Electrogenic Cl− absorption byAmphiuma small intestine: Dependence on serosal Na+ from tracer and Cl− microelectrode studies

Summary The Na⁺ requirement for active, electrogenic Cl^– absorption byAmphiuma small intestine was studied by tracer techniques and double-barreled Cl^–-sensitive microelectrodes. Addition of Cl^– to a Cl^–-free medium bathingin vitro intestinal segments produced a saturable (K _m =5.4mm) increase in shortcircuit current (I _sc) which was inhibitable by 1mm SITS. The selectivity sequence for the anion-evoked current was Cl^–=Br^–>SCN^–>NO ₃ ^– >F^–=I^–. Current evoked by Cl^– reached a maximum with increasing medium Na concentration (K _m =12.4mm). Addition of Na⁺, as Na gluconate (10mm), to mucosal and serosal Na⁺-free media stimulated the Cl^– current and simultaneously increased the absorptive Cl^– flux (J _ms ^Cl ) and net flux (J _net ^Cl ) without changing the secretory Cl^– flux (J _sm ^Cl ). Addition of Na⁺ only to the serosal fluid stimulatedJ _ms ^Cl much more than Na⁺ addition only to the mucosal fluid in paired tissues. Serosal DIDS (1mm) blocked the stimulation. Serosal 10mm Tris gluconate or choline gluconate failed to stimulateJ _ms ^Cl . Intracellular Cl^– activity (a _Cl ⁱ ) in villus epithelial cells was above electrochemical equilibrium indicating active Cl^– uptake. Ouabain (1mm) eliminated Cl^– accumulation and reduced the mucosal membrane potential _m over 2 to 3 hr. In contrast, SITS had no effect on Cl^– accumulation and hyperpolarized the mucosal membrane. Replacement of serosal Na⁺ with choline eliminated Cl^– accumulation while replacement of mucosal Na⁺ had no effect. In conclusion by two independent methods active electrogenic Cl^– absorption depends on serosal rather than mucosal Na⁺. It is concluded that Cl^– enters the cell via a primary (rheogenic) transport mechanism. At the serosal membrane the Na⁺ gradient most likely energizes H⁺ export and regulates mucosal Cl^– accumulation perhaps by influencing cell pH or HCO ₃ ^– concentration.     

Delayed hypersensitivity granuloma formation around Schistosoma mansoni eggs in vitro. III. Granuloma formation and modulation in human Schistosomiasis mansoni

An in vitro model of granuloma formation was used to study the cellular immune responses of Schistosoma mansoni-infected patients. The purposes of this study were to determine the relationship of granulomatous hypersensitivity to S. mansoni eggs in recent, well-defined infections and long-term chronic infections, and to determine the role of T cell subsets (OKT3, 4, and 8) defined by monoclonal antibodies in granulomatous hypersensitivity. Peripheral blood mononuclear cells obtained from patients with recent S. mansoni infections demonstrated increased granulomatous hypersensitivity responses in vitro when compared to peripheral blood mononuclear cells obtained from patients infected for 5 yr or more. The selective removal of infected for 5 yr or more. The selective removal of OKT3+ or OKT4+ cells reduced the ability of peripheral blood mononuclear cells to form granulomas in vitro. Positive selection for OKT4+ T cells produced optimal granulomatous hypersensitivity when compared to that produced by the unfractionated peripheral blood mononuclear cell population. OKT8+ cells demonstrated no ability to form granulomas in vitro. Selective removal of OKT8+ T cells produced variable results in the ability of the remaining peripheral blood mononuclear cells to form granulomas in vitro. These studies demonstrate the feasibility of investigating granulomatous hypersensitivity and immunoregulatory mechanisms operative in S. mansoni-infected patients by using in vitro technology.     

Some characteristics of monolayers of 1-palmitoyl-2-oleoyl-phosphatidylglycerol with and without dipalmitoylphosphatidylcholine during dynamic compression and expansion

Some properties of monolayers of $\text{1-}\text{palmitoyl}\text{-2-}\text{oleoyl}\text{-sn-}\text{glycero}\text{-3-}\text{phospho}\text{-rac-}\text{glycerol}$ (POPG) alone or of POPG in mixtures with $\text{1,2-}\text{dipalmitoyl}\text{-sn-}\text{glycero}\text{-3-}\text{phosphocholine}$ (DPPC) have been measured near 35°C during dynamic compression and expansion at 3.6 cm²·s^?1. (2) The mean values of minimum surface tension (corresponding to maximum surface pressure) which could be obtained with pure POPG monolayers at high compression ranged from 15 to 18 mN·m^?1 in the presence of Na⁺, Ca²⁺ or low pH (2.0) in the subphase. (3) The presence of Ca²⁺ or low pH in the subphase increased the collapse plateau ratios obtained on cyclic compression. This might represent enhanced respreading into the monolayer of pure POPG from a collapsed form during reexpansion of the surface. (4) Monolayers containing 10% or 30% POPG and 90% or 70% DPPC could be compressed to surface tensions approaching zero. (5) In such mixed monolayers, 10% or 30% POPG did not appear to enhance respreading, as measured by collapse plateau ratios, in the presence of Na⁺ or Ca²⁺ in the subphase.     

Initial Phases of Starvation and Activity of Bacteria at Surfaces

The activity of the hydrophilic Vibrio sp. strain DW1 and the hydrophobic Pseudomonas sp. strain S9, which both undergo starvation-induced responses, was examined at nutrient-enriched and nutrient-deficient interfaces. The initial period of response to a starvation regime (“dwarfing” phase) is a sequence of two processes: fragmentation and continuous size reduction of the fragmented cells. This dwarfing phase is also one of intense metabolic activity as supported by O₂ uptake measurements of the endogenous metabolism and the use of inhibitors of the proton flow, the electron transport chain, and membrane-bound ATPase. Hydrophilic bacteria become even smaller at nutrient-deficient surfaces than in the liquid phase upon starvation, and this is reflected in a higher endogenous metabolism exhibited by surface-associated cells compared with those in the liquid phase. On the other hand, hydrophobic bacteria dwarfing at surfaces did not exhibit a greater size reduction and exhibited an endogenous metabolism that was only slightly higher than that of cells in the liquid phase. Bacterial scavenging of surface-localized nutrients is related to the degree of irreversible binding of dwarf and starved bacteria, which in turn may be related to the degree of cell surface hydrophobicity.     

Hypoxanthine-guanine phosphoribosyltransferase in human erythroid cells: Properties of the isozymes

We have previously given evidence that the hypoxanthine-guanine phosphoribosyltransferase (HGPRT; EC 2.4.2.8) isozymes in human erythroid cells result from posttranslational modifications of a single gene product [Johnson, G. G., et al. (1982). Biochemistry 21:960]. In the present work we compare the properties of the unmodified and two major modified isozymes, which collectively account for 90% of the HGPRT enzyme activity in cell lysates. The modified isozymes differ from the parent molecule in the pH dependence of activity and in the relative utilization of the two purine base substrates, hypoxanthine and guanine. In contrast to the changes in the catalytic properties of the enzyme, the modifications have no detectable effects on the heat stability or on the equilibrium between enzyme dimers and enzyme tetramers.This work was supported by United States Public Health Service Grant 5 RO1 CA 16754-03 and by the San Diego State University Foundation.     

Uptake of Gallium-67 in Colonic and Rectal Tumours

The uptake of ⁶⁷Ga in biopsy specimens of normal and abnormal tissue was measured in 20 cases of colonic and rectal disease and the ratio between the ⁶⁷Ga uptake in these diseases and in the normal colon or rectum was determined. Uptake of the isotope was high in most of the 14 primary malignant tumours, being highest in poorly differentiated tumours. This uptake was found to be concentrated at the active tumour edge. Uptake of the isotope was generally low in non-malignant lesions.     

Lead Poisoning in Gurkha Soldiers in Hong Kong

Investigation of an outbreak of lead-poisoning in 121 Gurkha soldiers showed that this was due to the contamination of chilli powder (cayenne pepper), a constituent of curry powder, with lead chromate. Comprehensive systems of food sampling are needed in developing communities.     

A neural model for conditioned avoidance learning

A mathematical model for learning of a conditioned avoidance behavior is presented. An identification of the net excitation of a neural model (Rashevsky, N., 1960.Mathematical Biophysics. Vol. II. New York: Dover Publications, Inc.) with the instantaneous probability of response is introduced and its usefulness in discussing block-trial learning performances in the conditioned avoidance situation is outlined for normal and brain-operated animals, using experimental data collected by the author. Later, the model is applied to consecutive trial learning and connection is made with the approach of H. D. Landahl (1964. “An Avoidance Learning Situation. A Neural Net Model.”Bull. Math. Biophysics,26, 83–89; and 1965, “A Neural Net Model for Escape Learning.”Bull. Math. Biophysics,27, Special Edition, 317–328) wherein lie further data with which the model can be compared.