Orbital volume measurement in the management of pure blowout fractures of the orbital floor.

With the recent advent of accurate orbital volume assessment by computed tomography, a retrospective analysis was made of 31 patients with 'pure' blowout fracture of the orbital floor, managed either surgically or conservatively, to determine whether orbital volume measurement could provide an additional parameter of use in the management of such fractures. There was a significant difference in orbital volume discrepancy between patients managed surgically or conservatively suggesting that this investigation may be of use in decision making on surgical intervention in patients with orbital blowout fractures.     

Proteolytic Processing Mechanisms in the Biosynthesis of Neuroendocrine Peptides: The Subtilisin-like Proprotein Convertases

The recent discovery of a novel family of precursor processing endoproteases has greatly accelerated progress in understanding the complex mechanisms underlying the maturation of prohormones, neuropeptides, and many other precursor-derived proteins. At least six members of this family have been found thus far in mammalian species, several having alternatively spliced isoforms, and related enzymes have been identified in many invertebrates, including molluscs, insects, nematodes, and coelenterates. The proprotein convertases are all dependent on calcium for activity and all possess highly conserved subtilisin-like domains with the characteristic catalytic triad of this serine protease (ordered Asp, His, and Ser along the polypeptide chain). Two members of this family, PC2(SPC2) and PC1/PC3(SPC3), appear to play a preeminent role in neuroendocrine precursor processing. Both convertases are expressed only in the brain and in the extended neuroendocrine system, while another important family member—furin/PACE (SPC1)—is expressed more ubiquitously, in almost all tissues, and at high levels in liver. SPC2 and SPC3 exhibit acidic pH optima and other properties which enhance their activity in the acidic, calcium-enriched environment of the dense-core secretory granules of the regulated pathway in neuroendocrine cells, while furin has a neutral pH optimum and is localized predominantly to the trans Golgi network where it is retained by a C-terminal transmembrane domain. Furin processes a wide variety of precursors in the constitutive pathway, such as those of growth factors, receptors, coagulation factors, and viral glycoproteins. Recent findings on the processing of proopiomelanocortin, proinsulin, proglucagon, and several other neuroendocrine precursors by SPC2 and SPC3 are discussed, along with information on the structure, properties, evolution, developmental expression, and regulation or the convertases. An inherited defect in the fat/fat mouse which affects the processing of proinsulin, and probably also many other prohormones, due to a point mutation in carboxypeptidase E has recently been identified and has begun to provide new insights into the functional integration of the individual processing steps.     

Formulation of Vaccine Adjuvant Muramyldipeptides (MDP). 1. Characterization of Amorphous and Crystalline Forms of a Muramyldipeptide Analogue

A relatively nonhygroscopic crystalline form of the glycopeptide, N-acetylmuramyl-L--aminobu-tyryl-D-isoglutamine (I), containing approximately one molecule of water was prepared from amorphous material. The crystalline material, consisting of a mixture of the and anomers, exhibited better physical and chemical stability than the lyophilized amorphous material. The /-anomer ratios of I in both the crystalline and the amorphous state were approximately equal but different from that in solution.     

Pre-operative parenteral nutrition in patients with oesophageal cancer: a prospective, randomised clinical trial

A prospective randomised clinical trial was conducted to examine the efficacy of 2 weeks pre-operative parenteral nutrition (PPN) for the prevention of complications following surgery for oesophageal cancer. Forty patients were studied, the diet of twenty being supplemented by pre-operative parenteral nutrition. There were no significant differences in age, nutritional status, tumour staging and histology between the two groups of patients. The use of PPN resulted in a significant gain in body weight and nitrogen but failed to produce an overall reduction in post-operative morbidity and mortality rates. However patients receiving PPN exhibited two types of changes in serum albumin levels. Those with a fall in serum albumin levels associated with an increase in body weight (indicating an expansion of extracellular volume) had a significantly higher incidence of post-operative pulmonary complications than the group exhibiting a rise in serum albumin levels concomitant with increase in body weight. These data suggested that two weeks PPN might not be adequate in certain patients and a longer period of PPN is required. They also show no clinical benefit from the routine use of pre-operative parenteral nutrition in all patients, but do not exclude benefit in selected groups.     

Effect of defocus on visual acuity as measured by source and observer methods

The relation between refractive error and visual acuity has been measured by two very different methods. In one called "source methods," emmetropes or corrected ametropes view defocused stimuli presented on projection screens or photographs. In the type called "observer methods," focused stimuli are presented to the observers who are either uncorrected ametropes or emmetropes defocused by lenses placed (usually), in the spectacle plane. The study reported in this paper demonstrates for the first time that these two methods of defocusing retinal images and their effects on visual acuity can be correlated. Results show that the source method of producing defocus could be used interchangeably with the observer method in investigating the rates of change of visual acuity with defocus for young normal observers. The angular diameter of the defocused image of a point, the blur disc diameter in object space, allows the two methods to be compared. Although the results show that the two methods are highly correlated, they show that the source method gives a statistically but not clinically significant lower acuity. The results of both methods are used to derive an equation linking refractive error, visual acuity, and pupil diameter.     

Effects of lysine on bicarbonate and fluid absorption in the rat proximal tubule

The effects of lysine on bicarbonate and fluid reabsorption in the rat proximal tubule were studied by luminal and capillary perfusion in situ. The proximal tubule and peritubular capillaries were perfused with bicarbonate Ringer solution containing [14C]inulin. The rate of bicarbonate reabsorption (JHCO3) was estimated to be 124 +/- 9.5 peq.min-1.mm-1 using a pH membrane glass electrode. The rate of net fluid reabsorption (Jv) was 2.6 +/- 0.21 nl.min-1.mm-1. When 10 mM L-lysine was added to the luminal perfusate, a 35% reduction in JHCO3 and no change in Jv were observed. Increase of L-lysine concentration in the luminal perfusate to 20 mM did not reduce JHCO3 further nor did it influence Jv.l When 10 mM L-lysine was added to the capillary perfusate, a 13% reduction in JHCO3 was observed (NS). Increase of lysine concentration in the capillary perfusate to 20 mM significantly reduced JHCO3 by 26% (P less than 0.01). There was no significant change in Jv under both conditions. The effect of L-lysine in the lumen was related to its reabsorption kinetics, D-Lysine, which was not reabsorbed significantly, did not affect bicarbonate reabsorption in the proximal tubule. These results indicate that the inhibitory effect of L-lysine is related to the entry of lysine into the cell from the lumen.     

Thrombus of the ascending aorta: a rare cause of myocardial infarction.

We present two cases of a thrombus in the ascending aorta causing an acute myocardial infarction (AMI) and review the 10 other cases previously reported in the literature. This life-threatening condition appears to be more common in female smokers in their fifth decade. Suspicion should be raised in individuals at low risk for atherosclerotic disease with coronary angiographic findings not in keeping with the clinical presentation. The diagnosis may be obtained by transesophageal echocardiography, and we generally recommend surgical thrombectomy.