Role of endogenous cholecystokinin on vagally stimulated pancreatic secretion in dogs

Pancreatic exocrine secretion was evoked by electrical stimulation of the vagus nerves (EVS) in dogs to determine whether a gut hormone was responsible for the pancreatic stimulatory activity. In 39 dogs, pancreatic juice was continuously collected to measure volume, bicarbonate, and amylase output, while portal and femoral venous plasma concentrations of gastrin, cholecystokinin (CCK), vasoactive intestinal polypeptide (VIP), and pancreatic polypeptide (PP) were determined by radioimmunoassay. EVS produced a significant increase in the pancreatic secretion. Although concentrations of all four peptides significantly increased in plasma, only CCK at the concentration in venous circulation was bioactive in dispersed rat pancreatic acini preparations. This bioactivity of CCK was completely blocked by CR 1409, a CCK-receptor antagonist. The pancreatic secretion by EVS was reduced significantly by intravenous MK-329 (formerly L364,718) to as low as 22% of control values and was completely suppressed by intravenous atropine. The increment in plasma CCK by EVS was also significantly suppressed by atropine. The present study indicates that increased pancreatic secretion by EVS is in part mediated by endogenous CCK.

Ulcerogenic tumor syndrome of the pancreas associated with a nongastrin acid secretagogue

Among 30 patients with islet cell neoplasms or hyperplasia who exhibited marked gastric acid hypersecretion and peptic ulceration and/or diarrhea, fasting plasma gastrin concentrations were less than 150 pg/ml in 11 patients, whereas the remaining 19 patients had hypergastrinemia. Plasma extracts from seven of these 11 patients were assayed for acid secretagogue activity in rats. All seven plasma extracts had secretagogue activity that was not found in the plasma extracts of ten patients with ordinary duodenal ulcer disease. Each of the tumor or pancreatic tissue extracts obtained from nine patients exhibited secretagogue activity in rats even though tissue gastrin content was 101.9 pmol (213.8 ng).g-1 or less. The secretagogue activity of the tumor extracts was confirmed in conscious gastric fistula dogs. The tumors' secretagogue activity, in contrast to gastrin, was destroyed by trypsin. It was eluted between porcine motilin and human gastrin I from a Sephadex G-50 (Pharmacia LKB Biotechnology, Inc., Piscataway, NJ) superfine column and was not retained by CM-cellulose, at pH 8.5. Its retention time during reverse phase HPLC on a C18 column also differed from those of G17 and G34. Thus, this secretagogue activity appeared mediated by a small, acidic peptide with a molecular size of about 2000 to 3000 daltons. The present study indicates that plasma and tumor extracts of these 11 patients contain a gastric acid secretagogue activity mediated by a nongastrin peptide. We suggest that what may be a distinct clinical entity associated with endocrine neoplasms of the pancreas should be considered in the face of excessive acid hypersecretion without fasting hypergastrinemia.

Occurrence of Langerhans cells and expression of class II antigens on keratinocytes in malignant and benign epithelial tumors of the skin: an immunohistopathologic study with monoclonal antibodies

We used an avidin-biotin complex immunoperoxidase technique with various monoclonal antibodies to determine Langerhans cell densities, class II antigen expression on keratinocytes, and phenotypes of other infiltrating cells in several malignant and benign epithelial tumors of the skin. Our observations indicate (1) there are few Langerhans cells in nests of basal cell carcinoma and squamous cell carcinoma; (2) there are increased Langerhans cell densities in seborrheic keratoses, verrucous epidermal nevus, and Bowen's disease; (3) there is an expression of class II molecules on the keratinocytes and cancer cells of basal cell carcinoma, squamous cell carcinoma, Bowen's disease, seborrheic keratosis, and verrucous epidermal nevus; and (4) there is a netlike staining of the keratinocyte surface with OKM5 in the epidermal lesion of seborrheic keratosis, verrucous epidermal nevus, and Bowen's disease, as well as in the epidermis adjacent to the basal cell carcinoma and squamous cell carcinoma nests.

Effect of pancreatic juice diversion on secretin release in rats

We investigated a possible role of secretin in the mechanism of exocrine pancreatic secretion after exclusion of pancreatic juice from the intestine in anesthetized rats. Diversion of pancreatic juice from the duodenum resulted in a significant increase in plasma secretin concentration from 0.76 +/- 0.39 pM at 0 time to 3.09 +/- 0.30 pM at 4 h after diversion. This increase in secretin coincided with a steady but significant increase in pancreatic secretion of volume and bicarbonate. Intraduodenal administration of fresh pancreatic juice completely reversed the diversion-induced increases in both plasma secretin and pancreatic secretion. Intravenous injection of a rabbit-antisecretin serum blocked the increase of pancreatic secretion during diversion of pancreatic juice from the duodenum. Thus, we conclude that endogenous secretin is involved in a hormonal mechanism regulating increased pancreatic exocrine secretion in pancreatic juice-diverted rats.

Chloroplast thylakoid protein phosphatase is a membrane surface-associated activity

Chloroplast thylakoid protein phosphatase activity was measured using (32)P-labeled histone as an exogenous substrate and an assay of the (32)Pi released involving formation of a phosphomolybdate complex and organic extraction. The activity was liberated from wheat (Triticum aestivum) thylakoids by washing the membranes in NaCl-containing solutions followed by centrifugation. The liberated phosphatase activity had a pH optimum of approximately 6.75, was inhibited by addition of 10 millimolar EDTA or EGTA, and was stimulated by addition of millimolar amounts of dithiothreitol, magnesium, manganese, or calcium ions. The rate of thylakoid protein dephosphorylation was decreased following liberation of a portion of the protein phosphatase activity and was increased by addition of salt-liberated phosphatase fraction. These results suggest that at least a portion of wheat thylakoid protein phosphatase is a peripheral, rather than an integral, membrane protein.

Effect of magnesium sulfate on fetal heart rate variability in preeclamptic patients during labor

Forty-two preeclamptic patients between 36 and 41 weeks gestation were investigated for baseline fetal heart rate (FHR) variability 1 hour after the initiation of magnesium therapy, at midlabor, and at the time of delivery. With a standard regimen of intravenous magnesium sulfate therapy, the mean maternal serum magnesium levels at the three different sampling times were statistically different (f = 6.94, p less than 0.01 by one-way analysis of variance), documenting the cumulative effect of continuous intravenous magnesium administration. The majority of the fetuses (86%) that exhibited a decrease in long-term FHR variability were associated with a maternal serum magnesium level above the lower limit of the therapeutic range (4.8 mg/dl). Of all fetuses whose maternal serum magnesium levels were 4.8 mg/dl or greater at delivery, only 40% exhibited a decrease in FHR variability. A higher mean maternal magnesium level, a higher mean cord blood magnesium level, and a higher total dose of magnesium sulfate were observed in the group of fetuses showing a decrease in FHR variability than in the group showing no change in FHR variability. The good fetal outcome seen in both study populations suggests that the effect of magnesium sulfate on FHR variability is a transient, reversible phenomenon that should not be considered as a sign of fetal distress.

Uptake of radioactive calcium by hard tissue cells

45Ca was injected into prenatal mice to study the calcium uptake by tooth germ cells. Both dental papillae, containing the odontoblasts, and the enamel organs were found to actively metabolized the labeled calcium. The maximum specific radioactivity occurred at 15 minutes after injection. The subcellular organelles (e.g. mitochondria) of the papillae were more active in metabolizing the labeled calcium whereas a large portion of the radioactivity of the enamel organ was found in a fraction containing the precalcified material. In fetal tooth germs, the rate of incorporation of labeled calcium into the precalcified material was slower than in the postnatal tooth germs since a large portion of the radioactivity remained in the soluble fraction.