidonic acid uptake was inhibited by indometacin but not by nordihydroguaiaretic acid, in diabetic as well as in control subjects. The present results suggest that the increased arachidonic acid uptake by platelets from insulin-dependent diabetic patients and streptozotocin-diabetic rats depends on their increased platelet arachidonic acid utilization through the cyclooxygenase pathway.

Adolescent↗
PubMed1989

Effect of tactile stimulation pulse characteristics on sensation threshold and power consumption.

The psychophysical responses of human subjects to vibratory tactile stimulation of the skin were investigated experimentally. The parameters of the waveform important to the minimization of power consumed by the tactile array of electromechanical vibrators and the maximization of the skin sensitivity to the stimulus were explored to develop optimum stimulation. Parameters investigated included the amplitude, frequency, and duty cycle of the current waveform used to drive the vibrators as well as the number of pulses per stimulating burst and the recovery time between bursts. Graphical techniques were used to determine the optimal combination of the parameters which gave a stimulus that excited the skin to above tactile threshold while maintaining at a relative minimum the power required for the stimulus. The optimal stimulation waveform contains a burst of 10 rectangular pulses of 4% duty cycle separated by a period of nonstimulation of 2 s. Such a waveform can elicit a sensitivity of 29.4 mA-1 consuming only 55 microW of power.

Blindness↗
PubMed1989

Evaluation of aluminum-yttrium filtration for intraoral radiography.

In comparison with the use of traditional aluminum filtration, a radiation dose reduction of 40% at 90 kVp and 25% at 70 kVp was found with the use of aluminum-yttrium (Al-Y) filtration for intraoral bitewing and periapical radiographs. An increased exposure time, and consequent greater tube loading, was necessary to maintain film density. Extended gray-scales (i.e., reduced radiographic contrast) occurred at both energy levels tested with the use of Al-Y filtration. Subjective evaluation of image quality in terms of clarity, resolution, and contrast was carried out independently by nine periodontologists. Despite some interoperator variance, there was a preponderant preference for traditional aluminum filtration.

Aluminum↗
PubMed1989

Phase II study of multiple daily fractionations in the palliation of advanced pelvic malignancies: preliminary report of RTOG 8502.

This Phase II protocol was designed around the format of a previously reported study for the palliation of advanced pelvic malignancies (RTOG 7905). The large dose per fraction (1000 cGy) of the first study unexpectedly demonstrated frequent late gastrointestinal toxicity and was replaced in the present study by 2 days of twice daily fractionation (370 cGy/fraction totaling 1480 cGy/course) based on linear quadratic consideration of acute and late toxicities. The interval between courses of 4 weeks was retained and the total dose for three courses was 4440 cGy. A total of 152 patients were entered of which 142 have sufficient follow-up information for analysis. Fifty-nine percent of the patients completed all three courses, 20% completed two courses, and 20% received only one course. The primary sites were: gynecological (39.4%); colorectal (32.4%); genitourinary (24.7%); and other (2.8%). The best overall response was: complete remission (10%); partial remission (22%); no change (24%); progression (10%); and unknown (27%). For the patients completing all three courses, the response was: complete remission (14%); partial remission (31%); no change (40%); progression (7%); and unknown (8%). Median survival was 4.5 months and the actuarial survival at 12 months is 19%. In RTOG 7905, 90% of the late toxicities appeared by 12 months. For RTOG 8502, there were 32 patients alive at 9 months and 19 patients alive at 12 months available for evaluation of late toxicity. There has been one late grade 3 GI toxicity reported and only one acute grade 3 gastrointestinal toxicity. Even if the true rate of late toxicity for 8502 were 20%, the chance of seeing none or one toxicity would be 0.007. This toxicity report represents a marked reduction of the grade 3 and 4 late toxicity seen in RTOG 7905 (37% at 9 months and 45% at 12 months) without lowering the tumor response rate. The interval between courses in both protocols allows for potential tumor proliferation. To test for the effect of tumor proliferation, RTOG 8502 is continuing as a Phase III randomization between 4 weeks and 2 weeks separation.

Adult↗
PubMed1989

Hyperthermia quality assurance guidelines.

These Hyperthermia Quality Assurance guidelines are a result of a joint workshop of the Hyperthermia Committee of the American College of Radiology and the Hyperthermia Physics Center, which is the national quality assurance program under Contract No. N01-CM-37512 with the National Cancer Institute. Hyperthermia technology presently lacks the kind of standardization in equipment, treatment procedures, patient monitoring, and treatment documentation available in radiotherapy. Therefore, preventing unacceptable variability in treatment data demands a strong commitment to in-house quality control procedures and to centralized quality assurance reviews in cooperative multi-institutional trials. This paper presents a set of test procedures necessary to ensure proper operation of equipment, suggests a frequency for such tests, and also includes guidelines on quality control procedures to be used during treatment to improve the safety, effectiveness, and reproducibility of hyperthermia treatments. A set of forms are presented to indicate the minimum data, albeit incomplete, that must be collected for acceptable documentation of treatment. These guidelines should be valuable not only to the new entrants in the field but also to those participating in multi-institutional cooperative hyperthermia trials. They have been approved by the Hyperthermia Committees of American College of Radiology, American Society for Therapeutic Radiology and Oncology, Radiation Therapy Oncology Group and the American Association of Physicists in Medicine.

Forms and Records Control↗
PubMed1989

Effect of oral glutathione on hepatic glutathione levels in rats and mice.

Administration of oral glutathione (GSH) increases hepatic GSH levels in fasted rats, in mice treated with GSH depletors such as diethyl maleate and in mice treated with high doses of paracetamol. An increase in hepatic GSH levels after administration of oral GSH does not occur in animals treated with buthionine sulphoximine, an inhibitor of GSH synthesis. Administration of oral GSH leads to an increase in the concentration of L-cysteine, a precursor of GSH, in portal blood plasma. Oral administration of L-methionine produced a significant decrease of hepatic ATP in fasted rats, but not in fed rats. Administration of N-acetylcysteine or GSH did not affect the hepatic ATP levels. The results show that the oral intake of GSH is a safe and efficient form of administration of its constituent amino acids in cases when GSH synthesis is required to replete hepatic GSH levels.

Acetaminophen↗
PubMed1989

Effect of a uridine 5'-diphosphate glucose analogue on herpes simplex keratitis in rabbits and vaginal infection in guinea pigs.

A uridine 5'-diphosphate glucose analogue, active in vitro against herpes simplex type 1 and 2 viruses, was assayed in rabbit infected corneas with the above viruses. The infected eyes were treated by drug instillation thrice daily and evaluation of ocular lesion was performed by slit-lamp biomicroscopy. The compound [[[5'-(2'',3'',4'',6''-tetra-O-benzoyl-alpha-D-glucopyranosyl)oxy] carbonyl]amino)sulfonyl]uridine shows a moderate antiviral activity, resulting in a reduction in the severity of clinical illness during acute infection. Vaginal infection of guinea pigs with herpes simplex type 2 virus was treated topically by instillation twice daily with the compound. The effect on clinical evolution was related to viral shedding from the genital tract, and a moderate reduction of both parameters in respect to the infected untreated controls was observed.

Animals↗
PubMed1989

[In vitro bactericidal effect of a piperacillin-pefloxacin combination against isolated strains of nosocomial pneumopathies in intensive care].

Combinations of piperacillin and pefloxacin are evaluated in vitro using checkerboard and killing-curves methods against 19 clinical isolates: S. aureus, K. pneumoniae, K. oxytoca, C. freundii, P. stuartii, Ps. aeruginosa, Ps. maltophilia and Ac. anitratum. The static checkerboard method showed more synergistic antibacterial effects than the killing curves method. The best synergistic effects appeared against S. aureus, K. oxytoca, P. stuartii, Ps. aeruginosa Ac. anitratum, including a notable increase of the rapidity of bactericidal activity. The combination PIP 64 micrograms - PEF 4 micrograms prevents the frequent secondary regrowth seen after 6 hours with the antibiotics used alone. No activity is obtained against S. aureus meti-R and Ps. maltophilia.

Cross Infection↗
PubMed1988

A novel form of TNF/cachectin is a cell surface cytotoxic transmembrane protein: ramifications for the complex physiology of TNF.

Tumor necrosis factor (TNF) is a monocyte-derived cytotoxin that has been implicated in tumor regression, septic shock, and cachexia. The mechanism by which TNF induces these different disease states is unclear. We have identified and characterized a novel, rapidly inducible cell surface cytotoxic integral transmembrane form of TNF. The existence and behavior of this novel form of TNF may explain the complex physiology of this molecule. We suggest that activated monocytes synthesize transmembrane TNF at the site of inflammation and kill their targets by either cell-to-cell contact or local release of the TNF secretory component. In contrast, septic shock and cachexia may result from either acute or chronic systemic activation of monocytes, resulting in the widespread release of TNF secretory component into the circulation of the affected individual. We further suggest that cell borne cytokines and cytotoxins may be the primary mediators of directed inflammatory responses.

Cells, Cultured↗
PubMed1988

Acute epidural hematoma: an analysis of factors influencing the outcome of patients undergoing surgery in coma.

Mortality due to epidural hematoma is virtually restricted to patients who undergo surgery for that condition while in coma. The authors have analyzed the factors influencing the outcome of 64 patients who underwent epidural hematoma evacuation while in coma. These patients represented 41% of the 156 patients operated on for epidural hematoma at their centers after the introduction of computerized tomography (CT). Eighteen patients (28.1%) died, two (3.1%) became severely disabled, and 44 (68.8%) made a functional recovery. The mortality rate for the entire series was 12%, significantly lower than the 30% rate observed when only angiographic studies were available. A significant correlation was found between the final result and the mechanism of injury, the interval between trauma and surgery, the motor score at operation, the hematoma CT density (homogeneous vs. heterogeneous), and the hematoma volume. The patient's age, the course of consciousness before operation (whether there was a lucid interval), and the clot location did not correlate with the final outcome. The mortality rate was significantly higher in patients operated on within 6 hours or between 6 and 12 hours after injury than in those undergoing surgery 12 to 48 hours after injury. Compared with the patients operated on later, the patients undergoing surgery in the early period were, on the average, older and had more rapidly developing symptoms, more pupillary changes, lower motor scores at surgery, larger hematomas, a higher incidence of mixed CT density clots, more severe associated intracranial lesions, and higher postoperative intracranial pressure (ICP). The mechanism of trauma seems to influence the course of consciousness before and after surgery. Passengers injured in traffic accidents had a lower incidence of a lucid interval and longer postoperative coma than patients with low-speed trauma, suggesting more frequent association of diffuse white matter-shearing injury. The duration of postoperative coma correlated with the morbidity rate in survivors. Forty-eight patients (75%) had one or more associated intracranial lesions, and 70% of these required treatment for elevation of ICP after hematoma evacuation. An ICP of over 35 mm Hg strongly correlated with poor outcome; administration of high-dose barbiturates was the only effective means for lowering ICP in nine of 15 patients who developed severe intracranial hypertension after surgery. This study attempts to identify patients at greater risk for presenting postoperative complications and to define a strategy for control CT scanning and ICP monitoring.

Acute Disease↗
PubMed1988

Clinical, radiological, and pathological spectrum of angiographically occult intracranial vascular malformations. Analysis of 21 cases and review of the literature.

The clinical, radiological, and histopathological features of 21 cases of angiographically occult intracranial vascular malformations (AOIVM's) are analyzed, and a review of 241 additional appropriately documented, histologically verified cases collected from the literature is presented. In all, there were 115 (43.8%) arteriovenous malformations, 82 (31.2%) cavernous angiomas, 26 (9.9%) venous angiomas, 10 (3.8%) cases of capillary telangiectasis, and 29 (11%) mixed or unclassified angiomas. The result of the analysis shows that there are no essential differences in the patterns of clinical presentation, the computerized tomography (CT) appearance, or the surgical prognosis among these pathological types of vascular malformations. Certain histological features common to all AOIVM's (such as the small caliber, the more or less complete thrombosis of the malformed vessels, and the changes induced in the surrounding brain tissue by repeated microhemorrhages) seem to determine the biological behavior of the anomaly rather than the predominant type of vessel involved. Thus, subdivision of AOIVM's into the four classical pathological types has little practical value. Most AOIVM's are visualized by the CT scan and show a rather typical appearance. Surgical removal, which prevents rebleeding and ameliorates or suppresses seizure activity, is usually easy to perform and represents the treatment of choice for patients with clinically symptomatic AOIVM's.

Adolescent↗