Modeling rendille household herd composition

Previous analysis of Rendille household herd composition revealed a transition from camel to cattle ownership for sedentary impoverished Rendille pastoralists of northern Kenya. In an attempt to delineate determinants of livestock holdings, logistic regression analysis of 112 household herds from the Rendille settlement of Korr, Marsabit District, Kenya was undertaken. Results indicated that household wealth, measured in present livestock holdings, past drought losses, and livestock sales, formed better predictors of cattle ownership than did household characteristics pertaining to labor supply, wage earners, age-set membership, and birth order of household head. These results are discussed in light of pastoral strategies designed to minimize risk.     

Drought and economic differentiation among Ariaal pastoralists of Kenya

This paper examines the effects of the 1984 drought upon household wealth differences in a community of Ariaal pastoralists of northern Kenya. The database consists of 1985 post-drought livestock counts and informants' statements of species-specific drought loss, compared to 1976 livestock counts on the same 38 households. The analysis confirms the hypothesis that the drought resulted in increased household wealth inequalities. It is suggested that the combination of differential herd growth, differential participation in the cash market, and differential loss to the drought has contributed to a polarization within Ariaal of rich and poor, resulting in rural proletarianization and urban migration.     

Sensitive non-radioactive dot-blot hybridization using DNA probes labelled with chelate group substituted psoralen and quantitative detection by europium ion fluorescence.

A new labelling method for cloned DNA probes used in hybridization assays is described. The DNA insert of recombinant plasmid DNA was made partially single-stranded for the labelling reaction by a restriction enzyme digest, followed by a controlled exonuclease III incubation. A thiol-containing psoralen derivative was covalently bound through irradiation with UV-light to the remaining double-stranded region of the plasmid DNA. The psoralen-SH groups were labelled with a large number of metal chelators (diethylentriamine pentaacetic acid, DTPA) using poly-L-lysine as a macromolecular carrier. The main advantage of the labelling procedure is that a high degree of labelling is achieved without modification of the single-stranded DNA hybridizing sequences. The specific hybrids were labelled after filter hybridization with europium ions through the chelating groups of DTPA. The europium ions were quantitatively detected by time-resolved fluorometry. The sensitivity of the assay for target DNA detection was in the low picogram range, comparable to radioactively labelled DNA probes.     

Expression and characterization of a functional human insulin-like growth factor I receptor

Stable transfectants of Chinese hamster ovary (CHO) cells were developed that expressed the protein encoded by a human insulin-like growth factor I (IGF-I) receptor cDNA. The transfected cells expressed approximately 25,000 high affinity receptors for IGF-I (apparent Kd of 1.5 X 10(-9) M), whereas the parental CHO cells expressed only 5,000 receptors per cell (apparent Kd of 1.3 X 10(-9) M). A monoclonal antibody specific for the human IGF-I receptor inhibited IGF-I binding to the expressed receptor and immunoprecipitated polypeptides of apparent Mr values approximately 135,000 and 95,000 from metabolically labeled lysates of the transfected cells but not control cells. The expressed receptor was also capable of binding IGF-II with high affinity (Kd approximately 3 nM) and weakly recognized insulin (with about 1% the potency of IGF-I). The human IGF-I receptor expressed in these cells was capable of IGF-I-stimulated autophosphorylation and phosphorylation of endogenous substrates in the intact cell. This receptor also mediated IGF-I-stimulated glucose uptake, glycogen synthesis, and DNA synthesis. The extent of these responses was comparable to the stimulation by insulin of the same biological responses in CHO cells expressing the human insulin receptor. These results indicate that the isolated cDNA encodes a functional IGF-I receptor and that there are no inherent differences in the abilities of the insulin and IGF-I receptors to mediate rapid and long term biological responses when expressed in the same cell type. The high affinity of this receptor for IGF-II also suggests that it may be important in mediating biological responses to IGF-II as well as IGF-I.     

Monoclonal antibodies to the main immunogenic region of the nicotinic acetylcholine receptor bind to residues 61-76 of the alpha subunit

Monoclonal antibodies (mAbs) to the main immunogenic region (MIR) bind to fusion proteins containing region 37-200 of the alpha chain of Torpedo, mouse, and chicken nicotinic acetylcholine receptor. In the case of the mouse alpha chain, these mAbs react with sequence 61-216 but not with 74-216. A synthetic peptide M1, containing residues 61-76 of the mouse alpha chain, also binds these anti-MIR mAbs, showing that all or part of their binding site is included in this region. The conformational dependence and epitope specificity of the mAbs are discussed.     

In vitro toxicity testing for antibacterials against human keratinocytes

The use of cultured human keratinocytes in an in vitro comparison of topical antibacterial toxicity for epithelial cells was examined. The complement of three assessments allows testing of epithelial migration, growth, and survival. The three assessments included (1) flow cytometry for determination of cell survival, (2) a comparison of confluent cell culture growth after antibacterial exposures, and (3) an evaluation of cell migration using a technique of dermal explants to study radial migration. A comparative ranking of the toxicities of the various topical antibacterials was determined with the three assessments. This has confirmed anecdotal reports that many of the topical antibacterials are cell-toxic and may inhibit wound healing. This information can be directly extrapolated to the clinical setting, unlike many of the animal data for wound healing that currently exist.     

Versatility of anti-horseradish peroxidase antibody-gold complexes for cytochemistry and in situ hybridization: preparation and application of soluble complexes with streptavidin-peroxidase conjugates and biotinylated antibodies

Summary In previous studies we have employed a gold-labelled, affinity-purified polyclonal antibody against horseradish peroxidase (anti-HRP — gold) in the avidinbiotin peroxidase complex (ABC) technique and indirect labelled avidin-biotin methods. The gold-labelled antibody was used as final revealing reagent to replace the 3,3-diaminobenzidine (DAB) reaction by immunogold silver staining. The anti-HRP — gold reagent proved to be advantageous since blocking of endogenous peroxidase activity in the tissue sections was not further required and staining of superior contrast and resolution could be achieved in paraffin sections. In the present study we have optimized this technique by combining the last two incubation steps, i.e. HRP-conjugated streptavidin and anti-HRP — gold. Different ratios of the two reagents were tested empirically to establish the conditions for the formation of a soluble complex with optimal staining properties. Quantitative evaluation by densitometry of the staining intensity showed that the soluble streptavidin-HRP/anti-HRP — gold complex and the indirect labelled avidin-biotin method employing the gold-labelled anti-HRP antibody performed equally well. Thus, the availability of this complex simplifies the streptavidin-biotin immunogold technique for immunohistochemistry, lectin histochemistry and in situ hybridization and further demonstrates the versatility of anti-HRP — gold complexes.