Partial purification and characterization of the mRNA for rat preproinsulin.

Electrophoretically homogeneous messenger RNA for rat preproinsulin has been prepared from an islet cell tumor by the use of oligo(dT(-cellulose chromatography and sucrose density gradient centrifugation. The molecular weight of the mRNA is about 210,000, as determined by polyacrylamide gel electrophoresis in formamide, and its sedimentation coefficient is 9.3 S in sucrose gradients containing 0.2 M NaCl. These results indicate that the synthesis of preproinsulin is directed by a monocistronic mRNA 600 nucleotides in length and requires approximately 55% of the molecule's coding capacity.     

Physiology of sucking in the normal term infant using real-time US

Our study of 16 normal term, breast-fed infants documents real-time ultrasound as a technique for evaluating the oral portion of the sucking mechanism in infants. We also describe the mechanics of sucking used by the infants during breast-feeding.     

Biohybrid artificial pancreas. Long-term insulin secretion by devices seeded with canine islets

Long-term insulin secretion was investigated in seven biohybrid capillary devices seeded with canine islets. Approximately 50,000 islets could be isolated from a single canine pancreas using collagenase digestion in conjunction with the recently described Velcro technique. Devices were perfused with tissue culture medium 199 containing 300 mg/dl glucose. Insulin secretion fell during the first 1-2 days of culture from approximately 18 to 6 U/day. After 3-4 wk of perfusion, however, there was a gradual rise in insulin output that reached greater than 15 U/day after 7 wk. Insulin output eventually stabilized at 18-20 U/day. Two of these devices were studied for 80 and 86 days, respectively, and continued to secrete these same amounts of insulin. Glucose-induced insulin release was studied after 1 and 4 wk of culture and was well preserved.     

PREVALENCE OF MITRAL VALVE PROLAPSE IN HONG KONG CHINESE A CLINICAL AND AUTOPSY STUDY

The prevalence of mitral valve pro.lapse in Chinese was determined by screening 156 heal- thy subjects and by patholobic examination of 86 adult autopsies. Mitral valve prolapse was found in 7.7% in the clinical study and 5.8% in the autopsy study. A slight female preponderance was noted.     

Passive transfer of diabetes from BB/W to Wistar-Furth rats.

Autoimmune diabetes can be transferred to young, diabetes prone BB/W rats by injecting them intravenously with concanavalin A (Con A)-treated spleen cells from acute diabetic BB/W donors. This study describes the transfer of diabetes to the normal Wistar-Furth strain of rats using a similar procedure. For the successful transfer of diabetes it was necessary to immunosuppress recipient animals with a single intraperitoneal injection of cyclophosphamide 24-48 h before administering Con A-stimulated spleen cells from acute diabetic BB/W rats. Of 68 Wistar-Furth rats in immunosuppressed with a dose of 100-150 mg cyclophosphamide/kg body wt, 10 (15%) became diabetic. None of the control rats receiving either Con A-stimulated Wistar-Furth spleen cells (n = 28), freshly isolated BB/W spleen cells (n = 14), or fresh RPMI medium (n = 11) became diabetic. These data indicate that diabetes can be transferred from BB/W to Wistar-Furth rats. In addition, they support the hypothesis that cell-mediated immune processes are involved in the development of insulin-dependent diabetes and rule out any absolute requirement for BB-derived genes in the target pancreatic beta cells.     

A taxonomy of model structures for economic evaluation of health technologies

Models for the economic evaluation of health technologies provide valuable information to decision makers. The choice of model structure is rarely discussed in published studies and can affect the results produced. Many papers describe good modelling practice, but few describe how to choose from the many types of available models. This paper develops a new taxonomy of model structures. The horizontal axis of the taxonomy describes assumptions about the role of expected values, randomness, the heterogeneity of entities, and the degree of non-Markovian structure. Commonly used aggregate models, including decision trees and Markov models require large population numbers, homogeneous sub-groups and linear interactions. Individual models are more flexible, but may require replications with different random numbers to estimate expected values. The vertical axis of the taxonomy describes potential interactions between the individual actors, as well as how the interactions occur through time. Models using interactions, such as system dynamics, some Markov models, and discrete event simulation are fairly uncommon in the health economics but are necessary for modelling infectious diseases and systems with constrained resources. The paper provides guidance for choosing a model, based on key requirements, including output requirements, the population size, and system complexity.