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Biomedical subjects

J Bakker

Publications and source records attributed to J Bakker.

At least 109 records · Page 6Linked to original sources
PubMed1994

Patterns of sensitivity to cadmium and pentachlorophenol among nematode species from different taxonomic and ecological groups.

The variation of acute toxicity data among nematode species belonging to different taxonomic and ecological groups was investigated. Twelve different nematode species were extracted from the soil and directly exposed to cadmium and pentachlorophenol. LC50-values were estimated after 24, 48, 72, and 96 h of exposure in aqueous solutions. The species exhibited large differences in sensitivity. LC50-values (72 h) for pentachlorophenol ranged from 0.5 to more than 34.5 mumol/L and for cadmium from 29 to more than 800 mumol/L. These toxicity data could be described by a log-logistic distribution function. LC50-values for cadmium were not correlated with those for pentachlorophenol. Species of the subphylum Secernentia were less sensitive to pentachlorophenol than species of the subphylum Penetrantia, while no differences were observed for cadmium. In addition, no relationship was found between toxicity data and life-history strategies. Slow colonizers (K-strategists, sensu lato) were not more sensitive to cadmium and pentachlorophenol than opportunistic species (r-strategists, sensu lato). Nematodes appeared to be as sensitive to pentachlorophenol as other soil invertebrates. Nematodes were generally tolerant to cadmium.

Animals↗
PubMed1994

A semiautomated test apparatus for studying partner preference behavior in the rat.

A semiautomated three-compartment box (3CB) for studying partner preference behavior of rats is described. This apparatus automatically records the rat's time spent in each compartment, as well as the locomotor activity (i.e., the number of visits an animal pays to each compartment). Software was developed for calculating partner preference scores. Behavioral testing in the semiautomated 3CB, which is a modification of an earlier version, is less time consuming and less laborious. Three 3CBs can be observed simultaneously by two trained observers, and the behavioral interactions of three experimental animals with the stimulus animals can be observed and scored by hand. The use of the new apparatus was validated by studying adult partner preference behavior of neonatally ATD-treated male rats. The collected data fully corroborate previous results, obtained in the earlier version of the 3CB, again revealing the behavioral bisexual nature of these ATD males. A new finding was the much higher locomotor activity of the ATD males compared to controls.

Androstatrienes↗
PubMed1994

Effects of N-acetylcysteine in endotoxic shock.

PURPOSE: The release of oxygen-free radicals has been implicated in both peripheral vascular and myocardial alterations of septic shock. N-Acetylcysteine (N-AC), a substrate for the production of glutathione, has potent antioxidant effects. As a nitrosothiol, it may also improve capillary blood flow. We studied the effects of N-AC in a dog model of endotoxic shock. METHODS: Ten pentobarbital-anesthetized, mechanically ventilated dogs were randomly assigned to receive either N-AC (150 mg/kg loading dose in 1 hour, followed by 20 mg/kg.h maintenance dose) or D5W. After the loading dose, each dog received 3 mg/kg Escherichia coli endotoxin intravenously. After 30 minutes, saline infusion was started to restore and maintain baseline filling pressures. RESULTS: The loading dose of N-AC increased DO2 significantly (from 661 +/- 54 to 914 +/- 190 mL/min, P < .05), but VO2 remained stable. After the administration of endotoxin, fluid challenge restored cardiac output to baseline, in both groups. Hemoglobin and, thus, DO2 were slightly lower in the N-AC-treated dogs, but VO2 was similar in both groups. At the end of the study, O2ER was significantly higher in the N-AC-treated dogs than in the control dogs. Blood lactate levels fell more rapidly in the N-AC dogs than in the control dogs. Blood lactate levels returned to normal in the N-AC dogs but not in the control dogs. Tumor necrosis factor (TNF) also decreased significantly in the N-AC dogs but remained elevated in the control dogs. CONCLUSION: These data indicate that N-AC administration in endotoxic shock is well tolerated, may increase oxygen availability to the tissues, and is associated with an attenuation of TNF release.

Acetylcysteine↗
PubMed1994

Rhizobium nod factors reactivate the cell cycle during infection and nodule primordium formation, but the cycle is only completed in primordium formation.

Rhizobia induce the formation of root nodules on the roots of leguminous plants. In temperate legumes, nodule organogenesis starts with the induction of cell divisions in regions of the root inner cortex opposite protoxylem poles, resulting in the formation of nodule primordia. It has been postulated that the susceptibility of these inner cortical cells to Rhizobium nodulation (Nod) factors is conferred by an arrest at a specific stage of the cell cycle. Concomitantly with the formation of nodule primordia, cytoplasmic rearrangement occurs in the outer cortex. Radially aligned cytoplasmic strands form bridges, and these have been called preinfection threads. It has been proposed that the cytoplasmic bridges are related to phragmosomes. By studying the in situ expression of the cell cycle genes cyc2, H4, and cdc2 in pea and alfalfa root cortical cells after inoculation with Rhizobium or purified Nod factors, we show that the susceptibility of inner cortical cells to Rhizobium is not conferred by an arrest at the G2 phase and that the majority of the dividing cells are arrested at the G0/G1 phase. Furthermore, the outer cortical cells forming a preinfection thread enter the cell cycle although they do not divide.

Amino Acid Sequence↗
PubMed1993

Single juveniles of the potato cyst nematodes Globodera rostochiensis and G. pallida differentiated by randomly amplified polymorphic DNA.

Random amplified polymorphic DNA (RAPD) offers a potential basis for the development of a diagnostic assay to differentiate the potato cyst nematode species Globodera rostochiensis and G. pallida. Nine decamer primers have been tested for their ability to amplify species-specific DNA sequences. Primer OPG-05 produced 2 discrete DNA fragments, which were consistently present in 5 G. rostochiensis populations and absent in 5 G. pallida populations. These fragments were detectable in single females as well as in single 2nd-stage juveniles. Their amplification is extremely efficient, and reproducible over a wide range of template concentrations. One-fifth of a single juvenile is sufficient to generate reproducible RAPD markers. The amplification from single juveniles requires no DNA isolation. The use of a crude homogenate does not impair the polymerase chain reaction.

Animals↗
PubMed1993

Hormonal regulation of adult partner preference behavior in neonatally ATD-treated male rats.

Male rats, neonatally treated with ATD (1,4,6-androstatriene-3,17-dione), which blocks the aromatization of testosterone into estradiol (E2), were tested for adult partner preference behavior (PPB; estrous female vs. active male). Castration caused a decrease in preference for the female partner in all males, with ATD males showing lower preference for the female partner than controls. Long-term castrated males did not show preference for either partner. Precastration levels of PPB in control males occurred after treatment with E2 or dihydrotestosterone (DHT) plus E2. DHT alone had no effect on PPB. With E2 alone, the ATD males clearly preferred the male partner. When DHT was added, these ATD males showed no preference for either partner or a low preference for the female partner. In conclusion, adult PPB in male rats is activated by endogenous testosterone or by both its metabolites (DHT and E2) or by E2 alone. ATD males showed a much lower preference for the female. There was a differential effect of DHT and E2: DHT had no effect, but E2 clearly caused ATD males to prefer the male partner and control males to prefer the female partner.

Androstatrienes↗
PubMed1993

Organization of partner preference and sexual behavior and its nocturnal rhythmicity in male rats.

Male rats were neonatally treated with 1,4,6-androstatriene-3,17-dione (ATD), which blocks aromatization of testosterone (T) to estradiol (E2), from Days 0, 2, or 5 through 14. Adult partner preference behavior (PPB; choice between estrous female rat [F] and active male rat [M]) was studied in the early part of the dark phase of the light-dark (LD) cycle. ATD Day 0 Ms showed a preference for the stimulus M or showed no preference for either of the stimulus Ss. Controls preferred the estrous F. ATD Days 2 and 5 Ms showed PPB intermediate between ATD Day 0 Ms and controls. Thus the neonatally sensitive period for organization of adult PPB extends beyond Day 5. Furthermore, PPB showed a nocturnal rhythmicity in ATD Ms but not in controls. In the late part of the dark phase, all Ms showed a preference for the stimulus F. ATD Days 2 and 5 Ms and control Ms were no longer different in PPB, but ATD Day 0 Ms still showed significantly lower preference scores for F than all other Ms. Thus the E2 metabolite of T suppresses organization of an adult nocturnal rhythm in PPB.

Animals↗
PubMed1993

Effects of norepinephrine and dobutamine on oxygen transport and consumption in a dog model of endotoxic shock.

OBJECTIVES: Severe septic shock is associated with an imbalance between oxygen demand and oxygen supply (DO2) in the presence of an impaired oxygen extraction. Vasopressors are often used to restore a minimal perfusion pressure and inotropic agents are often used to increase myocardial contractility. However, optimal adrenergic support remains controversial. The present study investigated the effects of norepinephrine and dobutamine on DO2, oxygen consumption (VO2), and oxygen extraction in a dog model of endotoxic shock. DESIGN: Prospective, randomized, cross-over trial. SETTING: University intensive care laboratory. SUBJECTS: A total of 14 mongrel dogs anesthetized with pentobarbital and mechanically ventilated with air. INTERVENTIONS: The dogs received 2 mg/kg Escherichia coli endotoxin intravenously. After 30 mins, fluid administration with 0.9% saline was started to restore baseline filling pressures. The dogs randomly received dobutamine and norepinephrine. Each agent was infused for 20 mins followed by a drug free interval of 30 mins so that each dog could serve as his own control. Results for norepinephrine were grouped as low dose (0.1 and 0.2 micrograms/kg/min) and high dose (0.5 and 1.0 micrograms/kg/min). Results for dobutamine were also grouped as low dose (5 micrograms/kg/min) and high dose (10 micrograms/kg/min). MEASUREMENTS AND MAIN RESULTS: Norepinephrine increased both mean arterial pressure (MAP) and cardiac output without a significant change in systemic vascular resistance. Only high-dose norepinephrine increased DO2 (from 969 +/- 62 to 1240 +/- 49 mL/min [p < .001]) and VO2 (from 176 +/- 15 to 194 +/- 14 mL/min [p < .001]). Dobutamine increased both cardiac output and MAP. Both low- and high-dose dobutamine increased DO2 (from 891 +/- 91 to 1142 +/- 99 mL/min [p < .001] and from 847 +/- 54 to 1317 +/- 75 mL/min [p < .001], respectively) and VO2 (from 172 +/- 14 to 182 +/- 15 mL/min [p < .001] and from 168 +/- 13 to 184 +/- 14 mL/min [p < .001], respectively). The increase in VO2 for a given increase in DO2 was higher with high-dose norepinephrine compared with high-dose dobutamine. When all doses were taken together, DO2 increased more with dobutamine than norepinephrine. Oxygen extraction decreased with all doses for both norepinephrine and dobutamine. CONCLUSIONS: In this endotoxic shock model, both norepinephrine and dobutamine can increase DO2 and VO2 but dobutamine caused a more consistent increase in these parameters. The decrease in oxygen extraction was relatively similar with dobutamine and norepinephrine. The present study does not support a significant beneficial effect of norepinephrine on the tissue extraction capabilities in endotoxic shock.

Animals↗
PubMed1993

Relation between oxygen consumption and oxygen delivery in patients after cardiac surgery.

The relative contributions of oxygen delivery (DO2) and oxygen extraction (O2ER) to the increase in cellular oxygen uptake (VO2) after cardiopulmonary bypass were studied prospectively in 36 patients after coronary artery bypass grafting (n = 18), valve replacement (n = 17), and removal of a left atrial tumor (n = 1). VO2 was calculated from the Fick equation and DO2 from thermodilution cardiac output and arterial oxygen content. During the first 24 h after cardiac surgery, there was a strong relation between VO2 and DO2 (VO2 = 28 + 0.27 x DO2, r = 0.79, P < 0.0001) but not between VO2 and oxygen extraction. Mixed venous oxygen saturation (SVO2) was usually reduced when cardiac index was below 2.0 L.min-1.m-2. Patients with a prolonged intensive care unit course (> 24 h) had lower cardiac index and lower SVO2 than the other patients. Therefore, the progressive increase in VO2 after cardiac surgery is accomplished primarily by an increase in cardiac output and DO2. It is usually when cardiac function is compromised that O2ER increases and SVO2 decreases.

Aged↗
PubMed1992

Veno-arterial carbon dioxide gradient in human septic shock.

Recent reports have shown that venous hypercarbia, resulting in a widening of the veno-arterial difference in PCO2 (dPCO2), is related to systemic hypoperfusion in various forms of low-flow state. Although septic shock usually is a hyperdynamic state, other factors can influence the CO2 production and elimination, and thus dPCO2 in septic shock This study examined the dPCO2 and acid-base balance together with cardiac output measurements and oxygen-derived variables in 64 adult patients with documented septic shock. For a total of 191 observations, a significant exponential relation between dPCO2 and CO was found. At time of first measurement, 15 patients had an increased dPCO2 (above 6 mm Hg) and a higher mixed venous PCO2 (PvCO2) (47.2 +/- 10.0 vs 35.9 +/- 7.3 mm Hg, p less than 0.001). These patients had a lower cardiac index (2.9 +/- 1.3 vs 3.8 +/- 2.0 L/min.m2, p less than 0.01), a higher oxygen extraction ratio, but a similar VO2 than patients with normal dPCO2. The higher dPCO2 could also be related to an impaired CO2 elimination as indicated by a higher PaCO2 and a lower PaO2/FIO2 in these patients. Nonsurvivors had a significantly higher dPCO2 than survivors (5.9 +/- 3.4 vs 4.4 +/- 2.3 mm Hg, p less than 0.05) in the presence of similar cardiac output. The higher dPCO2 in these patients was probably related to the higher blood lactate levels (7.7 +/- 5.3 mmol/L vs 4.5 +/- 2.8 mmol/L, p less than 0.01) and the more severe pulmonary impairment (SaO2 90 +/- 8 percent vs 95 +/- 4 percent, p less than 0.001). Arteriovenous oxygen content difference (dAVO2) and VO2 were similar in survivors and nonsurvivors. In conclusion, dPCO2 patients with septic shock is related principally to cardiac output but apparently also to the degree of pulmonary impairment. Although dPCO2 is larger in nonsurvivors, its prognostic value is modest.

Adult↗
PubMed1992

Administration of anti-TNF antibody improves left ventricular function in septic shock patients. Results of a pilot study.

In this pilot study, murine monoclonal anti-TNF antibody (2 mg/kg) was administered to ten patients within 24 h of septic shock which persisted after initial resuscitation with intravenous fluids and adrenergic agents. This treatment resulted in a reduction in heart rate (from 122 +/- 10 to 113 +/- 10 beats per minute at 4 h, p less than 0.01) associated with an increase in LVSWI (from 26.5 +/- 5.6 to 31.5 +/- 10.5 g.m2 at 2 h, p less than 0.05), indicating in the absence of change in cardiac filling pressures, an improvement in ventricular function. Arterial oxygenation improved concurrently in six patients. These changes, however, appeared transient. The improvement in cardiac function following anti-TNF antibody administration in patients is in keeping with recent experimental studies indicating the role of TNF in the myocardial depression characterizing septic shock.

Aged↗
PubMed1991

Pneumopericardium and pneumomediastinum after polypectomy.

A case of colonic perforation followed by the development of pneumopericardium, pneumomediastinum and subcutaneous emphysema as complications of colonoscopic polypectomy is described. Surgical intervention with primary closure was successfully performed 24 hours after perforation.

Aged↗
PubMed1991

Blood lactate levels are superior to oxygen-derived variables in predicting outcome in human septic shock.

Recent reports have shown that oxygen delivery (Do2) and oxygen uptake (Vo2) could be related to outcome of critically ill patients. In this study, we examined measurements of cardiac output, oxygen-derived variables, and blood lactate levels in 48 patients with documented septic shock. There were 27 survivors and 21 nonsurvivors from the shock episode. For all 174 observations, there was a significant linear relationship between Vo2 and Do2 (Vo2 = 79 + 0.17 x Do2, r = 0.64, p less than 0.001). There were no significant differences in Do2 between survivors and nonsurvivors at the onset of septic shock (mean +/- SD, 540 +/- 219 vs 484 +/- 222 ml/min.m2, NS) or in the final phase of septic shock (506 +/- 163 vs 443 +/- 187 ml/min.m2, NS). Also, no significant differences were found in Vo2 and oxygen extraction between survivors and nonsurvivors. However, survivors had significantly lower blood lactate levels both initially (5.1 +/- 2.7 vs 8.2 +/- 5.4 mmol/L, p less than 0.05) and in the final phase of septic shock (2.6 +/- 1.9 vs 7.7 +/- 5.6 mmol/L, p less than 0.001). Only the survivors had a significant decrease in blood lactate levels during the course of septic shock (p less than 0.001). We conclude that the oxygen-derived variables, Do2 and Vo2, cannot be used as prognostic indicators in human septic shock. In contrast, blood lactate levels are closely related to ultimate survival from septic shock. Furthermore, decreases in blood lactate levels during the course of septic shock could indicate a favorable outcome. Therefore, blood lactate levels can serve as a reliable clinical guide to therapy.

Cardiac Output↗
PubMed1987

Maedi-visna control in sheep. III: Results and evaluation of a voluntary control program in The Netherlands over a period of four years.

The results of the first four years of the Dutch national voluntary maedi-visna control program, which was launched on January 1, 1982, are presented. At the end of the observation period, 1711 breeding flocks representing 70% of the registered breeding flocks participated. The program is based on accreditation of flocks that have passed two successive serological tests with an interval of six months between and post-accreditation tests every 12 months. The flocks have to conform to a set of specific regulations. Sheep sold from such flocks receive a certificate stating that their origin was accredited. A total of 1212 flocks gained accreditation. Of these flocks, 29.5% were free from infection from the beginning, 35.6% were created by total replacement of the original stock, 19.6% employed repeated testing and culling of positives, and 15.3% were created by artificial rearing of colostrum-deprived lambs. A total of 22 flocks lost accreditation due to detection of 36 seropositives. These positives and their progeny were culled, and all flocks regained accreditation after passing the two negative flock tests required. In a total of seven flocks, an unusual course of events during the pre-accreditation stage was observed; this was mainly attributed to late seroconversions and uncommon degrees of horizontal transmission. The results indicate that this certification yields a substantial guarantee of freedom from maedi-visna virus and they indirectly show that the basic design of the program has been adequate.

Animals↗
PubMed1984

[Long-term effects of a deworming program using flubendazole and levamisole on the percentage of condemned livers in slaughtering pigs].

A deworming programme continued over a period of twenty-four months was carried out to study the proportion of livers condemned because of milk spots, which was unacceptably high on a pig-fattening farm in the Province of Limburg, the Netherlands. In order to remove Ascaris suum from the fattening pigs initially present and to prevent subsequent contamination of the houses with worm eggs, three courses of deworming treatment with flubendazole were initiated on the farm. All newly incoming piglets were systematically treated with 2 ml. of 5 per cent levamisole from the beginning of the trial, this treatment being continued from December 1976 to January 1979. A total number of 3,861 animals took part in the trial. Observations in the slaughter-house started within eight months after the first treatment. The proportion of livers condemned wholly or in part had dropped to 3.6 per cent by that time and showed a further decrease to a mean level of 2.4 per cent during the 17-month period of observation. A significant increase of the mean daily growth was observed at the same time. These results were verified by a similar trial on another farm.

Animals↗