Tissue disposition and pharmacokinetics of recombinant human nerve growth factor after acute and chronic subcutaneous administration in monkeys.

In this study, we have characterized the metabolism, tissue disposition, excretion routes, and plasma pharmacokinetics of recombinant human nerve growth factor after single and multiple s.c. administration in male cynomolgus monkeys. Unlabeled nerve growth factor (NGF; 2 mg/kg) was administered three times a week for 4 weeks and a full pharmacokinetic profile was obtained for doses 1 and 12. For the tissue distribution studies, 0.8 microg/kg of trace (125)I-labeled recombinant human nerve growth factor was dosed. Histological analysis of emulsion-microautoradiography indicated that specific (125)I-NGF labeling was confined to sections of nerves most frequently localized adjacent to large vessels in sections of kidney, spleen, liver, and salivary gland. A small percentage of large neurons within the sympathetic ganglia were intensely labeled, as well as large neurons within the dorsal root ganglia. We found an increased disposition of (125)I-NGF in parts of the peripheral nervous system (including sympathetic ganglia) from 8 to 24 h postdose. In contrast, radioactivity in most non-neuronal tissues declined. This suggests specific uptake in these target tissues known to express specific receptors for NGF. We also identified changes in pharmacokinetic parameters after single versus chronic s. c. administration. These studies demonstrated that s.c. administration of NGF at 0.8 microg/kg doses in monkeys is capable of accessing and localizing in the target tissues.

Phase II study of weekly intravenous trastuzumab (Herceptin) in patients with HER2/neu-overexpressing metastatic breast cancer.

The HER2/neu proto-oncogene is overexpressed in 25% to 30% of patients with breast cancer. Trastuzumab (Herceptin; Genentech, San Francisco, CA), a recombinant humanized monoclonal antibody with high affinity for the HER2 protein, inhibits the growth of breast cancer cells overexpressing HER2. In this phase II study the efficacy and toxicity of weekly administration of trastuzumab was evaluated in 46 patients with metastatic breast cancer whose tumors overexpressed HER2. A loading dose of 250 mg trastuzumab was administered intravenously, which was followed by 10 weekly doses of 100 mg each. Upon completion of this treatment period, patients with no disease progression could receive a weekly maintenance dose of 100 mg. Patients in this trial had extensive metastatic disease, and most had received prior anticancer therapy. Ninety percent of patients achieved adequate serum levels of trastuzumab. Toxicity was minimal, and no antibodies against trastuzumab could be detected. Objective responses were observed in 5 of the 43 evaluable patients, which included 1 complete remission and 4 partial remissions, for an overall response rate of 11.6%. Responses were seen in mediastinum, lymph nodes, liver, and chest wall lesions. Minor responses (seen in 2 patients) and stable disease (14 patients) lasted for a median of 5.1 months. These results demonstrate that trastuzumab is well tolerated and clinically active in patients with HER2-overexpressing metastatic breast cancers who have received extensive prior therapy. The regression of human cancer through the targeting of putative growth factor receptors such as HER2 warrants further evaluation of trastuzumab in the treatment of breast cancer.

Phase II study of receptor-enhanced chemosensitivity using recombinant humanized anti-p185HER2/neu monoclonal antibody plus cisplatin in patients with HER2/neu-overexpressing metastatic breast cancer refractory to chemotherapy treatment.

PURPOSE: To determine the toxicity, pharmacokinetics, response rate, and response duration of intravenous (i.v.) administration of recombinant, humanized anti-p185HER2 monoclonal antibody (rhuMAb HER2) plus cisplatin (CDDP) in a phase II, open-label, multicenter clinical trial for patients with HER2/neu-overexpressing metastatic breast cancer. PATIENTS AND METHODS: The study population consisted of extensively pretreated advanced breast cancer patients with HER2/neu overexpression and disease progression during standard chemotherapy. Patients received a loading dose of rhuMAb HER2 (250 mg i.v.) on day 0, followed by weekly doses of 100 mg i.v. for 9 weeks. Patients received CDDP (75 mg/m2) on days 1, 29, and 57. RESULTS: Of 37 patients assessable for response, nine (24.3%) achieved a PR, nine (24.3%) had a minor response or stable disease, and disease progression occurred in 19 (51.3%). The median response duration was 5.3 months (range, 1.6-18). Grade III or IV toxicity was observed in 22 of 39 patients (56%). The toxicity profile reflected that expected from CDDP alone with the most common toxicities being cytopenias (n = 10), nausea/vomiting (n = 9), and asthenia (n = 5). Mean pharmacokinetic parameters of rhuMAb HER2 were unaltered by coadministration of CDDP. CONCLUSION: The use of rhuMAb HER2 in combination with CDDP in patients with HER2/neu-overexpressing metastatic breast cancer results in objective clinical response rates higher than those reported previously for CDDP alone, or rhuMAb HER2 alone. In addition, the combination results in no apparent increase in toxicity. Finally, the pharmacology of rhuMAb HER2 was unaffected by coadministration with CDDP.

The treatment of systemic lupus erythematosus (SLE) in NZB/W F1 hybrid mice; studies with recombinant murine DNase and with dexamethasone.

The effects of recombinant mouse DNase on a well established murine model of spontaneous SLE have been evaluated. Daily intraperitoneal injections of DNase were given to female NZB/NZW F1 mice during the period of disease development from 4 to 7 months of age or at the height of disease activity from the age of 7 months for 3 weeks. This treatment was compared with the injections of diluent and with an immunosuppressive dose of dexamethasone. The effects of treatment were evaluated using the immunological parameters of disease activity (antinucleoprotein antibody, immune complexes, serum immunoglobulins, anti-cardiolipin antibodies), protein-uria, serum creatinine and renal histopathology (light microscopy, immunofluorescence and electron microscopy). The dose of dexamethasone used (1 mg/kg per day from the age of 4 months) was sufficient to suppress the development of lupus entirely. Treatment with DNase starting at the age of 4 months postponed the development of the disease by about 1 months and extended the period from the onset of disease to death by about 30%. Mice treated for 3 weeks during the most active phase of the disease at 7 months of age showed more dramatic effects. Proteinuria and serum creatinine were significantly reduced and renal histopathology was strikingly less severe than in the control group. Immune complexes involving DNA-containing antigens are believed to play a crucial role in the pathogenesis of SLE. DNA-nucleoprotein, even in immune complexes, can be destroyed by DNase. This enzyme therefore provides a rational way to interfere with the disease process. The results reported here encourage a trial of recombinant human DNase in human SLE and lupus nephritis.

Phase II study of weekly intravenous recombinant humanized anti-p185HER2 monoclonal antibody in patients with HER2/neu-overexpressing metastatic breast cancer.

PURPOSE: Breast cancer frequently overexpresses the product of the HER2 proto-oncogene, a 185-kd growth factor receptor (p185HER2). The recombinant humanized monoclonal antibody (rhuMAb) HER2 has high affinity for p185HER2 and inhibits the growth of breast cancer cells that overexpress HER2. We evaluated the efficacy and toxicity of weekly intravenous administration of rhuMAb HER2 in patients with HER2-overexpressing metastatic breast cancer. PATIENTS AND METHODS: We treated 46 patients with metastatic breast carcinomas that overexpressed HER2. Patients received a loading dose of 250 mg of intravenous rhuMAb HER2, then 10 weekly doses of 100 mg each. Patients with no disease progression at the completion of this treatment period were offered a maintenance phase of 100 mg/wk. RESULTS: Study patients had extensive metastatic disease, and most had received extensive prior anticancer therapy. Adequate pharmacokinetic levels of rhuMAb HER2 were obtained in 90% of the patients. Toxicity was minimal and no antibodies against rhuMAb HER2 were detected in any patients. Objective responses were seen in five of 43 assessable patients, and included one complete remission and four partial remissions (overall response rate, 11.6%; 95% confidence interval, 4.36 to 25.9). Responses were observed in liver, mediastinum, lymph nodes, and chest wall lesions. Minor responses, seen in two patients, and stable disease, which occurred in 14 patients, lasted for a median of 5.1 months. CONCLUSION: rhuMAb HER2 is well tolerated and clinically active in patients with HER2-overexpressing metastatic breast cancers that had received extensive prior therapy. This is evidence that targeting growth factor receptors can cause regression of human cancer and justifies further evaluation of this agent.

Pharmacokinetics and pharmacodynamics of TP-9201, a gpIIbIIIa antagonist, administered in combination with recombinant tissue-type plasminogen activator, heparin, and aspirin in beagles.

The effect of heparin, aspirin, and recombinat tissue-type plasminogen activator (rt-PA) on TP-9201 pharmacokinetics and pharmacodynamics was investigated in beagles. Animals received TP-9201, an Arginine-Glycine-Aspartic acid (RGD)-containing synthetic peptide glycoprotein (gp)IIbIIIa antagonist as a bolus of 0.31 mg/kg, followed by a 4-h infusion of 0.5 mg/kg/h. rt-PA was administered as a modification of the weight-adjusted standard regimen. Heparin was administered as a bolus followed by an infusion producing a 1.5- to 2-fold increase in the activated prothromboplastin time (aPTT) above baseline values. Aspirin was administered orally, approximately 24 and 2 h before TP-9201. TP-9201 had a plasma clearance of 9.9 +/- 2 ml/min/kg and a volume of distribution that was larger than plasma volume. Administration of heparin and aspirin with TP-9201 did not affect the clearance of TP-9201, whereas rt-PA resulted in a faster clearance (p = 0.05). Whether the faster clearance is physiologic or a result of rt-PA interference in the TP-9201 assay is unclear. TP-9201 completely inhibited ADP-mediated platelet aggregation. After discontinuation of TP-9201, recovery of platelet aggregation had a half life (t1/2) of 2-3 h and was complete < or = 24 h. Coadministration of heparin did not interfere with TP-9201 pharmacodynamics, whereas aspirin and rt-PA slowed the recovery of platelet aggregation. The template bleeding time profile for the TP-9201-treated animals was similar to that of the aspirin-treated animals.

Pharmacokinetics and pharmacodynamics of TP-9201, a GPIIbIIIa antagonist, in rats and dogs.

Because activation of the glycoprotein IIbIIIa (GPIIbIIIa) on platelets represents the final common pathway of platelet aggregation, inhibition of fibrinogen binding to the GPIIbIIIa complex provides an excellent target for inhibiting platelet aggregation. Peptides containing the arginine-glycine-aspartic acid (RGD) sequence have been shown to inhibit the binding of fibrinogen to the GPIIbIIIa receptor on platelets competitively. We studied the pharmacokinetics of TP-9201, a synthetic cyclic peptide containing the RGD sequence, in rats and dogs after a 24-h intravenous (I.V.) infusion at three doses. The mean plasma clearance of TP-9201 after intravenous infusions of 30, 150, and 600 mg/kg/day in rats was 20.2, 18.7, and 18.5 ml/min/kg, respectively. In beagles, TP-9201 clearance was 9.0, 7.5, and 7.3 ml/min/kg, corresponding to infusions of 10, 75, and 600 mg/kg/day, respectively. The volume of distribution was larger than plasma volume, and the terminal half-life (t1/2) was short in both species studied ranging from 0.5 to 0.7 h in rats and from 2.5 to 2.6 h in dogs. The results suggest that TP-9201 follows linear pharmacokinetics over the dose range studied. Despite the multiple blood sampling procedure used in the study, there were no hemorrhagic complications. Pharmacodynamic assessment in beagles showed that TP-9201 produces a dose-dependent inhibition of ADP-mediated platelet aggregation. The estimated in vivo IC50 value and sigmoidicity were 124 and 3.5 ng/ml, respectively, suggesting that TP-9201 is a potent GPIIbIIIa antagonist with a steep concentration-effect relationship. TP-9201 is rapidly cleared from the circulation on termination of the intravenous infusion. There is a corresponding reversal of platelet inhibition as TP-9201 is cleared from the circulation.

Percutaneous absorption of co-administered N-methyl-2-[14C]pyrrolidinone and 2-[14C]pyrrolidinone in the rat.

The percutaneous absorption has been investigated in rats of a mixture (3:2, w/w) of N-methyl-2-pyrrolidinone (NMP) and 2-pyrrolidinone (2-P), a combination intended for use as a vehicle in the formulation of an antimycotic drug to enhance skin penetration on dermal application, following co-administration of the two 14C-radiolabelled compounds by the dermal and oral routes. Radioactivity was excreted predominantly in the urine after either route of administration, and comparison of the respective excretion profiles indicated that about three-quarters of the applied dose was absorbed through the skin. Plasma concentrations of each parent compound, as determined by radio-HPLC, reached peak values at 2 hr after oral dosing, and remained relatively uniform during 1-6 hr after application to the skin, suggesting constant percutaneous absorption during this period. NMP appeared to be absorbed through the skin more extensively and at a slightly faster rate than 2-P; total percutaneous absorption tended to be more extensive in female than in male rats. Together, these two 14C-compounds accounted for most of the plasma radioactivity up to 6-8 hr post-administration. However, by 12 hr (when plasma levels were relatively low), most of the radioactivity was associated with unknown polar metabolites. In view of the extensive percutaneous absorption and little first-pass metabolism of the two pyrrolidinones, the oral route was considered to represent a valid alternative to the dermal route for the assessment of the systemic toxicity of the two compounds.

Evaluation of the adult carrier state in juvenile tinea capitis caused by Trichophyton tonsurans.

The anthropophilic dermatophyte Trichophyton tonsurans is an occasional cause of scalp ringworm in adults. An asymptomatic adult carrier state also has been described. In this study the parents and/or grandparents of 50 children with proved T. tonsurans tinea capitis were evaluated. Cultures were obtained from the scalps of 46 asymptomatic adults; 14 of the cultures grew T. tonsurans. This population may provide a source for continued reinfection in children.

Elephantiasis nostras--a case report.

Elephantiasis nostras, the result of chronic lymphedema, is characterized by marked edema of the affected extremity with a thickened, verrucous, pebbly appearance of the skin. The pathogenesis is thought to be related to fibroblast proliferation following impaired lymphatic drainage, leading to fibrosis and further restriction of lymph drainage with progressive edema. A case report of a patient with massive chronic lymphedema of her feet is presented.

Large-artery welding with a milliwatt carbon dioxide laser.

Microvascular laser welding can be effectively used in large-diameter artery techniques. The carotid arteries of 12 anesthetized mongrel dogs were exposed. Following heparinization, the carotid arteries were transected, cleaned along their edges, and repaired on the right side by laser and on the left side by suture. The laser-assisted vascular anastomosis (LAVA) required four stay sutures and laser power for welding. Six-week patency for LAVA vs suture anastomosis was 100% vs 92%, respectively. Anastomotic time requirements were less with LAVA (seven vs 25 minutes). Intimal healing for both techniques immediately demonstrated an intraluminal thrombus, which resolved showing complete endothelial repair by four weeks. The laser seal demonstrated little inflammation compared with the giant cell reaction of suture anastomosis. Immediate wall tensions of 6 to 18 X 10(5) dynes/cm2 were tolerated after both techniques. Laser-assisted vascular anastomosis of large-diameter arteries is feasible, strong, and associated with minimal inflammation.

Leukocyte depletion enhances cultured endothelial retention on vascular prostheses.

Approximately 90% of endothelial cells that are seeded or cultured onto vascular prostheses are lost from the flow surface within 24 hours of implantation. To determine the contribution of leukocytes to endothelial cell loss, 111In-labeled, cultured canine jugular venous endothelial cells were grown to confluence on fibronectin-coated polyester elastomer tubes measuring 4 mm inner diameter and 30 mm in length. Autogenous cell-lined tubes were implanted as bilateral carotid replacement grafts in six dogs made leukopenic by cyclophosphamide. Similar unilateral grafts were placed in 12 control dogs. Grafts were removed and perfusion-fixed from six control animals after 2 hours of in vivo arterial perfusion and from the other six animals after 6 hours of perfusion. One graft was removed and perfusion-fixed from each leukopenic animal after 2 hours of implantation and the other after 6 hours. Attachment of endothelial cells to the grafts was measured by indium-labeling technique. Retention of endothelium on grafts removed after 2 hours was measured by planimetric counting with scanning electron microscopy and on those removed after 6 hours by radioisotope quantification. Endothelial cell retention after 2 hours was 37.6% +/- 27.0% in control dogs and 97.0% +/- 3.4% in leukopenic animals (p less than 0.0007). After 6 hours retention was 35.9% +/- 23.2% in control animals and 86.5% +/- 6.0% in leukopenic animals (p less than 0.0009). Leukocyte surface activity was present in less than 1% of the leukopenic dogs compared with 8.5% of the other in vivo midgrafts after 2 hours. These results suggest that leukocytes play a significant role in the loss of seeded endothelium from vascular prostheses.

Short-term in vivo stability of endothelial-lined polyester elastomer and polytetrafluoroethylene grafts.

A fibronectin substrate will significantly enhance the strength of endothelial cell attachment on grafts constructed of polyester elastomer (PE) and polytetrafluoroethylene (e-PTFE). This experiment was undertaken to determine the short-term in vivo stability of endothelium on these fibronectin coated surfaces. Eight mongrel dogs underwent bilateral carotid artery replacement with both graft materials. All grafts were inoculated with 2,000 cells/mm2 using cultured autogenous venous endothelium labelled with Indium-111-oxine. The Indium-111 label in the grafts was measured immediately prior to implantation, after 1 hour of in vivo perfusion, and at explantation after 24 hours. The percentage of inoculated cells attached to the grafts before perfusion was similar for both materials, 93.3 +/- 3.0% versus 92.2 +/- 7.2%, for PE and e-PTFE respectively. All grafts were patent at one hour after implantation. PE grafts were found to have 93.8 +/- 3.9% of the attached cells present at one hour while e-PTFE grafts had only 54.5 +/- 10.8% remaining, p less than .001. After 24 hours, 5/8 (62.5%) e-PTFE grafts and 2/8 (25.0%) PE grafts remained patent, p = .13. Of the patent grafts however, endothelial cell retention was still superior on the PE grafts with 78.0 +/- 0.6% of the attached cells remaining compared to only 24.5 +/- 6.1% on e-PTFE, p less than .001. Occluded PE grafts had fewer cells remaining at 24 hours than patent ones, 78.0 +/- 0.6% versus 31.1 +/- 32.8%, respectively, p = .13. Histologically, patent PE grafts demonstrated nearly confluent endothelial monolayers while e-PTFE had patches of endothelial cells surrounded by a platelet-fibrin carpet.(ABSTRACT TRUNCATED AT 250 WORDS)

Endothelium develops on seeded human arterial prosthesis: a brief clinical note.

Despite a considerable and growing body of evidence that endothelial cell seeding accelerates the healing of arterial prostheses in laboratory animals, there has been no histologic evidence thus far to indicate that a similar process occurs in human beings. A case is reported of histologically confirmed, extensive endothelial healing on a polytetrafluoroethylene femoropopliteal bypass graft 90 days after it was seeded and implanted.

Patency in canine inferior vena cava grafting: effects of graft material, size, and endothelial seeding.

We studied 117 inferior vena cava (IVC) replacements in dogs to determine the effects of graft material, graft size, endothelial seeding, and cultured endothelial linings on graft patency. As a control, the IVC was removed and reimplanted in 11 dogs. Dacron (n = 7) and expanded polytetrafluoroethylene (e-PTFE) grafts (n = 12) were seeded immediately with the use of enzymatically derived autogenous jugular vein endothelium. Cultured linings were prepared for e-PTFE grafts (n = 9) by inoculating the graft with jugular endothelium and nurturing the lining in tissue culture for 14 to 30 days before implantation. Unseeded grafts (n = 27) were prepared according to the manufacturer's recommendations. These six methods of preparation were tested in grafts measuring 6 mm I.D. and 60 mm in length. Other sizes were tested with a Latin square study design. After 30 to 60 days the grafts were perfusion fixed and studied with light and transmission electron microscopy. Patency was determined by contrast cavography after 7 and 30 days. Patency in the IVC reimplantation was 100% compared with 28.0% of the e-PTFE (p = 0.001) and none of the Dacron grafts that measured 6 mm I.D. and 60 mm long. e-PTFE and Dacron graft patency also differed significantly (p = 0.035). Seeded and culture-lined e-PTFE grafts in that same size were patent in 31.6% compared with 16.7% of unseeded e-PTFE. With grafts measuring 80 mm long, three of the five e-PTFE grafts were patent between 3 and 7 days. All progressed to occlusion by 30 days and compared poorly with all other graft sizes tested (2.6% progression to occlusion [p = 3 X 10(-8)]). Recanalization was not seen in 10 occluded grafts that were followed for 60 days. The histologic features of seeded grafts differed remarkably from grafts previously studied in the arterial circulation and from culture-lined and unseeded venous prostheses in that 60% had prominent large, random, endothelium-lined channels within the inner capsule. Larger graft diameters (p = 0.009) and the omission of an endothelial surface treatment (p = 0.004) were associated with anastomotic subendothelial fibrous hyperplasia. We conclude that graft material is the major determinant of patency in IVC replacements, that an extensive endothelial surface promotes patency, but that simply seeding e-PTFE or Dacron grafts with 10(5) endothelial cells does not provide sufficient endothelium to alter early patency.(ABSTRACT TRUNCATED AT 400 WORDS)

Endothelial seeding of Dacron and polytetrafluoroethylene grafts: the cellular events of healing.

To detect cellular differences in the healing of polytetrafluoroethylene (e-PTFE) and Dacron grafts up to 7 months after implantation, we studied 108 aortic graft interpositions in dogs. Each prosthesis was alternately prepared by endothelial seeding or by an unseeded control method. The grafts were perfusion fixed and studied with light, scanning, and transmission electron microscopy at intervals from before to 221 days after implantation. Seeding resulted in the development of an extensive endothelial flow surface in two out of three of the e-PTFE and none out of four of the Dacron grafts by 10 days after implantation (p = 0.053). After 30 days a microfibrillar subendothelial matrix ranging from 5 to 11 mu formed in all but three grafts with endothelial coverage. The inner capsule of mature Dacron grafts was significantly thicker (169 +/- 143 mu) than in e-PTFE grafts (22 +/- 32 mu; p = 0.002). Seeded and unseeded Dacron grafts had predominantly fibroblasts in the outer capsule of the graft by 10 days. Surface endothelium, vasa vasorum, fibroblasts, and myointimal cells appeared in the inner capsule between 10 and 30 days after implantation. In Dacron grafts, fibroblasts and myointimal cells predominated in the inner capsule at 30 days, with smooth muscle cells not being definitely identifiable until after 150 days. Neither fibroblasts nor myointimal cells were common (present but sparse in one of four e-PTFE grafts) at 30 days, and transmural vasa vasorum were never seen. The seeded endothelial cells migrated rapidly from the sites of initial adhesion near the e-PTFE onto the flow surface. Only one of four of the unseeded e-PTFE grafts had surface endothelium after 30 days, and only moderate coverage developed during 180 days. We conclude that endothelial healing is more rapid in seeded e-PTFE grafts than in seeded Dacron grafts and occurs by a different mechanism.

The quantitation of cultured cellular surface coverage: applications for transparent and opaque surfaces.

A planimetric technique is described for the analysis of cellular linings cultured on vascular prostheses and tissue culture plates. The method is not destructive of the cells and uses a calibrated eyepiece grid and an inverted microscope. The technique allows a rapid assessment of the percent of the prosthetic surface covered by cells, the average size of the cellular islands, and their distribution. In addition, the cells may be counted, their average surface area computed, and growth curves constructed for cells grown on tissue culture plates without the need for multiple concurrent cultures. Different cell types may be counted on the same surface. The method is more accurate than methods that require the resuspension of cells for counting, and it saves time and cells.

The peroxidase antiperoxidase staining of factor VIII-related antigen on cultured endothelial cells.

To prevent the premature occlusion of vascular prostheses, endothelium is being cultured experimentally onto synthetic flow surfaces. A rapid method of identifying cultured endothelium on the prosthesis is valuable for determining the degree of fibroblast and smooth muscle cell contamination and to screen for endothelial cell transformation. Fluorescent Factor VIII related antigen (FVIII-RA) staining has been used to identify cultured endothelium, but results in excessive staining of the underlying prosthesis, loss of morphologic detail, and deterioration of the FVIII-RA antibody reaction with time. We have applied the peroxidase antiperoxidase (PAP) method of antigen staining to permit staining of FVIII-RA and thereby to permit a sensitive and specific identification of human or canine endothelium with a concurrent analysis of morphologic detail.

The effect of diabetes on leucine and fucose incorporation into PNS myelin proteins.

Peripheral neuropathy is a common complication associated with diabetes mellitus. Segmental demyelination and other pathological changes frequently accompany loss of sensory amd motor nerve function. Morphological changes seen in diabetic nerve myelin may be a result of altered Schwann cell metabolism under hyperglycemic conditions. Using both alloxan and streptozotocin - induced diabetic rats of 2, 4 and 8 months duration of diabetes, metabolic changes in isolated sciatic nerve myelin were assessed using a double-label in vitro incubation system. Incorporation of 3H-fucose and 1-14C-leucine into myelin was determined per microgram protein. Specific activities of incorporated protein precursors were compared as a ratio of fucose to leucine. Using the Newman-Kuels test for multiple comparisons, statistically significant increases were found in the incorporation ratios of diabetic rats at 2 and 4 months of diabetes when tested against age-matched controls.