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Biomedical subjects

J de Ruiter

Publications and source records attributed to J de Ruiter.

11 recordsLinked to original sources
PubMed2005

Optimization of pheromone lure and trap characteristics for currant clearwing, Synanthedon tipuliformis.

Currant clearwing Synanthedon tipuliformis (Sesiidae) has been a pioneering and successful target of mating disruption in New Zealand, with virtually universal black currant industry adoption since c. 1990. Recent unexplained control failures using mating disruption lead to questions about pheromone efficacy. In this study, we have investigated the possible reasons for reduced control from mating disruption, and report improvements in trap catch based on pheromone loading and trap color. No differences were found in electrophysiological responses to pheromone components from two New Zealand populations. Male moth catches in traps baited with synthetic lures were disrupted in the presence of mating disruption dispensers ( > 99.99%) indicating no apparent barrier to efficacy from the pheromone formulation. Field behavioral observations confirmed this result. Male attraction to yellow delta traps was equivalent to green delta traps, but was greater than to red, black, blue, or white traps. Solid yellow delta traps were more attractive than black traps with yellow stripes, the latter designed to mimic the color pattern of the insect. Solid yellow funnel traps were less attractive than a composite of green, yellow, and white funnel traps. Trap catch increased as a function of pheromone loading, and trap color. In another experiment conducted in Tasmania, there was no difference in catch with single component [(E,Z)-2,13-octadecadienyl acetate] or two component lures [97% (E,Z)-2,13-octadecadienyl acetate:3% (E,Z)-3,13octadecadienyl acetate], refuting the suggestion of a different pheromone strain there.

Acetates↗
PubMed2001

Dose-response relationship and infusion requirement of cisatracurium besylate in infants and children during nitrous oxide-narcotic anesthesia.

BACKGROUND: To determine the effect of age on the dose-response relation and infusion requirement of cisatracurium besylate in pediatric patients, 32 infants (mean age, 0.7 yr; range, 0.3-1.0 yr) and 32 children (mean age, 4.9 yr; range, 3.1-9.6 yr) were studied during thiopentone-nitrous oxideoxygen-narcotic anesthesia. METHODS: Potency was determined using a single-dose (20, 26, 33, or 40 microg/kg) technique. Neuromuscular block was assessed by monitoring the electromyographic response of the adductor pollicis to supramaximal train-of-four stimulation of the ulnar nerve at 2 Hz. RESULTS: Least-squares linear regression analysis of the log-probit transformation of dose and maximal response yielded median effective dose (ED50) and 95% effective dose (ED95) values for infants (29+/-3 microg/kg and 43+/-9 microg/kg, respectively) that were similar to those for children (29+/-2 microg/kg and 47+/-7 microg/kg, respectively). The mean infusion rate necessary to maintain 90-99% neuromuscular block during the first hour in infants (1.9+/-0.4 microg x kg(-1) x min(-1); range: 1.3-2.5 microg x kg(-1) x min(-1)) was similar to that in children (2.0+/-0.5 microg x kg(-1) x min(-1); range: 1.3-2.9 microg x kg(-1) x min(-1)). CONCLUSION: The authors conclude that cisatracurium is equipotent in infants and children when dose is referenced to body weight during balanced anesthesia.

Age Factors↗
PubMed1989

Analysis of polyadenylation site usage of the c-myc oncogene.

The c-myc gene contains 2 well conserved polyadenylation (pA) sites. In all human and rat cell lines from various differentiation stages and tissue types the amount of mRNA terminating at the second pA site is 6-fold higher than the amount ending at the upstream site. This is not due to a difference in stability of the two mRNA types and therefore must be due to preferential usage of the downstream site. The usage of the pA sites is not altered during growth factor induction of quiescent cells. We have not been able to detect differences in behavior between mRNAs ending at either pA site. Both types of mRNA are induced upon treatment of cells with cycloheximide. Furthermore, we have shown that the poly(A) tail of c-myc mRNA is lost during degradation of the messenger, as was described previously for c-myc mRNA in an in vitro system. The time required for the loss of the poly(A) tail is similar to the half-life of c-myc mRNA.

Animals↗
PubMed1983

Model studies in adjuvant chemotherapy.

We have focused on three aspects of adjuvant chemotherapy applied to mice with one of the metastasizing tumors: Lewis lung carcinoma (LL) or mammary carcinoma 2661 (M2661). The first aspect concerned the timing of adjuvant chemotherapy. To investigate this, tumor-bearing mice were treated postoperatively with cyclophosphamide using a standard regimen. In M2661, adjuvant therapy was marginally effective in contrast to the clearly significant results obtained in LL. Any delay in the initiation of adjuvant therapy decreased the efficacy of the treatment. The effect of administering chemotherapy before surgery was also studied; normally, marginally effective adjuvant therapy was found to become effective when started preoperatively in M2661. In LL, effective adjuvant therapy was found to become less effective when started preoperatively. The second aspect considered was the comparability between the increase in relapse-free survival time and the increase in cure rate as alternate goals of adjuvant therapy. To study this, mice with small, medium, or large residual tumor loads were subjected to surgery and subsequently treated with cyclophosphamide. While the effect of adjuvant therapy on the cure rate increased proportionally with decreasing tumor load, the increase in lifespan in nonsurvivors was not related to tumor load. The final aspect of study was the selection procedure for drugs to be applied in adjuvant treatment in our models. Taking the volume response of large tumors as being predictive for the successful use of the same agent in adjuvant therapy, we obtained both false-negative and false-positive results in our tumor lines.

Amputation, Surgical↗
PubMed1982

Comparison of metastatic disease after local tumour treatment with radiotherapy or surgery in various tumour models.

Spontaneous metastases in lymph nodes and/or the lung were obtained after tumour cell inoculation of four mouse tumours and one rat tumour into the foot-pads of syngeneic animals or their F1 hybrids. Following local radiotherapy with doses of 45-80 Gy, significantly more mice died with metastases than following local amputation of the tumour-bearing foot when the 2661 carcinoma was involved. No significant difference was observed after these treatments for the other tumours. The enhancement of metastastic growth after local radiotherapy in the 2661 carcinoma seems not to be due to incomplete killing of tumour cells in the foot. The presence of irradiated normal structures and tumour tissue after radiotherapy promoted the outgrowth of 261 carcinoma cells which were outside the radiation field at the time of treatment. Evidently, even under similar experimental conditions, radiotherapy may enhance the growth of metastases from some tumours and not from others.

Amputation, Surgical↗
PubMed1979

Adjuvant chemotherapy: theoretical considerations and model studies.

Comparison of response of experimental tumors to adjuvant chemotherapy for minimal disease with the response of solid large tumors to similar drug regimens has indicated that for many tumors the small microscopic foci are more responsive. There are, however, a number of model tumors that respond far less to chemotherapy when applied to minimal disease than when applied to large tumors. The response of these tumors to adjuvant treatment shows similarities with the clinically observed response. The data do not support the hypothesis that the success of a drug combination given as adjuvant chemotherapy may be predicted from the success of the same treatment when applied for manifest disease.

Animals↗
PubMed1976

Studies on the enhancement by cyclophosphamide (NSC-26271) of artificial lung metastasis after labeled cell inoculation.

In a mouse model the retention of125I-5-iodo-2' -deoxyuridine-labeled tumor cells in the lung after iv injection was compared with the formation of tumor colonies in the lung 15 days after injection. The modification in lung retention after treatment with cyclophosphamide (CP), isophosphamide, Corynebacterium parvum, and heparin paralleled the changes in lung-colony numbers by these treatments. Since the modifications could be identified as early as 1 hour after iv administration of tumor cells, further evidence was obtained for the conclusion reached earlier that the modification of lung metastases by CP and Corynebacterium parvum is not due to immunologic mechanisms. Comparison with the lung retention of heat-killed tumor cells and living embryonic cells showed that CP induced an increased retention of all three cell types. In contrast, Corynebacterium parvum decreased the retention of living tumor cells, but failed to modify the retention of dead tumor cells, but did not affect the retention of living embryonic cells. Since no similar cell types were affected by the various treatments it seems likely that different mechanisms are involved. Apparently CP decreases the nonspecific resistance against the lodging and growth of any type of cell in the lung.

Animals↗