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Biomedical subjects

J M Weaver

Publications and source records attributed to J M Weaver.

At least 37 records · Page 2Linked to original sources
PubMed1994

Correlation of human bladder tumor histoculture proliferation and sensitivity to mitomycin C with tumor pathobiology.

This study examined the in vitro proliferation and mitomycin C (MMC) sensitivity of patient bladder tumors as a function of the tumor pathobiology. Surgical specimens of transitional cell carcinoma of the bladder were maintained as histocultures on collagen gels. The thymidine labeling index (LI) was determined by autoradiography and the labeling for proliferating cell nuclear antigen (PCNA) by immunohistochemistry. There was a linear correlation between the thymidine LI and the PCNA LI, but the PCNA LI were quantitatively lower than the thymidine LI. The mean thymidine LI were 30.9, 32.4 and 51.5% for the grade I, II and III tumors, 33.6 and 56.3% for the superficial (Tis, Ta and T1) and invasive (T2-T4) tumors, and 28.9 and 50.9% for the diploid and aneuploid tumors. Analysis of variance indicates that these differences were statistically significant. These data indicate that the proliferation of tumor histocultures paralleled the tumor aggressiveness in vivo. The tumor sensitivity to MMC, measured by the inhibition of the thymidine LI of tumor cells, was studied in 31 tumors. At a 2 hour exposure, as is currently used in intravesical therapy, the MMC concentrations required for 50% inhibition of thymidine LI (IC50) showed a 120-fold intertumor variation (0.102 to 12.4 micrograms./ml.). The sensitivity to MMC inversely correlated with tumor aggressiveness. The IC50 increased with tumor LI (p < 0.05). The mean IC50 were 2.61 and 5.79 micrograms./ml. for superficial and invasive tumors (p < 0.05), 1.06, 3.05 and 4.49 micrograms./ml. for grade I, II and III tumors (p < 0.05), and 2.53 and 4.31 micrograms./ml. for diploid and aneuploid tumors (p = 0.14). These data indicate a large difference in sensitivity of human bladder tumors to MMC, with greater sensitivity for well-differentiated superficial tumors and lesser sensitivity for undifferentiated, invasive tumors.

Autoradiography↗
PubMed1993

Evaluation of a clinical recovery score after general anesthesia.

A clinical recovery score (CRS) assessing recovery after general anesthesia was compared with the Digit-Symbol Substitution Test (DSST), Trieger Test (TT), a patient-completed visual analogue scale for alertness (VAS), and an independent observer's evaluation of recovery. The CRS included ratings of the following parameters: activity, respiration, circulation, consciousness, ambulation, color, and nausea and vomiting. Forty patients requiring the removal of three or four third molars participated in the study. All patients received the same general anesthetic technique. Each patient was evaluated by the five methods preoperatively, on admission to the recovery room, and at 15-min intervals until discharge. The four recovery tests (CRS, DSST, TT, VAS) were evaluated using chi 2 analysis to determine if there was any overall difference among the tests using the observer's determination of home readiness as the standard for discharge. The CRS was significantly more in agreement with the observer's determination than were the paper and pencil tests. The recovery tests were also evaluated with regard to instances of early dismissal or prolonged retention of the patient, again using the observer's determination as the "gold standard." The CRS was the only recovery test devoid of early dismissals. We conclude that the CRS provides a valid, simple measure of recovery that can be readily used in offices providing outpatient anesthesia and in studies measuring clinical recovery from anesthesia or sedation.

Ambulatory Surgical Procedures↗
PubMed1988

Verapamil increases the toxicity of local anesthetics.

The calcium channel blocker verapamil has, in addition to its other properties, been shown to be a local anesthetic. Its concurrent use in a patient undergoing regional anesthesia may, therefore, increase the potential risk for local anesthetic toxicity. To evaluate this possibility, the effect of verapamil on the median lethal dose (LD50) of lidocaine and bupivacaine in mice was determined. Immediate pretreatment with verapamil increased the mortality of mice given the LD50 dose of lidocaine to 74%, and in mice given the LD50 doses of bupivacaine, to 82%. In animals pretreated with verapamil and calcium chloride, the mortality associated with the administration of LD50 doses of lidocaine and bupivacaine decreased to 43% and 48%, respectively, thus returning the mortality rate back to the LD50 of the local anesthetics when administered alone. It seems that the combined administration of local anesthetic and verapamil results in a significant drug interaction: the resulting blockade of sodium and calcium channels apparently impairs membrane function to a greater degree than with either drug alone. Additional investigation is warranted, and caution should be exercised in giving verapamil to patients during regional anesthesia. Should an adverse drug interaction ensue, the administration of calcium may be beneficial.

Animals↗
PubMed1988

The effectiveness of flurazepam as night sedation prior to the removal of third molars.

Anxiety prior to dental treatment is a well-recognized problem. Although oral sedation has been recommended the night before appointments to reduce this anxiety, there are no well-controlled studies to support this claim. The present double-blind cross-over study investigated the effect of 30 mg of flurazepam taken the night before the removal of impacted third molars. Preoperative anxiety, visuomotor performance and sleep patterns were investigated in 20 adult patients with similarly impacted third molars. While preoperative flurazepam led to a statistically significant improvement in sleep patterns, there was no reduction in pre-operative anxiety on the morning of surgery. In addition, the flurazepam-treated group demonstrated significantly impaired visuo-motor performance 60 min after intravenous sedation compared to this group where intravenous sedation was used only preceded by placebo. Patients had a significant preference for flurazepam over placebo as a night-time sedative.

Adult↗
PubMed1986

Sulfur influences on rumen microorganisms in vitro and in sheep and calves.

When continuously cultured ruminal microbes were given orchardgrass hay and sufficient sulfuric acid or hydrochloric acid to maintain a pH of 5.5, fermentation and numbers of protozoa were reduced compared with cultures whose pH was controlled with phosphoric acid. Likewise, when sulfur-deficient, purified diets were supplied to cultures, less methane (mmol X liter-1 X d-1), 3.2 vs 32.6, was produced and fewer cellulolytic bacteria (log10/ml), 5.8 vs 7.2 were present than when cultures were given the same diet supplemented with .3% elemental sulfur. The rumen of sheep fed the .04% sulfur diet had reduced digesta weights (1.69 vs 3.2 kg) compared with sheep fed the diet with .34% sulfur at the same intake. There also was reduced methanogenesis 12.3 vs 25.8 mmol X liter-1 X d-1) and reduced numbers of cellulolytic bacteria (7.4 vs 8.4 log10/ml) in sulfur-deficient sheep in comparison to sulfur-supplemented sheep. In growing calves, the same types of bacteria predominated in the rumen, but more facultative anaerobic bacteria were isolated from calves fed .04% sulfur than from calves fed diets with .34 to 1.72% sulfur. None of the dietary levels of sulfur appeared toxic. Regardless of treatment, volatile fatty acids were more predominant than lactic acid as end-products of fermentation of ruminal microbes in fermenters, sheep and calves. The greater methanogenesis and the greater cellulolytic bacterial numbers of sulfur-supplemented sheep compared with sulfur-deficient in vitro cultures, is interpreted to be the result of recycling of sulfur to the rumen in sheep where it is efficiently scavengered by ruminal bacteria.

Animal Feed↗
PubMed1985

Sodium-dependent hypertension produced by chronic central angiotensin II infusion.

Experiments were performed to characterize the hypertension produced by chronic intracerebroventricular (ICV) infusion of angiotensin II (ANG II) in conscious rats. Infusion of ANG II into a lateral cerebral ventricle for 5 days (1 or 6 micrograms/h) produced dose-dependent increases in mean arterial pressure associated with increased water intake. No consistent changes in heart rate, urinary electrolyte excretion, or water balance were observed. Similarly, no alterations in plasma sodium and potassium concentration, plasma osmolality, or plasma ANG II levels were seen during ICV ANG II infusion. Controlling fluid intake at 40 ml/day did not alter the development of hypertension in this model. Hypertension was found to be sodium dependent, with high sodium intake augmenting the increase in arterial pressure in response to chronic ICV ANG II. Although plasma aldosterone concentrations were increased in some situations during ICV ANG II infusion, adrenalectomy failed to alter the course of hypertension. This study demonstrates that chronic selective stimulation of brain ANG II receptors by means of continuous ICV infusion of ANG II produces sodium-sensitive increases in arterial pressure associated with, but not dependent on, increased fluid intake. This form of hypertension cannot be attributed to sodium and water retention, elevations in plasma aldosterone, or leak of significant amounts of ANG II from cerebrospinal fluid into the peripheral circulation.

Adrenalectomy↗
PubMed1984

Mesoionic pyridazine ribonucleosides. A novel biologically active nucleoside metabolite.

4-Cyano-3-oxido-1-beta-D-ribofuranosylpyridazinium (10a) has been prepared from 4-cyano-3(2H)-pyridazinone (4) by using a low-temperature, kinetically controlled, silyl Hilbert-Johnson reaction followed by deblocking of the resulting triacetate derivative, 8a, with NaHCO3 in methanol. 10a is apparently the first example of a mesoionic analogue of a pyrimidine nucleoside. It was discovered as a urine metabolite of 4-cyano-3(2H)-pyridazinone (4) in mice. 10a possesses Gram-negative antibacterial activity in vivo against a systemic Escherichia coli infection in mice with an ED50 of 25-50 mg/kg. A series of 4-substituted 3-oxidopyridazinium ribonucleosides, 11a-h, were synthesized as analogues of 10a. 4-Chloro-3-oxido-1-beta-D-ribofuranosylpyridazinium (11a) was found to be several times more active than 10a against E. coli in vitro although it showed no in vivo activity.

Animals↗
PubMed1983

Will chronic intracerebroventricular saralasin infusion produce selective blockade of brain angiotensin II receptors in the rat?

In an attempt to produce chronic, selective, pharmacological blockade of brain angiotensin II (AII) receptors, we infused saralasin (1sar, 8ala-angiotensin II), a competitive AII receptor antagonist, into the cerebral ventricles of rats for 5 days. We found that i.c.v. saralasin infusion at a dose of 12 micrograms/hr selectively blocked brain AII receptors, as determined by pressor responses to acute i.c.v. and i.v. AII. Infusion of this dose of saralasin in rats maintained on a high sodium intake produced a pressor response that was not seen in rats maintained on a normal sodium intake. The cardiovascular responses to chronic i.c.v. saralasin were similar to those seen in response to chronic i.c.v. AII, suggesting that i.c.v. saralasin acts as an agonist at central AII receptors in rats maintained on a high sodium intake. The apparent agonistic activity of saralasin may limit its usefulness in assessing the physiological role of the central effects of AII.

Angiotensin II↗
PubMed1981

Blood pressure and heart rate responses to anticipated high-stress dental treatment.

Twenty-four healthy adults participated in a study to determine the effects of anticipated high-stress dental treatment on blood pressure and heart rate. Blood pressure, heart rate, and state anxiety were assessed prior to four consecutive dental appointments. Appointments 1, 2, and 4 were of relatively low stress and appointment 3 was of relatively high stress. Blood pressure was unaffected while heart rate was highest prior to appointment 3 and lowest prior to appointment 1.

Adolescent↗
PubMed1979

Recognition and management of the depressed dental patient.

Depressive illness may affect the patient's response to dental care. It has been implicated both as a causal factor and a sequela in facial pain syndromes. Depression is treated with various medications that may influence function and health of the oral cavity and that may adversely interact with drugs used to control pain and anxiety.

Antidepressive Agents, Tricyclic↗
PubMed1979

Teaching advanced life support to predoctoral dental students.

The purpose of this project was to determine if senior dental students were capable of meeting the rigid didactic and clinical performance requirements of the American Heart Association's course in advanced life support. The course includes cardiopulmonary resuscitation, mechanical ventilation, endotracheal intubation, intravenous cannulation, interpretation of certain electro-cardiographic dysrhythmias, synchronized cardioversion, defibrillation and the use of intravenous vasopressors, cardiotonics, and antiarhythmics. Of 30 students who were randomly selected from over 120 applicants for this senior elective course, 27 met the minimum proficiency requirement of 85 percent on a standardized written examination, and no one scored less than 78 percent. Of the students who were offered clinical testing stations, 19 out of 20 met the clinicae support can be considered a feasible addition to other instruction in emergency care in the undergraduate dental curriculum.

Clinical Competence↗
PubMed1977

Tetrahydrofolate and other growth requirements of certain strains of Ruminococcus flavefaciens.

Two strains of Ruminococcus flavefaciens were studied. Each grew in a chemically defined minimal medium containing: minerals; ammonium sulfate as a nitrogen source; amino acids as a nitrogen source, a growth promotant(s) or as both; cellobiose as an energy and carbon source; isobutyric acid, isovaleric acid, carbonic acid, and bicarbonate as additional carbon sources; and biotin, thiamine, and tetrahydrofolic acid as vitamins. Tetrahydrofolic acid (5 ng/ml) served as a replacement for rumen fluid that was required in previous media tested for the growth of these bacteria. The present bacteria differ from many of the ruminococci previously studied in that they do not require either p-amino-benzoic acid or folic acid but do require tetrahydrofolic acid for maximum growth. Dihydrofolic acid and 5-methyltetrahydrofolic acid can substitute for tetrahydrofolic acid in minimal chemically defined medium. Thus, there must be extensive metabolic interaction between the microbes inhabitating the rumen, because the R. flavefaciens isolated had complex requirements for growth and yet was among the predominant bacteria in the rumen of cattle fed a simple vitamin B-deficient, nonprotein nitrogen, high-fiber, purified diet.

Acetates↗