Transesterification of fatty acid ethoxylates in supercritical methanol, then gas chromatography-mass spectrometric determination of the derived methyl esters, for identification of the initiators.

Unknown fatty acid ethoxylate samples have been transesterified in supercritical methanol, using a loop made of a stainless-steel tubing as the reactor vessel. The initiator acids, now present as the corresponding methyl esters, were determined by gas chromatography-mass spectrometry (GC-MS). Quantitative transesterification is achieved by heating a solution of the ethoxylate sample in methanol at 280 degrees C for 10 min under pressure. The influence of reaction time, temperature, and presence of a Lewis acid catalyst has been investigated. The method of transesterification was optimized in respect of low cost, short reaction time, and availability to laboratories with standard analytical equipment.

Somatostatin-like immunoreactivity in cerebroventricular fluid of patients with basal midline tumours.

The concentration of somatostatin-like immunoreactivity (SLI) was determined by specific radioimmunoassay in the cerebroventricular fluid of patients with tumours of the basal midline and compared to findings in patients with multiple sclerosis. Mean SLI levels of the two groups were not significantly different. In patients with basal tumours (astrocytoma, craniopharyngioma, etc.) SLI levels varied widely and tended to increase with increased intracranial pressure. Lateral ventricular SLI levels decreased in patients with blockade of foramen Monro and in patients with communicating hydrocephalus or post-radiation encephalopathy. There was no apparent correlation with dysfunction of the hypothalamohypophyseal axis.

Molecular size distribution of somatostatin-like immunoreactivity in the cerebroventricular fluid of neurosurgical patients.

The molecular size distribution of somatostatin-like immunoreactivity (SLI) in the cerebroventricular fluid of patients with Parkinson's disease, dystonic syndromes, multiple sclerosis, basal and midline tumors, epilepsy and pain syndromes was investigated by separation with a Sephadex G-50f column and subsequent radioimmunoassay of the eluate. Marked heterogeneity of SLI was observed in most of the pools investigated. The most conspicuous feature of the elution profiles was the preponderance of the peak coeluting with synthetic somatostatin-14, whereas the peaks comigrating with synthetic somatostatin-28 and attributable to precursor-like SLI represented only minor or trace amounts of total immunoreactivity. These findings are consistent with the greater biological activity of somatostatin-14 in the human central nervous system, whereas somatostatin-28 appears to represent the more active form in the pituitary and in the intestinal mucosa. Solely in the case of brain tumor patients, some differences could be seen, resulting in an approximately equal distribution of somatostatin-14 and somatostatin-28 in two pools of ventricular fluid and by the detection of a degradation product of somatostatin-14 in another one. These observations could be explained by a lowered barrier function as a consequence of increased intracranial pressure in case of brain tumors, which is well in accordance with a markedly elevated total protein content being a sign of a lowered barrier function.

Molecular size distribution of somatostatin-like immunoreactivity in the cerebrospinal fluid of patients with degenerative brain disease.

The molecular size distribution of somatostatin-like immunoreactivity (SLI) in the cerebrospinal fluid (CSF) of patients with brain disease was investigated by separation with a Sephadex G-25 superfine column and subsequent radioimmunoassay of the eluate. Marked heterogeneity of SLI in the CSF of control subjects as well as in demented patients, was observed. Controls and schizophrenics exhibited an SLI distribution pattern consisting mainly of two pronounced peaks: the first eluting with the void volume of the column; the second being compatible with a peptide of N-terminally extended somatostatin-14. SLI from the CSF of patients with senile dementia of the Alzheimer type (SDAT), multi-infarct dementia (MID) and normal pressure hydrocephalus (NPH) showed the same two peaks found in controls and schizophrenics; and in addition, a third peak co-eluting with somatostatin-14. However, this peak was more pronounced in patients with SDAT and MID than in patients with NPH. Re-chromatography of G-25 sf void volume immunoreactivity afforded two fractions of an apparent molecular weight of about 10,000 daltons and 15,500 daltons, respectively.