Active potassium transport by rabbit descending colon epithelium

Summary Previous studies of rabbit descending colon have disagreed concerning potassium transport across this epithelium. Some authors reported active K⁺ secretion underin vitro short-circuited conditions, while others suggested that K⁺ transport occurs by passive diffusion through a highly potassium-selective paracellular route. For this reason, we re-examined potassium fluxes across the colon in the presence of specific and general metabolic inhibitors. In addition, electrochemical driving forces for potassium across the apical and basolateral membranes were measured using conventional and ion-sensitive microelectrodes. Under normal conditions a significant net K⁺ secretion was observed (J _net ^K =–0.39±0.081 eq/cm²hr) with⁴²K fluxes, usually reaching steady-state within approximately 50 min following isotope addition. In colons treated with serosal addition of 10^–4 m ouabain,J _sm ^K was lowered by nearly 70% andJ _ms ^K was elevated by approximately 50%. Thus a small but significant net absorption was present (J _net ^K =0.12±0.027 eq/cm²hr). Under control conditions, the net cellular electrochemical driving force for K⁺ was 17 mV, favoring K⁺ exit from the cell. Cell potential measurements indicated that potassium remained above equilibrium after ouabain, assuming that passive membrane permeabilities are not altered by this drug. Net K⁺ fluxes were abolished by low temperature.The results indicate that potassium transport by the colon may occur via transcellular mechanisms and is not solely restricted to a paracellular pathway. These findings are consistent with our previous electrical results which indicated a nonselective paracellular pathway. Thus potassium transport across the colon can be modeled as a paracellular shunt pathway in parallel with pump-leak systems on the apical and basolateral membranes.     

Quantitation and interaction of glycosaminoglycans with Alcian blue in dimethyl sulfoxide solutions.

An improved method is described for the quantitation of glycosaminoglycans separatedon cellulose acetate, stained with Alcian blue, and dissolved in a dimethyl sulfoxide solution. Standard curves are shown for all eight glycosaminoglycans. It is shown that absorption at the Alcian blue orthochromatic E_max is depressed under conditions which favor formation of dye-glycosaminoglycan complexes. The interaction between Alcian blue and the eight glycosaminoglycans was studied in dimethyl sulfoxide solutions of varying composition. It was shown that the extent of complex formation depends both on the glycosaminoglycan and the composition of the dimethyl sulfoxide solution. A dimethyl sulfoxide solution which contains 0.094 m H₂SO₄ is described which maximizes dye-glycosaminoglycan dissociation and thus the absorbance. Also, an improved staining method is described which improves dye uptake by the glycosaminoglycans and consequently increases the sensitivity of glycosaminoglycan quantitation.     

Investigation of the pH dependence of proton uptake by porcine heart mitochondrial malate dehydrogenase upon binding of NADH

The pH dependence of proton uptake upon binding of NADH to porcine heart mitochondrial malate dehydrogenase (l-malate: NAD⁺ oxidoreductase, EC 1.1.1.37) has been investigated. The enzyme has been shown to exhibit a pH-dependent uptake of protons upon binding NADH at pH values from 6.0 to 8.5. Enzyme in which one histidine residue has been modified per subunit by the reagent iodoacetamide (E. M. Gregory, M. S. Rohrbach, and J. H. Harrison, 1971, Biochim. Biophys. Acta253, 489–497) was used to establish that this specific histidine residue was responsible for the uptake of a proton upon binding of NADH to the native enzyme. It has also been established that while there is no enhancement of the nucleotide fluorescence upon addition of NADH to the iodoacetamide-modified enzyme, NADH is nevertheless binding to the modified enzyme with the same stoichiometry as with native enzyme. The data are discussed in relation to the involvement of the essential histidine residue in the catalytic mechanism of “histidine dehydrogenases” recently proposed by Lodola et al. (A. Lodola, D. M. Parker, R. Jeck, and J. J. Holbrook, 1978, Biochem. J.173, 597–605) and the catalytic mechanism of “malate dehydrogenases” recently proposed by L. H. Bernstein and J. Everse (1978, J. Biol. Chem.253, 8702–8707).     

Effects of inorganic amendments (N,P and K) to soil on the rhizosphere microflora of antirrhinum plants infected withVerticillium dahliae Kleb

Summary A study of the inorganic amendments (N, P and K) to soil, and their effect on the rhizosphere microflora, as well as their relation to the control of wilt of antirrhinum plants caused byVerticillium dahliae Kleb. was done. Ammonium sulphate was the only chemical found to be significantly inhibitory toV. dahliae in vitro. Soil amendments (NPK) affected the rhizosphere microorganisms of the antirrhinum plants. Higher concentration of the chemicals were phytotoxic. It was further observed that ammonium sulphate, and the combined chemicals (NPK 25%) in soil delayed the senescence in healthy plants, suggests that chemical fertilisers affected the host plants directly. Addition of ammonium sulphate (0.25%), calcium nitrate (0.25%, 0.5%) combined NPK (0.25%) to soil caused considerable reduction in disease severity. It is assumed that this reduction may be caused by the (1) fungitoxic nature of the chemicali.e. ammonium sulphate, (2) antagonistic environment for the pathogen in the rhizosphere was boostedi.e. where calcium nitrate was added as soil amendments and (3) reduction in disease severity in soil-amended with combined NPK, may be due to the fact that antagonistic actinomycete population was boosted in the rhizosphere.     

The heterocytotoxicity of human serum. II. Role of natural antibody and of the classical and alternative complement pathways.

Mouse lymphoid cells and tumor cell lines were employed as target cells for the investigation of the mechanism of heterocytotoxicity in human serum samples. It was shown that the heterocytotoxic effects were due to two differing mechanisms. Cytotoxicity was mediated in part, by activation of the alternative complement pathway on target cell membrane, a process which was antibody-independent. A second mechanism of cytotoxicity was induced by natural antibodies to a target cell, which probably mediated activation of the classical complement pathway. These data may shed light on the frequently observed cytotoxicity in mammalian sera for various target cells.     

Group mating among Norway rats I. Sex differences in the pattern and neuroendocrine consequences of copulation

The copulatory pattern of groups of rats (Rattus norvegicus) was studied in the laboratory in a seminatural environment. In a given mating session, every oestrous female copulated with each male; likewise, every male copulated with each oestrous female. While individual males and females experienced similar amounts of copulation, there were dramatic sex differences in sequence and temporal pattern. Males mated in a multiple intromission pattern and had more ejaculatory series when several females were in oestrus. In contrast, females received intromissions and ejaculations in a random order, not in the sequence of a male ejaculatory series. Males copulated at shorter intervals than females did, a temporal sex difference that was determined by the pattern of female solicitations and male approaches. These sex differences are used to discuss the different units of analysis that are appropriate for male and female sexual behaviour in this species. Furthermore, the sex differences in the temporal pattern of copulation which emerged during group mating parallel the known sex differences in the temporal parameters of the neuroendocrine reflexes which mediate successful reproduction in the domestic strain.     

Group mating among Norway rats II. The social dynamics of copulation: Competition,cooperation, and mate choice

The social interactions within groups of Norway rats (Rattus norvegicus) had a strong impact on the individual pattern of copulation which, in turn, affects sperm precedence and the probability of implantation in this species. Males alternated uninterrupted ejaculatory series, augmenting each others' copulatory investment. Females took turns mating after receiving an intromission, collectively potentiating the males' copulatory behaviour; increasing the number of oestrous females increased the number of intromissions and ejaculations achieved by each male but did not affect the amount of copulation experienced by each female. These turn-taking patterns within each sex provided the opportunity to change partners and permitted the emergence of different sex-typical patterns of copulation. Furthermore, the dominant male contributed more intromissions and tended to give each female more ejaculations than the subordinates did. Dominant males were also more likely to inhibit the subordinates' sperm transport. Females competed among themselves for the opportunity to mate with a male as he approached ejaculation and were likely to protect more of the dominant male's sperm transport than the subordinate male's.     

Defect in 3'-phosphoadenosine 5'-phosphosulfate synthesis in brachymorphic mice. II. Tissue distribution of the defect

The tissue distribution of the defective PAPS synthetic pathway in homozygous brachymorphic mice ($\text{bm}\text{bm}$) has been investigated using four different criteria: (i) incorporation of ³⁵SO₄^2? into adenosine 5′-phosphosulfate (APS), 3′-phosphoadenosine 5′-phosphosulfate (PAPS), and endogenous macromolecular acceptors, (ii) APS kinase (adenylylsulfate kinase; ATP:adenylylsulfate 3′-phosphotransferase, EC 2.7.1.25) activity, (iii) ATP sulfurylase (sulfate adenylyltransferase; ATP:sulfate adenylyltransferase, EC 2.7.7.4) activity, (iv) thermostability of ATP sulfurylase. With respect to the first three criteria, the results indicate that liver is affected as profoundly as cartilage (K. Sugahara and N. B. Schwartz, Arch. Biochem. Biophys. (1982) 214, 589–601). In contrast, skin and brain show no differences between normal and mutant. Kidney is significantly, but only moderately, affected. The results from thermostability studies demonstrate that ATP sulfurylase activity is more labile in $\text{bm}\text{bm}$ cartilage, liver, and kidney, but not in skin or brain, supporting the above-observed distribution of the defect. Therefore, the present results indicate a multiple, but not universal, tissue distribution of the defective PAPS synthetic pathway in $\text{bm}\text{bm}$ mice. Furthermore, these findings support the suggestion that ATP sulfurylase as well as APS kinase is defective in brachymorphic mice.     

Activated T lymphocytes resist the toxic effects of the adenosine deaminase inhibitor, 2-deoxycoformycin

Tonsil lymphocytes from three adults and three children were examined for immunoglobulin (Ig) production before and after Epstein-Barr virus (EBV) transformation. T-cell depletion was required to obtain cell lines from EBV-seropositive individuals. Cytoplasmic Ig was mainly IgG in adult lymphocytes before and after transformation; IgA and IgM were more prominent after than before. IgM and IgG predominated in lymphocytes of children before and after transformation; IgA was more prominent after than before. Cytoplasmic Ig of peripheral blood lymphocytes from these individuals was mainly IgM. Secreted Ig from tonsil lymphocytes was mainly IgA or IgG; after transformation IgM predominated with adult cell lines, and IgG or IgM with cell lines from children. IgE was consistently sparse in spite of ragweed and/or grass allergies of the adults.     

Quantitative changes in potassium,sodium, and calcium in the submaxillary salivary gland and blood serum of rats exposed to 2880-MHz microwave radiation

Na⁺, K⁺, and Ca²⁺ concentrations in the blood serum and submaxillary salivary gland (SSG) were investigated in adult, male rats exposed to 2880-MHz microwaves modulated with 1.5-μs pulses at a pulse repetition rate of 1000 Hz or in a hyperthermal environment. Rats were exposed, one at a time, for 30 min to microwaves producing a specific absorption rate (SAR) of: 4.2, 6.3,6.8,8.4, 10.8, or 12.6 W/kg, or were sham exposed under similar environmental conditions. In a second series, one group of rats was exposed singly for 15, 30, or 60 min to microwaves producing an SAR of 9.5 W/kg and other rats were exposed for similar periods at 40 °C; and 10 rats were sham exposed. Flame photometric analysis indicated that the thresholds of microwave radiation required to induce a change in Na⁺, K⁺, and Ca²⁺ concentrations in the salivary glands are 6.8, 6.8, and 6.3 W/kg, respectively. The directions of Na⁺, K⁺, and Ca²⁺ ion shifts in exposed rats' salivary glands are similar, whether affected by microwaves or hyperthermia. Greater changes in Na⁺ and K⁺ concentrations in SSG of rats exposed to microwaves for 15 and 30 min were found than in those exposed at 40 °C. On the other hand, exposure to hyperthermia at 40 °C or to microwaves for 1 h caused Na⁺ concentration to be increased by 68.7 and 59.5% and K⁺ concentration to be decreased by 29.6 and 21.7%, respectively.