Biomedical subjects

J L Spencer

Publications and source records attributed to J L Spencer.

At least 19 recordsLinked to original sources

PubMed2005

Economic analysis of dynamic management strategies utilizing. Transgenic corn for control of western corn rootworm (Coleoptera: Chrysomelidae).

We studied management strategies for western corn rootworm, Diabrotica virgifera virgifera LeConte, using transgenic corn, Zea mays L., from both a biological and an economic perspective. In areas with and without populations adapted to a 2-yr rotation of corn and soybean (rotation-resistant), the standard management strategy was to plant 80% of a cornfield (rotated and continuous) to a transgenic cultivar each year. In each area, we also studied dynamic management strategies where the proportion of transgenic corn increased over time in a region. We also analyzed management strategies for a single field that is the first to adopt transgenic corn within a larger unmanaged region. In all areas, increasing the expression of the toxin in the plant increased economic returns. In areas without rotation-resistance, planting 80% transgenic corn in the continuous cornfield each year generated the greatest returns with a medium toxin dose or greater. In areas with alleles for rotation-resistance at low initial levels, a 2-yr rotation of nontransgenic corn and soybean, Glycine max (L.) Merr., may be the most economical strategy if resistance to crop rotation is recessive. If resistance to crop rotation is additive or dominant, planting transgenic corn in the rotated cornfield was the most effective strategy. In areas where rotation-resistance is already a severe problem, planting transgenic corn in the rotated cornfield each year was always the most economical strategy. In some cases the strategies that increased the proportion of transgenic corn in the region over time increased returns compared with the standard strategies. With these strategies the evolution of resistance to crop rotation occurred more rapidly but resistance to transgenic corn was delayed compared with the standard management strategy. In areas not managed by a regional norm, increasing the proportion of transgenic corn and increasing toxin dose in the managed field generally increased returns. In a sensitivity analysis, among the parameters investigated, only density-dependent survival affected the results.

Agriculture↗

PubMed2004

The fate of a genetically modified Pseudomonas strain and its transgene during the composting of poultry manure.

The fate of the genetically modified (GM) Pseudomonas chlororaphis strain 3732 RN-L11 and its transgene (lacZ insert) during composting of chicken manure was studied using plate count and nested polymerase chain reaction (PCR) methods. The detection sensitivity of the nested PCR method was 165 copies of the modified gene per gram of moist compost or soil. Compost microcosms consisted of a 100-g mixture of chicken manure and peat, whereas soil microcosms were 100-g samples of sandy clay loam. Each microcosm was inoculated with 4 x 1010 CFU of P. chlororaphis RN-L11. In controlled temperature studies, neither P. chlororaphis RN-L11 nor its transgene could be detected in compost microcosms after incubation temperature was elevated to 45 degrees C or above for one or more days. In contrast, in the compost microcosms incubated at 23 degrees C, the target organism was not detected by the plate count method after 6 days, but its transgene was detectable for at least 45 days. In compost bins, the target organism was not recovered from compost microcosms or soil microcosms at different levels in the bins for 29 days. However, the transgene was detected in 8 of the 9 soil microcosms and in only 1 of the 9 compost microcosms. The compost microcosm in which transgene was detected was at the lower level of the bin where temperatures remained below 45 degrees C. The findings indicated that composting of organic wastes could be used to reduce or degrade heat sensitive GM microorganisms and their transgenes.

Animals↗

PubMed2003

Carbohydrate intolerance and kidney stones in children in the Goldfields.

Renal stones have been reported as a common finding in Australian Aboriginal children. The stones are predominantly urate in composition. We report on five children with nephrolithiasis from the Goldfields region of Western Australia. All were diagnosed when under 5 years of age, the majority being under 3 years. All five children also had lactose intolerance, and we postulate that carbohydrate malabsorption, together with the ensuing chronic diarrhoea and intraluminal breakdown of sugars by enteric bacteria may result in a situation of chronic metabolic acidosis. Chronic metabolic acidosis can lead to protein catabolism, increased urate excretion and the formation of renal stones. Carbohydrate intolerance may be an aetiological factor in the development of renal stones and possibly chronic renal disease, particularly in Aboriginal Australians. Renal disease represents one of the most significant factors affecting the health of Australian Aboriginal people. The incidence of end stage renal failure in this population exceeds that of non-Aboriginals by a factor of 13:1, and this disproportionate figure is increasing. It is likely that chronic renal damage is multifactorial; however, it is probable that at least some aetiological factors have their onset during childhood.

Carbohydrates↗

PubMed2003

Economics versus alleles: balancing integrated pest management and insect resistance management for rotation-resistant western corn rootworm (Coleoptera: Chrysomelidae).

Western corn rootworm, Diabrotica virgifera virgifera LeConte, has overcome crop rotation in several areas of the central United States. We expanded a simple model of adult behavior and population genetics to explain how rotation resistance may have developed and to study ways to manage the western corn rootworm in a landscape of corn, soybean, and winter wheat where evolution of resistance may occur. We modeled six alternative management strategies over a 15-yr time horizon, as well as a strategy involving a 2-yr rotation of corn and soybean in 85% of the landscape, to investigate their effectiveness from both a biological and economic perspective. Generally, resistance to crop rotation evolves in fewer than 15 yr, and the rate of evolution increases as the level of rotated landscape (selection pressure) increases. When resistance is recessive, all six alternative strategies were effective at preventing evolution of rotation resistance. The two most successful strategies were the use of transgenic rotated corn in a 2-yr rotation and a 3-yr rotation of corn, soybean, and wheat with unattractive wheat (for oviposition) preceding corn. Results were most sensitive to increases in the initial allele frequency and modifications of the density-dependent survival function. Economically, three alternative strategies were robust solutions to the problem, if technology fees were not too high. Repellant soybean, attractive rotated corn, and transgenic rotated corn, all in 2-yr rotations, were economically valuable approaches. However, even the currently common 2-yr rotation was economical when resistance was recessive and the actual costs of resistance would not be paid until far in the future.

Agriculture↗

PubMed2001

Modeling the dynamics of adaptation to transgenic corn by western corn rootworm (Coleoptera: Chrysomelidae).

A simulation model of the population dynamics and genetics of the western corn rootworm, Diabrotica virgifera virgifera LeConte, was created for a landscape of corn, soybean, and other crops. Although the model was created to study a 2-locus problem for beetles having genes for resistance to both crop rotation and transgenic corn, during this first phase of the project, the model was simulated to evaluate only resistance management plans for transgenic corn. Allele expression in the rootworm and toxin dose in the corn plant were the two most important factors affecting resistance development. A dominant resistance allele allowed quick evolution of resistance to transgenic corn, whereas a recessive allele delayed resistance >99 yr. With high dosages of toxin and additive expression, the time required to reach 3% resistance allele frequency ranged from 13 to >99 yr. With additive expression, lower dosages permitted the resistant allele frequency to reach 3% in 2-9 yr with refuges occupying 5-30% of the land. The results were sensitive to delays in emergence by susceptible adults and configuration of the refuge (row strips versus blocks).

Adaptation, Physiological↗

PubMed1999

Detection of avian leukosis virus in albumen of chicken eggs using reverse transcription polymerase chain reaction.

A reverse transcriptase polymerase chain (RT-PCR) assay was developed to detect avian leukosis retrovirus (ALV) in egg albumen. Eggs of Single Comb White Leghorns were from a commercial breeder (stock F) and from a pathogen-free flock (stock N). RT-PCR was undertaken on isolated RNA from 20 unfertilized egg samples using seven sets of primers that correspond to the ALV gp85 envelope glycoprotein which determines the ALV subgroup classification. An ELISA assay for ALV gs antigen of egg albumen was positive for all stock F birds tested and negative for all stock N birds. Virus isolation was undertaken by inoculating egg albumen, feather pulp, or blood from five stock F chickens onto cultures of chicken embryo fibroblasts (C/E). IFA analysis of the inoculated C/E cultures indicated that all stock F birds tested contained infectious ALV. For the virus-positive stock F chickens, RT-PCR analyses using primers designed to detect all ALV subgroups detected ALV in 15/15 (100%) egg albumen samples, while primers designed to detect subgroup A ALV were positive for 12/15 (80%) egg albumen samples. RT-PCR products were not detected from five egg albumen samples from five stock N chickens by any primer sets. Direct sequencing using primers specific for subgroup A ALV verified the viral subgroup in the RT-PCR amplification products. The combined use of RT-PCR and direct sequencing of the RT-PCR product provides a new approach for identifying ALV-infected poultry.

Albumins↗

PubMed1998

An epidemic of renal failure among Australian Aboriginals.

OBJECTIVE: To define recent trends (1993-1996) in incidence of endstage renal disease (ESRD) among Australian Aboriginal people in the Top End of the Northern Territory (NT). DESIGN: Analysis of hospital and clinical records of the Darwin-based ESRD treatment program from 1993 to 1996 and comparison with data accumulated since 1978. PARTICIPANTS: All people entering the ESRD treatment program from 1978 to 1996. MAIN OUTCOME MEASURES: Number of patients treated for ESRD; their ethnicity, age and sex; comorbidities in Aboriginal patients; treatment methods and outcomes. RESULTS: More Aboriginal people presented with ESRD between 1993 and 1996 (87) than in the previous 15 years of the program (68). The incidence of ESRD in Aboriginals reached 838 per million in 1996, and is doubling every 4 years. Aboriginal people presenting with ESRD are younger than non-Aboriginal people with ESRD, and, in contrast to non-Aboriginals, ESRD rates are higher in women than men. The numbers and proportions of Aboriginal ESRD patients who have hypertension, type 2 diabetes and cardiac disease are rising. Haemodialysis remains the most common form of treatment, and the number of dialysis treatments is doubling every 2.5 years. Only 9% of Aboriginal patients entering the program in 1993-1996 were treated with chronic ambulatory peritoneal dialysis and only 3% received transplants. Despite their younger age, survival of Aboriginal people on dialysis is low (median 3.3 years v. 6.5 years in non-Aboriginals), and graft survival after transplant is poor (37% at 5 years v. 88% in non-Aboriginals). Survival has not improved in the past 4 years, with fewer deaths from infection offset by more deaths from cardiovascular disease. CONCLUSIONS: The predicted doubling of ESRD incidence among Aboriginal people by the year 2000 will add an enormous burden to limited resources. Risk factors for renal disease underlie all the excess morbidity and mortality in NT Aboriginal adults, and arise out of accelerated lifestyle changes and socioeconomic disadvantage. Better living conditions and education, robust and integrated primary healthcare programs, and systematic screening for early renal disease and treatment of those with established disease are all matters of urgency.

Adolescent↗

PubMed1997

Developmental lead exposure and two-way active avoidance training alter the distribution of protein kinase C activity in the rat hippocampus.

Long-term exposure to a low level of lead is associated with learning deficits. Several types of learning have been correlated to hippocampal protein kinase C (PKC) activation. This study was designed to determine if there is a correlation between the effects of lead on hippocampal PKC activation and those on learning performance. Rats were exposed to 0.2% (w/v) lead acetate at different developmental stages including a maternally exposed group, a postweaning exposed group, and a continuously exposed group. The continuously lead exposed rats tended to avoid less frequently and not respond more frequently in two-way active avoidance training than did controls. This training process was associated with translocation of hippocampal PKC activity from cytosol to membrane. Two-way analysis of variance of data indicates that there is a significant training and lead treatment interaction in the ratio of membrane to cytosolic PKC activity (F3,32 = 3.013; p = 0.044). The interaction is attributable to the absence of the training-induced PKC translocation in the continuously lead exposed rats. In addition, no significant changes were observed in learning performance and training-induced hippocampal PKC activation after maternal and postweaning lead exposure. Continuous and longer duration of lead exposure appears to affect the learning performance and hippocampal PKC activation. These data suggest that a change in the activation of hippocampal PKC may be involved in the lead-induced deficit in learning.

Analysis of Variance↗

PubMed1997

The influence of complex carbohydrates on Salmonella typhimurium colonization, pH, and density of broiler ceca.

Salmonella typhimurium colonization, pH, and density of ceca were measured in 3-, 5-, and 6-wk-old broilers fed either a control ration or rations with added fructooligosaccharides (FOS) or lactose derivatives (LD). The purpose was to compare dietary crude FOS from Jerusalem artichokes with refined FOS and two LD for ability to reduce Salmonella colonization as determined by semi-quantitative procedures. Chicks were challenged commencing at 5 d, by exposure to chicks orally infected with S. typhimurium. With the exception of chicks fed crude FOS, the high prevalence of Salmonella infection at 3 wk declined as chicks aged. At 6 wk, broilers fed crude FOS had higher Salmonella counts than all other broiler groups, whereas broilers fed refined FOS had lower infections than control broilers. The decline of Salmonella infection of broilers fed either refined FOS or LD ceased after dietary additives were discontinued at 5 wk of age. At 6 wk, infection rates of the latter groups were at least as high as those of control broilers. Both FOS and LD reduced cecal pH and density. Broilers fed the control ration had higher pH at 5 and 6 wk and higher cecal densities at 3 and 5 wk than those of broilers fed rations containing 5% (wt/wt) carbohydrates. Treatment differences for cecal pH and density disappeared within 1 wk of withdrawal of carbohydrates from 5-wk-old broilers. No consistent effect of cecal pH and density on Salmonella infection was observed. Density was dependent on cecal volume, and at 6 wk of age, on broiler size.

Aging↗

PubMed1997

Amphotericin B enzyme-linked immunoassay for clinical use: comparison with bioassay and HPLC.

OBJECTIVE: To evaluate a new enzyme-linked immunosorbent assay (ELISA) for amphotericin B in serum samples. Results are compared with those obtained by HPLC and bioassay. DESIGN: Comparison of results obtained by ELISA, HPLC, and bioassay. METHODS: We developed a new ELISA using a polyclonal rabbit antibody to measure serum amphotericin B concentrations. Blinded samples of amphotericin B in concentrations of 0.15-78 micrograms/mL were prepared in human serum and assayed simultaneously by the ELISA, HPLC, and bioassay. The results of each assay were derived from standard curves and evaluated by using the Table Curve 2D computer program. These data were compared by using correlation analysis with evaluation of Pearson's correlation coefficient by Student's t-test. RESULTS: ELISA and bioassay compared favorably at amphotericin B concentrations of 0.3-20 micrograms/mL with a correlation coefficient of r = 0.993, while ELISA and HPLC compared with a correlation coefficient of r = 0.944. The average coefficient of variation over the range 0.3-20.0 micrograms/mL was 28% +/- 7% for HPLC, 26% +/- 9% for ELISA, and 13% +/- 4% for bioassay. Comparison of all three assays revealed the highest correlation with the ELISA assay (r = 0.998) for the range of concentrations (0.3-20 micrograms/mL) routinely achieved. Samples containing concentrations in excess of 20 micrograms/mL could be diluted. Desiccation for concentrations less than 0.3 microgram/mL was not tested. CONCLUSION: The determination of serum amphotericin B concentrations by ELISA gave results similar to those obtained by a bioassay and HPLC technique. Although variability appears greater with ELISA, the ease of performing yjis assay expedites the evaluation of amphotericin B concentrations from lipid formulations without interference from coadministered antibacterials of azole antifungals.

Amphotericin B↗

PubMed1995

Dynamic assessment of the electrocardiographic QT interval during citrate infusion in healthy volunteers.

OBJECTIVE: To investigate changes in the electrocardiographic QT interval during rapidly induced, sustained hypocalcaemia in healthy volunteers. DESIGN: Serial rate corrected QT measurements were made during and after a variable rate trisodium citrate infusion designed to "clamp" the whole blood ionised calcium concentration 0.20 mmol/l below baseline for 120 min. SUBJECTS: 12 healthy teetotallers aged 19- 36 years who were not receiving medication known to influence calcium homoeostasis. MAIN OUTCOME MEASURES: Whole blood ionised calcium concentration and QaTc intervals (onset of the Q wave to T wave apex divided by the square root of the RR interval). RESULTS: Mean (SD) ionised calcium concentration decreased from 1.18 (0.03) mmol/l preinfusion to values close to target (0.98 mmol/l) between 10 and 120 min. The QaTc interval lengthened from a baseline of 0.309 (0.021) to a maximum 0.343 (0.024) s0.5 at 10 min before returning to a stable level from 15 to 120 min (0.334 (0.023) and 0.330 (0.023) s0.5 respectively). The change from baseline of both variables expressed as a ratio (delta QaTc/ delta [Ca2+]) was greater during rapid induction of hypocalcaemia (at 5 and 10 min) than at other times during and after the infusion (P < 0.02). CONCLUSIONS: The disproportionate prolongation of QaTc interval during prompt induction of hypocalcaemia suggests rate dependency which can be represented by a hysteresis relation between (ionised calcium, QaTc) coordinates. This finding may have clinical implications.

Adult↗

PubMed1995

Influence of the alv6 recombinant avian leukosis virus transgene on production traits and infection with avian tumor viruses in chickens.

The biological costs of the alv6 recombinant transgene that in chickens induces dominant resistance to the subgroup A avian leukosis virus (ALV), in terms of effects on production traits, were studied. Four generations of White Leghorn chickens of Line TR, segregating for alv6 but free of endogenous viral genes, as well as two generations of crosses between TR and Ottawa Line WG (WGTR) were tested under a specific-pathogen-free environment. In the birds studied, the transgene appeared unchanged compared to the original alv6: No major changes in alv6 DNA were detected by restriction analysis, the transgene did not express the group-specific antigen of ALV, and its presence was associated with absence of immune response to ALV. In most test years, and both TR and WGTR genomic backgrounds, alv6 was associated with delayed sexual maturity by 4 to 6 d, reduced egg production to 497 d of age by 20 to 46 eggs, and a 3.6 to 15% decline in egg production rate. No consistent effects on other traits, including mortality, were detected. When inoculated with the AC-1 isolate of Marek's disease virus in a separate experiment, TR birds with alv6 had a significantly lower body weight gain to 10 d of age than their sibs without the transgene. Thus, transgenesis has biological costs that have to be assessed against desirable effects of transgenes.

Animals↗

PubMed1994

Glucose turnover in pregnant women with acute malaria.

1. Hypoglycaemia is a serious complication of falciparum malaria, especially in pregnant patients. To investigate malaria-associated changes in glucose metabolism in pregnancy, steady-state [6,6-2H2] glucose turnover and clearance were measured in 10 women (eight with uncomplicated falciparum malaria and two with vivax malaria at 16-30 weeks gestation) before treatment, after intravenous quinine infusion (patients with falciparum malaria) and in convalescence. 2. Admission basal plasma glucose concentrations were higher than those in convalescence [median (range); 4.8 (3.6-7.0) versus 4.0 (3.6-4.6) mmol/l, P = 0.02], and there was a significant fall during initial quinine treatment in patients with falciparum malaria [5.0 (4.3-7.6) to 3.6 (3.2-5.4) mmol/l, P < 0.01]. Basal plasma insulin levels were comparable at presentation and follow-up (P = 0.35) and rose an average of only 2m-units/l during quinine infusion (P < 0.05). Pretreatment glucose turnover rates [3.37 (2.57-4.16) mg min-1 kg-1] were comparable with those found in a previously reported study of non-pregnant severely ill patients [3.22 (2.12-4.82) mg min-1 kg-1, n = 11] and correlated significantly with the admission parasitaemia (P < 0.025). In the eight patients with falciparum malaria, there was a significant fall in turnover during intravenous quinine infusion [3.42 (2.58-4.16) to 2.66 [1.94-3.94) mg min-1 kg-1] whereas clearance did not change significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1993

Platelet-activating factor and lipid metabolism in acute malaria.

Platelet-activating factor (PAF) contributes to a range of pathophysiological responses in severe illness. To examine PAF metabolism in acute malaria, venous blood was drawn from 10 untreated adults with falciparum malaria, from 8 with untreated vivax malaria, and from 10 controls. Plasma lyso-PAF, produced from PAF through the enzyme acetylhydrolase (AH), was bioassayed, after acetylation to PAF, by platelet [14C]-serotonin release. AH activity was measured by hydrolysis of [3H]-acetyl-PAF. Amounts of plasma lyso-PAF were lower in falciparum (median [range] 24 [9-221] ng/ml) and vivax (35 [7-236] ng/ml) infected patients than in controls (399 [212-504] ng/ml; P < 0.01), and correlated significantly with serum total and HDL-cholesterol (P < 0.001). Plasma AH activities were similar in the control, falciparum and vivax malaria groups. These data suggest that in malaria plasma lyso-PAF values fall together with other blood lipids, but independently of changes in AH activity. This may reflect a generalised decrease in lipid and phospholipid synthesis. However, the reduction of plasma lyso-PAF concentrations in our patients was much greater than that of serum lipoproteins. This is consistent with conversion of lyso-PAF to PAF or with increased PAF-receptor interactions. These two possibilities would have pathophysiological implications.

Acute Disease↗

PubMed1992

Measures of capillary permeability in acute falciparum malaria: relation to severity of infection and treatment.

Capillary permeability was investigated in 32 Thai patients aged 14-49 years who had acute falciparum malaria with use of three distinct techniques: quantitation of the urinary albumin/creatinine ratio (ACR), estimation of the transcapillary escape rate of radiolabeled albumin (TER), and retinal photography/fluorescein angiography. Fourteen patients had uncomplicated infections and 18 were severe cases. The severely ill patients had significantly higher ACRs (median, 4.8 mg/mmol; 95% confidence limits, 2.4-19.9 mg/mmol) and TERs (median, 8.3%/h; 95% confidence limits, 6.2-13.2%/h) than the uncomplicated cases (ACR: median, 2.1 mg/mmol; 95% confidence limits, 6.2-13.2%/h) than the uncomplicated cases (ACR: median, 2.1 mg/mmol; 95% confidence limits, 1.0-8.8 mg/mmol; TER: median, 5.9%/h; 95% confidence limits, 3.8-10.6%/h; P = .014 and .042). Both variables were significantly associated with biochemical indices of disease severity including total serum bilirubin levels (rs greater than or equal to 0.398, P less than .025 in each case), but there were no significant differences between ACRs and TERs among comatose and noncomatose patients with severe infections (P greater than or equal to .08). Retinopathy (hemorrhages, cotton-wool spots, capillary nonperfusion, and/or extravasation of fluorescein) was found in eight severely ill patients and in two uncomplicated cases. Fluorescein leakage was evident in six patients. Although fluorescein leakage had the strongest parametric correlation with the presence of coma relative to both ACR and TER in the full patient series (r = 0.58, P less than .01), multiple linear regression analysis indicated that concentrations of plasma lactate (t = 2.998, P = .006) and serum creatinine (t = 2.200, P = .036) were the factors responsible for this association. These data do not support a role for tissue edema in the pathogenesis of cerebral malaria but reveal an association between markers of disease severity and a generalized increase in systemic capillary permeability.

Adolescent↗

PubMed1991

Endogenous viral genes: association with reduced egg production rate and egg size in White Leghorns.

Endogenous viral (ev) genes are DNA sequences residing permanently in the genome of most chickens that have a high degree of homology to avian leukosis viruses (ALV). Association of ev genes with production trait differences was studied in White Leghorns free of exogenous ALV. The Cornell Strain K and S chickens used in Experiment 1 had multiple ev genes. In each of four lines of chickens in Experiment 2, there was a 1:1 segregation of full-sibs free of ev genes and those carrying one ev gene: ev-12 that produces the complete endogenous virus, ev-3 or ev-6 that express certain viral antigens, or ev-1, a silent gene. In Experiment 1, the presence of genes ev-10 or ev-19, known to produce the complete virus, was associated with a 9% reduction in the annual egg production rate (P less than .05) in Strain S. Similarly, the presence of the virus-producing ev-12 in Experiment 2 was associated with an 8% reduction of annual egg production rate (P less than .05), a 2.2-g reduction in egg weight (P less than .01), and a .003 reduction in egg specific gravity (P less than .01). No significant effects of ev genes on age at first egg, Haugh unit score, percentage of eggs with blood spots, and body weight of hens were observed. It was concluded that ev genes producing complete endogenous virus are associated with production trait differences similar to those associated with subclinical infections with exogenous ALV.

Animals↗

PubMed1988

Semen traits and fertility of White Leghorn males shown to be positive or negative for lymphoid leukosis virus in semen and feather pulp.

1. Males from strains selected for high egg production (and other economic traits) and from unselected control strains were used to determine the frequency of shedding of lymphoid leukosis virus (LLV) into semen. The effect of the male's LLV status on semen production, fertility and hatchability was also examined in males of the unselected control strains. 2. The frequency of detection of exogenous LLV in semen by the phenotypic mixing test, and high concentrations of the viral group specific antigen in feather pulp by the complement fixation test, were both higher in control strains than in strains selected for high egg production. 3. Semen production was not reduced in LLV-shedding males. 4. Significant associations of LLV shedding with higher incidence of abnormal spermatozoa and reduced fertility were found in some populations but not in others. No significant effect of LLV shedding on hatchability was detected. 5. Tests for group specific antigen in feather pulp proved useful in identifying males that shed LLV in semen.

Animals↗

PubMed1987

Importance of the medullary macrophage in the replication of lymphoid leukosis virus in the bursa of Fabricius of chickens.

Electron microscopy and immunocytochemistry were used to study the development of lymphoid leukosis virus infection in the bursa of Fabricius of experimentally infected chicken embryos and chickens. In embryos infected at 7 days of incubation and killed 10 days later, virus particles and group-specific viral antigen were confined mainly to the connective tissue of the lamina propria of the bursal mucosal folds; a few developing follicles had discrete virions and group-specific antigen between cells. In chickens infected at 1 day of age, infection (as determined by use of electron microscopy and immunocytochemistry) was maximal in 1- to 4-month-old birds, and the greatest concentration of virus and group-specific viral antigen was in the medulla of the follicles. Although lymphoid leukosis virus was released from lymphocytes, epithelial cells, and macrophages, virus replication in the medullary macrophages was more active than that in the other cells. Normal medullary macrophages had cell membrane vesicles (50 to 80 nm in diameter) that covered part of all of the cell membrane surface. In infected chickens, virus particles frequently developed within these vesicles. Comparable vesicles were not found on cortical macrophages. Results of the present study indicated that the medullary macrophage was the principal host cell for replication of lymphoid leukosis virus in the bursa of Fabricius of the chicken.

Animals↗