Development of cells containing catecholamines and somatostatin-like immunoreactivity in neural crest cultures: relationship of DNA synthesis to phenotypic expression

The goal of our work is to understand the mechanisms which regulate the differentiation of embryonic neural crest cells into a number of adult cell types, including several classes of neurons. As one aspect of this analysis, the relationship between DNA synthesis and the ontogeny of cells with catecholamines and somatostatin-like immunoreactivity (SLI) in neural crest cell cultures has been investigated. Most of the precursors of the catecholamine- and SLI-positive cells carry out DNA synthesis. As these cells differentiate, their ability to carry out DNA synthesis declines. However, a small percentage of cells continue to synthesize DNA after they become catecholamine or SLI positive. There is no apparent difference between the temporal pattern of DNA synthesis in the precursors of catecholamine-positive cells with SLI and those without SLI. Thus, the time of withdrawal from the cell cycle does not distinguish the lineage of cells that are catecholamine and SLI positive from those that are catecholamine positive and SLI negative.     

Effect of haloperidol withdrawal on somatostatin level and binding in rat brain

The effects of withdrawal on the level and specific binding of somatostatin in the frontoparietal cortex and hippocampus of the rat after chronic haloperidol treatment were examined using¹²⁵I-Tyr¹¹ somatostatin as tracer. One week after haloperiodol withdrawal the number of specific somatostatin receptors in both brain areas returned to control values, after having decreased as the result of chronic administration. Neither administration of haloperidol nor withdrawal of it affected the levels of somatostatin-like immunoreactivity (SLI) in the two brain areas studied. The return of the somatostatin receptor number to control values after haloperidol withdrawal may be related to the motor side-effects that are clinically observed when the haloperidol treatment is terminated.     

Cortical Substance P-Like Immunoreactivity in Cases of Alzheimer's Disease and Senile Dementia of the Alzheimer Type

Abstract: The concentration of substance P-like immunoreactive material (SPLI) and somatostatin-like immunoreactive material (SLI) and the activity of acetyl-CoA: choline- O -acetyltransferase (ChAT; EC 2.3.1.6.) were measured in eight brain regions of 13 normal patients and 12 patients with Alzheimer disease/senile dementia of the Alzheimer type (AD/SDAT). SPLI was significantly lower in five of eight regions in the patients with AD/SDAT. Younger patients with AD/SDAT had significantly lower SLI in the parietal cortex than older patients. ChAT activity and SPLI in the parietal cortex of the presenile patients with ADISDAT were not significantly different from values found in older patients.     

Localization of somatostatin-like immunoreactivity in the Golgi apparatus of central and peripheral neurons.

With the indirect immunofluorescence technique of Coons and collaborators somatostatin-like immunoreactivity (SLI) was observed in certain neurons of the central and peripheral nervous system of the rat. In the cell bodies a strong SLI was observed with a distribution resembling that of the Golgi apparatus. In addition a weak SLI was diffusely distributed in the cytoplasm. After photography the sections processed for immunocytochemistry were stained with the thiamine pyrophosphatase technique of Novikoff and Goldfischer. The latter technique is assumed to be a specific marker for the Golgi complex. It was found that the strong SLI and the thiamine pyrophosphatase activity had an identical distribution. Thus, one pool of somatostatin appears to be localized to the Golgi apparatus.     

Plasma somatostatin-like immunoreactivity during growth-hormone-releasing hormone therapy in non-growth-hormone-deficient children

To date, the effects of long-term growth hormone (GH)-releasing hormone [GHRH(1-29)-NH2] treatment on the plasma concentrations of somatostatin-like immunoreactivity (SLI) remain undefined. In the present study, the effect of GHRH(1-29)-NH2 therapy on plasma SLI levels has been studied in 11 non-GH-deficient children. The pattern of administration was 5 micrograms/kg body weight, given subcutaneously once every day. There was no significant change in plasma SLI levels after bolus injection of GHRH(1-29)-NH2 before and during GHRH(1-29)-NH2 therapy. However, plasma SLI rose in basal plasma and nocturnal sleep after 3 months of GHRH(1-29)-NH2 therapy and remained the same during 6 months of treatment with GHRH(1-29)-NH2. The reason for this finding is uncertain, but an increase in SLI release from the enteroinsular axis is a possible explanation. The association of our findings with the role of the circulating SLI on nutrient homeostasis and the effects of GNRH on growth velocity is discussed.     

Localization of somatostatin-like immunoreactivity in the Golgi apparatus of central and peripheral neurons

Summary With the indirect immunofluorescence technique of Coons and collaborators somatostatin-like immunoreactivity (SLI) was observed in certain neurons of the central and peripheral nervous system of the rat. In the cell bodies a strong SLI was observed with a distribution resembling that of the Golgi apparatus. In addition a weak SLI was diffusely distributed in the cytoplasm. After photography the sections processed for immunocytochemistry were stained with the thiamine pyrophosphatase technique of Novikoff and Goldfischer. The latter technique is assumed to be a specific marker for the Golgi complex. It was found that the strong SLI and the thiamine pyrophosphatase activity had an identical distribution. Thus, one pool of somatostatin appears to be localized to the Golgi apparatus.This work was supported by grants from the Swedish Medical Research Council (04X-2887, 19X-3412), Magnus Bergvalls Stiftelse, Harald och Greta Jeanssons Stiftelse, and funds from the Karolinska Institute     

Postmortem stability of somatostatin-like immunoreactivity in mouse brain under conditions simulating handling of human autopsy material

The postmortern stability of somatostatin-like immunoreactivity (SLI) has been investigated in mice cooled after death at a rate which approximates the rate of cooling of the human brain in situ under normal mortuary conditions. Significant changes in SLI levels were observed within the first few hours after death, but concentrations measured 6–24 hr after death seem to be similar to those existing at the time of death.     

Processing of somatostatin precursors: evidence for enzymatic cleavage by hypothalamic extract

The action of enzymes extracted from rat hypothalamus on the previously characterized high molecular weight forms of hypothalamic somatostatin-like immunoreactivity (4 K SLI and 25 K SLI) has been investigated in vitro in order to further define the role of these molecules as possible precursors for tetradecapeptide somatostatin (SRIF). Studies of the degradation of endogenous SLI and of synthetic SRIF by hypothalamic enzymes showed that the time course of breakdown of endogenous SLI is markedly slower than that of synthetic SRIF due to the relative stability of 25 K SLI as well as the generation of at least two new immunoreactive molecules. Incubation of purified 25 K SLI with SLI-free hypothalamic extract showed after 10 to 30 min newly formed immunoreactive material of an intermediate size between 25 K SLI and 4 K SLI and after 60 min the emergence of material coeluting with SRIF. These data show that the hypothalamus contains the enzymes necessary for degrading endogenous SLI and for processing the 25 K SLI molecule to SRIF providing further evidence that 25 K SLI might be a biosynthetic precursor for SRIF.     

Somatostatin content and binding in small intestinal mucosa from fed, fasted, and refed rabbits

The present study is an investigation of the effects of 12- to 96-hours' starvation and 96-hours' starvation plus 48-hours' refeeding on both somatostatin-like immunoreactivity (SLI) and cytosolic somatostatin binding sites in rabbit small intestinal mucosa. The SLI concentration increased after 24 h in duodenal and jejunal mucosa, but not in ileal mucosa, and reached its highest value after 96 h of fasting. The number of specific high and low-affinity somatostatin binding sites, but not their affinity, decreased with the duration of fasting in the same gut segments, refeeding of fasted animals resulted in a return to normal control values for small intestine mucosal SLI and somatostatin binding.     

Characterization of the somatostatin-like immunoreactivity extracted from an adrenal medullary tumour

Significant amounts of somatostatin-like immunoreactivity (SLI) were detected in the extract of a human catecholamine-secreting adrenal medullary tumour. After salt fractionation and reconstitution the major portion of SLI was purified by gel filtration and two HPLC steps; in all three systems it eluted in the position of somatostatin-14. The purified somatostatin-like peptide inhibited, in a dose-related manner, growth hormone release from stimulated perfused rat anterior pituitary cells in vitro. Amino acid analysis showed the purified peptide to have an identical composition to somatostatin found in other species.     

Gastrin and somatostatin levels in patients with gastric cancer

Gastrin and somatostatin-like immunoreactivity (SLI) levels were studied by means of radioimmunoassay in peripheral venous blood of healthy volunteers and patients suffering from gastric adenocarcinoma or duodenal and gastric ulcers. Gastrin and SLI levels were also evaluated in patients in blood drawn from gastric veins during surgery. The elevations of gastrin and SLI levels were found in patients with gastric cancer as compared with healthy people and patients suffering from ulcers. The impairment of the negative feedback between gastrin and somatostatin secretions in patients with gastric cancer was suggested.     

Response of plasma somatostatin-like immunoreactivity to the administration of alloxan in dogs.

The present study was designed to examine the effects of intravenously injected alloxan (75 mg/kg) upon plasma somatostatin-like immunoreactivity (SLI), glucagon (IRG), insulin (IRI) and glucose levels in 6 dogs. Within 2 hours of the injection of alloxan, SLI and IRI levels decreased significantly below their respective baselines, while IRG and plasma glucose concentrations increased. At 8 hours SLI levels had increased significantly by 55 pg/ml, together with a rise in IRI and a decrease in IRG and glucose concentrations. After 24 hours, marked hyperglycemia and hyperglucagonemia had developed whereas SLI levels were not different from preinjection values.     

Absence of a relationship between immunoreactive-gastrin and somatostatin-like immunoreactivity secretion in the perfused rat stomach

The possible interaction between somatostatin-like immunoreactivity (SLI) and immunoreactive-gastrin release was studied in an isolated perfused rat stomach preparation. Gastrin release was abolished by antrectomy but basal and gastric inhibitory polypeptide-stimulated SLI levels were unchanged from control experiments, implicating the corpus as the major source of SLI released into the vasculature. Perfused stomachs of vagotomized rats exhibited basal hypergastrinaemia with no alteration in basal or stimulated SLI release, suggesting an uncoupling of SLI and gastrin release. This study indicated that SLI released into the vasculature originated in the acid secretory region of the stomach and therefore may be involved in the regulation of acid secretion at the level of the parietal cell mass.     

Immunofluorescent localisation of somatostatin-like cells in the esophagus of a protochordate

By means of the indirect immunofluorescence method, somatostatin-like immunoreactive (SLI) cells are detected in the esophagus of the ascidian Styela plicata. They are of the "open" type; they act probably by a paracrine mechanism on the esophageal secretin-like cells. The ascidian SLI cells are negative to all the specific cytochemical methods characteristic of vertebrate somatostatin (D) cells, which were applied in this work. In consequence, special SLI cells are probably present in ascidians.     

Cerebrospinal fluid levels of immunoreactive substance P and somatostatin in patients with multiple sclerosis and inflammatory CNS disease.

Cerebrospinal fluid (CSF) levels of substance-P like immunoreactivity (SPLI) and somatostatin-like immunoreactivity (SLI) were measured in 43 patients with multiple sclerosis (MS), differentiated according to course and activity of the disease, in 23 patients with inflammatory disease of known bacterial or viral etiology and in 16 control patients using specific radioimmunoassay. SPLI and SLI levels were not significantly different from controls in MS patients whereas SLI was significantly increased in patients with infectious disease of central nervous system and/or subarachnoidal space. It is assumed that CSF SPLI and SLI cannot serve as a diagnostic or prognostic indicator of disease state in multiple sclerosis. Analysis of immunoreactivity by reverse phase HPLC-RIA revealed marked molecular heterogeneity of both neuropeptides.     

Evidence for the presence of dihydro (reduced) somatostatin-14 in the guinea pig brain

Analysis of somatostatin-like immunoreactivity (SLI) in guinea pig brain by HPLC and radioimmunoassay revealed an unexpected peak of SLI eluting at a retention time slightly later than standard somatostatin-14. The following evidence argues that this peak represents dihydro (H2) somatostatin-14. (1) The peak had the same retention time as standard [H2]somatostatin. (2) The possibility of a reduction artefact due to tissue processing was excluded by adding exogenous somatostatin-14 or 125I-labeled N-Tyr-somatostatin-14 to tissue and observing that no corresponding reduced peptides were generated. (3) Mild oxidation of brain extracts with H2O2 decreased, whereas mild reduction with dithiothreitol increased, the proposed peak of [H2]somatostatin. (4) Reaction of tissue extracts with iodoacetamide decreased the size of the proposed [H2]somatostatin peak but resulted in generation of a new peak co-eluting with standard carboxymethylated somatostatin-14. The proportion of the [H2]somatostatin peak in five brain regions, the hypothalamus, amygdala, cerebral cortex, brainstem and cerebellum, ranged from 6 to 20% of total SLI. The probability of somatostatin-14 existing endogenously in reduced or oxidized forms may have implications for its biological function in the guinea pig.     

Plasma somatostatin-like immunoreactivity responses to a mixed meal and the heterogeneity in healthy and non-insulin-dependent (NIDDM) diabetics

Peripheral plasma somatostatin-like immunoreactivity (SLI) was estimated in non-extracted plasma using a specific somatostatin-14 (SS-14) antiserum. The basal plasma SLI level in healthy subjects (n = 18) was 43 +/- 2.9 pg/ml (mean +/- SE) and rose significantly to 8.3 +/- 2.7, 7.3 +/- 1.1 and 5.8 +/- 2.1 pg/ml above the mean basal level 20, 30, and 40 min after a mixed meal, respectively (P less than 0.05). Basal plasma SLI levels in diet (n = 8), sulfonyl urea (n = 8), and insulin groups (n = 8) of non-insulin-dependent maturity onset diabetics (NIDDM) were 50 +/- 1.6, 59 +/- 4.5, and 74 +/- 5.8 pg/ml, respectively. The basal levels for patients with NIDDM were significantly higher than those for healthy subjects (P less than 0.05). No significant increases in plasma SLI were observed after a mixed meal in any group of NIDDM subjects. Elevated plasma SLI levels are considered to be closely related to the severity of the diabetes. The ratios of SS-14 and SS-28 to the total amount of basal plasma SLI were analyzed using high pressure liquid chromatography (HPLC). The ratio of SS-14 to the total SLI was 71-80% in healthy subjects. The ratio of SS-28 to the total SLI increased from 26-30% in the diet group to 50-55% in the group on insulin. These findings suggest a possible pathophysiological role for gastrointestinal somatostatin in NIDDM.     

Processing of synthetic somatostatin-28 and a related endogenous rat hypothalamic somatostatin-like molecule by hypothalamic enzymes

Synthetic somatostatin-28 (S-28) as well as a related endogenous rat hypothalamic somatostatin-like compound (3K SLI) were incubated with hypothalamic extracts from which endogenous somatostatin-like immunoreactivity (SLI) had been removed by immunoabsorption. The reaction products were analyzed by gel chromatography, HPLC as well as two different radioimmunoassays for tetradecapeptide somatostatin (S-14) in which S-28 crossreacted either 100% (RIA R149) or < 0.001% (RIA S39). The results indicate that incubation of S-28 with SLI free hypothalamic extracts results in a rapid decrease of total immunoreactivity measured with RIA R149 ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 14}\text{min}$). By contrast, with RIA S39 a rise from zero to a peak value at 8 min was measured suggesting the formation of S-14. This was confirmed by subsequent analysis by gel chromatography and HPLC. Using endogenous 3K SLI a decrease of total R149-immunoreactivity with a similar time course ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 17}\text{min}$) was observed simultaneously with the emergence of material that corresponded to S-14. This converting activity seems to be specific for SLI-containing tissues since similar rates of conversion were observed with extracts from cerebral cortex and cerebellum but not with lung and liver extracts.It is concluded that (1) S-28 is converted to S-14 by hypothalamic enzymes; (2) the processing of 3K SLI is similar, suggesting the two molecules are closely related, if not identical, and (3) the regulation of S-28 to S-14 conversion could represent an important mechanism for controlling the functional activity of somatostatinergic cells.     

Somatostatin Precursor in the Rat Striatum: Changes After Local Injection of Kainic Acid

The molecular forms of somatostatin contained in the rat striatum were separated by size-exclusion HPLC. Three major peaks of somatostatin-like immunoreactivity (SLI) were resolved. Two peaks cochromatographed with synthetic somatostatin-14 (SS-14) and somatostatin-28 (SS-28), respectively. One peak exhibited a higher molecular weight (about 10,000) and may contain a proform of somatostatin. Local injection of the neurotoxin kainic acid (1 microgram) into the left striatum resulted in a persistent decrease (65-85%) of all three forms of somatostatin. In the contralateral--not injected--striatum a decrease of SLI was also observed which was maximal (45%) after 2 days and was largely abolished after 7 days. This decrease of SLI in the contralateral striatum, however, was due mainly to a decrease of SS-14 and SS-28 but not of the putative proform. Our data suggest that kainic acid causes a destruction of somatostatin-containing perikarya in the injected striatum, whereas in the contralateral striatum increased release with subsequent inactivation of SS-14 and SS-28 takes place. The putative somatostatin proform may serve as neurochemical marker for somatostatin-containing perikarya in the striatum.     

Hypersomatostatinemia in chronic renal failure

Plasma concentrations of somatostatin-like immunoreactivity (SLI) were determined in uremic patients on maintenance hemodialysis. Plasma SLI levels were significantly (p less than 0.001) elevated in 26 diabetic uremic patients (67.1 +/- 6.8 pg/ml, mean +/- SE) and in 24 non-diabetic uremic patients (43.5 +/- 7.2 pg/ml), when compared with 60 healthy subjects (5.0 +/- 0.7 pg/ml). Paired pooled plasma from uremic patients before and after hemodialysis was subjected to a reverse-phase octadecasilyl-silica (C-18) cartridge and then the extract was gel filtered on a Sephadex G-25 column (1.6 X 90 cm). Both elution profiles showed two peaks of SLI which coeluted with synthetic somatostatin (SS)-28 and SS-14 markers, respectively. The SS-28-like immunoreactivity (LI) peak, which was estimated by using SS-14 as a reference standard, was 3-fold larger than that for SS-14 LI. On the basis of immunoequivalency of the two components in the present assay, SS-28 LI constitutes approximately 75% of circulating somatostatin. In conclusion, plasma SLI is substantially high in uremic patients of both diabetic and non-diabetic etiology and the SS-28 is a predominant form of circulating SLI in these patients, probably, in part, for a lower clearance of this molecule.