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Biomedical subjects

H G Hall

Publications and source records attributed to H G Hall.

14 recordsLinked to original sources
PubMed1999

Modification of the AFLP protocol applied to honey bee (Apis mellifera L.) DNA.

The established amplified fragment-length polymorphism (AFLP) protocol was simplified and optimized for honey bee DNA (Apis mellifera L.). Compared to the original method, the following simplifications were made: (i) the digestion of DNA and ligation of the adapters are performed in one reaction vs. two, (ii) one restriction enzyme is used vs. two and (iii) amplification is accomplished in one reaction vs. two. PCR products are resolved in agarose-Synergel instead of polyacrylamide and are visualized by ethidium bromide staining rather than by autoradiography of labeled primers. Using the modified procedure for honey bee DNA, high reproducibility of the band patterns of PCR products and low sensitivity to the amplification conditions were seen. Analysis of honey bee DNA revealed considerable genetic variability within and between African and European bee samples. African- and European-specific fragments were found.

Animals↗
PubMed1998

PCR amplification of a locus with RFLP alleles specific to African honey bees.

An anonymous honey bee locus, detected previously with a cloned probe, has HhaI RFLP alleles specific to African bees or common to both African and European bees. To facilitate identification of these alleles, this region, 1231, was made analyzable with the PCR. The two halves of the region, excluding the termini, were amplified as two overlapping segments. Restriction sites were mapped, and the site differences responsible for the allelic RFLP patterns were determined. In the first half of the region, two polymorphic HhaI sites are present in the common alleles, whereas one, the other, or both of the sites are absent in the African alleles. In the second half, a third polymorphic HhaI site is present or absent in both common and African alleles. A short part of the second half of the region, including more of the terminus, was amplified as a third segment. Within this segment, close to this terminus, a fourth polymorphic HhaI site is absent in some African alleles.

Alleles↗
PubMed1996

Achievement of thermal stability by varying metabolic heat production in flying honeybees.

Thermoregulation of the thorax allows endothermic insects to achieve power outputs during flight that are among the highest in the animal kingdom. Flying endothermic insects, including the honeybee Apis mellifera, are believed to thermoregulate almost exclusively by varying heat loss. Here it is shown that a rise in air temperature from 20 degrees to 40 degrees C causes large decreases in metabolic heat production and wing-beat frequency in honeybees during hovering, agitated, or loaded flight. Thus, variation in heat production may be the primary mechanism for achieving thermal stability in flying honeybees, and this mechanism may occur commonly in endothermic insects.

Animals↗
PubMed1991

Distinguishing African and European honeybee matrilines using amplified mitochondrial DNA.

Previous DNA studies have revealed that feral neotropical African bees have largely retained an African genetic integrity. Additional DNA testing is needed to confirm these findings, to understand the processes responsible, and to follow African bee spread into the temperate United States. To facilitate surveys, the polymerase chain reaction was utilized. African and European honeybee mitochondrial DNA (mtDNA) was identified through amplified segments that carry informative restriction site and length polymorphisms. The ability to discriminate among honeybee subspecies was established by testing a total of 129 colonies from Africa and Europe. Matriline identities could thus be determined for imported New World bees. Among 41 managed and feral colonies in the United States and north Mexico, two European lineages (west and east) were distinguished. From neotropical regions, 72 feral colonies had African mtDNA and 4 had European mtDNA. The results support earlier conclusions that neotropical African bees have spread as unbroken African maternal lineages. Old and New World African honeybee populations exhibit different frequencies of a mtDNA length polymorphism. Through standard analyses, a north African mtDNA type that may have been imported previously from Spain or Portugal was not detected among neotropical African bees.

Africa↗
PubMed1990

Parental analysis of introgressive hybridization between African and European honeybees using nuclear DNA RFLPs.

African honeybees, introduced into Brazil 33 years ago, have spread through most of South and Central America and have largely replaced the extant European bees. Due to a paucity of genetic markers, genetic interactions between European and African bees are not well understood. Three restriction fragment length polymorphisms (RFLPs), detected with random, nuclear DNA probes, are described. The polymorphisms are specific to bees of European descent, possibly specific to certain European races. Each European marker was found present at a high frequency in U.S. colonies but absent in South African bees. Previous mitochondrial DNA studies of neotropical bees have revealed negligible maternal gene flow from managed European apiaries into feral African populations. The findings reported here with nuclear DNA show paternal gene flow between the two but suggest asymmetries in levels of introgressive hybridization. Managed colonies in southern Mexico, derived from European maternal lines, showed diminished levels of the European nuclear markers, reflecting significant hybridization with African drones. The European alleles were present only at low frequencies in feral swarms from the same area. The swarms were of African maternal descent. In Venezuelan colonies, also derived from African maternal lines, the European markers were almost totally absent. The results point to limited paternal introgression from European colonies into the African honeybee populations. These findings dispute other views regarding modes of Africanization.

Africa↗
PubMed1989

Evidence from mitochondrial DNA that African honey bees spread as continuous maternal lineages.

African honey bees have populated much of South and Central America and will soon enter the United States. The mechanism by which they have spread is controversial. Africanization may be largely the result of paternal gene flow into extant European populations or, alternatively, of maternal migration of feral swarms that have maintained an African genetic integrity. We have been using both mitochondrial and nuclear DNA restriction fragment length polymorphisms to follow the population dynamics between European and African bees. In earlier reports, we suggested that if African honey bees had distinctive mitochondrial (mt) DNA, then it could potentially distinguish the relative contributions of swarming and mating to the Africanization process. Because mtDNA is maternally inherited, it would not be transmitted by mating drones and only transported by queens accompanying swarms. Furthermore, the presence of African mtDNA would reflect unbroken maternal lineages from the original bees introduced from Africa. The value of mtDNA for population studies in general has been reviewed recently. Here we report that 19 feral swarms, randomly caught in Mexico, all carried African mtDNA. Thus, the migrating force of the African honey bee in the American tropics consists of continuous African maternal lineages spreading as swarms. The mating of African drones to European queens seems to contribute little to African bee migration.

Animals↗
PubMed1986

Characterization of the intermediate filament proteins of murine mammary gland epithelial cells. Response to collagen substratum.

The insoluble cytoskeletal material remaining after detergent lysis of 'Normal' Murine Mammary Gland (NMuMG) cells, growing on plastic or collagen gel substrata, was analyzed by two-dimensional gel electrophoresis. The identity of the cytoskeletal elements was determined by their solubility properties, electrophoretic separation pattern, and immunoreactivity using monoclonal antibodies against intermediate filament proteins (AIF), keratins (AE1 and AE3) and actin. The electrophoretic pattern of the cytoskeletal elements from the NMuMG cell strain was found to be very similar to that of primary mouse mammary epithelial cells. Both NMuMG and primary mammary epithelial cells when grown on collagen exhibited an increased expression of a 49 kD protein with a pI of 5.6, that appeared to be a cytokeratin. Many of the cytoskeletal proteins remained tightly attached to the collagen gel substratum after cell lysis. These results demonstrate that the NMuMG cell strain has retained a stable expression of cytokeratins that remains responsive to the presence of extracellular matrix material.

Animals↗
PubMed1986

DNA differences found between Africanized and European honeybees.

The harmful en masse introduction of Africanized honeybees into the United States will occur within 5 years. Possible means of control are dependent on a reliable way to distinguish the Africanized bees from the extant European bees. Current means of identification are inadequate. Reported here are the encouraging initial results to distinguish the bees by their nuclear DNA. With 9 restriction enzymes and 16 probes, six genetic differences have been found among three samples of European bees from California. Twelve additional differences were detected between the European samples and a sample of Africanized bees from Costa Rica.

Africa↗
PubMed1982

Lumen formation by epithelial cell lines in response to collagen overlay: a morphogenetic model in culture.

Two cell lines--Madin-Darby canine kidney (MDCK) and normal murine mammary gland (NMuMG)--growing as monolayers on collagen gels were overlaid with another collagen gel. The cells responded to the overlay by undergoing reorganization resulting in the creation of lumina. MDCK cells formed lumina that coalesced to form large cavities comparable in size with a tubule. NMuMG cells formed clusters surrounding small lumina, which appeared similar to acini of glandular tissue. The characteristic arrangements, described here by light and electron microscopy, resembled the morphology of the tissues of cell line origin. MDCK cells, grown in the presence of serum, formed lumina whether or not serum was removed at the time of overlay, whereas NMuMG cells required either a nondialyzable component of serum or hormonal supplements in serum-free defined media. Lumen formation was delayed by MDCK cells in the presence of the glutamine analog 6-diazo-5-oxo-L-norleucine, but this compound did not affect NMuMG lumen formation. In both cell lines, lumen formation was unaffected by the absence of sulfate, the presence of an inhibitor of sulfated glycosaminoglycan synthesis, or an inhibitor of collagen synthesis. DNA synthesis accompanied lumen formation but was not required.

Animals↗
PubMed1978

Hardening of the sea urchin fertilization envelope by peroxidase-catalyzed phenolic coupling of tyrosines.

Within minutes after its elevation from the egg surface, the sea urchin fertilization envelope (FE) becomes "hardened" by a reaction that renders it resistant to agents that solubilize, denature or degrade most proteins. Peroxidase activity is released into the surrounding seawater from Stronglyocentrotus purpuratus eggs during fertilization. Evidence from several sources indicate that the catalytic action of the peroxidase is responsible for hardening the FE through the phenolic coupling of tyrosyl residues of the FE proteins. First, the peroxidase is localized within the hardened FE and within the crystalline FE precursor material released from egg cortical granules during the fertilization reaction. Second, a direct correlation is established between the effectiveness of compounds in inhibiting the cortical granule peroxidase (CGP) and their effectiveness in inhibiting hardening of the FE. Third, the CGP catalyzes the cross-linking of tyrosines in solution, a reaction known to be catalyzed by horseradish peroxidase (HRP). Fourth, acid hydrolysates of hardened FEs contain cross-linked tyrosines that are identified by comparing their chromatographic ultraviolet absorption and fluorescent characteristics to those known for cross-linked tyrosines formed by HRP. Finally, when eggs are fertilized in the presence of 125I, the CGP heavily labels proteins of the FE and of the crystalline FE precursor material released with the enzyme from the cortical granules. The iodide label reflects the localization of the CGP and may reflect the sites of peroxidase-generated tyrosyl phenyl radicals involved in the tyrosine coupling reaction. Maximal iodide labeling occurs during the first 5 min period following fertilization, corresponding to the period of FE hardening.

Animals↗