Effects of meal ingestion on plasma amylin concentration in NIDDM and nondiabetic humans

Recent interest has focused on the potential role of amylin in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM). This 37-amino acid peptide is found in extracellular amyloid deposits in approximately 50% of pancreatic islets of patients with NIDDM and has been shown to inhibit skeletal muscle glycogen synthesis in vitro. Immunocytochemical studies have colocalized amylin and insulin within beta-cell secretory granules in nondiabetic humans, provoking the following questions. Is amylin cosecreted with insulin? Are circulating amylin concentrations higher in patients with NIDDM either before or after food ingestion? To answer these questions, we developed a sensitive and specific immunoassay to measure plasma concentrations of amylin in humans. Use of this assay indicated that, in lean nondiabetic subjects, glucose ingestion resulted in an increase (P less than 0.001) in the plasma concentration of amylin (from 2.03 +/- 0.22 to 3.78 +/- 0.39 pM) and insulin (from 48.3 +/- 3.1 to 265 +/- 44 pM). There was a significant correlation between the concentrations of insulin and amylin (r = 0.74, P less than 0.001) and the increase in insulin and amylin concentration (r = 0.65, P less than 0.005). Fasting concentrations of amylin did not differ in diabetic and weight-matched nondiabetic subjects and showed a similar pattern of change after ingestion of a mixed meal. We conclude that amylin is secreted in response to ingestion of either glucose or a mixed meal and circulates at concentrations that do not differ in patients with NIDDM and nondiabetic subjects. It remains to be determined whether amylin at physiological concentrations influences carbohydrate metabolism and if so whether its effects differ in diabetic and nondiabetic humans.

Surfactant protein D is a divalent cation-dependent carbohydrate-binding protein

Surfactant protein D (SP-D, CP4) is a collagenous surfactant-associated glycoprotein synthesized by lung type II epithelial cells. SP-D can be selectively and efficiently eluted from isolated rat surfactant with glucose, maltose, and certain other saccharides. We therefore examined the ability of the purified protein to interact with carbohydrates in vitro. Saccharide-substituted bovine serum albumins (BSA neoglycoproteins) were adsorbed to plastic wells, and binding of purified SP-D was quantified with monospecific antibodies to SP-D using an indirect immunoassay. SP-D showed specific calcium-dependent binding to alpha-D-glucosidophenyl isothiocyanate-BSA and maltosyl-BSA, but negligible binding to beta-D-glucosidophenyl isothiocyanate-BSA or unconjugated BSA. The most efficient inhibitors of SP-D binding were alpha-glucosyl-containing saccharides (e.g. isomaltose, maltose, malotriose). SP-D showed quantitative binding to maltosyl-agarose and was specifically eluted with maltose or EDTA. High affinity binding to maltosyl-BSA was also demonstrated using a solution-phase polyethylene glycol precipitation assay. These studies demonstrate that SP-D is a calcium dependent lectin-like protein and that the association of SP-D with surfactant is mediated by carbohydrate-dependent interactions with specificity for alpha-glucosyl residues.

Seasonality of births among Bedouin Arabs residing in the Negev Desert of Israel

From 1 January 1981 to 31 December 1982 information on all births to Bedouin Arab women residing in the Negev Desert of Israel showed a previously unreported seasonal pattern. The peak season, November-February, coincided with the period of cool temperatures and the Bedouin Arab cultural seasons of winter and spring. This pattern is different from those of Jewish and Christian groups in the same region, a difference not attributable to religion alone. Sociodemographic factors associated with the peak season of birth include traditional occupations of fathers, multiparae 2+, and traditional place of residence. This pattern has persisted over the past 15 years although it is less apparent among the more recently sedentarized Bedouin Arabs.

Effects of endothelin on porcine coronary arterial strips

Endothelin, a novel endothelium derived 21-residue vasoconstrictor peptide synthesized by Peninsula Laboratories, provoked a concentration-dependent contraction of porcine coronary arterial strips. EC50 value for endothelin was 14 +/- SD 4 nmol/L (n = 6), and significantly lower than the values for 5-hydroxytryptamine (5-HT, 0.28 +/- 0.07 mumol/L, n = 6) and 15-methyl-prostaglandin F2 alpha (15-methyl-PGF2 alpha, 4 +/- 3 mumol/L, n = 7). The maximal increase in tension caused by endothelin was 5.4 +/- 1.1 g, being much greater than that induced by 5-HT (3.7 +/- 0.8 g, P less than 0.05) and 15-methyl-PGF2 alpha (3.7 +/- 0.6 g, P less than 0.01). The changes in tension provoked by endothelin (2-20 nmol/L) were attenuated significantly after pretreated with tetrodotoxin (TTX, 30 mumol/L, P less than 0.05 or 0.01). The results suggest that endothelin is one of the most potent vasoconstrictive agents, and its action is partially related to voltage-sensitive Na+ channel in the cell membrane.

Host genetics as a cause of overdispersion of parasites among hosts: how general a phenomenon?

In the white-footed mouse, Peromyscus leucopus, the tapeworm Hymenolepis citelli occurs at low (2-3%) prevalence in the field. We found that mature infections (i.e., with egg production) developed in up to 100% of hosts. In the laboratory, a majority of hosts lost their infection by 28 days postintubation. In wild mice infected in the laboratory and returned to the field, infections were more prolonged, with half of the mice still infected at 100 days postintubation. A majority of previously infected hosts resisted challenge infection. Our introduction of laboratory-infected mice into a natural population of hosts appeared to cause infections among previously uninfected mice, leading to an increase in the prevalence of tapeworm infection among mice not intubated. Although genetically based expulsion of tapeworms before maturity is important in causing low prevalence in a similar host-parasite system, such resistance cannot explain low prevalence in the present system. It appears that both heterogeneous distribution and rarity of intermediate hosts as well as short parasite lifespan contribute to low prevalence and overdispersion. Host-parasite dynamics of 2 very similar systems appear to differ markedly.

Regulation of collagen production by medial smooth muscle cells in hypoxic pulmonary hypertension

Pulmonary hypertension is associated with abnormal connective tissue deposition in the media of pulmonary arteries. Lobar arteries from calves maintained for up to 15 days at simulated high altitude showed a 35% increase in collagen and a greater than 40% increase in crosslinked elastin per microgram protein. Labeling of artery tissue with [14C]proline revealed a nearly twofold increase in relative collagen synthesis. There was increased incorporation into Types I, III, IV, and V collagen with an increase in the proportion of newly synthesized Type IV collagen. Quantitation of collagen mRNA by slot-blot assay demonstrated increased levels of Types I and IV collagen message. In addition, medial smooth muscle cells isolated from the hypertensive calves demonstrated a nearly twofold increase in relative collagen synthesis, a twofold increase in the accumulation of newly synthesized collagen per microgram DNA, and increased levels of Types I and IV collagen mRNA. Exposure of pulmonary artery smooth muscle cells, adventitial cells, and fetal calf ligament fibroblasts to conditioned calf serum harvested from cultures of medial cells from hypertensive animals increased their levels of collagen as well as elastin mRNA. These studies suggest that the increased production of collagen in hypertensive arteries is mediated at a pre-translational level by soluble factor(s) generated by medial smooth muscle cells.

Purification and biochemical characterization of CP4 (SP-D), a collagenous surfactant-associated protein

CP4 is a collagenous glycoprotein (43 kDa, reduced) synthesized by rat type II pulmonary epithelial cells in primary culture (Persson et al., 1988). In order to better characterize this protein, CP4 was isolated from rat bronchoalveolar lavage and EDTA extracts of lung surfactant by adsorption to barium sulfate and elution with sodium citrate followed by reverse-phase HPLC. Amino acid analysis of purified CP4 demonstrated 4-hydroxyproline (Hyp), hydroxylysine (Hyl), and acid-labile components coeluting with Hyl glycosides. In addition, gas-phase amino-terminal microsequencing of two CP4 CNBr peptides demonstrated nonoverlapping collagenous sequences comprised of nine and six Gly-X-Y triplets, containing a total of four residues of Hyp and two of Hyl. There was less than 50% sequence homology of these peptides with the cDNA-derived sequence of the collagenous domain of rat SP-A. Two-dimensional IEF/SDS-PAGE resolved the protein into a charge train of basic isoforms (pI approximately 6-8), similar to those of newly synthesized CP4 and the class D surfactant proteins (Phelps & Taeusch, 1985). Gel filtration of nondenatured CP4 on 4% agarose showed a high apparent molecular mass complex comprised of disulfide-bonded trimers of the 43-kDa subunits. Antibodies to purified lavage CP4 showed specific binding to newly synthesized and surfactant-associated CP4. We propose that CP4 be designated "surfactant protein D" (SP-D) in accordance with an accepted nomenclature for surfactant-associated proteins.

Isolation and characterization of bovine pancreastatin

Bovine pancreastatin, a 47 amino acid residue peptide, was isolated from the pancreas and the pituitary gland using a chemical method which detects its C-terminal glycine amide structure. The complete amino acid sequence of the pancreatic peptide is 74% homologous to that of porcine pancreastatin and is identical to bovine chromogranin A-(248-294), as deduced from its cDNA sequence. The sequence of the first 28 amino-terminal residues of the pituitary peptide was determined to be identical to the corresponding sequence of the pancreatic peptide. Since the pituitary peptide also contains the C-terminal glycine amide, it is therefore likely to be identical in structure to the pancreatic peptide. Thus, we conclude that bovine chromogranin A is the precursor of bovine pancreastatin. Synthetic bovine pancreastatin inhibited pancreatic exocrine secretion in a similar manner to porcine pancreastatin.

CP4: a pneumocyte-derived collagenous surfactant-associated protein. Evidence for heterogeneity of collagenous surfactant proteins

Type II pneumocytes secrete pulmonary surfactant and are known to synthesize SP-35, a collagenous surfactant-associated protein. Freshly isolated type II cells also synthesize other bacterial collagenase-sensitive and hydroxyproline-containing proteins, including a glycoprotein designated CP4. CP4 was isolated from rat pneumocyte culture medium by immune precipitation with polyclonal antibodies to rat surfactant proteins or by DEAE chromatography and reverse-phase or gel permeation HPLC. CP4 did not cross-react with polyclonal antibodies to SP-35 and was completely resolved from SP-35 by SDS-PAGE (Mr 43K reduced) or isoelectric focusing. Unlike SP-35, which consists of acidic isoforms assembled as disulfide-bonded dimers and multimers, CP4 was secreted as basic isoforms assembled as disulfide-bonded trimers. Differences in primary structure were demonstrated by CNBr and V8 protease peptide mapping. The secretion of both proteins was inhibited by 2,2'-dipyridyl, an inhibitor of posttranslational prolyl and lysyl hydroxylation and collagen triple helix formation. CP4 was isolated from EDTA extracts of rat surfactant. These studies provide evidence for the heterogeneity of pneumocyte-derived collagenous surfactant-associated proteins.

Digitonin-permeabilized colonic cell layers. Demonstration of calcium-activated basolateral K+ and Cl- conductances

Sheets of isolated turtle colon were exposed to digitonin on the mucosal side to chemically remove the apical membrane as a permeability barrier. Increases in the mucosal uptake of 86Rb, [3H]mannitol, and 45Ca-EGTA, and the appearance of the cytosolic marker enzyme lactate dehydrogenase in the mucosal bath confirmed the permeabilizing effect of the detergent. Basolateral K+ and Cl- currents were generated by imposing transmural ion gradients, and cytosolic free Ca2+ was manipulated by means of a Ca2+-EGTA buffer system in the mucosal bathing solution. Raising the cytosolic free Ca2+ concentration from the nanomolar to the micromolar range activated basolateral conductances for K+ and Cl-. Differences in ion selectivity, blocker specificity, calcium activation kinetics, and divalent cation activation selectivity indicated that the Ca2+-induced increases in the K+ and Cl- conductances were due to separate populations of channels. The results are consistent with the notion that the apical membranes of turtle colon epithelial cells can be functionally removed under conditions that preserve some of the conductive properties of the basolateral membrane, specifically Ca2+-activated conductive pathways for K+ and Cl-. This permeabilized preparation should offer a means for the identification of macroscopic currents that are due to presumed Ca2+-activated channels, and may also provide a model system for the functional reconstitution of channel regulatory mechanisms.

Effects of CRF and ANG II on ACTH and vasopressin release in conscious dogs

The aim of the present study was to examine the effects of corticotropin-releasing factor (CRF) in conscious dogs and to determine whether the stimulation of adrenocorticotropic hormone (ACTH) release by angiotensin II (ANG II) results from potentiation of the action of CRF. In addition, the possible role of CRF in the stimulation of vasopressin released by ANG II was investigated. The following experiments were performed: 1) intravenous saline infusion; 2) ANG II (10 ng.kg-1.min-1) alone; 3) vasopressin (1 ng.kg-1.min-1) alone; 4) CRF (0.001, 0.01, or 0.1 microgram/kg iv) bolus; 5) vasopressin (1 ng.kg-1.min-1) and CRF (0.1 microgram/kg) together; 6) CRF (0.001, 0.01, or 0.1 microgram/kg) and ANG II (10 ng.kg-1.min-1) together; 7) ANG II (10 ng.kg-1.min-1) followed 15 min later with CRF (0.001, 0.01, or 0.1 microgram/kg). Each dose of CRF was tested on a different day. Infusion of ANG II alone stimulated the release of ACTH, cortisol, and vasopressin. Administration of CRF produced dose-dependent increases in plasma ACTH and cortisol concentrations, and the highest dose of CRF increased plasma vasopressin concentration. CRF given together with ANG II did not potentiate the stimulation of ACTH release by CRF. Vasopressin at the dose tested did not stimulate ACTH release but potentiated the ACTH response to CRF. ANG II stimulated vasopressin release but did not potentiate the AVP response to CRF. These results show that, in conscious dogs, ANG II and CRF each increase plasma ACTH concentration and that the ACTH response to CRF is potentiated by vasopressin but not by ANG II.(ABSTRACT TRUNCATED AT 250 WORDS)

A sensitive radioimmunoassay for somatomedin-C/insulin-like growth-factor I based on synthetic insulin-like growth factor 57-70

We have developed a region-specific radioimmunoassay for somatomedin-C/insulin-like growth factor-I (IGF-I) directed against IGF-I 57-70. This sequence includes part of the A region and all of the carboxyterminal D region. In addition to being highly specific, this immunoassay is sensitive to as little as 1 ng/ml of IGF-I, and has half-maximum displacement by 10 ng/ml of IGF-I. Comparison to other existent immunoassays for IGF-I shows correlation coefficients of greater than 0.95. This immunoassay has the advantage of being directed against a known region of the IGF-I molecule which is on the exterior of the 3-dimensional structure, and can use a readily available synthetic peptide as both radioligand and standard.

Solitary non-parasitic liver cyst treated by cyst-gastrostomy

A 66 year old female presented with a symptomatic solitary non-parasitic liver cyst. This was treated by a cyst-gastrostomy following which the patient has remained well without complications for 12 years. Given an appropriate anatomical relationship of cyst and stomach, this would appear to be a safe and effective operation.