Aggregation of insulin, containing surfactants, in contact with different materials.

The aggregation of insulin and of insulin protected with surfactants was studied by shaking at 37 degrees C in glass, in polypropylene and polystyrene vials, and in CPI and Auto-Syringe insulin syringes and infusion sets. Surfactants such as Pluronic 17R8 and 25R5 hastened the aggregation, whereas Pluronic F68 was effective in preventing it. Furthermore, there was no change in the immunoreactivity of insulin containing Pluronic F68 even after 8 days of shaking. Unprotected insulin aggregated in all the vials. There appears to be little problem with the commercial syringes tested, but the infusion sets could cause aggregation of insulin if used over an extended period of time. Although Pluronic F68 prevented insulin aggregation in situ, it extracted more impurities from the contacting plastics. Further development in materials and design of insulin sets and insulin containers appears necessary.

Evaluation of plasma polymerized hexamethylcyclotrisiloxane biomaterials towards adhesion of canine platelets and leucocytes.

Silicone coated Celgard-2400 and Silastic membranes were prepared by plasma polymerization of hexamethylcyclotrisiloxane. The adhesion of canine platelets and leucocytes was tested by passing whole blood from the anaesthetized mongrel dog in an ex-vivo shunt system. The silicone control Celgard and silicone coated Silastic membranes had fewer platelets and fewer leucocytes compared to those on the control Silastic membranes. Furthermore, these blood cells underwent fewer morphological changes on the silicone coated Celgard and Silastic compared to those on the control Silastic. From these observations the silicone coated biomaterials were judged to be better than the Silastic as far as the adhesion of platelets and leucocytes are concerned.

Characterization of plasma polymerized polypropylene coatings.

Propylene was polymerized at low pressure in a radio frequency plasma reactor. The plasma polymerized propylene (PPP) films were insoluble in toluene. Thermal analysis of PPP showed no phase transition took place up to 255 degrees C. From these results, it was concluded that PPP is a highly crosslinked polymer. To further characterize the deposited PPP, Fourier Transform infrared (FTIR) spectroscopy in the attenuated total reflection (ATR) mode was used. The deposited material was shown to be polymerized propylene as a spectrum of the material showed absorption bands characteristic of polypropylene.

Enhanced albumin binding to polypropylene beads via anhydrous ammonia gaseous plasma.

Plasma surface modification technique was used to add amino groups onto the surfaces of polypropylene beads by exposing them to anhydrous ammonia plasma. Through these amino groups, albumin was attached to the polypropylene beads. Attached albumin was further stabilized by crosslinking with glutaraldehyde. The effect of washing albuminated polypropylene beads with saline and human plasma was investigated. It was found that after initial rapid removal of albumin, the concentration of attached albumin tended to reach a steady-state. After 52 h of washing, the amount of albumin retained on the beads varied between 125 and 171 micrograms/cm2.

Ascitic fluid cholesterol in differential diagnosis of ascites.

Cholesterol was estimated in ascitic fluid of 89 patients (29 malignant and 60 non-malignant ascites). Mean ascitic cholesterol level was significantly higher in malignant ascites (89.52 mg/dl) as compared to non-malignant ascites (29.93 mg/dl). At a cut off value of 48 mg/dl, the sensitivity, specificity, positive and negative predictive value and overall diagnostic accuracy for diagnosing malignant ascites is 96.5%, 96.6%, 93.3%, 98.3% and 96.6% respectively. Ascitic fluid cholesterol estimation is an easy and reliable test for differentiating malignant ascites from non-malignant ascites.

A rare presentation of midgut malrotation as an acute intestinal obstruction in an adult: Two case reports and literature review.

INTRODUCTION: Midgut malrotation is a congenital anomaly presenting mainly in the childhood. Its presentation as an acute intestinal obstruction is extremely rare in adults usually recognized intra-operatively, therefore a high index of suspicion is always required when dealing with any case of acute intestinal obstruction. PRESENTATION OF CASE: We report two cases of young adults who presented with symptoms of acute intestinal obstruction and were diagnosed intra-operatively as cecal volvulus and paraduodenal hernia, respectively, caused by midgut malrotation. Post-operative CT scan confirmed these findings. DISCUSSION: Malrotation of the intestinal tract is a product of an aberrant embryology. The presentation of intestinal malrotation in adults is rare (0.2-0.5%). Contrast enhanced CT can show the abnormal anatomic location of a right sided small bowel, a left-sided colon and an abnormal relationship of the superior mesenteric vein (SMV) situated to the left of the superior mesenteric artery (SMA) instead of to the right. CONCLUSION: Anomalies like midgut malrotation can present as an operative surprise and awareness regarding these anomalies can help surgeons deal with these conditions.

Colocolic intussusception in an older child: a rare case report and a literature review.

Intussusception is a common cause of intestinal obstruction and colicky abdominal pain in the children, particularly infants, the commonest being the ileocolic variety with colocolic variety being a very rare entity. We present a case of colocolic intussusception in a 13-year-old boy which is otherwise seen in adults, precipitated by colonic malignancies. The patient presented with acute abdominal pain and bleeding perrectum with obstipation for 7 days. Preoperative USG abdomen was normal, and abdominal X-rays showed multiple air fluid levels. Intraoperative findings included a polypoidal growth in the descending colon as the leading point with the formation of a colo-colic intussusception. Following reduction and segmental resection, histopathology reported mucinous adenocarcinoma of colon which is also a rarity in pediatric age group. This case has been compared with previous cases reported in the literature.

Use of plasma polymerization for preparing silicone-coated membranes for possible use in blood oxygenators.

The plasma polymerization of hexamethylcyclotrisiloxane (D3) and octamethylcyclotetrasiloxane (D4) over the microporous polypropylene membrane Celgard 2400, over polypropylene filter membranes, and over glass slides was investigated. The rate of polymer deposition was dependent upon the location of the substrate materials in the reaction vessel. The increase in weight of all the substrates was linear with the time of reaction, indicating a uniform polymerization rate. The rate of polymer deposition over polypropylene filters was found to be 2.27 micrograms/cm(2)/min for both D3, and D4, whereas over the glass slides it was 1.53 and 1.87 microgram/cm(2)/min for D3 and D4, respectively. The coated Celgard membranes showed better blood compatibility that Silastic sheeting or glass.

A novel filler free silicone rubber biomaterial. II. Radiation chemical and physical evaluation.

Hexamethylcyclotrisiloxane was polymerized at 60 degrees C by gamma radiation to yield filler free silicone rubber (FFSR). The G (crosslinking) value of 23.5 was found for the FFSR polymerized for 4 hours, compared to about 2 for the pure polydimethylsiloxane (PDMS). The sol fractions for both FFSR and cross-linked PDMS varied between 5-7%. The FFSR and the cross-linked PDMS both had tensile strength of about 1 kg per cm2 but FFSR was not brittle and could be extended as much as 500% before breaking. It is believed that the marked improvement in physical properties of FFSR is due to the formation of domains of highly cross-linked material which act as "internal filler".

In vivo interactions between novel filler free silicone rubber and blood.

To evaluate the thrombogenicity of the novel filler free silicone rubber (FFSR) prepared in our laboratory, its interactions with blood were studied. The test samples (FFSR) along with control Silastic samples were placed in an extracorporeal shunt and primed with sterilized normal saline. The blood from an anaesthetized and systemically heparinized dog was passed over these samples for predetermined time intervals. After washing, fixing, etc., the platelets adhering to the samples were counted under light microscopy. To study the morphological changes of the platelets adhering to the samples, they were examined under scanning electron microscope. The number of platelets adhering to the FFSR samples was very small compared to the Silastic samples. For example, when the blood was passed over the samples for 10 min the number of platelets sticking per 0.14 mm2 surface area was 10 for FFSR samples compared to 380 for Silastic. Furthermore, there were no leukocytes on FFSR samples compared to 10 on Silastic. From these studies, the novel filler free silicone rubber prepared in our laboratory was judged to be more compatible with formed elements of blood compared to the Silastic material.

Toxicity evaluation of a novel filler free silicone rubber biomaterial by cell culture techniques.

Cytotoxicity of a novel filler free silicone rubber (FFSR) was evaluated by studying its effect on mouse L929 cells. Silastic and a laboratory rubber tubing (RT) were used as control materials. Three different experimental methods were used. In method A, after six days of cell culturing in the sample extracts, there were 95, 80, and 50% of control viable cells for FFSR, Silastic, and RT, respectively. Similarly, in method B, after six days of direct contact between samples and the cells, there were 80, 40, and 20% of control viable cells for FFSR, Silastic, and RT, respectively. For the Agar Overlay Test, method C, the cells under the FFSR samples were normal and healthy compared to those under Silastic and RT. From these studies it was concluded that FFSR had the least cytotoxicity of the three materials studied.