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Biomedical subjects

L Bäckström

Publications and source records attributed to L Bäckström.

At least 19 recordsLinked to original sources
PubMed2000

Bronchoalveolar lavage cytology and hematology: a comparison between high and low health status pigs at three different ages.

Bronchoalveolar lavages (BALs) were performed with a bronchoscope on 5- and 7.5-week-old, anesthetized, high health status pigs (n = 14). At 10 weeks of age, pigs (n = 28) were necropsied, lungs were removed, and BAL samples were collected from the right diaphragmatic lobe with a modified 12-Fr (4-mm) Foley catheter. Peripheral blood was sampled from all pigs (n = 28) before each BAL procedure. Peripheral blood and BAL samples were collected according to a similar study design at 5, 7.5, and 10 weeks of age from 12 low health status pigs, which were raised according to standard farm procedures (n = 6) or as segregated early weaned pigs (n = 6). Bronchoalveolar lavage cytology and hematologic 95% confidence intervals were determined for 5-, 7.5-, and 10-week-old high (group A) and low health status pigs (groups B and C). The results were compared between the different groups. Repeated BALs were easily performed in all pigs, making this an additional tool for evaluation of respiratory health. Total numbers of cells and neutrophils in peripheral blood and BAL samples were greater in low health status pigs than in high health status pigs. Hematologic results paralleled the findings in BAL fluid. Segregated early weaning of low health status pigs in a less challenging environment mainly reduced the number of neutrophils in BAL samples and peripheral blood.

Age Factors↗
PubMed1999

A 15-week experimental exposure of pigs to airborne dust with added endotoxin in a continuous flow exposure chamber.

The purpose of this study was to evaluate the effect of longterm exposure to airborne dust and endotoxin on the respiratory system of pigs. A continuous flow exposure chamber was built for the purpose of exposing pigs to selected airborne contaminants. Pigs (n = 6) were exposed to a combination of a very fine corn/soybean meal (40.6 mg/m3) with added lipopolysaccharide (LPS; 12.4 microg/m3) for 8 h/d over 5 d for 15 wk (75 d of exposure). Control pigs (n = 6) were housed in a room with minimal contamination of these airborne contaminants. Surprisingly, dust in the exposure chamber and the control room was highly contaminated with peptidoglycan. Changes in the lung were monitored by collecting bronchoalveolar lavage (BAL) fluid for cytology at 5 different time points throughout the exposure period. Blood samples were collected at the same time for hematology. A non-specific respiratory inflammatory response was found in exposed and control pigs, as suggested by the increased neutrophils in BAL fluid and the small inflammatory areas in the lung tissue. No macroscopic lung lesions were observed in control or exposed pigs. The findings in the control pigs imply that even low dust concentrations and possibly peptidoglycan contamination can induce cellular changes in the BAL fluid and that a true control pig does not exist. In addition, the exposed pigs developed a mild eosinophilia, indicating an allergic response to the airborne contaminants.

Air Pollutants↗
PubMed1998

Health problems in veterinary students after visiting a commercial swine farm.

In October 1993 and 1994, respectively, 77 and 76 third-year veterinary students visited a swine farm to work with pigs for 3 h. On both occasions, a large number of students reported flu-like symptoms after the visit. To further investigate this, the students were presented with a questionnaire modeled after the standard questionnaire used for evaluating organic dust exposure. General and/or respiratory symptoms were reported by 103/142 (72.5%) students. General symptoms, such as eye irritation, headache and tiredness were experienced by 60/103 (42.2%) students. Cough, nasal and throat irritation, and sinus trouble were the most prevalent respiratory symptoms and were reported by 94/103 (91%) of the students. Symptoms mostly developed the same day and disappeared within 3 d after exposure. The presence of respiratory and/or general symptoms was not significantly different between students who wore a mask during the lab or those who did not. Students with pre-existing allergies were more likely to develop respiratory symptoms than non-allergic students.

Adult↗
PubMed1998

Airborne contaminants and farmers health in swine farms with high and low prevalence of respiratory diseases in pigs.

The main purpose of this study was to investigate the relationship between prevalence of respiratory disease in swine and respiratory health of swine farmers. Fourteen farms were selected based on clinical history and slaughtercheck evidence of respiratory problems in pigs. The farms were divided into two groups with either high (n = 7) or low (n = 7) prevalence of respiratory disease in pigs. Airborne dust, endotoxin and peptidoglycan were measured once in farrowing, gestation, nursery and finishing of each farm. Respiratory health of farmers in participating farms was evaluated by questionnaire and pulmonary function test. A mean of 71% of the pigs in high prevalence farms had pneumonic lesions at slaughter, compared with 7% in low prevalence farms. No significant relationship was found between prevalence of respiratory disease in pigs and airborne dust, endotoxin or peptidoglycan. More farmers in high prevalence farms reported chest tightness (p = 0.038). The percentage predicted FEF 25%-75%; was lower (p = 0.046) in farmers working in high prevalence farms. Significant differences disappeared after adjusting for smoking status. Our study suggests that farmers working on farms with a high prevalence for respiratory disease in pigs may have more respiratory problems than farmers working in farms with low prevalence of such diseases.

Adult↗
PubMed1997

Tangential torque effects on the control of grip forces when holding objects with a precision grip.

When we manipulate small objects, our fingertips are generally subjected to tangential torques about the axis normal to the grasp surface in addition to linear forces tangential to the grasp surface. Tangential torques can arise because the normal force is distributed across the contact area rather than focused at a point. We investigated the effects of tangential torques and tangential forces on the minimum normal forces required to prevent slips (slip force) and on the normal forces actually employed by subjects to hold an object in a stationary position with the use of the tips of the index finger and thumb. By changing the location of the object's center of gravity in relation to the grasp surface, various levels of tangential torque (0-50 N x mm) were created while the subject counteracted object rotation. Tangential force (0-3.4 N) was varied by changing the weight of the object. The flat grasp surfaces were covered with rayon, suede, or sandpaper, providing differences in friction in relation to the skin. Under zero tangential force, both the employed normal force and the slip force increased in proportion to tangential torque with a slope that reflected the current frictional condition. Likewise, with pure tangential force, these forces increased in proportion to tangential force. The effects of combined tangential torques and tangential forces on the slip force were primarily additive, but there was a significant interaction of these variables. Specifically, the increase in slip force for a given increment in torque decreases as a function of tangential force. A mathematical model was developed that successfully predicted slip force from tangential torque, tangential force, and an estimate of coefficient of static friction in the digit-surface interface. The effects of combined tangential torques and forces on the employed normal force showed the same pattern as the effects on the slip force. The safety margin against frictional slips, measured as the difference between the employed normal force and the slip force, was relatively small and constant across all tangential force and torque levels except at small torques (< 10 N x mm). There was no difference in safety margin between the digits. In conclusion, tangential torque strongly influences the normal force required for grasp stability. When controlling normal force, people take into account, in a precise fashion, the slip force reflecting both tangential force and tangential torque and their interaction as well as the current frictional condition in the object-digit interface.

Adult↗
PubMed1993

Actinobacillus pleuropneumoniae culture supernatants interfere with killing of Pasteurella multocida by swine pulmonary alveolar macrophages.

The effect of Actinobacillus pleuropneumoniae culture supernatant on swine pulmonary alveolar macrophage (PAM) functions was studied. The A. pleuropneumoniae culture supernatant was toxic to PAMs when tested by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and lactate dehydrogenase (LDH) release assays. Biological activity of the supernatant was ascribed to cytotoxins. Both the LDH and MTT assays were used for measurement of crude A. pleuropneumoniae cytotoxin concentration with good reproducibility. A preparation containing 6,800 toxic units/mL (determined by MTT assay) was used for subsequent experiments. The objective was to study the effect of crude cytotoxin on the ability of swine PAMs to kill Pasteurella multocida. Phagocytosis of opsonized P. multocida type A by PAMs was not efficient. Only 8% of incubated organisms were ingested by noncytotoxin-treated PAMs after 30 min phagocytosis. The bactericidal effect of noncytotoxin-treated PAMs only last for 60 min, after which, the rate of growth of surviving P. multocida exceeded the rate of bacterial killing by PAMs. Complete elimination of P. multocida by PAMs was not observed in this study. A total loss of ability to kill P. multocida by PAMs was seen when the PAMs were pretreated with a high concentration (340 toxic units/mL) of A. pleuropneumoniae cytotoxin. If the PAMs were pretreated with a low concentration (3.4 toxic units/mL) of cytotoxin, a significant reduction in the killing of P. multocida was still observed. The reductions in phagocytosis, phagosome-lysosome fusion (demonstrated using yeast particles of Candida albicans), and oxidative burst (demonstrated by nitro blue tetrazolium reduction (NBT) assay) may have contributed to the impaired killing of P. multocida by PAMs.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinobacillus pleuropneumoniae↗
PubMed1992

Somatosensory control of precision grip during unpredictable pulling loads. I. Changes in load force amplitude.

In manipulating 'passive' objects, for which the physical properties are stable and therefore predictable, information essential for the adaptation of the motor output to the properties of the current object is principally based on 'anticipatory parameter control' using sensorimotor memories, i.e., an internal representation of the object's properties based on previous manipulative experiences. Somatosensory afferent signals only intervene intermittently according to an 'event driven' control policy. The present study is the first in a series concerning the control of precision grip when manipulating 'active' objects that exert unpredictable forces which cannot be adequately represented in a sensorimotor memory. Consequently, the manipulation may be more reliant on a moment-to-moment sensory control. Subjects who were prevented from seeing the hand used the precision grip to restrain a manipulandum with two parallel grip surfaces attached to a force motor which produced distally directed (pulling) loads tangential to the finger tips. The trapezoidal load profiles consisted of a loading phase (4 N/s), plateau phase and an unloading phase (4 N/s) returning the load force to zero. Three force amplitudes were delivered in an unpredictable sequence; 1 N, 2 N and 4 N. In addition, trials with higher load rate (32 N/s) at a low amplitude (0.7 N), were superimposed on various background loads. The movement of the manipulandum, the load forces and grip forces (normal to the grip surfaces) were recorded at each finger. The grip force automatically changed with the load force during the loading and unloading phases. However, the grip responses were initiated after a brief delay. The response to the loading phase was characterized by an initial fast force increase termed the 'catch-up' response, which apparently compensated for the response delay--the grip force adequately matched the current load demands by the end of the catch-up response. In ramps with longer lasting loading phases (amplitude greater than or equal to 2 N) the catch-up response was followed by a 'tracking' response, during which the grip force increased in parallel with load force and maintained an approximately constant force ratio that prevented frictional slips. The grip force during the hold phase was linearly related to the load force, with an intercept close to the grip force used prior to the loading. Likewise, the grip force responses evoked by the fast loadings superimposed on existing loads followed the same linear relationship.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Somatosensory control of precision grip during unpredictable pulling loads. III. Impairments during digital anesthesia.

During manipulation involving restraint of 'active' (mechanically unpredictable) objects, it is presumed that the control of the grip and other reaction forces more regularly relies on somatosensory input than during manipulation of 'passive' (mechanically predictable) objects. In companion studies we have shown that grip forces are automatically adjusted to the amplitude and the rate of distal pulling loads imposed through an 'active' object held in a precision grip. In this study anesthesia of either one or both digits holding the manipulandum was used to examine whether the grip force regulation was dependent on afferent signals from the digits. Five types of trapezoidal load force profiles of various rate and amplitude combinations were given in an unpredictable sequence while the subject was prevented from seeing the hand. Grip forces, load forces and position of the manipulandum in the pulling direction were recorded. With both digits anesthetized the load amplitude changes yielded considerably less grip force modulation and in many trials obvious grip force responses were absent. Moreover, the latencies between the onset of the load changes and the observed grip force responses were much prolonged. However, there was pronounced inter-individual variation. Subjects exhibiting a lower stiffness in the pulling direction, probably due to more flexed fingers when holding the manipulandum, showed a higher force modulation, higher responsiveness to the load ramps and shorter latencies. Hence, under certain conditions afferent input from receptors proximal to the digits could be utilized to provide some grip regulation. The evoked grip force responses showed an initial response similar to the normally occurring 'catch-up' response, but it was not graded by the load force rate. Also, there was no 'tracking' response, suggesting that the latter was contingent upon a moment-to-moment control using afferent input from the digits. With only one digit anesthetized (thumb) the handicap was less severe. Thus, the grip force regulation was impaired under any condition of digital anesthesia, i.e., afferent input from both index finger and thumb was required for the adequate operation of the grip force regulation.

Adult↗
PubMed1989

Pasteurella multocida and Bordetella bronchiseptica in atrophic rhinitis and pneumonia in swine.

A total of 163 pigs from nine farrow-to-finish herds representing various levels of atrophic rhinitis (AR) were selected for postslaughter examination of AR and pneumonia. Nasal swabs and lungs were cultured for detection of Bordetella bronchiseptica and Pasteurella multocida. Seventy-three pigs were examined at eight weeks of age and 90 contemporaries at six months of age. Mean AR scores were 1.21 and 1.11 for the eight week and six month old pigs, respectively (0 = normal, 3 = severe). In individual pigs increasing AR score was related to increasing pneumonia score in eight week old pigs but not in six month old hogs. In eight week old pigs, B. bronchiseptica and P. multocida were isolated more frequently from pigs with higher AR scores. From nasal swabs of six month old hogs, Bordetella was almost never recovered while Pasteurella was frequently isolated score. Toxigenic type DP. multocida was isolated from nasal cultures of only seven (4%) pigs and from lung cultures of only one pig. Pasteurella was never isolated from lungs of the eight week old pigs and Bordetella never from the six month old hogs. The isolation rate of P. multocida, predominantly type A, from lungs of six month old pigs increased from 11% in grossly normal lungs to 86% in lungs with severe pneumonia. Pigs from one herd free from lesions of AR and pneumonia were also examined; type AP. multocida was isolated from nasal cultures of one of six eight week old pigs. Somatic antigens of P. multocida were determined for 94 nasal and 20 lung isolates. Somatic serovar 3 was found in 93% of the nasal isolates and in all lung isolates.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1985

Effect of atrophic rhinitis on growth rate in Illinois swine herds.

Influence of atrophic rhinitis (AR) on mean daily weight gain (MDG) was studied in hogs randomly selected from 7 farrow-to-finish herds in Illinois. Herds were selected to obtain a wide range of clinical signs and lesions of the disease; thus, prevalence of clinical signs of AR in finishing hogs ranged from 0% to 20% among herds, and in hogs examined at slaughter the proportion of hogs with turbinate lesions ranged from 5% to 92%. None of the herds investigated had any obvious problems with pneumonia; nevertheless, hogs with moderate to severe pneumonic lesions were excluded from the study, to minimize any combined effect of AR and pneumonia. In 3 herds, MDG in AR-free pigs was 15% to 18% better than in pigs with severe AR lesions. Prevalence of clinical signs ranged from 5% to 20%, and of turbinate lesions, from 66% to 92%. In 4 herds in which MDG appeared to be unaffected by AR, prevalence of clinical signs of the disease ranged from 0% to 5%, and of turbinate lesions, from 5% to 74%. No consistent pattern of influence on AR lesions was found for bacterial infections, as determined by culturing of nasal swab specimens on MacConkey agar and blood agar.

Animals↗
PubMed1984

Clinical study of mastitis-metritis-agalactia in sows in Illinois.

Mastitis-metritis-agalactia (MMA) occurred in 6.9% of 16,405 farrowings recorded over 1 year (1981) in 31 Illinois swine herds. Prevalence of MMA among herds ranged from 1.1% to 37.2% and was not correlated to herd size. There was a significant positive correlation between the prevalence of MMA and the housing system wherein sows were moved from pasture gestation to crates immediately before farrowing. A significant seasonal peak of MMA was found for the third quarter of the year (10.3%). Mean prevalence of MMA was 13% in pluriparous sows and 4.2% in primiparous sows. The difference was not significant. Sows with MMA gave birth to more live pigs per litter compared with healthy sows (+0.7 pigs per litter). The number of stillbirths and pigs found dead after birth also was higher in sows with MMA (+4.6%). Total pig mortality until 1 week of age was 56% in litters of pluriparous sows with MMA and 17% in litters of healthy pluriparous sows and, respectively, 41% and 15% in litters of primiparous sows. The mean number of pigs per litter surviving at 1 week of age was 5.6 in pluriparous sows with MMA and 9.3 in healthy sows and, respectively, 6.2 and 8.3 in primiparous sows. For all herds investigated, mean litter size at birth (including stillbirths) was 11.0. Total pigs mortality until 1 week of age was 31%. Pig losses attributable to MMA, at 6.9% prevalence of the disease, were 4% of all pigs born and 12.9% of the pig mortality until 1 week of age.

Age Factors↗
PubMed1983

Bacterial endotoxin in blood of dysgalactic sows in relation to microbial status of uterus, milk, and intestine.

Clinical cases of lactation failure in sows from 6 swine herds in Illinois were investigated for the presence of bacterial endotoxins in blood and the concurrent microbial status of uterus, milk, and intestine. Twenty-five affected sows were compared with 13 contemporary healthy sows (controls) in the same herds. A higher prevalence of bacterial endotoxin in blood of affected sows than in the controls, although not statistically significant, supported earlier theories of endotoxin involvement in the disease. Further, a positive relationship was noticed between prevalence of solely gram-negative bacteria in ileum and milk and development of dysgalactia and endotoxemia. No such relationship was found for bacterial isolates from the uterus, suggesting lack of association between lactation failure and metritis.

Animals↗
PubMed1978

On the agalactia post partum in the sow. A clinical study.

The purpose of the present investigation was to study the clinical symptoms of agalactic sows post partum in randomly selected swine herds. The study comprised 71 sows affected with agalactia post partum and 71 healthy sows from the same herds used as controls. Average morbidity of the disease in these 50 herds, consisting of an average of 25 sows, was 12.8%. Sixty-three per cent of the agalactic sows were affected within one day after farrowing. There was no difference in gestation length between healthy sows and agalactic sows. The body temperature was significantly higher for affected than for healthy sows. Mastitis was diagnosed in 35 out of 71 agalactic sows. The criteria for mastitis were swelling and herdening of one or several udder glands. Vaginal discharge was recorded for affected sows (55/57) as well as for healthy sows (51/58) and is therefore not significantly associated with agalactia. The temperament of the agalactic sows was moderately or severely affected in 62 out of 71 agalactic sows. Constipation was recorded for 13/59 agalactic sows and for 3/57 normal sows. The agalactic sows had significantly higher number of piglets per litter at birth while the litter size was higher for healthy sows at weaning. Numerically, more sows were culled among agalactic sows (16/48) than among normal sows (6/42). Moreover, sows affected with agalactia at the previous parturition were more inclined to meet with the disease at the next parturition. Further studies comprising large groups of animals are, however, necessary for evaluation of this question.

Animals↗
PubMed1977

Atrophic rhinitis in swine fattener herds. A field study of the spread of the disease with infected pigs bought at market.

In three different fattener herds pigs primarily AR infected as baby piglets were mixed in the fattening units with healthy pigs at an age of 11--13 weeks. Snout alterations were registered on cut snouts at a slaughter weight of about 70 kg. Severe AR was registered in the groups of primarily infected pigs (Tables I--III). The incidence of snout alterations was lower in the groups of pigs infected at an age of 11--13 weeks, but was much higher than in the groups of healthy control pigs or in the normal pig population in the region (Table IV). The results indicate that pigs infected at a rather late age in the fattening units can develop severe atrophic rhinitis.

Animals↗