Spinodal decomposition in a model colloid-polymer mixture in microgravity

We study phase separation in a deeply quenched colloid-polymer mixture in microgravity on the International Space Station using small-angle light scattering and direct imaging. We observe a clear crossover from early-stage spinodal decomposition to late-stage, interfacial-tension-driven coarsening. Data acquired over 5 orders of magnitude in time show more than 3 orders of magnitude increase in domain size, following nearly the same evolution as that in binary liquid mixtures. The late-stage growth approaches the expected linear growth rate quite slowly.

Simian immunodeficiency virus infection induces severe loss of intestinal central memory T cells which impairs CD4+ T-cell restoration during antiretroviral therapy

BACKGROUND

Simian immunodeficiency virus (SIV) infection leads to severe loss of intestinal CD4(+) T cells and, as compared to peripheral blood, restoration of these cells is slow during antiretroviral therapy (ART). Mechanisms for this delay have not been examined in context of which specific CD4(+) memory subsets or lost and fail to regenerate during ART.

METHODS

Fifteen rhesus macaques were infected with SIV, five of which received ART (FTC/PMPA) for 30 weeks. Viral loads were measured by real-time PCR. Flow cytometric analysis determined changes in T-cell subsets and their proliferative state.

RESULTS

Changes in proliferative CD4(+) memory subsets during infection accelerated their depletion. This reduced the central memory CD4(+) T-cell pool and contributed to slow CD4(+) T-cell restoration during ART.

CONCLUSION

There was a lack of restoration of the CD4(+) central memory and effector memory T-cell subsets in gut-associated lymphoid tissue during ART, which may contribute to the altered intestinal T-cell homeostasis in SIV infection.

Time-dependent strength of colloidal gels

Colloidal silica gels are shown to stiffen with time, as demonstrated by both dynamic light scattering and bulk rheological measurements. Their elastic moduli increase as a power law with time, independent of particle volume fraction; however, static light scattering indicates that there are no large-scale structural changes. We propose that increases in local elasticity arising from bonding between neighboring colloidal particles can account for the strengthening of the network, while preserving network structure.

Limits to gelation in colloidal aggregation

We show that the dynamics of large fractal colloid aggregates are well described by a combination of translational and rotational diffusion and internal elastic fluctuations, allowing both the aggregate size and internal elasticity to be determined by dynamic light scattering. The comparison of results obtained in microgravity and on Earth demonstrates that cluster growth is limited by gravity-induced restructuring. In the absence of gravity, thermal fluctuations ultimately inhibit fractal growth and set the fundamental limitation to the lowest volume fraction which will gel.

Mucus transport in the airways by two-phase gas-liquid flow mechanism: continuous flow model

Mucus transport speed induced by two-phase gas-liquid interaction was measured in the continuous two-phase annular flow tube models, and factors influencing the transport speed were assessed in conjunction with rheological properties of mucus. The flow model was made with 1.0-cm-ID glass tubes and positioned either vertically or horizontally. During a continuous passage of airflow through the model tube, mucus stimulants were supplied into the tube at a rate of 0.5-2.0 ml/min. The advancing speed of the leading edge of the mucous layer and mean mucous layer thickness were then measured. The transport speed in the vertical tube model ranged from 1.1 to 3.1 cm/min with a mucus feed rate of 0.5 ml/min at airflow rates of 0.33-1.17 l/s and increased with increasing airflow rates but decreased rapidly with increasing viscosity of mucus. The transport speed increased almost proportionally with increasing mucus feed rate. Elasticity of mucus did not affect the transport speed itself. However, more elastic mucus caused lower flow resistance and thereby could be transported with a much reduced work load. The transport speed in the horizontal tube model was 5-60% faster than that in the vertical tube model. The mean mucous layer thickness in the vertical tube model was found to be in the range of 0.5-1.5 mm in the experimental conditions used, and decreased rapidly with increasing airflow rate and decreasing viscosity of mucus. From these data the transport speed could be functionally related to airway diameter, mucous layer thickness, and mucus production rate.

Value of endoscopic retrograde pancreatography in pancreatic ascites

Endoscopic retrograde pancreatography was easily performed preoperatively in six patients with pancreatic ascites, and no complications resulted from this procedure. The abnormalities observed during the procedure were unpredictable and varied. Endoscopic pancreatograms provided delineation of the pancreatic ductal system, showing one or more sites of ductal leaks into pseudocysts or segmental narrowing of the main pancreatic duct. This preoperative information was invaluable in selecting appropriate surgical procedures.

Pancreatic pseudocysts communicating with the stomach: demonstration by endoscopic retrograde pancreatography

The use of endoscopic retrograde pancreatography (ERP) provides important information in the management of pancreatic pseudocysts unavailable by other methods. When the pseudocysts communicate with a hollow viscus, the surgeon is better able to deal with the problem if aware of this fact prior to operative intervention. A pancreatic pseudocyst communicating with the stomach was demonstrated by ERP in each of four patients. One of these patients had pancreatic ascites and the other had left-sided pleural effusion, and both were treated successfully by distal pancreatectomy. The other two patients responded to nonoperative treatment. This report emphasizes the potential diagonstic value of ERP in determining the presence and the fate of pseudocysts.

Penetrating wounds of the neck: principles and some controversies

Some of the principles, pitfalls, and controversies in the management of penetrating wounds of the neck have been reviewed. All three policies to exploration of the neck advocated by different authors have merit and can be considered optimal under certain circumstances. Since delayed surgical treatment of major vascular and esophageal injuries results in higher morbidity and mortality, exploratory operations are appropriate when such injuries are suspected, even though preoperative studies are inconclusive. A systematic approach to the management of penetrating wounds of the base of the neck has been outlined. The role of a shount to maintain adequate cerebral blood flow during repair of carotid artery injuries has been discussed. In patients who have severe preoperative neurologic deficit and no blood flow in the injured carotid artery at operation, ligation of the artery rather than repair of injury appears to be indicated.

Pancreatic ascites: recognition and management

In a patient with chronic ascites, an abnormally raised ascitic fluid amylase concentration and a protein content above 2.5 gm/100 ml is diagnostic of pancreatic ascites. Thirty-one episodes in 26 patients treated between 1958 and 1975 have been analyzed. Twenty patients (65%) experienced abdominal pain and ten (32%) had concomitant pleural effusions roentgenographically. Although a leaking pancreatic pseudocyst was the cause of ascites in at least 21 episodes (70%), an abdominal mass could only be palpated in two of 26 patients. Roentgenographic series of the upper part of the gastrointestinal tract failed to demonstrate pancreatic pseudocyst in 7 of 21 episodes (33%). Endoscopic retrograde pancreatography is invaluable in delineating the pancreatic ductal system and, in conjunction with intraoperative pancreatography, makes a vital contribution to rational surgical therapy. Medical treatment or external drainage during 18 episodes resulted in death in four (22%) and recurrences of ascites or pancreatic pseudocyst in nine (64%). Since routine pancreatography followed by pancreatic resection or internal drainage has been instituted, mortality and recurrence have been reduced to zero.

Thoracic aortic clamping for prophylaxis against sudden cardiac arrest during laparotomy for acute massive hemoperitoneum

Experimental studies in dogs were performed to develop a model simulating clinical patients with penetrating wounds of the major abdominal vessels who develop sudden cardiac arrest following laparotomy and decompression of an acute massive hemoperitoneum. Hypovolemic dogs with a saline-distended tense abdomen and major arterial bleeding after laparotomy develop a sudden deterioration of cardiac function despite raped blood infusion, thus simulating the clinical problem. However, thoracic aortic occlusion before laparotomy and until control of distal arterial bleeding prevented such a cardiovascular collapse. Increased intra-abdominal pressure it itself was determental to cardiovascular function; its sudden release by laparotomy was associated with an improvement in cardiovascular function. An approach of thoracic aortic control before laparotomy is recommended in patients with acute massive hemoperitoneum who remain hypotensive before laparotomy.

The natural and unnatural history of pancreatic pseudocysts

Experience with 131 pseudocysts of the pancreas in 112 patients has been analysed with a view to answering specific questions. Spontaneous regression was documented in 8 per cent. Complications occurred in 33-5 per cent of the pseudocysts, including obstruction of adjacent organs, rupture, haemorrhage and pancreatic ascites. In 14 pseudocysts, rupture into the gastrointestinal tract, the peritoneal cavity or the pleural cavity when unassociated with haemorrhage, had a mortality rate of 14 per cent. Sixteen patients with significant haemorrhage associated with a pseudocyst had a mortality rate of 61 per cent; early direct surgical control is advocated. Pancreatic ascites was associated with 14-5 per cent of the pseudocysts and had a 40 per cent recurrence rate, which can be greatly diminished when operative procedures are guided by pancreatography. The mortality rate for the surgical treatment of 97 uncomplicated pseudocysts was 6 per cent and the recurrence rate was 11 per cent. The prime cause of death was haemorrhage. Seven of the 131 pseudocysts were synchronous and 12 were metachronous. The actual figure is probably higher. Small cysts of the head of the pancreas, impalpable at operation but demonstrable by pancreatography, may be the cause of severe, continuing or recurrent symptoms.