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Biomedical subjects

B Barr

Publications and source records attributed to B Barr.

At least 19 recordsLinked to original sources
PubMed2006

Host propagation permits extreme local adaptation in a social parasite of ants.

The Red Data Book hoverfly species Microdon mutabilis is an extreme specialist that parasitises ant societies. The flies are locally adapted to a single host, Formica lemani, more intimately than was thought possible in host-parasite systems. Microdon egg survival plummeted in F. lemani colonies > 3 km away from the natal nest, from c. 96% to 0% to < 50%, depending on the hoverfly population. This is reflected in the life-time dispersal of females, measured at < 2 m, resulting in oviposition back into the same ant nests for generation after generation. To counter destabilizing effects on the host, Microdon manipulates the social dynamics of F. lemani by feeding selectively on ant eggs and small larvae, which causes surviving larvae to switch development into queens. Infested colonies rear double the number of new queens, thus propagating the vulnerable local genotype and compensating for damage to the host colonies. The consequences of such extreme host specificity for insect conservation are discussed.

Adaptation, Physiological↗
PubMed2006

Prevalence of gastric squamous ulceration in horses with abdominal pain.

REASONS FOR PERFORMING STUDY: Prevalence of gastric ulcerations differs widely according to breed and circumstances of management. Further study of the biological variables involved is required in order to identify more exactly the reasons for the reported range. OBJECTIVES: The objectives of this present study, which do not appear to have been addressed previously in the literature, were 1) the prevalence of gastric ulceration in horses with abdominal pain. 2) difference in prevalence in horses responding to medical therapy and those requiring surgical intervention. 3) whether gastric ulceration is associated with any particular gastrointestinal tract lesion. METHODS: Horses were included in the study if gastroscopy was performed within 24 h of presentation. The presence and grade of gastric ulceration was recorded together with the medical records. Data were analysed categorically using a Fisher's exact test or Chi-squared test. RESULTS: One hundred horses met the selection criteria. Forty-nine percent (49/100) of horses had gastric ulceration, 63% (63/100) responded to medical therapy and 37% (37/100) to surgical intervention, and prevalence was higher in the former (59%) than the latter (32%). Horses with duodenitis-proximal jejunitis (DPJ) had a trend towards higher prevalence of gastric ulceration compared to those with other GI lesions. Sixty-eight percent (13/19) of horses diagnosed with DPJ, 32% (8/25) with a large colon impaction and 14% (1/7) with large colon volvulus had gastric ulceration. CONCLUSIONS: The presence of gastric ulceration in all horses with abdominal pain was moderate. Horses responding to medical therapy had a higher prevalence of gastric ulceration compared to horses requiring surgery and there was a trend towards higher prevalence in cases of DPJ compared to other GI lesions. There was not a statistically significant difference in gastric ulceration detected between specific lesions, including large colon impactions and large colon volvulus. POTENTIAL RELEVANCE: The clinical relevance of ulceration is still unclear and further studies are required to differentiate between incidental and clinically important gastric ulceration.

Abdominal Pain↗
PubMed2005

Limits on gravitational-wave emission from selected pulsars using LIGO data.

We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multidetector analysis of the data collected during the second science run of the LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational-wave signals. The unprecedented sensitivity of the detectors allows us to set strain upper limits as low as a few times 10(-24). These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than 10(-5) for the four closest pulsars.

Journal Article↗
PubMed2000

Climate change is affecting altitudinal migrants and hibernating species.

Calendar date of the beginning of the growing season at high altitude in the Colorado Rocky Mountains is variable but has not changed significantly over the past 25 years. This result differs from growing evidence from low altitudes that climate change is resulting in a longer growing season, earlier migrations, and earlier reproduction in a variety of taxa. At our study site, the beginning of the growing season is controlled by melting of the previous winter's snowpack. Despite a trend for warmer spring temperatures the average date of snowmelt has not changed, perhaps because of the trend for increased winter precipitation. This disjunction between phenology at low and high altitudes may create problems for species, such as many birds, that migrate over altitudinal gradients. We present data indicating that this already may be true for American robins, which are arriving 14 days earlier than they did in 1981; the interval between arrival date and the first date of bare ground has grown by 18 days. We also report evidence for an effect of climate change on hibernation behavior; yellow-bellied marmots are emerging 38 days earlier than 23 years ago, apparently in response to warmer spring air temperatures. Migrants and hibernators may experience problems as a consequence of these changes in phenology, which may be exacerbated if climate models are correct in their predictions of increased winter snowfall in our study area. The trends we report for earlier formation of permanent snowpack and for a longer period of snow cover also have implications for hibernating species.

Altitude↗
PubMed2000

B lymphocyte pathology in human colorectal cancer. Experimental and clinical therapeutic effects of partial B cell depletion.

Accumulating data are showing that the humoral immune response against tumors could favor tumor progression. However, no B lymphocyte pathology has been reported in cancer. Using anti-IgM Ab we nonspecifically depleted B cells in tumor-bearing mice, a treatment that resulted in significant reduction of tumor burden. We analyzed the B lymphocyte phenotype of abdominal lymph nodes and peripheral blood from advanced colon cancer patients by flow cytometry, and compared the B cell phenotype with that found in samples from normal donors. In both lymph nodes and peripheral blood of cancer patients, abnormal populations of B lymphocytes appeared that express an increased CD21 and/or sTn antigens on their cell surface. All patients showed a reduction of CD19+ cells. In a limited clinical test, we analyzed the effects of a partial B cell depletion with Rituximab. The treated patients did not develop any side-effects; the CD21-hyperpositive lymphocytes were reduced, but the proportion of sTn-positive lymphocytes remained unaffected. Apparent reduction of the tumor burden was reported in 50% of the patients when the treatment was ended.

Animals↗
PubMed2000

Divergent proliferative responses to a gastrin receptor ligand in synchronized and unsynchronized rat pancreatic AR42J tumour cells.

Depending upon experimental model, the CCK-B/gastrin receptor ligand CI-988 exhibits either agonist or antagonist activity. To confirm that CI-988 behaves as an antagonist toward gastrin-stimulated growth, its effects on cell proliferation were investigated in unsynchronized and synchronized AR42J rat pancreatic tumour cells. In unsynchronized cultures CI-988 alone had no effect, but inhibited gastrin-stimulated cell proliferation. In contrast, in synchronized cultures, CI-988 stimulated cell proliferation. Similarly, CI-988 inhibited gastrin-stimulated cAMP production in unsynchronized cells, but stimulated cAMP formation in synchronized cultures. Therefore, CI-988 stimulation of cAMP production and proliferation in AR42J cell cultures appears to be cell cycle-dependent. CI-988 inhibited gastrin-stimulated intracellular calcium ([Ca2+]i) mobilization in both populations and thus acted as an antagonist toward this pathway. Because CCK receptor densities and affinities were similar in both cell populations, the data suggest that CI-988's divergent effects on cell proliferation are governed by postreceptor signalling events which vary with cell cycle.

Animals↗
PubMed2000

Gabapentin-induced mitogenic activity in rat pancreatic acinar cells.

Gabapentin induces pancreatic acinar cell tumors in rats through unknown, yet apparently nongenotoxic mechanisms. The primary objective of this study was to determine whether gabapentin acts as a tumor promoter by stimulating acinar cell proliferation in rat pancreas. To this end, indices of pancreatic growth, including increased pancreatic weight, stimulation of acinar cell proliferation, and/or enhanced expression of immediate-early oncogenes were monitored in rats given gabapentin in the diet at 2 g/kg/day for up to 12 months. Rats fed raw soy flour (RSF), a known inducer of pancreatic acinar cell tumors through cholecystokinin-mediated mitogenic stimulation, were used throughout as positive controls. In addition, recent data suggests that gabapentin binds to the alpha(2)delta subunit of a voltage-gated, L-type calcium channel. Because signaling pathways for proliferative processes in pancreatic acinar cells involve intracellular calcium mobilization, the effects of gabapentin on intracellular calcium mobilization ([Ca(2+)](i)) and (3)H-thymidine incorporation were investigated in pancreatic acinar cells isolated from normal rat pancreas and in the AR42J rat pancreatic tumor cell line. As indicated by BrdU labeling indices, acinar cell proliferation increased 3-fold by Day 3 of RSF treatment and remained slightly greater than controls throughout the experiment. Pancreatic weights of RSF-fed rats were 32 to 56% greater than controls throughout the experiment. In contrast, gabapentin had no effect on pancreatic weight or acinar cell labeling index, and therefore had no apparent effect on pancreatic growth. In isolated pancreatic acinar cells, however, gabapentin induced mobilization of intracellular calcium and caused a slight increase in (3)H-thymidine incorporation. The data suggest that gabapentin may possess low level mitogenic activity, which is not easily detectable in in vivo assays.

Acetates↗
PubMed1995

Phenytoin increases markers of osteogenesis for the human species in vitro and in vivo.

Phenytoin therapy is a well recognized cause of gingival hyperplasia, a condition characterized by increased gingival collagen synthesis, and may also cause acromegalic-like facial features. Based on these clinical findings suggestive of anabolic actions, we sought to test the hypothesis that phenytoin acts on normal bone cells to induce osteogenic effects. To test the direct actions of phenytoin on human bone cells, we measured the dose responses to phenytoin for [3H]thymidine incorporation, cell number, alkaline phosphatase specific activity, and collagen synthesis in human hip bone-derived cells. Phenytoin significantly and reproducibly increased [3H]thymidine incorporation, cell number, alkaline phosphatase specific activity, and collagen synthesis in a biphasic manner with optimal stimulatory doses between 5-10 mumol/L. Thus, micromolar concentrations of phenytoin can act directly on human bone cells to stimulate osteoblast proliferation and differentiation. We next sought to test the hypothesis that phenytoin stimulates bone formation in humans in vivo. Accordingly, three serum biochemical markers of bone formation, i.e. osteocalcin, skeletal alkaline phosphatase, and procollagen C-terminal extension peptide, were measured in 39 male epileptic patients, 20-60 yr of age, with an average duration of phenytoin therapy of 10.5 +/- 1.62 yr (mean +/- SEM). In this group of patients, the mean serum phenytoin level was 9.56 +/- 0.90 mg/L (mean +/- SEM; equivalent to 34.9 +/- 3.3 mumol/L). Thirty apparently healthy male subjects of similar age and taking no medication were included as controls. Serum calcium, 25-hydroxyvitamin D3, and PTH levels in the phenytoin-treated patients were not significantly different from those in the age-matched controls and were within the clinical laboratory normal range of our hospitals, indicating that the patients did not develop hypocalcemia, vitamin D deficiency, or secondary hyperparathyroidism. Serum levels of osteocalcin, skeletal alkaline phosphatase, and procollagen peptide in the phenytoin-treated patients were significantly increased compared to those in the age-matched subjects; in each case these biochemical markers were significantly correlated with the serum phenytoin level, but not with the dose or duration of phenytoin treatment. These findings are consistent with the interpretation that phenytoin increases the bone formation rate in humans in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Direct measurement of oxygen free radicals following cardiac failure of ischemic dog myocardium with the electron spin resonance technique.

OBJECTIVE: To determine whether the involvement of oxygen-derived free radicals in the pathogenesis of ischemic cardiac failure in dogs. DESIGN: Free radicals were measured in normal and ischemic myocardium from dogs with cardiac failure induced by acute coronary occlusion. The changes in free radical production in ischemic myocardium (compared with normal myocardium with or without polymorphonuclear leukocytes) were studies, with plasma superoxide dismutase and malondialdehyde analyzed concurrently. MAIN RESULTS: The results showed that the oxygen free radicals in the ischemic myocardium were about 42.5% higher than those in the normal myocardium, about 67.8% higher than those in the normal myocardium washed with normal saline and about 60.5% higher than those in the ischemic myocardium washed with normal saline (P < 0.05). Compared with controls, the concentration of malondialdehyde in ischemic dog myocardium was increased markedly. The activity of plasma superoxide dismutase was not significantly different between control dogs and dogs with ischemic cardiac failure. CONCLUSIONS: The current results indicate that there was increased production of free radicals and peroxidative damage in ischemic myocardium of dogs with cardiac failure. Polymorphonuclear leukocytes appear to be a main source of free radicals in dog with ischemic cardiac failure.

Animals↗
PubMed1989

Herpes-like viral dermatitis in a beluga whale (Delphinapterus leucas).

Approximately 3.5 mo following its capture, a beluga whale (Delphinapterus leucas) developed focal pale gray skin lesions. These lesions persisted for at least 8 mo. A biopsy from one of these sites revealed epithelial intranuclear inclusions. Herpes-like viral particles were seen by transmission electron microscopy. The eventual regression of skin lesions and lack of other clinical signs suggests the virus was only mildly pathogenic in this animal.

Animals↗
PubMed1988

A longterm follow-up study of children born to women with contagious diseases at delivery.

Data are presented from a long-term follow-up study of 308 live born children to women admitted post partum to the Department of Infectious Diseases (DID), Danderyd Hospital, Sweden, during a 10-year period (1975-1984) for avoiding nosocomial transmission of infections in the obstetrical wards. The rate of stillbirths (1/309 deliveries) was not higher than reported for all births in Stockholm. 20% of the live born children were transferred within 24 h after birth to the pediatric department for observation, but half of them could return to their mothers at the DID within 6 days (generally 3 days). Four newborns were treated at an intensive care unit. Only 3 fatalities occurred, all of them among newborns to mothers with an overt infection at delivery. The fatality rate (1.8%) was significantly higher among the newborns of these mothers than normally (0.3%) noted among all children born in Stockholm county during the period studied. Two of the 3 newborns, who all died within 3 days of life, had a low birth weight (600 and 1,000 g). The total number of newborns with low birth weights (less than 2,500 g) was, however, not higher in the above-mentioned group of newborns than for all children born in Stockholm county 1980. None of the 3 fatalities was caused by infection transmitted from the mother. No further deaths occurred. Infections in pregnancy at term, at birth or post partum were transmitted from the women to 41 (13%) of their newborns.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Infections↗
PubMed1983

Outcome of rubella during pregnancy with special reference to the 17th-24th weeks of gestation.

The consequences of rubella during pregnancy were studied with special reference to infections occurring during the 17th to 24th weeks of gestation. Laboratory confirmed rubella infected pregnancies were followed and the infants were examined clinically and serologically at a mean age of 20 months. In addition children born to mothers with verified rubella in earlier epidemics were examined clinically at the age of 4 or 7 yr. 491 cases of rubella in pregnant women from 1978-1980 were reported and 118 children were followed-up. Intrauterine transmission occurred in greater than 50% during the 16 first weeks of pregnancy compared to in 17% during the 21st to 24th weeks. Rubella defects appeared in a declining rate from 5/6 congenitally infected during the first 12 weeks to 1/7 at weeks 15 and 16. Three cases with deafness were found among the 65 children from earlier epidemics. Only 1 child with hearing impairment was found among children whose mothers were infected after the 16th week. Although rubella infections during the 17th to 24th weeks of pregnancy result in transmission to the fetus in about one fifth, sequelae seem to be a rare event.

Child↗
PubMed1982

Teratogenic hearing loss.

The total incidence of congenital defects, as reported by various authors, varies considerably with figures ranging from 1 to 3% depending on geographic locality and ethnic origin basis and only in a few percent the cause of the congenital defect can be traced to a known environmental factor. In contrast to other defects, congenital hearing impairment is often attributable to exogenous agents affecting the fetus during pregnancy. Nevertheless, in congenitally deaf children, the unknown etiological group remains the largest and here the most important object for future research is to recognize hitherto unknown exogenous agents, with the ultimate aim of preventing such causes of deafness. A brief survey is given on the present state of knowledge on the harmful effects of drugs and infections on the fetus's hearing organ, supplemented with some personal observations.

Deafness↗