Calcium uptake by isolated rat intestinal cells

Intestinal cells were isolated by a combination of mechanical and enzymatic means, and their calcium uptake was assayed by a rapid filtration procedure. Calcium uptake was a time- and concentration-dependent process that was markedly elevated at 25 and 37°C, as compared to 0°C. Cells isolated from rat duodenum exhibited higher uptakes than cells from jejunum, which in turn took up more calcium than cells from the ileurn. Duodenal cells from vitamin D-deficient animals took up less calcium than cells from vitamin D-replete cells. In vivo vitamin D repletion with 1,25-dihydroxyvitamin D₃ raised calcium uptake by duodenal cells from treated animals toward that of cells from replete rats. Furthermore, calcium uptake by duodenal cells from vitamin D-deficient animals approximated that of ileal cells from replete rats. These findings with isolated cells parallel prior findings of tissue calcium transport and suggest that cellular calcium uptake may be related to the saturable component of intestinal calcium absorption. Isolated intestinal cells may therefore constitute one experimental model for the study of transcellular calcium transport.     

Antigenic relationships between Aracoccidioides loboi and other pathogenic fungi determined by immunofluorescence

Summary The fluorescent antibody technique was used to study antigenic relationships betweenParacoccidioides loboi and other pathogenic fungi. The findings suggest thatP. loboi is more closely related antigenically to certainP. brasiliensis strains than to others and that it has antigens in common with the yeast form ofHistoplasma capsulatum, H. duboisii, Blastomyces dermatitidis, Candida albicans and also the mycelial form ofCoccidioides immitis. Serum globulins from 3 cases of keloidal blastomycosis were labelled with fluorescein isothiocyanate. These conjugates showed slight or no reactivity withP. loboi, the yeast forms ofP. brasiliensis, H. capsulatum, H. duboisii andB. dermatitidis, However, they stained brightlyC. albicans, serotypes A and B, the tissue form ofC. immitis and the yeast form ofSporotrichum schenckii. Adsorption of these reagents withC. albicans eliminated all staining except that forS. schenckii. These patients had no history of clinical sporotrichosis.Deceased. Last address: Fundacão Gonçalo Moniz, Salvador, Bahia, Brazil. Requests for reprints should be sent to Dr.William Kaplan.Dr.Miranda is in private practice in Rio de Janeiro, Brazil.     

An electron microscopic study of the cerebral blood vessels of the opossum

Summary Blood vessels of the opossum brain are paired, artery and vein, and end in a closed loop. Both anatomically and physiologically they are true end-arteries. The two limbs are enclosed within a single basement membrane and are separated from each other by an intercapillary cell thought to be analogous to the usual capillary pericytes. The similarity of this vascular arrangement to that in the rabbit placenta and in the medulla of the kidney is discussed in relation to the counter-current multiplier system.This work was supported in part by the Beaumont-May Institute of Neurology and by a grant, B-425, from the United States Public Health Service.Research Fellow of the National Multiple Sclerosis Society.     

Circular dichroism measurements of benzyl L-aspartate–nitrobenzyl L-aspartate copolymers and their use in detecting and characterizing preferred polymer conformations

We have examined the nature of the circular dichroism band at 330 mμ for a series of copolymers of β-p-nitrobenzyl L -aspartate with β-benzyl L -aspartate. The circular dichroism band arises from an electronic transition in the nitroaromatic group. In order to interpret the effect quantitatively, we employed a simplified statistical treatment and curve fitting for six copolymers. Both approaches gave consistent results, which indicates that the dichroism comes from pairwise interactions between two nitrobenzyl groups. We constructed a molecular model that meets the constraints and requirements of the analyses developed in this paper. In this model, it is proposed that the main chain forms a right-handed α-helix and that nitrobenzyl groups separated by four residues interact with each other.     

A Symbolic Model for the Regulation by Bone Metabolism of the Blood Calcium Level in Rats

The control by bone metabolism of the blood calcium level in young rats may be described in terms of a regulator-type system. The model presented here comprises a feedback loop involving only a proportional control in thyroparathyroidectomized, and a combination of proportional and integral controls in normal animals. It accounts for the variations observed when the system was subjected to a variety of experimental constraints. The implications, limitations, and possible extensions of the model are discussed.     

SDSE: A software package to simulate the evolution of a pair of DNA sequences

An algorithm to simulate DNA sequence evolution under a generalstochastic model, including as particular cases all the previouslyused schemes of nucleotide substitution, is described. The simulationis carried out on finite, variable length, DNA sequences througha strict stochastic process, according to the particular substitutionrates imposed by each scheme. Five FORTRAN programs, runningon an IBM PC and compatibles, carry out all the tasks neededfor the simulation. They are menu driven and interfaced to thesystem through a principal menu. All sequence data files usedand generated by the SDSE package conform to the standard GenBankdatabase format, thus allowing the use of any sequence retrievedfrom this databank, as well as the application of other packagesto analyse, manipulate or retrieve simulated sequences. Received on August 23, 1988; accepted on November 15, 1988