Phylogenetic star contraction applied to Asian and Papuan mtDNA evolution.

In the past decade, mitochondrial DNA (mtDNA) of 826 representative East Asians and Papuans has been typed by high-resolution (14-enzyme) restriction fragment length polymorphism (RFLP) analysis. Compared with mtDNA control region sequencing, RFLP typing of the complete human mitochondrial DNA generally yields a cleaner phylogeny, the nodes of which can be dated assuming a molecular clock. We present here a novel star contraction algorithm which rigorously identifies starlike nodes (clusters) diagnostic of prehistoric demographic expansions. Applied to the Asian and Papuan data, we date the out-of-Africa migration of the ancestral mtDNA types that founded all Eurasian (including Papuan) lineages at 54,000 years. While the proto-Papuan mtDNA continued expanding at this time along a southern route to Papua New Guinea, the proto-Eurasian mtDNA appears to have drifted genetically and does not show any comparable demographic expansion until 30,000 years ago. By this time, the East Asian, Indian, and European mtDNA pools seem to have separated from each other, as postulated by the weak Garden of Eden model. The east Asian expansion entered America about 25,000 years ago, but was then restricted on both sides of the Pacific to more southerly latitudes during the Last Glacial Maximum around 20,000 years ago, coinciding with a chronological gap in our expansion dates. Repopulation of northern Asian latitudes occurred after the Last Glacial Maximum, obscuring the ancestral Asian gene pool of Amerinds.

A qualitative investigation into the physical stability of polypropylene and polyethylene in liquid isoflurane and sevoflurane.

The interaction between medical plastics and drugs is complex. Drug absorption into plastics may affect drug dosage and the migration of plastics' additives into a drug solution may affect drug composition. We investigated the stability of those plastics which may be used in infusion systems to inject liquid volatile anaesthetic drugs directly into an anaesthetic breathing system. Samples of two types of polypropylene from a syringe barrel and plunger and low- and high-density polyethylene from extension tubing were exposed to isoflurane and sevoflurane for 1, 7 or 250 days. All samples were from the same batches. Samples of the plastics (n = 24) and the liquid volatile anaesthetics (n = 24) were subjected to Fourier transform-infrared spectroscopy to produce series of absorption spectra. By reference to control sample absorption spectra, this allows detection of anaesthetic drug absorption into the plastics or migration of the plastics or their additives into the liquid anaesthetics. We found no evidence of migration of the plastic components or their additives into the liquid anaesthetic drugs at any of the exposure periods. Similarly, we found no evidence of absorption of isoflurane or sevoflurane by any of the plastic components during short-term exposure of either 1 or 7 days. However, there was evidence of some absorption of the anaesthetic drugs by the polyethylene plastics after about 8 months' exposure. It would appear that low- and high-density polyethylene and polypropylene are suitably safe for use in infusion systems for the direct injection of isoflurane and sevoflurane into anaesthetic breathing systems.

Amsorb: a new carbon dioxide absorbent for use in anesthetic breathing systems.

BACKGROUND: This article describes a carbon dioxide absorbent for use in anesthesia. The absorbent consists of calcium hydroxide with a compatible humectant, namely, calcium chloride. The absorbent mixture does not contain sodium or potassium hydroxide but includes two setting agents (calcium sulphate and polyvinylpyrrolidine) to improve hardness and porosity. METHODS: The resultant mixture was formulated and subjected to standardized tests for hardness, porosity, and carbon dioxide absorption. Additionally, the new absorbent was exposed in vitro to sevoflurane, desflurane, isoflurane, and enflurane to determine whether these anesthetics were degraded to either compound A or carbon monoxide. The performance data and inertness of the absorbent were compared with two currently available brands of soda lime: Intersorb (Intersurgical Ltd., Berkshire, United Kingdom) and Dragersorb (Drager, Lubeck, Germany). RESULTS: The new carbon dioxide absorbent conformed to United States Pharmacopeia specifications in terms of carbon dioxide absorption, granule hardness, and porosity. When the new material was exposed to sevoflurane (2%) in oxygen at a flow rate of 1 l/min, concentrations of compound A did not increase above those found in the parent drug (1.3-3.3 ppm). In the same experiment, mean +/-SD concentrations of compound A (32.5 +/- 4.5 ppm) were observed when both traditional brands of soda lime were used. After dehydration of the traditional soda limes, immediate exposure to desflurane (60%), enflurane (2%), and isoflurane (2%) produced concentrations of carbon monoxide of 600.0 +/- 10.0 ppm, 580.0 +/- 9.8 ppm, and 620.0 +/-10.1 ppm, respectively. In contrast, concentrations of carbon monoxide were negligible (1-3 ppm) when the anhydrous new absorbent was exposed to the same anesthetics. CONCLUSIONS: The new material is an effective carbon dioxide absorbent and is chemically unreactive with sevoflurane, enflurane, isoflurane, and desflurane.

Genetic variation in North Africa and Eurasia: neolithic demic diffusion vs. Paleolithic colonisation.

The hypothesis that both genetic and linguistic similarities among Eurasian and North African populations are due to demic diffusion of neolithic farmers is tested against a wide database of allele frequencies. Demic diffusion of farming and languages from the Near East should have determined clines in areas defined by linguistic criteria; the alternative hypothesis of cultural transmission does not predict clines. Spatial autocorrelation analysis shows significant gradients in three of the four linguistic families supposedly affected by neolithic demic diffusion; the Afroasiatic family is the exception. Many such gradients are not observed when populations are jointly analyzed, regardless of linguistic classification. This is incompatible with the hypothesis that major cultural transformations in Eurasia (diffusion of related languages and spread of agriculture) took place without major demographic changes. The model of demic diffusion seems therefore to provide a mechanism explaining coevolution of linguistic and biological traits in much of the Old World. Archaeological, linguistic, and genetic evidence agree in suggesting a multidirectional process of gene flow from the Near East in the neolithic. However, the possibility should be envisaged that some allele frequency patterns can predate the neolithic and depend on the initial spread of Homo sapiens sapiens from Africa into Eurasia.

Lumenal labeling of rat hepatocyte endocytic compartments. Distribution of several acid hydrolases and membrane receptors.

We used a combination of subcellular fractionation and lactoperoxidase-mediated iodination to examine the polypeptide compositions of three hepatocyte endocytic compartments: early endosomes, late endosomes, and lysosomes. A chemical conjugate of asialoorosomucoid and lactoperoxidase which binds specifically to asialoglycoprotein receptors was perfused through isolated rat livers at 37 degrees C. Subcellular fractions enriched in various endocytic compartments were then isolated by differential and isopycnic centrifugation, and the lactoperoxidase moiety of the internalized conjugate was used to catalyze the iodination of lumenal-facing proteins. The 125I profiles of early and late endosomes were strikingly similar after gel electrophoresis. Using immunoprecipitation, we directly identified and compared the relative amounts of the Na+,K(+)-ATPase and several different acid hydrolases and membrane receptors in all three fractions. The asialoglycoprotein receptor and the low density lipoprotein related protein were approximately nine times more abundant in early endosomes than late endosomes, suggesting that they recycle from early endosomes. In addition, cathepsin D, but not cathepsin L, beta-glucuronidase, and lgp 120, was detected in early endosomes; however, all of these molecules were detected in lysosomes. Our findings provide strong evidence that early endosomes mature into late endosomes and that there is either selective delivery or selective retention of hydrolases at discrete points in the endocytic pathway.

Degradation of epidermal growth factor receptor in rat liver. Membrane topology through the lysosomal pathway.

We have generated and characterized three rabbit polyclonal antibodies that recognize different regions of the epidermal growth factor receptor (EGF-R) and used them to study the degradation of the receptor in the isolated perfused rat liver. Quantitative immunoblot analyses of rat liver homogenates prepared from tissue biopsies collected at various times after epidermal growth factor (EGF) addition showed that both the ectoplasmic and cytoplasmic domains of rat liver EGF-Rs were degraded with similar kinetics (t1/2 = 3.5-3.8 h at 25 degrees C with cycloheximide). No immunoreactive intermediate breakdown products were detected. EGF-stimulated degradation of both receptor domains was inhibited by the thiol protease inhibitor leupeptin, suggesting lysosome involvement in the hydrolysis of the whole molecule. To study this further, protease protection experiments were performed on endosome- and lysosome-enriched fractions isolated from leupeptin-treated livers. We found that the cytoplasmic domains of greater than 90% of the EGF-Rs in endosomal fractions were accessible to digestion when proteinase K was added to the intact vesicle populations, while the ectoplasmic domain was unaltered. In contrast, both the ectoplasmic and cytoplasmic domains of approximately 55% of the EGF-Rs present in lysosome-enriched fractions were inaccessible to proteinase K digestion in the absence of detergent. These findings suggest that movement of EGF-Rs from the limiting membrane of endosomes to the lumen of lysosomes permits the degradation of the entire EGF-R molecule within lysosomes.

Sequential processing of epidermal growth factor in early and late endosomes of rat liver.

We have used isolated perfused rat livers to examine the intracellular processing of 125I-epidermal growth factor (EGF) and to determine where in the endocytic pathway the hydrolases which degrade EGF are acting. Following uptake of 125I-EGF at 37 or 16 degrees C, subcellular fractions enriched in endosomes and lysosomes were isolated, and their 125I-EGF content was examined by reverse-phase high performance liquid chromatography. Three forms of EGF processed at their carboxyl termini are generated in endosomes. At 37 degrees C, EGF is first processed in early endosomes by a carboxypeptidase B-like protease and is further processed in late endosomes by a trypsin-like protease and then a carboxypeptidase B-like protease. At 16 degrees C, entry of EGF into late endosomes is slowed, and only the first processed form is generated over 60 min. Longer perfusions (180 min) at 16 degrees C result in some processing (7%) by proteases found in late endosomes. EGF-horseradish peroxidase cytochemistry confirmed that the additional processing detected at 180 min correlated with movement of EGF from tubulovesicular to multivesicular endosomes. These results, combined with in vitro incubations of EGF in isolated endosomal and lysosomal fractions, suggest that different proteases are active at selective points in the endocytic pathway and that the full complement of proteases needed for complete degradation of EGF is active only in lysosomes.

Neuroendocrine islet cell tumour producing gastrin and ACTH in a patient with calcifying chronic pancreatitis.

A patient with a calcifying chronic pancreatitis was found to have a neuroendocrine islet cell tumour (a previously unreported association). The tumour secreted both gastrin and ACTH leading to clinical manifestations of both the Zollinger-Ellison syndrome and Cushing's syndrome.