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Biomedical subjects

R Langer

Publications and source records attributed to R Langer.

At least 541 records · Page 30Linked to original sources
PubMed1983

Shark cartilage contains inhibitors of tumor angiogenesis.

Shark cartilage contains a substance that strongly inhibits the growth of new blood vessels toward solid tumors, thereby restricting tumor growth. The abundance of this factor in shark cartilage, in contrast to cartilage from mammalian sources, may make sharks an ideal source of the inhibitor and may help to explain the rarity of neoplasms in these animals.

Animals↗
PubMed1983

Angiogenesis inhibition and tumor regression caused by heparin or a heparin fragment in the presence of cortisone.

Heparin or a heparin fragment administered with cortisone inhibited angiogenesis, caused regression of large tumor masses, and prevented metastases. Oral administration of heparin resulted in the release of non-anticoagulant heparin fragments in the serum which, in the presence of cortisone, had similar anti-angiogenic and antitumor effects. Of all the heparin fragments tested, the most potent inhibition of angiogenesis in the presence of cortisone was provided by a hexasaccharide with a molecular weight of about 1600.

Animals↗
PubMed1983

Zero-order controlled-release polymer matrices for micro- and macromolecules.

Theoretical and experimental analyses demonstrate that a hemispheric polymer-drug matrix laminated with an impermeable coating, except for an exposed cavity in the center face, can be used to achieve zero-order release kinetics. Hemispheric systems for low molecular weight drugs were prepared by heating and compressing polyethylene and drug (sodium salicylate) in a brass mold. Hemispheric systems for high molecular weight drugs were prepared by casting ethylene-vinyl acetate copolymer and protein in a hemispheric mold at -80 degrees, followed by a two-step drying procedure (-20 and 20 degrees). In both systems, cavities were made in the center face of the hemispheres and the remainder of the matrices coated with an impermeable material. Zero-order release for 60 days at a rate of 0.5 mg/day was achieved from polymer matrices containing bovine serum albumin (mol. wt. 68,000).

Chemistry, Pharmaceutical↗
PubMed1983

In vivo and in vitro release of macromolecules from polymeric drug delivery systems.

In vivo release rates of a macromolecule from an ethylene-vinyl acetate copolymer have been shown to be indistinguishable from those of identical implants tested in vitro. The studies were conducted for approximately 2 months, and two different techniques were used to assess release rates. One of these techniques, using [3H]inulin as a marker, may be particularly useful in future studies assessing in vivo release rates from drug delivery systems. The appearance of [3H]inulin in the urine of rats bearing implants allowed continuous monitoring of release. A histological evaluation of tissue sections surrounding polymer implanted for 7 months showed no inflammatory cell reaction.

Delayed-Action Preparations↗
PubMed1983

A micro sustained release system for epidermal growth factor.

A technique for ensuring the controlled release of microgram and smaller amounts of biologically active epidermal growth factor (EGF) from polymeric delivery systems is described. We show that albumin in milligram quantities can facilitate the sustained release of picogram amounts of EGF for at least 3 wk. The EGF-containing polymer matrix can be placed directly into cell culture and will increase the proliferation rate of serum-starved cells. The method reported here should be suited particularly to the delivery of biologically active growth factors that are obtainable in only microgram or smaller amounts.

Animals↗
PubMed1983

Angiogenesis inhibitors and their delivery systems.

The extensive vascularity of solid tumors has been recognized for over 100 yr (1). However, only in the past 15 yr has the importance of this phenomenon been appreciated and only in the past 6 yr has the possibility of chemical interference been apparent. In this article, we review the emerging field of tumor vascularization inhibitors.

Angiogenesis Inhibitors↗
PubMed1983

"Milking"--a conservative surgical technique for a tubal gestation.

Milking technique was utilized in 13 patients with tubal pregnancies. Following this procedure there were we intrauterine pregnancies in nine women and 10 live births in eight women. No ectopic pregnancies recurred in this group. These results suggest that the milking procedure, whenever possible, may represent a valuable method for conservative surgical treatment of tubal gestation.

Fallopian Tubes↗
PubMed1983

Prediction of respiratory distress syndrome by the fetal lung maturity analyzer microviscosimeter on newborn gastric aspirate.

To predict the development of respiratory distress syndrome (RDS), the authors determined the fluorescent polarization values on gastric aspirates obtained from 67 premature infants within 30 minutes of birth. In 29 cases these results were also compared with the fluorescent polarization values measured on the corresponding amniotic fluid samples. Measurements for microviscosity were made by fetal lung maturity analyzer. Among 15 of 67 premature infants who developed RDS, the fluorescent value measured on gastric aspirates in all 15 infants was greater than 0.320. The fluorescent polarization values were less than 0.320 in all 52 infants in whom RDS did not develop, a predictability of 100%. Direct comparison found fluorescent polarization values measured on gastric aspirates to be somewhat lower than the corresponding amniotic fluid fluorescent polarization values. The results indicate that gastric aspirate obtained within 30 minutes of birth contains swallowed amniotic fluid. In cases where amniotic fluid samples were not available for surfactant evaluation prenatally, the determination of fluorescent polarization values on the newborn's gastric aspirate may accurately predict the development of RDS. The use of the fetal lung maturity analyzer microviscosimeter provides a simple, reliable, and rapid (45 minutes) method for assessment of surfactant in premature infants.

Amniotic Fluid↗
PubMed1982

An enzymatic system for removing heparin in extracorporeal therapy.

The need to fully heparinize patients undergoing extracorporeal therapy often leads to hemorrhagic complications. To enable heparinization of only the extracorporeal circuit, a blood filter containing immobilized heparinase was developed. This filter degraded 99 percent of heparin's anticoagulant activity within minutes in both canine and human blood.

Extracorporeal Circulation↗
PubMed1982

Differential anticoagulant activity of heparin fragments prepared using microbial heparinase.

Heparin of an average molecular weight of 13,000 with known polydispersity was degraded using microbial heparinase. The kinetics of this degradation were followed by four assays which measured the anticoagulant activity of the heparin digestion products. Both clotting and amidolytic chromogenic assays were used to measure heparin-potentiated inhibition of both thrombin and Factor Xa. These assays showed different profiles throughout the digestion and were related to the average molecular weight of the digestion products.l The final products of this enzymatic digestion were fractionated on the basis of size and their anticoagulant activities were measured. Fragments causing Factor Xa inhibition but not thrombin inhibition were isolated. Anticoagulant activity was found in a fragment as small as a tetrasaccharide.

Animals↗
PubMed1982

Mode of action of heparin lyase on heparin.

Heparinase (heparin lyase, EC 4.2.2.7) prepared from Flavobacterium heparinum was used to digest heparin. The products of digestion were examined with a viscosometric assay at various stages of the reaction to measure their average molecular weight. By comparison with computer simulations of various models, heparinase was shown to act in a random endolytic mode. The relative abundance of intermediates in heparin degradation catalyzed by heparinase immobilized on Sepharose 4B was measured by high pressure liquid chromatography (HPLC) at various time points. The results obtained using HPLC were consistent with a random endolytic mechanism. The heparin digestion products were separated and identified using gel permeation chromatography. The final distributions of heparin degradation products for free and immobilized heparinase were identical. Contaminating sulfatases and glycuronidases which could have subsequently acted on heparin degradation products were not found in significant amounts in the heparinase preparation studied.

Chromatography, Gel↗
PubMed1982

Improved fertility following ectopic pregnancy.

The reproductive performance subsequent to operative removal of ectopic pregnancy was examined in 154 women. They represent 64% of 242 women admitted for ectopic pregnancy between 1969 and 1979. The follow-up period averaged 4.2 years. The patients at risk had a conception rate of 81%, with a repeat ectopic pregnancy incidence of 7.8%, and 65% had at least one live birth. Postoperative infertility was significantly associated with (1) previous sterility, (2) coexistent periadnexal adhesions and/or tubual disease, (3) rupture of the ectopic pregnancy, and (4) older age. A statistically significant advantage of conservative over radical treatment, as regards future fertility, was demonstrated only in 53 patients with either history or findings suggestive of previously impaired fertility. Early, prerupture diagnosis and treatment, coupled with conservative and restorative measures, might account for the improved reproductive performance.

Adolescent↗
PubMed1982

Conservative surgery for tubal pregnancy.

Fifty-seven conservative surgical procedures for unruptured tubal pregnancy were performed on 54 patients. Salpingotomy was performed in 44 cases and fimbrial expression of the ectopic gestation was performed in 13 cases. In this patient group, 80% of the patients (39 of 49) experienced intrauterine pregnancy following surgery and 71% (35 of 49) had a live birth. The recurrence rate of tubal pregnancy was 12%. Ninety percent of the patients with a normal contralateral tube had an intrauterine pregnancy following surgery and a 7% recurrence rate of tubal pregnancy, a ratio of 1:15. It is suggested that the indications for the conservative surgical management in patients with unruptured tubal pregnancy should be broadened to all patients interested in future pregnancies and should also be considered in those cases with normal contralateral tube.

Fallopian Tubes↗