Biochemical stabilization of glucagon at alkaline pH

BACKGROUND

For patients with type 1 diabetes mellitus, a bihormonal artificial endocrine pancreas system utilizing glucagon and insulin has been found to stabilize glycemic control. However, commercially available formulations of glucagon cannot currently be used in such systems because of physical instability characterized by aggregation and chemical degradation. Storing glucagon at pH 10 blocks protein aggregation but results in chemical degradation. Reductions in pH minimize chemical degradation, but even small reductions increase protein aggregation. We hypothesized that common pharmaceutical excipients accompanied by a new excipient would inhibit glucagon aggregation at an alkaline pH.

METHODS AND RESULTS

As measured by tryptophan intrinsic fluorescence shift and optical density at 630 nm, protein aggregation was indeed minimized when glucagon was formulated with curcumin and albumin. This formulation also reduced chemical degradation, measured by liquid chromatography with mass spectrometry. Biological activity was retained after aging for 7 days in an in vitro cell-based bioassay and also in Yorkshire swine.

CONCLUSIONS

Based on these findings, a formulation of glucagon stabilized with curcumin, polysorbate-80, l-methionine, and albumin at alkaline pH in glycine buffer may be suitable for extended use in a portable pump in the setting of a bihormonal artificial endocrine pancreas.

Molecular placement of experimental electron density: a case study on UDP-galactopyranose mutase

The structure of UDP-galactopyranose mutase, the enzyme responsible for the conversion of UDP-galactopyranose to UDP-galactofuranose, has been solved. The structure solution required the use of two crystal forms and a selenomethionine variant. Crystal form P2(1) was used to collect a complete MAD data set, a native data set and a single-wavelength non-isomorphous selenomethionine data set. A starting set of MAD phases was then improved by non-crystallographic averaging and cross-crystal averaging of all P2(1) data. The initial maps were of such low quality that transformation matrices between cells could not be determined. It was therefore assumed that although there were large changes in unit-cell parameters, the molecule occupied the same position in each cell. This starting assumption was allowed to refine during the averaging procedure and did so satisfactorily. Despite a visible increase in the quality of the map allowing some secondary-structural elements to be located, the overall structure could not be traced and refined. The rediscovery of the second crystal form, P2(1)2(1)2(1), allowed the collection of a native data set to 2.4 A. Molecular placement of electron density was used to determine the relationship between the two unit cells. In this study, only the already averaged P2(1) experimental density could be placed in the P2(1)2(1)2(1) map. Less extensively density-modified maps did not give a clear solution. The study suggests even poor non-isomorphous data can be used to significantly improve map quality. The relationship between P2(1) and P2(1)2(1)2(1) could then be used in a final round of cross-crystal averaging to generate phases. The resulting map was easily traced and the structure has been refined. The structure sheds important light on a novel mechanism and is also a therapeutic target in the treatment of tuberculosis.

Abnormal amianthoid collagen fibers in meningioma

Electron microscopic examination of a spinal meningioma demonstrated broad zones with large amianthoid collagen fibers in the tumor. Normal native collagen fibrils were found in small scattered clumps particularly around the blood vessels in the tumor. Such abnormal large collagen fibrils have not been seen previously in meningiomas. The significance of the amianthoid fibers is unknown. The only other unusual feature of the tumor was that it had many pale-staining cells by light microscopy and was classified as a clear cell variant of meningioma.

Eosinophilic granuloma occurring in a patient with Hodgkin disease

A case of eosinophilic granuloma involving bone and lung in a patient with Hodgkin disease is reported. The lesion appeared several months after the patient had completed a course of chemotherapy. The single bony lesion was resected and the pulmonary lesions disappeared spontaneously. The occurrence of eosinophilic granuloma in a patient with Hodgkin disease has rarely been reported.

Histopathology of marine vibrio wound infections

Although marine vibrio wound infections and septicemia are being reported with increasing frequency, description of the histopathologic changes has been scanty. The histologic alterations in three patients with primary marine vibrio wound infections are presented. The lesions are characterized by intense acute cellulitis of the subcutis with much tissue destruction and extension into the adjacent dermis. The superficial dermis is devitalized and lacks an inflammatory cellular infiltrate. Subepidermal noninflammatory bullae are formed. Many organisms are seen both within the areas of intense acute inflammation and in devitalized areas. Organisms and inflammation are especially oriented around vessels, with associated acute vasculitis. It is concluded that the morphologic picture in marine vibrio wound infections is nonspecific yet characteristic.

Primary monomorphic adenoma of the middle ear

The benign, monomorphic adenoma, derived from the respiratory epithelium of the middle ear, is a well circumscribed, greyish, avascular tumor. Its histology--documented by light and electron micrographs contained in this report--supports a distinct entity and pathogenesis apart from the malignant adenocarcinoma. Utilizing two case reports, this compendium emphasizes the clinical presentations, as well as radiographic and audiometrical characteristics, of the tumor. The first case represents the typical tumor with conductive hearing loss. The second case is the first reported facial paralysis associated with hemorrhagic infarction of an adenoma which was reversible by surgical resection of the tumor. Based on the histology and four year postoperative follow-up, the authors conclude the adenoma may be effectively managed by surgical resection.

Elastic tissue dysplasia of the internal carotid artery

Elongation with kinking of the internal carotid artery is not an uncommon finding. Cerebral vascular insufficiency has been reported secondary to this abnormality. Although arteriosclerosis is a frequent cause in adults, the etiology in children has never been explained. Three children with significant kinking of the internal carotid artery are reported here. Each underwent surgical correction by excision and reconstruction. Histological review showed the elastic tissue to be disrupted, diminished in amount, and unevenly distributed. Retrospective examination of this elastic tissue dysplasia showed it to be localized, there being normal morphology both proximally and distal to the involved area. There was recurrence of elongation and kinking in one patient due to incomplete excision. Correction was accomplished after re-excision of the involved tissue with a vein graft interposition. From this study, it can be concluded that elongation and kinking of the internal carotid artery in children is secondary to elastic tissue dysplasia. It is imperative that the entire involved area be removed in order to prevent recurrence. The excised specimen should be studied histologically with elastic tissue stains. Such stains cannot be performed as frozen section. Should permanent studies show the margins of resection not to be beyond the dysplastic tissue, careful followup of these children is essential to recognize recurrence.

An unusual Rh immunization

Anti-C was present in the serum of a woman of the Rh phenotype R1Wr (CwDe/cde), as far as we know the first anti-C to be found in a Cw person.

Carcinoid tumour of the thymus gland: report of a case

CARCINOID OF THE THYMUS IS A RARE PROBLEM A case is reported to add to only 16 previously reported. None of these 17 patients had the carcinoid syndrome. Complete surgical excision, if possible, is the treatment of choice.

Experience with fresh venous allografts as an arterial substitute

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