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Biomedical subjects

K Forman

Publications and source records attributed to K Forman.

12 recordsLinked to original sources
PubMed2000

Characterization of purine receptors in fetal lamb pulmonary circulation.

Activation of P1 purinergic receptors by adenosine and P2 receptors by ATP plays an important role in pulmonary vasodilation that occurs at birth in fetal lambs. Purine receptors occur in several subtypes, and the effects of their stimulation vary with the specific type involved. We characterized the subtypes of P1 receptors in fetal lamb pulmonary circulation at 128-132 d gestation by investigating the effects of the following adenosine analogs: N6-cyclopentyl adenosine (A1 selective), 2-phenylaminoadenosine (A2 selective), 2-p-(2-carboxyethyl)phenethyl-amino-5'-N-ethylcarboxamidoadenosine (A2A selective), N6-benzyl-5'-N-ethylcarboxamidoadenosine (A3 selective), and adenosine and 5'-N-ethylcarboxamidoadenosine (nonselective). We repeated the studies after treatment of animals with A1 antagonist 1,3-dipropyl-8-cyclopentylxanthine or A2 antagonist 1,3-dipropyl-7-methylxanthine. Identification of P2 receptors was done by investigation of the effects of P2x agonist beta,gamma-methylene-L-ATP and P2x and P2y agonist ATP. The studies were repeated after the treatment of animals with P2x antagonist suramin and the P2y antagonist cibacron blue. N6-cyclopentyl adenosine caused a significant decrease in heart rate and did not change pulmonary blood flow or pulmonary vascular resistance (PVR). The effect of N6-cyclopentyl adenosine on heart rate was abolished by 1,3-dipropyl-8-cyclopentylxanthine but not by 1,3-dipropyl-7-methylxanthine. 2-Phenylaminoadenosine, 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine, 5'-N-ethylcarboxamidoadenosine, and adenosine caused significant increases in pulmonary flow and decreases in PVR, and their vasodilator effects were attenuated by the A2 antagonist 1,3-dipropyl-7-methylxanthine and not by 1,3-dipropyl-8-cyclopentylxanthine. N6-benzyl-5'-N-ethylcarboxamidoadenosine did not alter pulmonary flow or PVR. The P2x agonist beta,gamma-methylene-L-ATP caused a decrease in heart rate and had no effect on pulmonary flow and PVR. ATP caused a significant increase in pulmonary flow and decrease in PVR without affecting heart rate. The vasodilator effects of ATP were attenuated by cibacron blue and not by suramin. These data demonstrate that adenosine and ATP cause pulmonary vasodilation by activation of A2A and P2y receptors, respectively, in fetal lambs.

Animals↗
PubMed1999

Early allogeneic transplantation for refractory or relapsed acute leukaemia following remission induction with FLAG.

The prognosis for patients with secondary AML, primary resistant AML or ALL and early (<12 months) relapse of acute leukaemia remains extremely poor with conventional chemotherapy. As part of a strategy to improve the outcome for these patients we have treated 22 consecutive patients (18 AML, four ALL, median age 35 years) with either primary resistant disease (n=3), early relapsed leukaemia (n= 12) or secondary AML (n= 7, four RAEBt, two antecedant ALL and one antecedant Hodgkin's disease) with 'FLAG' induction chemotherapy with the aim of proceeding to early allogeneic transplantation either from sibling or unrelated donors. Eighteen patients achieved CR after one course of FLAG, including five patients who had documented p-glycoprotein-induced multidrug resistance and 10 patients with adverse cytogenetic abnormalities. Eight patients were consolidated with a second course of FLAG prior to transplantation and so far 16 patients have undergone allogeneic transplantation, 10 from unrelated donors and six from sibling donors (one mismatched). By the time of transplant three patients had progressed and were in early relapse and all have relapsed post BMT. Of the remaining 13 patients transplanted in remission, nine remain in CCR at a range of 4-26 months, three have died of transplant-related complications (18%) and one patient has relapsed. We conclude that the use of FLAG induction therapy followed by early allogeneic transplantation from either a sibling or unrelated donor can be an effective strategy for the treatment of this difficult group of young patients with poor risk acute leukaemia and appears to be associated with a low procedure-related risk.

Adolescent↗
PubMed1998

The effects of serial stretch loading on stretch work and stretch-shorten cycle performance in the knee musculature.

Training methods to optimize stretch-shorten cycle performance and an active muscle's ability to resist a sudden stretch (stretch work) and the relationship between the two have not been fully explored. The purpose of this study was to examine the effects of an 8-week strengthening program of serial stretch loading on stretch work and stretch-shorten cycle performance in the quadriceps and hamstring muscles. Thirty-one asymptomatic subjects participated in pre- and post-tests of maximum voluntary isometric contractions, stretch work and stretch-shorten cycle trials, and single-leg vertical jumps. The training portion consisted of progressively resisted isotonic single-leg squats. One leg exercised against an isotonic load with serial stretch loading, while the other leg exercised against isotonic load alone. Training resulted in strength gains in both legs indicated by the increase in weight lifted during training, but not by maximum voluntary isometric contractions. Vertical jump height increased in both legs. In the hamstring, stretch work decreased and stretch-shorten cycle performance increased in both legs. In the quadriceps, serial stretch loading intervention resulted in increased stretch-shorten cycle performance and no significant change in stretch work. The correlation between stretch-shorten cycle and stretch work was weak but significant. These findings suggest that the use of serial stretch loading could improve muscular performance and enhance a muscle's potential for dynamic stabilization.

Adult↗
PubMed1997

Purine nucleotides contribute to pulmonary vasodilation caused by birth-related stimuli in the ovine fetus.

We investigated the hypothesis that the purine nucleotides ATP and adenosine mediate the pulmonary vasodilation that occurs at birth in fetal lambs. We instrumented 44 fetal lambs to measure left pulmonary arterial pressure and flow. In control studies, we investigated the effects of sequential ventilation with 10, 50, and 100% O2 on fetal pulmonary arterial pressure and flow and pulmonary vascular resistance (PVR). We also measured the blood and plasma ATP levels in the pulmonary artery and left atrium in the control studies. In three separate groups of studies, we investigated the effects of 8-phenyltheophylline, an adenosine-receptor antagonist, and cibacron blue, an inhibitor of ATP-sensitive P2y receptors, given alone or in combination, on the response of PVR to sequential ventilation. Fetal arterial PO2 increased during ventilation with 50 and 100% O2 but not with 10% O2. Ventilation with 10% O2 caused a 4-fold increase in pulmonary blood flow and a 10-fold decrease in PVR. Ventilation with 50 and 100% O2 caused a 7-fold increase in pulmonary blood flow and a 20-fold decrease in PVR. Blood and plasma ATP levels in the pulmonary artery and blood ATP levels in the left atrium increased significantly during ventilation with 50 and 100% O2 but not with 10% O2. Pretreatment of animals with 8-phenyltheophylline attenuated the increase in pulmonary flow and decrease in PVR caused by ventilation at all fractions of inspired O2 (FIO2 levels). Pretreatment of animals with cibacron blue attenuated pulmonary vasodilation at 50 and 100% FIO2. Combined treatment with 8-phenyltheophylline and cibacron blue caused complete inhibition of the decrease in PVR in response to ventilation at the three FIO2 levels. Incubation of fetal red blood cells in vitro with 100% O2 caused an increase in ATP production. An increase in arterial PO2 in the fetus causes an increase in blood ATP levels, and an inhibition of ATP receptors attenuates the O2-induced decrease in PVR. Adenosine-receptor inhibition attenuates both ventilation- and O2-induced changes in PVR. Increased synthesis and release of ATP plays a major role in causing pulmonary vasodilation in response to birth-related stimuli in the ovine fetus.

Adenosine↗
PubMed1991

The efficacy of topical ciprofloxacin and norfloxacin in the treatment of experimental Pseudomonas keratitis.

An aminoglycoside-resistant strain of Pseudomonas aeruginosa was injected intrastromally into the corneas of rabbits, and keratitis was allowed to develop over a 22-h period. Rabbits were treated with either 0.75% ciprofloxacin, 1% norfloxacin, or 1.36% tobramycin administered topically every 15 min for 1 h and then every 30 min for the following 3 h. All therapy ceased 26 h postinoculation. Rabbits were killed 1 h after the treatment, and the number of bacteria per cornea were quantified in terms of bacterial colony-forming units. Aqueous humor specimens were obtained from rabbits receiving norfloxacin and ciprofloxacin, and bioassays were performed to determine drug concentration. Ciprofloxacin caused a 5 log reduction in the number of bacterial colony-forming units, as compared with untreated controls (p less than 0.0001); it also produced a significantly greater reduction in bacterial colony-forming units than either norfloxacin or fortified tobramycin drops (p less than 0.0001). Norfloxacin produced a 2 log reduction in bacterial colony-forming units, as compared with untreated controls (p less than 0.0001). The mean aqueous concentration of norfloxacin (7.5 micrograms/ml) was substantially less than that achieved by ciprofloxacin (30.5 micrograms/ml). We conclude that ciprofloxacin may be a useful broad spectrum, topical chemotherapeutic agent in the therapy of aminoglycoside-resistant P. aeruginosa keratitis.

Administration, Topical↗
PubMed1984

Paroxysmal nocturnal haemoglobinuria. A clinicopathological study of 26 cases.

26 patients, 13 male and 13 female, with paroxysmal nocturnal haemoglobinuria (PNH) are described. The diagnosis was based on the finding of a positive Ham's test. PNH developed in 4 patients with aplastic anaemia, and 3 patients with established PNH developed marrow hypoplasia during the course of the disease. In 2 cases autoimmune haemolysis was also present; this association has not been described previously. The majority of patients presented with anaemia and dark urine, or with evidence of thrombosis. A high index of suspicion was needed to avoid missing the diagnosis. Haemolytic crises were usually precipitated by infection, and renal failure requiring dialysis sometimes resulted; a positive direct antiglobulin test was often found at times of increased haemolysis. Thromboses were the most frequent complication, and when intra-abdominal vessels were affected, pain was particularly troublesome. The disease had a widely variable course; 4 patients made a complete recovery and 10 died, 8 from thrombotic complications and 2 from infections associated with marrow hypoplasia. Survival ranged from 1 year to 30 years and the median survival in those who died was 3.5 years.

Adolescent↗