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Biomedical subjects

W E Kerr

Publications and source records attributed to W E Kerr.

13 recordsLinked to original sources
PubMed1995

Effects of juvenile hormones I, II and III, in single and fractionated dosage in Melipona bees.

Applications of Juvenile Hormones JH I, II and III in single or fractionated doses to larvae of Melipona compressipes, Melipona quadrifasciata, Melipona rufiventris and Melipona scutellaris at the L3 and beginning of cocoon-spinning phase (pre-defecating larvae - LPD) activated feminizing genes, inducing differentiation of female larvae into queens. The technique of fractionated treatment proved to be highly efficient in Melipona species for producing of queens. It is difficult to obtain 100% queens with single dosage of JH in some species which implies in a mechanism of JH degradation by specific esterases. One hundred per cent of queen production occurs only when an adequate amount of Juvenile Hormone is administered within the period that is critical for caste determination. The threshold dosage of JH I for Melipona compressipes (below which it is not possible to obtain 100% queens) was 0.1mu JH I 4 applications of 0.25mu g each. For Melipona quadrifaciata the threshold dose for obtaining the highest proportion of queens was 0.2mu g JH I in 4 applications of 0.05mu g each. For Melipona scutellaris 0.025mu g JH I/mj 1 in single dosage induced 100% of queens. No 100% production of queens in Melipona Rufiventris treated larvae were obtained; the highest proportion was 86% of queens with 0.2mg g JH I/mu 1. In order to obtain expression of the feminizing genes in Melipona species, JH I was the most efficient followed by JH III. Each species respond differentialy to JH dosage, and this dosage must be tested before use.

Animals↗
PubMed1977

Estimation of the number of sex alleles and queen matings from diploid male frequencies in a population of Apis mellifera.

The distribution of diploid males in a population of Apis mellifera was obtained by direct examination of the sexual phenotypes of the larvae. Using these data, estimates are derived for the number of sex alleles and the number or matings undergone by the queen. The number of sex alleles is estimated to be 18.9. The estimate is larger than previous ones, which have ranged between 10 and 12. However, the increase in the number of sex alleles can be explained by the large effective population number for our data. The best estimator of the number of matings by a queen is a maximum likelihood type that assumes a prior distribution on the number of matings. For the data presented here, this estimate is 17.3. This estimate is compared to others in the literature obtained by different approaches.

Alleles↗
PubMed1976

Teratogenic and toxicological examination of 2,4,5-trichlorphenoxyacetic acid in developing chick embryos.

Practical grade 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), dissolved in dimethylsulfoxide (DMSO), was injected into the air space of fertilized chicken eggs prior to incubation. Doses of 2,4,5-T administered were 12.5, 25, 50, 75, 100, and 125 mg/kg to determine herbicide toxicity on the first day of incubation. A similar group was studied on day 5 of incubation with doses of 2,4,5-T at 50, 75, 100 and 250 mg/kg. LD50 was estimated to be 62 mg/kg on day zero and 68 mg/kg on day 5. Additionally, embryos were exposed to 2,4,5-T at 50 mg/kg on day zero of gestation and sacrificed after 48 h of incubation. Serial sections were examined for teratological and developmental anomalies. None were found.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1975

Genetic component in learning ability in bees.

Twenty-five bees, five from each of five hives, were trained to collect food at a table. When the bee reached the table, time was recorded for 12 visits. Then a blue and yellow pan was substituted for the original metal pan, and time and correct responses were recorded for 30 trips (discrimination phase). Finally, food was taken from the pan and extinction was recorded as incorrect responses for 20 visits. Variance analysis was carried out, and genetic variance was undetected for discrimination, but was detected for extinction. It is concluded that learning is very important for bees, so that any impairment in such ability affects colony survival.

Animals↗
PubMed1975

Sex determination in bees. IV. Genetic control of juvenile hormone production in Melipona quadrifasciata (Apidae).

Cell number and volume of corpora allata was determined for 8 phases of development, the first prepupal stage to adults 30 days old, in the social Apidae Melipona quadrifasciata. In the second prepupal stage a strong correlation was found between cell number and body weight (r = 0.651), and cell number and corpora allata volume in prepupal stage (r = 0.535), which indicates that juvenile hormone has a definite role in caste determination in Melipona. The distribution of the volume of corpus allatum suggest a 3:1 segregation between bees with high volume of corpora allata against low and medium volume. This implies that genes kappa a and kappa b code for an enzyme that directly participates in juvenile hormone production. It was also concluded that the number of cells in the second prepupal stage is more important than the weight of the prepupa for caste determination. A scheme summarizing the genic control of sex and caste determination in Melipona bees in the prepupal phase is given.

Alleles↗
PubMed1975

Population genetic studies in bees (APIDAE, Hymenoptera). I. Genetic load.

Three populations of Apis mellifera each predominantly of a different subspecies (mellifera, ligustica and adansonii) and 7 species of stingless bees (Meliponinae, Apidae) were manipulated for applying the MORTON, CROW & MULLER's methodology in order to estimate the lethal equivalents (B) of each population. A total of 249 queens were used, 27 being meliponids and 222 Apis mellifera. The populations of Apis have a B that does not differ significantly when they are compared to each other (1.29, 1.36, 1.32) and the balanced average equals 1.33. When the x-alleles are not considered, this balanced value is 0.262. The figures for B in the seven species of stingless bees ranged between 0.104 and 0.159 with balanced average of 0.132. The main reason for this smaller load in meliponids may rest in their effective population numbers, which are smaller than those of Apis. The average mortality for diploid females (0.141) and for haploid males (0.163) allows the estimation of the total elimination (sigma E = 0.073). Since for haplo-diploid systems the total mutation rate is sigma mu = 2 sigma E divided by 3 the figure 0.048 is obtained. Since about 15% of the genes in Apis mellifera are sex limited, this value of sigma mu should be added of 0.0072 (that is 0.15 X 0.048) and then, the total mutation rate becomes 0.055. Using a quite different method, the one by MORTON, CROW & MULLER, the figure 0.076 was obtained. If a mutation rate of 10(-5) is assumed, the number of genes in Apis mellifera that can make a contribution to the genetic load would vary between 5,500 and 7,600.

Animals↗