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Biomedical subjects

R Lucas

Publications and source records attributed to R Lucas.

At least 109 records · Page 6Linked to original sources
PubMed1989

Transforming growth factor beta. A biologic chorioretinal glue.

Transforming growth factor beta (TGF-beta) stimulates fibrosis. We studied its possible role as a bioactive substance for inducing localized chorioretinal wound healing along the edge of a retinal tear. The TGF-beta was applied to induced retinal tears that were examined histopathologically. One day after surgery, neither control nor TGF-beta-treated eyes developed chorioretinal wound healing. Four days, two weeks, and two months after surgery, the control eyes still had not developed chorioretinal wound healing. In contrast, the edges of the retinal tear treated with TGF-beta were adherent to the underlying Bruch's membrane via localized fibrous tissue without apparent effects elsewhere. These results demonstrate intraocular in vivo bioactivity of TGF-beta and suggest that TGF-beta may have a potential role as an alternative means for inducing a chorioretinal adhesion in the treatment of retinal tears.

Animals↗
PubMed1989

Effect of SMS201-995 (a long-acting somatostatin analog) on bile-induced acute hemorrhagic pancreatitis in the dog.

Recent reports claim a beneficial role for SMS201-995 (SMS) in pancreatitis. To study the effects of SMS in a canine pancreatitis model, four groups of eight dogs each were subjected to laparotomy; and after cannulation of the dorsal pancreatic duct, a mixture of bile and trypsin was infused to induce pancreatitis. Group I constituted the control group and received no SMS. Group II received SMS intravenously at 5 micrograms/hr beginning 1 hour before the induction of pancreatitis. Group III and Group IV received SMS at the same dose starting at 2 hours and 6 hours, respectively, after the induction of pancreatitis. Infusions were maintained until 24 hours after the induction of pancreatitis. Leukocyte counts, serum lipase and amylase levels were obtained preoperatively and at 24 hours. All dogs were killed at 24 hours and autopsies performed. At autopsy, severity of pancreatitis was graded, based on survival, the presence or absence of pancreatic edema, hemorrhage, and necrosis, as well as the presence and severity of bloody ascites. Only on a dog (Group III) died before the 24-hour period. When SMS was used before the induction of pancreatitis, the pancreatitis seen was less severe (Group I vs Group II, P = .022). No effects were found when using SMS after the induction of pancreatitis (Group III or Group IV vs Group I). The serum lipase, amylase, and leukocyte counts changed significantly in all the dogs (P less than .001) with the onset of pancreatitis, but this difference was not significant between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1987

The transforming growth factor-beta system, a complex pattern of cross-reactive ligands and receptors.

A new homodimer form of transforming growth factor-beta (TGF-beta), TGF-beta 2, has been identified in porcine blood platelets. TGF-beta 2 is homologous to ordinary TGF-beta (TGF-beta 1), which is also present in platelets. TGF-beta 1.2, a heterodimer containing one TGF-beta 1 chain and one TGF-beta 2 chain, has also been isolated. TGF-beta 1 and TGF-beta 2 interact differently with a family of receptors in target cells. A 280 kd receptor displays high affinity for both TGF-beta 1 and TGF-beta 2. Occupancy of this receptor by TGF-beta 1 or TGF-beta 2 correlates with the ability of these TGF-beta s to inhibit cell proliferation. In contrast, 65 kd and 85 kd receptors have high affinity for TGF-beta 1 but lower affinity for TGF-beta 2. The existence of distinct forms of TGF-beta that interact differently with a family of TGF-beta receptors could provide flexibility to the regulation of tissue growth and differentiation by the TGF-beta system.

Amino Acid Sequence↗
PubMed1987

Low-dose vaccination against hepatitis B in children: one-year follow-up.

Six hundred forty-three children, negative for markers of hepatitis B virus (HBV) infections, were given three X 2-micrograms doses of Merck, Sharp and Dohme (MSD) plasma derived hepatitis B vaccine (H-B-Vax) at monthly intervals. Twelve months after the first dose of vaccine, antibody to hepatitis B surface antigen (anti-HBs) was detected in 89% of children by radioimmunoassay (RIA) and in 83% by enzyme immunoassay (EIA). Seroconversion rates and anti-HBs titres were significantly greater in 1-4-year-olds than in older children (p less than 0.01). Eighteen children with no anti-HBs or other markers of HBV at this time were given 10 micrograms of vaccine and tested one month later. Seventeen developed anti-HBs, 12 at levels consistent with an anamnestic response. Forty-nine HBV-marker-negative children seroconverted for antibody to hepatitis B core antigen (anti-HBc) in the 8-month period before or the 12-month period following vaccination. Forty-six of these children were positive for anti-HBs, and one has been confirmed as a chronic carrier of hepatitis B surface antigen (HBsAg). Three cases of clinical hepatitis B in children have been seen in the community since the vaccination programme began. Two of these were amongst the estimated 5% of children who were not vaccinated. The third was in a vaccinee and occurred 4 1/2 months after the last dose of vaccine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Immunogenicity of low doses of hepatitis B vaccine in children: a study in 650 New Zealand children.

Six hundred and fifty New Zealand children from 2-12 years of age were vaccinated three times with 2 mcg intramuscular (IM) doses of Merck Sharp and Dohme plasma-derived hepatitis B vaccine (H-B-Vax), at 0, 1, and 6 months, and tested 2-3 months later for antibody to hepatitis B surface antigen (anti-HBs) by radioimmunoassay (RIA). Overall, 96.5% of the children seroconverted for anti-HBs by RIA, having levels greater than 2.1 RIA S/N units, with 91.2% having values greater than 10 S/N units. Anti-HBs levels were also determined by enzyme immunoassay (EIA), by which method a significantly better response was demonstrated in 2-4-year-olds than in older children. This study demonstrated that a satisfactory anti-HBs response was obtained using one-fifth of the recommended doses of hepatitis B vaccine.

Child↗
PubMed1979

Juvenile Reiter's syndrome.

A case of Reiter's syndrome occurring in an 11-year-old, pre-pubertal boy is described. The boy was a heterozygote for the histocompatibility antigen B27 and other arthritic members of his family included his mother with colitic arthritis and an aunt with ankylosing spondylitis. His HLA-B27 negative sibs have remained well. Shigella Salmonella and Yersinia organisms have been previously incriminated as precipitating factors in some patients with Reiter's syndrome but no evidence of recent infection with any of these agents was found in this patient. The case is reported because of the rarity of the condition at this age.

Arthritis, Reactive↗
PubMed1977

Effect of a spirolactone on plasma and urinary aldosterone in primary aldosteronism.

In primary aldosteronism due to an adrenal adenoma (n=2), treatment with a spirolactone (160 mg Canrenone/day for 7 days) decreased plasma aldosterone and urinary aldosterone-18-glucuronide. However, in the presence of a normalization in urinary aldosterone 18-glucuronide plasma aldosterone remained elevated above normal. Continued therapy with higher doses (320 mg/day for 7 days and 480 mg/day for 28 days) did not significantly alter plasma aldosterone, while urinary aldosterone-18-glucuronide returned to values comparable to those obtained before therapy. Cessation of the drug resulted in a marked increase in plasma aldosterone and urinary aldosterone-18-glucuronide. The results indicate that in primary aldosteronism due to an adrenal adenoma, the spirolactone (Canrenone) inhibits aldosterone biosynthesis and seems to influence aldosterone degradation.

Adenoma↗
PubMed1976

[Plasma renin activity and plasma aldosterone in essential hypertension: effect of age and diastolic blood pressure].

In patients with essential hypertension a gradual decrease in basal and stimulated renin secretion was found with increasing age. Stimulated plasma aldosterone decreased similarly; however, the observed changes were less pronounced. Young patients (less than 35 years) with high renin hypertension had lower diastolic blood pressure than patients with low renin hypertension in the same age group. Contrary to these findings, a markedly higher diastolic blood pressure was observed in patients over 35 years of age with high renin hypertension than in the group of patients with low renin hypertension. These results indicate that neither high nor low renin essential hypertension patients represent homogeneous groups. Furthermore, the dissociation between changes in renin activity and plasma aldosterone points to a disturbed relationship between the renin angiotensin system and aldosterone secretion in essential hypertension.

Adolescent↗
PubMed1976

Pulmonary valvulotomy under inflow stasis for isolated pulmonary stenosis.

One hundred ten patients were operated upon between 1961 and 1972 for isolated pulmonary stenosis by the inflow stasis technique. Analysis of the preoperative and postoperative clinical and catheterization data define the role of inflow stasis as an acceptable method of pulmonary valvulotomy except in relieving stenosis due to a dysplastic pulmonary valve. Patient ages ranged from 2 days to 36 years. All underwent preoperative catheterization and 69 (63%) were restudied postoperatively. Mean preoperative and postoperative peak systolic gradients were 93 and 23 mm Hg, respectively. Mean valve areas before and after operation were 0.38 and 1.10 cm2/m2. Operative mortality was 3.6% (4 patients), and there was 1 late death. Two of the dead were children 2 and 9 days old, respectively. Four patients required reoperation for residual gradients; 2 had dysplastic pulmonary valves. The overall results were excellent or good in 78%, fair in 15%, and poor in 7%. Patients with dysplatic pulmonary valves were in the poor or fair group, and it is recommended that the inflow stasis technique not be used for this type of pulmonary stenosis. The excellent surgical exposure, adequate time for valvulotomy, low morbidity, and freedom from problems of cardiopulmonary bypass are reasons for continued use of this technique for treatment of selected patients with pulmonary valve stenosis.

Adolescent↗