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Biomedical subjects

G Nyman

Publications and source records attributed to G Nyman.

At least 37 records · Page 2Linked to original sources
PubMed1999

Ventilation-perfusion relationships during exercise in standardbred trotters with red cell hypervolaemia.

In order to evaluate the pulmonary gas exchange during exercise in Standardbred trotters with red cell hypervolaemia (RCHV), 12 horses with RCHV were compared with 9 normovolaemic (NV) horses. VO2 and VCO2 were determined with an open bias flow system. Cardiovascular and haemodynamic data were recorded during exercise at 4 different speeds on a treadmill. Pulmonary gas exchange was assessed by conventional blood gas variables (arterial and mixed venous blood gas tensions), and the ventilation-perfusion distribution VA/Q was estimated by the multiple inert gas elimination technique. VA and AaDO2 were calculated. Dispersions of perfusion and ventilation distribution (SDQ, SDV) were determined. HR, RR, Qt, VO2, VA, log SDV, C(a-åv)O2 and lactate did not differ between groups. The degree of hypoxaemia was more pronounced in the RCHV than in the NV (PaO2 = 54 and 59 mmHg; AaDO2 = 41 and 34 mmHg in RCHV and NV, respectively, at highest workload). Further, pH was lower in the RCHV and PaCO2 and VCO2 was significantly higher in the RCHV during the course of exercise (pH = 7.24 and 7.29; PaCO2 = 56 and 51 mmHg; VCO2 = 156 and 135 ml/kg x min in RCHV and NV, respectively, at highest workload). The PaO2 predicted from the VA/Q distribution was higher than actually measured in blood during heavy exercise which may suggest a certain diffusion limitation over the alveolar-capillary membranes in both groups but there was no difference between the 2 groups. The more pronounced hypoxaemia observed in RCHV trotters was mainly caused by increased VA/Q mismatch expressed as a significantly increased log SDQ (0.78 and 0.45 in RCHV and NV, respectively, at highest workload).

Animals↗
PubMed1998

Three-dimensionally slanted illusory contours capture stereopsis.

In stereo capture a stereogram of a crossed illusory figure pulls a texture bounded by the illusory contours to the same depth plane with the illusory figure. We investigated whether three-dimensionally curved and slanted illusory figures could capture a repeating background texture. According to results, stereoscopic capture was perceived when a disparate illusory contour was slanted provided that the period of the background texture was consistent with the three-dimensional geometry of the illusory surface. We suggest that stereo capture is actually induced by disparate rows of points defined by vertical cut-out sectors and the induced disparity spread is constrained by illusory contours and possible discrete matches of the background texture.

Adult↗
PubMed1997

Shape priming in a complex visual search task.

Shape priming was studied in four experiments comprising a complex search task in which subjects searched for a target shape presented among three distractors and reported the location of the target. Localization performance improved as a function of the duration of stimulus exposure and prime lead time. The efficiency of shape primes in improving performance decreased when lateral masks were presented near the target. Generally, both preprimes and simultaneous primes improved localization accuracy. With laterally masked stimuli, the preprimes and simultaneous primes were equally effective; when neighboring mask items were absent, the effect of preprimes was more pronounced. The results suggest that different strategies were used in the preprime and in the simultaneous-prime conditions.

Cues↗
PubMed1997

Occlusion constraints and stereoscopic slant.

In binocular vision horizontal magnification of one retinal image leads to a percept of three-dimensional slant around a vertical axis. It is demonstrated that the perception of slant is diminished when an occlusion interpretation is possible. A frontoparallel plane located in the immediate vicinity of a slanted surface in a location which allows a perception of occlusion reduces the magnitude of perceived slant significantly. When the same plane is placed on the other side, the slant perception is normal because there is no alternative occlusion interpretation. The results indicate that a common border between the occluder and a slanted surface is not a necessary condition for the reduction effect. If the edges are displaced and the edge of the slanted surface is placed in a location in which it could be occluded, the effect still appears.

Depth Perception↗
PubMed1997

Endogenous nitric oxide in the airways of different animal species.

BACKGROUND: High amounts of endogenous nitric oxide (NO) have been demonstrated in the human upper airway, but the role of nasal NO is still unclear. The present study aims to describe nasal NO excretion in different animal species with special living conditions or anatomy. METHODS: Domestic animals (horse, cow, pig, sheep, dog, cat) and zoo-animals (Rhesus monkey, chimpanzee, gorilla, elephant, fur seal, alpaca, yak, dolphin, camel, capybara, bear, tiger, wolf, giraffe, alligator, Harris' hawk, kangaroo) were studied awake, resting or anaesthetised. NO concentrations were measured by chemiluminescence using different analysers and techniques, including measurements on mixed exhaled air, during continuous or intermittent gas sampling, and on single breaths. RESULTS: Rhesus monkeys (number of individuals N = 5) and pigs (N = 2) were compared and displayed quite different excretion patterns. Allowing NO to accumulate in the nose during timed occlusions yielded peak concentrations in monkeys of 0.46 +/- 0.07 parts per million (ppm, mean +/- SEM), 0.59 +/- 0.08 ppm, 0.70 +/- 0.08 ppm and 1.02 +/- 0.05 ppm NO after 15, 30, 60 and 120 s of occlusion. In pigs, 0.012-0.021 ppm NO were recorded, independent of occlusion time. The chimpanzee was similar to the Rhesus monkey and the highest NO value, 2.9 ppm, was recorded after 4-5 min of occlusion. In single breaths from 3 elephants 0.031-0.082 ppm, from 1 gorilla 0.029 ppm, and from 1 chimpanzee 0.069 +/- 0.003 ppm NO (8 observations) were recorded. CONCLUSIONS: We found considerable species difference in nasal NO excretion with pronounced amounts only in primates and elephants. The physiological implications of these findings remain to be defined.

Animals↗
PubMed1996

Depth asymmetry in da Vinci stereopsis.

We investigated processes that determine the depth localization of monocular points which have no unambiguous depth. It is known that horizontally adjacent binocular objects are used in depth localization and for a distance of 25-40 min arc monocular points localize to the leading edge of a depth constraint zone, which is an area defined by the visibility lines between which the points in the real world must be. We demonstrate that this rule is not valid in complex depth scenes. Adding other disparate objects to the scene changes the localization of the monocular point in a way that cannot be explained by the da Vinci explanation of monocular-binocular integration. The effect of additional disparate objects is asymmetric in depth: a crossed object does not affect the da Vinci effect but an uncrossed object biases the depth localization of monocular objects to uncrossed direction. We conclude that a horizontally adjacent binocular plane does not completely determine the depth localization of a monocular point and that depth spreading from other binocular elements biases the localization process.

Depth Perception↗
PubMed1996

Total blood volume in the normally performing Standardbred trotter: age and sex variations.

The purposes of this study were to elucidate the influences of age and sex on the mass specific blood volume parameters: total blood volume (TBV/BW, ml/kg), plasma volume (PV/ BW, ml/kg), total red cell volume (CV/BW, ml/kg) and maximal packed cell volume (PCV, l/l, i.e. after total mobilisation of the splenic red cell reservoir) and to establish reference values for these in normally performing Standardbred trotting race horses. In total 205 horses were studied. They were all, according to their owners and/or trainers, performing satisfactorily in racing or training for shortly impending racing. Blood volume determination was done with the Evans blue dye dilution technique after exercise induced emptying of the spleen. Both age and sex were found to influence variation of these parameters significantly, with the possible exception of PV/BW, whereas the primary variation appeared to be in CV/BW. It was concluded that taking age and sex dependent variations into consideration will render prediction of normal values for the blood volume parameters in the athletic Standardbred trotter more reliable and the detection of abnormal deviations more precise if five age and sex groups are used for comparisons.

Aging↗
PubMed1996

Foveal-to-peripheral priming in letter identification reflects response bias, not enhanced visibility.

Several studies have suggested that it might be easier to identify a letter when its replication is simultaneously presented in the visual display. We have measured identification accuracy for a memorized target letter that was shown in the peripheral field in two conditions in which a letter either identical or different in shape was flashed simultaneously at fixation. The results of three forced-choice experiments showed that, contrary to Geiger and Lettvin's (1986) previous findings, an identity prime did not improve the visibility of a temporally backward masked target letter. However, the foveal prime letter could apparently bias the subject's decision so that he/she was much more ready to report the more visible prime letter as the peripheral target.

Adult↗
PubMed1996

Effects of additional premedication on romifidine and ketamine anaesthesia in horses.

The clinical and cardiorespiratory effects of premedication with acepromazine, butorphanol or diazepam in addition to romifidine before induction of anaesthesia with ketamine were studied in 6 horses on 4 random occasions. Administration of romifidine alone or in combination with butorphanol resulted in an increase in arterial blood pressure, accompanied by a significant decrease in heart rate with second-degree atrio-ventricular heart block. Induction of anaesthesia with ketamine returned the heart rate to baseline value, but the arterial blood pressure was significantly increased compared to baseline. Including acepromazine in the premedication prevented the hypertension and bradycardia induced by romifidine. The respiratory rate was slightly decreased after premedication in all groups, but returned to the baseline value after induction of anaesthesia. Mild hypercapnia and significant hypoxaemia were observed during sedation and anaesthesia, reflecting an impairment of pulmonary function. Premedication with acepromazine before sedation with romifidine resulted in a fast induction and good anaesthesia. Inclusion of butorphanol in the premedication resulted in individual variation in the quality of induction and anaesthesia. Addition of diazepam to the sedation with romifidine resulted in good muscle relaxation with a smooth induction and maintenance of anaesthesia and an increased time before the horses responded to noxious stimuli, compared with romifidine and ketamine anaesthesia. All horses reached a standing position at the first attempt, but horses premedicated with diazepam in combination with romifidine showed mild ataxia after recovery.

Acepromazine↗
PubMed1995

Anaesthetics for general anaesthesia in growing pigs.

A comparison was made between different anaesthetics for general anaesthesia in growing pigs, with focus on minor surgery under field conditions and for experiments in clinical research. Healthy cross-breed pigs (Hampshire x Yorkshire x Swedish Landrace) weighing 20-45 kg were used. The anaesthetics combinations compared were 1) azaperone plus metomidate (AM), 2) Zoletil (zolazepam + tiletamine) plus xylazine (ZX), and 3) Zoletil plus xylazine plus ketamine (ZXK). Parameters measured were: heart rate, respiratory rate, blood pressure, body temperature, and depth of analgesia (pin-prick). Minor surgery was performed to test the reliability of the "pin-prick" tests. It was clearly shown that AM produces anaesthesia with good cardiovascular stability and is a drug combination that is suitable for minor surgery. ZX also produces a good anaesthesia characterized by reliable and rapid induction. Good cardiovascular function is maintained, and the laryngeal relaxation makes intubation possible. These characteristics are very useful in a laboratory environment, as easy handling to avoid stress is necessary for research. Although it is difficult to evaluate the quality of analgesia from this study, it is concluded that ZX did not provide a superior anaesthesia and analgesia compared to AM in crossbreed pigs. However, these drugs are too expensive for regular use in ambulatory practice. The effects of ZXK resemble those of ZX, but the ZXK-drug combination has no anaesthetic advantages and is more laborious to work with.

Anesthesia, General↗
PubMed1992

Distribution studies of theophylline: microdialysis in rat and horse and whole body autoradiography in rat.

After intravenous administration of theophylline, microdialysis has been used for studying the non protein bound theophylline concentration in blood and in lung tissue in the rat as well as in two horses. The distribution pattern of 14C-theophylline in the rat was also investigated. When the distribution of theophylline was completed the time course of free drug in the interstitial fluid in lung tissue was in good agreement with the total concentration-time profile in plasma in both species. In the rat the free concentration of theophylline in the lung was slightly lower than the free concentration in the blood from 40 to 300 min. The in vivo protein binding in blood was 48.8 +/- 6.2% in the rats (n = 9) and 8-25% in the horses (n = 2). The whole body autoradiography study in rat showed that the concentration of radioactivity in the lung followed the blood concentration very closely up to 24 h after injection. The effect of theophylline in the lung can be assumed to be related to the plasma concentration of theophylline, since the concentration-time profile in plasma reflects the time course in the lung.

Animals↗
PubMed1992

Green Spring criteria for medical necessity of outpatient treatment and its use in a mental health utilization review program.

The authors have developed a two-tiered method for utilization review of outpatient mental health services. The methodology looks at initial and continued treatment evaluation and uses diagnosis, symptoms, plan of treatment, and the Global Assessment Scale (GAS) among other indicators to determine appropriateness of treatment. Preliminary program experience has been positive and is included.

Ambulatory Care↗
PubMed1991

Discontinuation of neuroleptic medication in older, outpatient schizophrenics. A placebo-controlled, double-blind trial.

Thirty-five schizophrenic outpatients over the age of 52 who had been stable on neuroleptic medication were all switched to haloperidol. Ten patients were unable to tolerate the haloperidol and two dropped out of the study. The remaining 23 patients were randomly and blindly assigned to haloperidol or placebo and then followed for 6 months. Five patients did not complete the study due to medical or administrative reasons. Among the patients who completed the study, five of 10 randomized to placebo relapsed compared with only one of eight randomized to haloperidol. However, three of 10 patients randomized to placebo have remained stable without medication for 2.5 years.

Age Factors↗
PubMed1991

Pulmonary gas exchange correlated to clinical signs and lung pathology in horses with chronic bronchiolitis.

Eight horses (mean weight 438 kg) with chronic obstructive pulmonary disease (COPD) were studied for clinical signs, ventilation/perfusion relationships (VA/Q) and lung morphology. Four horses were killed and necropsied after the study. In horses with COPD, minute ventilation was almost twice as high as normal, whereas PaO2 was significantly decreased. Cardiac output was normal, but pulmonary artery pressure and pulmonary vascular resistance were significantly increased. The VA/Q distribution was abnormal with an increased scatter of VA/Q ratios. However, shunt (VA/Q = 0) was increased in one horse only. Ventilation of dead space and high VA/Q regions (VA/Q greater than 10) were increased markedly and comprised 74 per cent of minute ventilation. On lung biopsy, all horses showed chronic bronchiolitis with epithelial hyperplasia and metaplasia. Diffuse acinar hyperinflation also was evident at necropsy. There was a significant inverse correlation between the respiratory rate and the fractional ventilation of normal VA/Q regions. Also, there was a significant agreement between the extent of bronchiolar epithelial hyperplasia in necropsy specimens of lungs and the degree of ventilation of high VA/Q regions and dead space. The findings suggest that hyperinflation of the lung due to obstructed airways may be the common denominator of increased ventilation of high VA/Q regions and dead space ventilation and of elevated pulmonary artery pressure in horses with COPD from chronic bronchiolitis.

Animals↗