Calcitonin inhibits the phosphorylation of various proteins in rat brain synaptic membranes

The present report examines the effect of different calcitonins and analogs on the in vitro phosphorylation of brain synaptic membrane proteins. The findings demonstrate that calcitonin is a potent inhibitor of several brain synaptic proteins and that salmon and eel calcitonins are considerably more potent than thyrocalcitonin in eliciting this effect. Deletion of leucine from position 16 in salmon calcitonin sequence resulted in a drastic loss of inhibitory activity, indicating the importance for a hydrophobic residue at position 16 in the intact calcitonin molecule. The mechanism of calcitonin inhibition of protein phosphorylation was likely due to the blockade of stimulation of protein kinases by calmodulin.     

Role of solute drag in intestinal transport

This study presents experiments related to the role of solvent drag and solute drag in the transmembrane movement of nonelectrolytes in a perfused rat intestine preparation. Conditions were chosen to simulate the effects of luminal hyperosmolarity on the permeability of tracer solutes. Data are presented on net water flux, transepithelial potentials, and lumen-to-blood and blood-to-lumen tracer solute movements during control electrolyte perfusion and after making the perfusate hyperosmotic. The results indicate that both solvent drag and solute drag can play significant roles in the transepithelial movement of solute and solute permeabilities in the rat ileum preparation. It is suggested that the potential roles of solvent drag and solute drag should be accounted for or considered during the characterization of the mechanisms of biological membrane function.     

Covalent cross-linking of vasoactive intestinal peptide (VIP) to its receptor in intact colonic adenocarcinoma cells in culture (HT 29)

[125I]Monoiodinated vasoactive intestinal peptide (125I-VIP) was cross-linked with human colonic adenocarcinoma cells (HT29 cells) grown as a monolayer using dithiobis(succinimidylpropionate) as cross-linking reagent. The cross-linked polypeptides were separated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. A major polypeptide of Mr = 67 000 was characterized and it behaved like a high-affinity binding site for VIP according to the following data. The concentration of native VIP (0.5 nM) giving half-maximum inhibition of 125I-VIP covalent cross-linking with this polypeptide was very similar to that giving half-maximum displacement of 125I-VIP on HT 29 cells (0.6 nM). Glucagon or insulin was unable to inhibit the labelling of the Mr-67 000 component. In our experimental conditions neither specific 125I-VIP binding nor covalent labelling was observed with monolayers of Madin Darby canine kidney epithelial cells (MDCK cells) or African green monkey kidney fibroblasts (Vero cells) while the Mr-67 000 polypeptide was also characterized with human rectal adenocarcinoma cells (HRT 18 cells), known to possess the VIP receptor. Preincubation of HT 29 cells with native VIP at 37 degrees C, before 125I-VIP binding and subsequent cross-linking reaction, decreased the labelling of the Mr-67 000 polypeptide up to 80%. Assuming one molecule of 125I-VIP cross-linked per polypeptide, we have characterized, for the first time, a major polypeptide of Mr = 64 000, which belongs to the high-affinity VIP binding site of an intestinal human cell line.     

Internalization of the vasoactive intestinal peptide (VIP) in a human adenocarcinoma cell line (HT29)

The time course of internalization of radioiodinated vasoactive intestinal peptide (VIP) in HT29 cells was obtained using the technique of acetic acid removal of cell-surface-bound peptide. Even after 10 min incubation at 37 degrees C, 125I-VIP, initially bound on the HT29 cell surface, was compartmentalized within the cells. During the same time, degraded radioactive material was released by cells in the incubation medium. Localization of internalized 125I-VIP was investigated using two different subcellular fractionation techniques. 10 min after the onset of internalization, 125I-VIP labelling was found in intermediate structures and 10 min later the bulk of the radioactivity was detected in a low-density fraction containing very large lysosomes with a multivesicular aspect. The lysosomotropic agent NH4Cl appeared to inhibit 125I-VIP internalization, degradation and appearance of radiolabelled peptide in the large lysosomes in a time-dependent manner. Moreover, the effect of NH4Cl resulted in an accumulation of radioactive material in fractions containing microsomal structures. On the other hand, bacitracin, together with methylamine, highly enhanced 125I-VIP labelling in a membrane fraction, suggesting that these agents possibly act on a cell surface component of HT29 cells. These results support the conclusion that in HT29 cells, prelysosomal structures and large secondary lysosomes are probably part of the intracellular pathway of internalized VIP.     

Internal antigen and immune network

The network hypothesis postulates the existence of internal idiotopic structures which mimic nominal antigens. Experimental evidence for idiotope internal antigen is presented and its implication for the Network hypothesis is discussed. The exploitation of the internal idiotope antigens (or preparation of vaccines) is a realistic possibility.     

Chronic administration of dehydroepiandrosterone reduces pancreatic beta-cell hyperplasia and hyperinsulinemia in genetically obese Zucker rats

The Zucker obese (fa/fa) rat is a model of hypertrophic/hyperplastic obesity. These rats develop marked hyperinsulinemia, insulin resistance, and pancreatic beta-cell hyperplasia. In the present study, chronic (22 weeks) administration of the 17-ketosteroid, dehydroepiandrosterone (DHEA), to obese Zucker rats significantly decreased body weight, and retroperitoneal and parametrial fat pad weights. In addition, beta-cell hyperplasia was reduced as well as pancreatic insulin content. DHEA treatment of lean Zucker rats also reduced body weight, fat depot weight, pancreatic islet diameter, and pancreatic insulin content. These data indicate that DHEA treatment appears to inhibit insulin synthesis and beta-cell proliferation. Whether this is due to a direct effect on the pancreas or due to improvement of peripheral insulin sensitivity remains to be elucidated.     

Demographic characteristics of a rural area in Kenya in 1974-80

A longitudinal, epidemiological study was carried out in a rural area of Kenya with a population of about 28,000 between 1974 and 1980. Population registration during this time showed that population growth was very high between 1974 and 1978 (4.4%/year) and much lower in 1979 and 1980 (1.1%). Natural increase was nearly as high as in Kenya as a whole (3.7%) in this period. Fertility was somewhat lower than in all Kenya (the crude birth rate was 46/1000) while mortality was substantially lower (7/1000). These rates are believed to be genuine and not due to under reporting of infant deaths. The most likely reason for these low infant mortality levels is the existence of favorable economic, social and hygienic conditions in the area compared to other parts of Kenya. The adult mortality rates are low too, in particular for the population aged 65 and over. The main reason is the overestimation of ages, in particular of women in the older age brackets, which has led to too large a denominator of the age specific rates in these age groups. Levels of temporary and permanent migration are high and probably characteristic for many parts of Kenya. Of the 19% of the registered population absent when visited by the fieldworkers, there were more males (23%) than females (14%). The % of absenteeism is higher for males between 20-59 years old, and also for females between 15 and 30. About 3% of the population is away for a short time, visiting relatives, attending weddings and funerals or occupied as traders. The large majority of absentees (14%) consists of temporary labor migrants and family members accompanying them. Many are gainfully employed in Nairobi and other towns in Kenya; some are farmers who seasonally move to another farm which they own outside the area. Others are wives and children who temporarily join their husbands, or polygamous men who are temporarily staying with another wife outside the area. All permanent movements to and from the study area, as well as within it, show that on average migration inwards and outwards balanced each other in the 7-year period. The gross migration rate is substantially higher for females than for males. This is due to family related reasons: marriage, divorce, separation. Other categories of migrants are those families who establish a new business or farm elsewhere, teachers and pastors who are transferred, and farm laborers, housemaids and servants. Poor economic conditions of 1979/80, due to a drop in coffee prices and poor harvests of coffee, maize and beans, led to more emigration and less immigration.     

Changes in cell-surface expression of MHC and Thy-1.2 determinants following treatment with lipid modulating agents

Treatment of normal mouse spleen cells with lipid fluidity modulators changes the expression of cell-surface H-2 determinants. BALB/c spleen cells treated for 1 to 2 hr with cholesteryl hemisuccinate (CHS) displayed reduced levels of all tested H-2 determinants (H-2L, H-2K, and H-2D) as evaluated by flow microfluorometry and increased membrane lipid packing density as determined by 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence polarization. In contrast, decreasing membrane lipid packing density by phosphatidylcholine treatment decreased DPH fluorescence polarization and increased the expression of MHC determinants. The effects were selective in that expression of Thy-1.2 determinants was decreased by the latter treatment and not increased by CHS. The results are discussed in terms of passive modulation of antigenic expression.     

Intravenous versus inhaled atropine for inhibiting bronchoconstrictor responses in dogs

We studied whether the muscarinic antagonist, atropine, given intravenously or by inhalation, inhibits the bronchoconstrictor responses to inhaled acetylcholine and to acetylcholine released by electrical stimulation of the vagus nerves to the same degree. We assessed bronchoconstrictor responses in anesthetized dogs by determining the increase in total pulmonary resistance before and after increasing doses of atropine and then constructing inhibition dose-response curves. Before atropine the responses to the two stimuli were equal in magnitude. After intravenous atropine (initial dose 0.12 micrograms/kg, total dose 16 micrograms/kg) both responses were progressively inhibited to a similar degree. By contrast, after inhaled atropine (initial dose 0.02 micrograms/kg, total dose 2.4 micrograms/kg) the response to acetylcholine inhalation was inhibited to a much greater degree than the response to vagal stimulation. Thus, in studies designed to inhibit bronchoconstriction due to an inhaled muscarinic agonist to the same degree as bronchoconstriction due to a vagal reflex, atropine might better be given intravenously than by inhalation.     

"Whey" proteins of milk of the red (Macropus rufus) and eastern grey (Macropus giganteus) kangaroo

1. A comparison is made of gel electrophoretic patterns of the "whey" proteins of the milk of red (Macropus rufus) and eastern grey (Macropus giganteus) kangaroos at various stages of lactation. Qualitative and quantitative changes occur with time during the mature phase of lactation of both types. Their onset is related solely to the stage of lactation. "Whey" proteins are isolated and characterised and the nature of protein changes determined for the first time. 2. The anodic electrophoretic pattern is divided into 6 main zones (designated A F in order of decreasing mobility) and 2 cathodic zones (G and H) that are only detected in the milk of M. giganteus. 3. Zones A, B and C are milk specific. Zone B is present throughout lactation in both species and is an alpha-lactalbumin. Zones A and C are present only in late lactation, zone C, usually, but not always, appearing first. Zone A is an alpha-lactalbumin in M. giganteus, but is not an alpha-lactalbumin in M. rufus. Zone C appears to be the same protein in both species and is possibly a beta-lactoglobulin. 4. Zone D is kangaroo serum albumin and zone E is possibly a beta 2-microglobulin. Zone F contains three main iron (III) binding bands whose relative intensity varies with stage of lactation. Their intensity differs from the corresponding blood serum transferrin bands. 5. Zone H of Macropus giganteus is a lysozyme. 6. Lactose is present in the milk, but is not the principal sugar. 7. The significance of the results is discussed.