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Biomedical subjects

A Forman

Publications and source records attributed to A Forman.

At least 127 records · Page 7Linked to original sources
PubMed1980

Termination of pregnancy in patients with missed abortion and intrauterine dead fetuses by a single intracervical application of prostaglandin E2 in viscous gel.

To terminate pregnancy 15 women with an established diagnosis of missed abortion or intrauterine dead fetuses were treated with 1.0 mg Prostaglandin E 2 in viscous gel applied as a single intracervical dose. -- Abortion was induced after a mean of 7.0 hours in 8 patients with a mean gestational age of 15.0 weeks, and a subsequent evacuation of the uterine cavity was easily performed. -- Complete abortion/delivery was obtained in 7 patients with a gestational age of 33 weeks. The over-all mean induction/delivery time was 7.5 hours. -- Apart from pain related to uterine contractions no side effects were observed and no complications occurred. It is concluded that the present technique represents a promising alternative in the treatment of patients with missed abortion or intrauterine dead fetuses.

Abortion, Missed↗
PubMed1979

Ligated chlorophyll cation radicals: Their function in photosystem II of plant photosynthesis.

Magnesium tetraphenylchlorin, a synthetic model for chlorophyll, exhibits significant variations in the unpaired spin densities of its cation radicals with concomitant changes in oxidation potentials as a function of solvent and axial ligand. Similar effects are observed for chlorophyll (Chl) a and its cation radicals. Oxidation potentials for Chl --> Chl(+.) as high as +0.9 V (against a normal hydrogen electrode) are observed in nonaqueous solvents, with linewidths of the electron spin resonance signals of monomeric Chl(+.) ranging between 9.2 and 7.8 G in solution. These changes in electronic configuration and ease of oxidation are attributed to mixing of two nearly degenerate ground states of the radicals theoretically predicted by molecular orbital calculations. Comparison of the properties of chlorophyll in vitro with the optical, redox, and magnetic characteristics attributed to P-680, the primary donor of photosystem II which mediates oxygen evolution in plant photosynthesis, leads us to suggest that P-680 may be a ligated chlorophyll monomer whose function as a phototrap is determined by interactions with its (protein?) environment.

Journal Article↗
PubMed1979

Relaxant effects of nifedipine on isolated, human myometrium.

Myometrial tissue was obtained from non-pregnant women subjected to hysterectomy because of various gynaecological disorders, and from women undergoing caesarean section. Strip preparations were dissected and isometric tension was recorded. Nifedipine (2.9 X 10(-8)--2.9 X 10(-6)M) inhibited spontaneous contractile activity, mainly by reducing the amplitude of contraction in both non-pregnant and pregnant myometrium. The drug also inhibited potassium induced contractions in a concentration dependent manner. This effect seemed to be more pronounced in pregnant than in non-pregnant tissue. In preparations of pregnant human myometrium, normally polarized or potassium depolarized, oxytocin induced a contractile activity that was effectively inhibited by nifedipine. Nifedipine also relaxed contractions induced by vasopressin in isolated non-pregnant myometrium. It is concluded that the relaxant effect of nifedipine on isolated pregnant and non-pregnant human myometrium can be explained by inhibition of calcium influx. The results thus support the view, that calcium influx is an important step in the initiation of contractile activity in human uterine smooth muscle.

Adult↗
PubMed1978

Effects of nifedipine on the smooth muscle of the human urinary tract in vitro and in vivo.

Smooth muscle preparations of the urethra, bladder, and ureter were obtained from patients undergoing operations for various urological disorders. The urethral preparations were contracted by noradrenaline (0.1-3 microgram . ml-1), prostaglandin F2alpha (1-10 microgram . ml-1), and potassium (127 mM), the bladder preparations by carbacholine (0.004-1 microgram . ml-1), prostaglandin F2alpha (1-10 microgram . ml-1), potassium (127 mM), and barium chloride (3 mM), and the ureter preparations by potassium (127 mM), and barium chloride (3 mM). Irrespective of the mode of activation, pretreatment with nifedipine (0.1 microgram . ml-1) for 10 min. reduced the responses. Nifedipine also relaxed preparations contracted by the contractile agents used. In 19 female patients, aged 20 to 73 years, undergoing investigation because of urgency and/or urge incontinence, simultaneous urethrocystometry at rest was performed before and after oral administration of 20 to 40 mg nifedipine. Bladder capacity and residual urine were also determined. Nifedipine did not affect the pressures within the bladder and urethra, nor did it increase the bladder capacity. However, after nifedipine intake there was a statistically significant increase in residual urine. The results suggest that nifedipine can inhibit contractile activity induced by drugs with different modes of action; the drug does not affect the tone in bladder and urethra.

Administration, Oral↗
PubMed1978

Effects of prostaglandins on the smooth muscle of the urinary tract.

A short review is given of the effects of prostaglandins on the smooth muscle of the bladder, urethra and ureter. In several animal species and in man, prostaglandins of the E and F types contract the detrusor. The contractions develop slowly and are not affected by tetrodotoxin, phenoxybenzamine, or atropine, suggesting a direct effect on the smooth muscle cell. However, evidence is also available suggesting a role of the prostaglandins as modulators of transmitter release in the bladder. In animals as well as in man, urethral smooth muscle is contracted by prostaglandin F2alpha, but relaxed by prostaglandins E1 and E2. The smooth muscle of the ureter seems to react similarly, but published results vary. The detailed mode of action, and the role of prostaglandins in the control of activity in urinary tract smooth muscle remain to be established.

Animals↗
PubMed1978

Relaxing effects of Nifedipine on the nonpregnant human uterus in vitro and in vivo.

The effects of the calcium antagonist Nifedipine were investigated on isolated human myometrium and on uterine activity in healthy women during their first menstrual days. Nifedipine (0.01-1.0 microgram/ml) had a concentration-related inhibiting effect on spontaneous activity of the myometrial strips, and relaxed preparations contracted by potassium. In vivo, Nifedipine (20-30 mg) given orally, effectively and rapidly reduced uterine activity, decreasing both amplitude and frequency of uterine contractions, and reduced basal tone. A moderate increase in heart rate and a transient facial flushing were noted, but otherwise no side effects were observed. Calcium antagonists like Nifedipine represent a new approach to the problem of relaxing the myometrium, and might be an interesting therapeutic alternative in situations where inhibition of unwanted uterine activity is desirable.

Adult↗
PubMed1975

Primary charge separation in bacterial photosynthesis: oxidized chlorophylls and reduced pheophytin.

Bacteriopheophytin, the magnesium-free base of bacteriochlorophyll, undergoes reversible one-electron reduction in organic solvents to yield an anionic free radical with characteristic optical and electron spin resonance spectra. The reduction potential of bacteriopheophytin, E1/2 approximately --0.55 V against a normal hydrogen electrode, compared to E1/2 approximately --0.85 V for bacteriochlorophyll, renders it a likely electron acceptor in the primary charge separation of photosynthesis. Comparison of these data with picosecond optical changes recently observed upon pulsed laser excitation of bacterial reaction centers leads us to propose that bacteriopheophytin is indeed a transient electron acceptor and that the primary charge separation of bacterial photosynthesis occurs between the bacteriochlorophyll complex P870 and bacteriopheophytin to yield the radicals of the oxidized chlorophyll dimer cation and reduced pheophytin anion.

Bacteriochlorophylls↗
PubMed1974

The cation radicals of free base and zinc bacteriochlorin, bacteriochlorophyll, and bacteriopheophytin.

One-electron oxidation of zinc tetraphenylbacteriochlorin and its metal-free base yielded stable cation radicals. Electron spin resonance hyperfine splittings were assigned by selective deuterations. These results indicate that the protons of the saturated rings of the bacteriochlorins carry large spin densities, in accord with molecular orbital calculations. Comparison in vitro of the optical spectra of bacteriochlorins and their cation radicals with those of bacteriochlorophyll show close correspondence and suggest that the electron spin resonance data from the former may also prove a guide to the biological molecule. The surprising similarity in properties between the radicals of free base and zinc bacteriochlorins is maintained in the chlorophylls: cation radicals of bacteriopheophytin and methyl pheophorbide (the free bases of bacteriochlorophyll and methyl chlorophyllide, respectively) exhibit electron spin resonance properties similar to those of their magnesium-containing derivatives. The possibility that metal-free chlorophylls participate in photosynthesis is discussed.

Journal Article↗
PubMed1971

Compounds I of catalase and horse radish peroxidase: pi-cation radicals.

Two-electron oxidation of cobaltous octaethylporphyrin [Co(II)(Et)(8)P] yields a stable pi-cation radical [Co(III)(Et)(8)P](2+.), the optical spectrum of which exhibits spectral changes dependent upon the nature of the counterion. Comparison of these spectra with those of Compounds I of horseradish peroxidase and catalase leads us to propose that these Compounds I contain a pi-cation radical of the heme prosthetic group. This proposal explains the oxidation level, optical spectra, and stability of the primary compounds without recourse to properties such as stoichiometric mixtures of special porphyrins, stable Fe(V) porphyrins, or unique conformers of heme porphyrins. Explanations are advanced to account for the missing electron spin resonance signal of Compound I of horseradish peroxidase.

Catalase↗