Biomedical subjects

A I Stern

Publications and source records attributed to A I Stern.

34 records · Page 2Linked to original sources

PubMed1982

Impaired pancreatic polypeptide release to insulin hypoglycaemia in chronic autonomic failure with postural hypotension: evidence for parasympathetic dysfunction.

1. Release of pancreatic polypeptide (PP) is largely under vagal control and measurement of change in PP after insulin hypoglycaemia offers a non-invasive method of assessing vagal activity. 2. Changes in blood sugar and PP after intravenous insulin (0.2 unit/kg) were examined in six patients with idiopathic chronic autonomic failure (AF) and 12 control subjects. Six of the controls were studied before and after atropine treatment. 3. The PP levels in controls rose from 32 +/- 9 (mean +/- SEM) to 236 +/- 54 pmol/l after 45 min. Patients had similar baseline values (23 +/- 5 pmol/l) but a markedly reduced and delayed PP response to hypoglycaemia (49 +/- 19 pmol/l at 90 min). This impaired PP response was similar to that seen in controls after atropine. 4. The impaired PP response to insulin hypoglycaemia in patients with AF strongly suggests a dysfunction of vagal activity which is often clinically inapparent.

Aged↗

PubMed1981

Pancreatic polypeptide release in gastric ulcer.

The pancreatic polypeptide (PP) response to a protein-rich meal has been studied in similarly aged patients with gastric ulcer, duodenal ulcer, and controls. The response of the gastric ulcer patients was significantly lower at all points than that of the duodenal ulcer patients or controls, which were similar to one another. Vagal stimulation is probably the single most important factor in PP release, and it is possible that diminished PP release in the gastric ulcer patients is a reflection of vagal underactivity.

Adult↗

PubMed1981

Secretin stimulated pancreatic polypeptide: a test for chronic pancreatitis.

The level of serum pancreatic polypeptide (PP) in response to intravenous Boots secretin has been measured by radioimmunoassay in 50 patients with documented chronic pancreatitis and 33 controls with no evidence of pancreatitis. Both groups showed significant increases in serum PP but patients with chronic pancreatitis had a significantly smaller response than controls. An abnormal PP response to Boots secretin has been defined as a peak/basal ratio of less than five. Using this criterion. 90% of patients with chronic pancreatitis had a ratio of less than 5, whereas 91% of controls had a ratio of 5 or greater. There was a 92% correlation between a normal or abnormal pancreatic bicarbonate concentration and a normal or abnormal peak/basal PP ratio in response to Boots secretin. These results suggest that the serum PP response to Boots secretin may provide a simple, inexpensive and noninvasive method of accurately diagnosing chronic pancreatitis.

Adult↗

PubMed1981

Influence of smoking on healing rate of duodenal ulcer in response to cimetidine or high-dose antacid.

Fifty consecutive patients with symptomatic endoscopically proven duodenal ulcer were randomized double-blind to Mylanta II or cimetidine treatment schedules. Smoking habits were noted, but patients were not advised to alter these. Healing was determined by reendoscopy at 6 wk. Eighty percent of patients on active cimetidine and 52% on active Mylanta II had healed at 6 wk (not significantly); 85% of nonsmokers healed compared to 44% of smokers (p less than 0.03). In smokers, cimetidine achieved healing in 50%, Mylanta II in 39% (not significantly); while in nonsmokers, cimetidine achieved healing in 100%, Mylanta II in 67% (not significantly). These results indicate a significant and equally adverse effect of smoking on the healing rate of duodenal ulcer achieved by either cimetidine or Mylanta II.

Adolescent↗

PubMed1980

Pancreatic polypeptide. Release following surgery for duodenal ulcer disease.

The pancreatic polypeptide (PP) response to food has been measured by radioimmunoassay in patients with duodenal ulcer and 3 months following proximal gastric vagotomy (PGV), 18 and 49 months following truncal vagotomy and pyloroplasty (TV), 35 months following Billroth II gastrectomy (BII), and 35 months following truncal vagotomy and antrectomy (TV&A). Basal PP levels and those in response to food were similar in DU and PGV, but these values were significantly higher than those 18 months or 49 months after TV, or after BII and TV&A. The responses in the latter four groups were similar and in particular, the levels 18 and 49 months after TV were the same. These results indicate that the release of PP by food in unoperated patients consists of two phases, a primary phase which requires both intact vagi and an intact stomach and a secondary phase which also depends on vagal innervation and normal gastric anatomy. Disturbances in vagal innervation or gastric integrity lead to profound changes in PP release which may be due to interruption of neural arcs or loss of gastric hormones. Unlike others, we have been unable to document a return of PP secretion towards normality with time after TV.

Adult↗

PubMed1979

Effects of long-term cimetidine on serum gastrin in duodenal ulcer.

Basal and food-stimulated gastrin were measured in 16 patients with duodenal ulcer before and during long-term maintenance therapy with 400 mg cimetidine twice daily. Basal gastrin (mean +/- SE) rose significantly from 27.5 +/- 3.1 pmol/liter precimetidine to 32.8 +/- 2.1, 37.2 +/- 2.6, and 38.5 +/- 3.3 pmol/liter at 1, 3, and 6 months, respectively. The total integrated gastrin response to a protein meal was 1.67 +/- 0.18 nmol/liter/120 min pre-, and 2.54 +/- 0.35, 3.29 +/- 0.3, and 4.36 +/- 0.4 nmol/liter/120 min at 1, 3, and 6 months, respectively. These increases were significantly higher at each time period. This study has thus demonstrated a progressive increase in both basal and food-stimulated gastrin during cimetidine therapy, and this increase could theoretically lead to an increase in gastric acid secretion following cessation of cimetidine.

Aged↗

PubMed1979

The Mallory-Weiss lesion as a cause of upper gastrointestinal bleeding.

A prospective study of patients with upper gastrointestinal bleeding admitted to a haematemesis and melaena unit has revealed an incidence of Mallory-Weiss tears of 8% (59 of 762 patients undergoing endoscopy). Prior vomiting was present in 60% and an associated upper gastrointestinal lesion in 44 percent. The majority of patients had a recent ingestion of alcohol and/or analgesics, whilst 34% had chronic heavy alcohol intake. Approximately 50% of patients required no blood transfusion, while 37% had over three units of blood. No patient in the group required surgical intervention, and one patient died because of general debility. This study suggests that the Mallory-Weiss tear accounts for a significant proportion of patients admitted with upper gastrointestinal bleeding, but that the mortality and morbidity are low.

Adolescent↗

PubMed1979

Serum gastrin after 12 months' continuous cimetidine therapy for duodenal ulcer.

Serum immunoreactive gastrin was measured in 14 patients with duodenal ulcer before and during a 12-month course of cimetidine 400 mg bd. All patients were symptomatically well during the cimetidine therapy and both basal gastrin and that in response to a protein rich meal were assessed before, at six months and at 12 months during therapy. The basal and post-prandial gastrin were significantly higher at six and 12 months on cimetidine than before cimetidine but the six and 12 month levels were similar. This study thus shows that the progressive increase in serum gastrin during six months of continuous cimetidine therapy does not occur beyond this time period.

Adult↗

PubMed1977

Isolation and some properties of ribulose-1, 5-bisphosphate carboxylase-oxygenase from red kidney bean primary leaves.

Purification of ribulose-1,5-bisphosphate carboxylase from primary leaves of Phaseolus vulgaris var. Red Kidney with ammonium sulfate precipitation, ion exchange chromatography, and gel filtration resulted in the complete loss of detectable oxygenase activity and the retention of a low velocity and a high K(m) form of both the carboxylase and oxygenase. The polyethylene glycol-6000-purified ribulose-1, 5-bisphosphate oxygenase displayed a broad pH optimum (7.9-9.4) and a high K(m) for O(2) and ribulose 1,5-bisphosphate (0.90 mm and 0.25 mm, respectively). Initiation of the oxygenase reaction with protein rather than ribulose 1,5-bisphosphate resulted in reduced activity. The enzymes prepared by the two purification procedures were electrophoretically different.Etiolated primary leaf tissue exhibited low rates of both carboxylase and oxygenase. Similar developmental kinetic activity was observed for both reactions during greening. Photosynthetic (14)CO(2) fixation was inhibited 95% by 100% N(2) gas during the first 24 hours of greening, but the inhibition was rapidly overcome by 48 to 72 hours of light exposure.

Journal Article↗

PubMed1973

Photophosphorylation during Chloroplast Development in Red Kidney Bean: II. Photophosphorylation and Photoreduction Appear Concomitantly but Initially are Uncoupled.

Cyclic phosphorylation with phenazine methosulfate and noncyclic phosphorylation and reduction with ferricyanide were detected in isolated chloroplasts from greening bean leaves after 3 to 4 hours of illumination. Activity commenced when rapid synthesis of chlorophyll was initiated. Rates of photophosphorylation were comparable to mature levels by 15 to 18 hours of development. Photoreduction of ferricyanide attained a peak value by 12 hours of illumination and subsequently fell to normal levels by 15 to 18 hours. With ferricyanide, the P/e(2) ratios were initially less than 0.1 but were close to 1.0 after 18 hours of illumination. The data suggested that photosystems I and II appeared concomitantly in the chloroplast but were not fully operative until later in development. Proplastids and immature chloroplasts exhibited high capacities to reduce ferricyanide in the dark. The rates of dark reduction rapidly diminished to low levels by 15 hours of illumination when normal rates of photochemical activity were observed. After a 2-to 3-day lag, a rapid increase in leaf fresh weight was noted at the time total chlorophyll content reached steady state values on a fresh weight basis. With fresh weight as an index of growth, primary leaves completed their development after 6 to 7 days of illumination.

Journal Article↗

PubMed1970

The effect of 3-(3,4-dichlorophenyl)-1,1-dimethylurea on chloroplast development and maintenance in Euglena gracilis. I. Ultrastructural characterization of light-grown cells by the techniques of thin sectioning and freeze-etching.

The ultrastructure of light-grown Euglena gracilis var. bacillaris was examined by the techniques of thin sectioning and freeze-etching. Thin sectioning revealed the typical organelles previously observed in chemically fixed Euglena. In addition to confirming the observations on thin sections, the freeze-etch technique has revealed the presence in E. gracilis of a complex multilaminar pellicle, and an ordered arrangement to the paramylon granule. The chloroplast thylakoids are particulate and similar to those observed in higher plants.

Chloroplasts↗

PubMed1969

Photophosphorylation during Chloroplast Development in Red Kidney Bean. I. Characterization of the Mature System and the Effect of BSA and Sulfhydryl Reagents.

Optimal conditions were determined for photophosphorylation and reduction in mature chloroplasts from Phaseolus vulgaris var. Red Kidney. Bovine serum albumin (BSA) at 1 mg/ml and various sulfhydryl reagents (0.1-0.5 mm) greatly enhanced cyclic and noncyclic phosphorylation, but had little effect on photoreduction. BSA and reduced glutathione also stimulated cyclic phosphorylation in spinach chloroplasts. BSA was needed in the reaction from the start to provide high rates of phosphorylation. BSA also protected against atebrin uncoupling but not against uncoupling by ammonium ions or inhibition by 3,-(3,4-dichlorophenyl)-1,1-dimethylurea. Similarly, BSA and glutathione protected against atebrin inhibition of cyclic phosphorylation. Chloroplasts incubated at 0 degrees rapidly lost the ability to catalyze phosphorylation and BSA did not protect against inactivation.

Journal Article↗

PubMed1966