Improving HyperCEST performance by favorable xenon exchange conditions in liposomal nanocarriers

MRI reporters that combine signal enhancement from saturation transfer with hyperpolarized ¹²⁹ Xe show nanomolar detection sensitivity for in vitro studies. However, they need further improvement for accelerated CEST build-up that sufficiently dominates the intrinsic loss of hyperpolarization under in vivo conditions. This study introduces liposomes with a HyperCEST-active lipopeptide to enhance the efficiency of a well known Xe host, CrA-ma, with medium Xe exchange kinetics in aqueous environment, by two orders of magnitude. The depolarization time for constant saturation power but increasing saturation time is used as a comparative measure to rank different nanocarrier formulations. A variable cage load illustrates that the available CEST sites should be well distributed throughout the nanocarriers to avoid inefficiency from back exchange. For a liposome loading with only 2 mol% CrA-lipopeptide, the higher exchange kinetics allowed us to work even with 17-fold lower saturation power than for CrA-ma itself to achieve significant image contrast with ¹²⁹ Xe. Overall, this study illustrates the wide parameter space that is now available when incorporating CrA-labelled lipopeptides into liposomal carriers.

A miniaturized readout strategy for endogenous histone deacetylase activity

Histone deacetylases are important drug targets, which are difficult to characterize due to their poor accessibility. We have developed a miniaturized assay for the multi-site readout of deacetylase activity and profiled the substrate selectivity of HDACs for acetylation sites on histone H4 and tumor suppressor protein p53.

Analysis of phosphorylation-dependent protein-protein interactions of histone h3

Multiple posttranslational modifications (PTMs) of histone proteins including site-specific phosphorylation of serine and threonine residues govern the accessibility of chromatin. According to the histone code theory, PTMs recruit regulatory proteins or block their access to chromatin. Here, we report a general strategy for simultaneous analysis of both of these effects based on a SILAC MS scheme. We applied this approach for studying the biochemical role of phosphorylated S10 of histone H3. Differential pull-down experiments with H3-tails synthesized from l- and d-amino acids uncovered that histone acetyltransferase 1 (HAT1) and retinoblastoma-binding protein 7 (RBBP7) are part of the protein network, which interacts with the unmodified H3-tail. An additional H3-derived bait containing the nonhydrolyzable phospho-serine mimic phosphonomethylen-alanine (Pma) at S10 recruited several isoforms of the 14-3-3 family and blocked the recruitment of HAT1 and RBBP7 to the unmodified H3-tail. Our observations provide new insights into the many functions of H3S10 phosphorylation. In addition, the outlined methodology is generally applicable for studying specific binding partners of unmodified histone tails.

Facile synthesis of colorimetric histone deacetylase substrates

Here we report a simple procedure for generating colorimetric histone deacetylase (HDAC) substrates by solid-phase peptide synthesis based on racemization-free couplings of amino acid chlorides. We demonstrate the applicability of these substrates in HDAC assays.

Site-specific mapping and time-resolved monitoring of lysine methylation by high-resolution NMR spectroscopy

Methylation and acetylation of protein lysine residues constitute abundant post-translational modifications (PTMs) that regulate a plethora of biological processes. In eukaryotic proteins, lysines are often mono-, di-, or trimethylated, which may signal different biological outcomes. Deconvoluting these different PTM types and PTM states is not easily accomplished with existing analytical tools. Here, we demonstrate the unique ability of NMR spectroscopy to discriminate between lysine acetylation and mono-, di-, or trimethylation in a site-specific and quantitative manner. This enables mapping and monitoring of lysine acetylation and methylation reactions in a nondisruptive and continuous fashion. Time-resolved NMR measurements of different methylation events in complex environments including cell extracts contribute to our understanding of how these PTMs are established in vitro and in vivo.

[Thrombosis and embolism as causes of the acute peripheral ischemia syndrome--differential diagnosis and differential therapy]

A total of 572 patients were treated 628 times for acute peripheral vascular occlusion. Arterial embolism was most frequent with 65% followed by arterial thrombosis and traumatic vascular occlusion. For differential diagnosis other causes had to be considered. The method of choice is extraction of the thrombus by Fogarty catheter or ring stripper. The results depend on the time between occurrence and operative treatment of the occlusion. Angiography is not necessary in a clear case of embolism, but essential when exact preoperative classification of the vascular occlusion is not possible.

[Xeroangiographic findings in patients with haemodialysis fistulas in the arm (author's transl)]

The authors report on a simple and accurate method for xeroangiographic visualisation of haemodialysis shunts in the arm which has been performed so far in 98 patients without complications. By this method, approx. 45 ml metrizamide (80 mg iodine/ml) are injected into the venous limb during short-term hypersystolic congestion. Single xeroradiography performed subsequently shows both the arterial and the venous vessels. The pathological findings established during the examinations (stenoses, pseudoaneurysms, venous thromboses) were confirmed by subsequent surgery.

[The effect of intraductal duct occlusion with a fast hardening amino acid solution in acute animal experimental pancreatitis]

The effect of the occlusion of the pancreatic duct system by Ethibloc was studied in cases of acute pancreatitis in animal experiments. Application of 4,5 ml Ethibloc leads to high significant reduction of amylase increase. The favourable effect is markedly reduced after application of 9 ml Ethibloc. A partial excretory function could be demonstrated also after disintegration of Ethibloc. Histological follow-up shows a progredient fibrotic atrophy of pancreas parenchyma.

[Experience with the surgical treatment of peripheral arterial occlusions]

A total of 293 patients were treated 320 times for acute peripheral vascular occlusion. Arterial embolism was most frequent followed by arterial thrombosis and traumatic vascular occlusion. For differential diagnosis other causes had to be considered. The method of choice is extraction of the thrombus by Fogarty catheter or ringstripper. The results depend on the time between occurrence and operative treatment of the occlusion. Angiography is not necessary in a clear case of embolism, but essential when exact preoperative classification of the vascular occlusion is not possible.

[Pancreatic duct occlusion following duodeno-pancreatectomy in cancer surgery]

In 19 patients with a carcinoma of the pancreas an intraoperative occlusion of the pancreatic duct was performed with a partial duodenopancreatectomy by instillation of Ethibloc. In 13 cases a carcinoma of the papilla and in 6 cases a carcinoma of the head of pancreas were found. In two cases the duct was primarily closed by suture, which was followed by a pancreatic fistula that disappeared after 2 weeks. Therefore, a pancreaticojejunal anastomosis was performed in the other patients. One patient died owing to a total necrosis of the remaining pancreas, but no other local complications were seen at the time of pancreatic anastomosis. Lethality was approximately 5% and was therefore significantly lower than in other reports.

Rupture of the aortic wall with compression of bronchial arteries

A case of closed traumatic rupture of the aortic wall with compression of the bronchial arteries is described. No comparable case has been reported in the literature so far. The effect on pulmonary perfusion and gas exchange is demonstrated. The compression, displacement and transportation of the bronchial arteries (vasa privata) is shown is postmortem angiography.

[Meckel's diverticulum (author's transl)]

Complications (inflammation, bleeding, perforation) occurred in 20 of 38 patients with Meckel's diverticulum. Complications were disproportionately common in children up to ten years of age. Because of the high mortality rate in the presence of complications (20%) it is recommended to search actively for Meckel's diverticulum during every upper-abdomen laparotomy, as long as the underlying disease and the operative procedure allow it.

[The Caroli syndrome]

Caroli's disease is characterized by congenital pseudocystic dilatation of the biliary tree. Inflammation and stone formation lead to clinical manifestation in the second decade. ERC and computed tomography are main diagnostic procedures. In cases, where the alterations are limited partial hepatectomy has been recommended. If dilatations are diffuse, the aim of surgical treatment is the performance of a choledochojejunostomy to realize drainage and prevent recurrent ascending cholangitis.

[Experimentally induced pancreatitis (author's transl)]

Pancreatitis was produced in 29 mini-pigs by partial occlusion of the pancreatic duct; occlusion was performed by implanting a T-drain into the duct. Inflammatory changes were induced additionally by applying radiopaque material in excess. Acute and chronic pancreatitic lesions could be diagnosed by X-ray examination, evaluation of blood chemistry and by histology.

[Acute pancreatitis in animal experiments - a new method]

Acute pancreatitis was induced in 30 minipigs (Göttingen) by implantation of a T-drain into the Ductus Wirsungianus. The distal part of the T-drain, which led into the duodenum was stenosed to 1/3 of the original diameter. The inflammation was caused by stenosis of the Ductus Wirsungianus additionally by application of contrast medium. The course of the inflammation was demonstrated by biochemical, roentgenological and histological examinations.

[Surgical management of incontinence in rectal constipation (author's transl)]

In rectal constipation chronic filling of the rectum with feces will cause continuous rectal dilatation, a permanent stimulus for defecation and finally rectal incontinence. Reduction of rectal volume and perfect continence may be achieved in these cases by surgical removal of part of the elongated colon; thus surgery may have its place as an alternative to medical treatment of this disease. Patients with rectal constipation do not have an aganglionic segment of the colon, as is the case in Hirschsprung's disease; the dilated part of the colon is characterized on the contrary by hypertrophic intestinal wall.