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Biomedical subjects

M Tucker

Publications and source records attributed to M Tucker.

At least 73 records · Page 4Linked to original sources
PubMed1990

Behavior of acyl carrier proteins on western blots.

Acyl carrier proteins (ACPs) from Escherichia coli and Euglena were analyzed on Western blots using rabbit antibodies raised against E. coli ACP. Euglena ACP, unlike that from E. coli, behaves upon electrophoresis under denaturing conditions as its size would predict. Oligomeric forms of both ACPs were evident on Western blots, but the bacterial ACP had more tendency to aggregate. That the oligomeric forms were not due to impurities was shown by their regeneration from low-Mr protein, reaction with antibodies isolated from low-Mr protein, and by molecular weight determination of the ACP by low-angle laser light scattering.

Acyl Carrier Protein↗
PubMed1990

Ethanol inhibits zymosan-stimulated and enhances nonstimulated platelet-activating factor production in a clonal macrophage cell line.

Ethanol was examined for its effects on zymosan phagocytosis and synthesis of platelet-activating factor (PAF) using a clonal macrophage cell line. PAF, identified as 1-O-alkyl-2-acetyl-sn-glycerol-3-phosphocholine, is a biologically active ether phospholipid produced by various cells types. PAF also activates a variety of inflammatory cells including the cells which produce PAF. Ethanol at 20 to 100 mM inhibited phagocytosis of unopsonized zymosan and concomitantly decreased PAF concentration in the stimulated macrophages. In contrast, in cells not stimulated with zymosan, ethanol increased the recoverable PAF. Ethanol, at 100 mM, inhibited the uptake of exogenous PAF but did not alter the distribution of PAF metabolites in the clonal macrophage cell line. The effect ethanol has on PAF synthesis appears dependent on the activation state of the cell. Two situations were identified in this study: 1) one linked to phagocytosis or cell stimulation which is inhibited by ethanol, and 2) PAF synthesis which is not dependent on overt cell activation that is enhanced by ethanol.

Animals↗
PubMed1989

One hundred pregnancies after treatment with pulsatile luteinising hormone releasing hormone to induce ovulation.

OBJECTIVE: To review treatment with pulsatile luteinising hormone releasing hormone in infertile women who do not ovulate and are resistant to clomiphene after 100 pregnancies achieved with this treatment. DESIGN: Retrospective analysis of 146 courses of treatment over 434 cycles. SETTING: Infertility clinic. PATIENTS: 118 Women whose failure to ovulate was due to idiopathic hypogonadotrophic hypogonadism (n = 39), amenorrhoea related to low weight (n = 17), organic pituitary disease (n = 15), or polycystic ovaries (n = 47). INTERVENTIONS: Dose of 15 micrograms luteinising hormone releasing hormone/pulse subcutaneously every 90 minutes given with a miniaturised pump throughout cycle monitored by ultrasound. Women with hypogonadotrophic hypogonadism had 48 courses, women with amenorrhoea related to low weight 23, women with organic pituitary disease 18, and women with polycystic ovaries 57. END POINT: Follow up of 100 pregnancies achieved in 77 women during six years after introducing treatment. MEASUREMENTS and main results--One hundred pregnancies (seven multiple, 28 miscarriages). Cumulative rates of pregnancy were 93-100% at six months in women with idiopathic hypogonadotrophic hypogonadism, amenorrhoea related to low weight, and organic pituitary disease. In women with polycystic ovaries (cumulative rate of pregnancy 74%) adverse prognostic factors were obesity, hyperandrogenism, and high luteinising hormone concentrations, which were also associated with a high rate of early pregnancy loss. CONCLUSIONS: Treatment with pulsatile luteinising hormone releasing hormone is safe, simple, and effective, and the preferred method of inducing ovulation in appropriately selected patients. Compared with exogenous gonadotrophin treatment there is little need for monitoring, no danger of hyperstimulation, and a low rate of multiple pregnancies.

Abortion, Spontaneous↗
PubMed1988

Synergism of pulsatile LHRH therapy with oral clomiphene treatment.

Eighteen anovulatory patients who were resistant to induction of ovulation with clomiphene and with subcutaneous pulsatile LHRH were treated with these two agents given simultaneously. Twelve of the 14 patients with polycystic ovary syndrome, 1 patient with weight-related amenorrhea and 1 of 3 patients with intrinsic pituitary disease responded to the combined treatment. Serial determinations of serum gonadotropin concentrations showed that these remained unchanged by clomiphene treatment, suggesting a direct action on the ovary. For induction of ovulation for in vivo fertilization, the combination of oral clomiphene with subcutaneous pulsatile LHRH is worth trying before proceeding to intravenous LHRH or hMG therapy.

Administration, Oral↗
PubMed1986

Different calcium dependence of the capping and cutting activities of villin.

The concentration of ionized calcium required for the capping of barbed filament ends by villin is about 4 orders of magnitude lower than that required for the cutting activity of villin. Capping was 50% complete at about 10-30 nM Ca2+, a level expected in resting cells, whereas the cutting rate was half-maximal at about 200 microM, making it possible to completely separate filament capping from filament cutting. Analysis of capping in terms of coupled equilibria between calcium binding to villin and calcium-villin binding to the barbed ends of actin filaments gives a value of 10(16)-10(17) M-2 for the product of the two binding constants. By comparison the binding constant reported for the rapidly exchanging calcium sites on villin is 2 X 10(5) M-1 and that for binding of calcium-saturated villin to barbed ends has a minimum value of 10(11) M-1 giving a product of 2 X 10(16) M-1. The close similarity of the two sets of values suggests that capping is regulated by the rapidly exchanging calcium sites on villin. In terms of coupled equilibria the calcium requirement for filament capping decreases with increasing concentrations of free villin. The scant information on the mechanism of cutting allows only an estimate of the maximal value for the calcium-binding constant of the site regulating cutting which is about 2-5 X 10(3) M-1. Cutting is followed by rapid capping of the newly released barbed ends.

Actins↗
PubMed1985

Successful pregnancies from the transfer of pronucleate embryos in an outpatient in vitro fertilization program.

Twenty-nine infertile women were given clomiphene citrate (100 mg/day, days 3 to 7), human menopausal gonadotropin (150 IU/day, days 7 to 12 or 13), and human chorionic gonadotropin (2000 IU) for the induction of ovulation. Eggs were collected by laparoscopy and preincubated for 6 hours before being cultured with spermatozoa for fertilization. Approximately 16 to 18 hours after insemination, the eggs that showed two pronuclei were transferred to the patient's uterus. As confirmed by the ultrasonic appearance of a gestational sac, six women who received pronucleate embryos became pregnant, and three pregnancies resulted in normal full-term deliveries. These results confirm that, unlike requirements for most laboratory and farm animals, the requirements of synchrony between the preimplantation human uterus and developing embryos are not very stringent. In vitro fertilization treatment procedures can thus be made simpler by the transfer of embryos at the pronucleate stage.

Adult↗
PubMed1984

Induction of ovulation with pulsatile luteinising hormone releasing hormone.

Ovulation was successfully induced with luteinising hormone releasing hormone in 28 women with hypothalamic amenorrhoea who had failed to respond to treatment with clomiphene. Luteinising hormone releasing hormone was administered in a pulsatile manner with miniaturised automatic infusion systems. The rate of ovarian follicular maturation, as monitored by serial pelvic ultrasonography, was similar to that observed in spontaneous cycles. Endocrine assessment by serial measurement of gonadotrophin, oestradiol, and progesterone concentrations showed hormone concentrations to be within the normal range. Intravenous treatment was required in only two patients, the remainder responding satisfactorily to subcutaneous infusion. All patients conceived within six cycles of treatment, and only one multiple pregnancy occurred.

Adult↗
PubMed1984

A miniature infuser for the pulsatile administration of LHRH.

This paper describes a compact, battery-powered infuser that is light, unobtrusive and simple to operate. A novel direct-drive method is used to deliver intermittent boluses of hormone at predetermined time intervals via a special prefilled syringe. Normal pregnancy rates were achieved in anovulatory women when infused with luteinising hormone releasing hormone (LHRH).

Biomedical Engineering↗
PubMed1984

The role of subcutaneous luteinising hormone releasing hormone in the induction of ovulation.

Induction of ovulation using pulsatile luteinising hormone releasing hormone (LHRH) has been performed in 53 anovulatory women who had previously failed to respond to clomiphene. Pelvic ultrasound imaging prior to treatment provided an accurate means of predicting the subsequent response to subcutaneous and intravenous therapy and was of particular value in differentiating patients with ovarian enlargement due to multiple intraovarian follicles. Subcutaneous administration was appropriate in the majority of patients. Thirty-eight conceptions have been confirmed.

Adult↗
PubMed1984

Ultrasound assessment of changes in the ovary and the uterus during LHRH therapy.

Twenty-seven women with secondary amenorrhoea have been treated with pulsatile subcutaneous luteinising hormone releasing hormone (LHRH). Serial ultrasonic observations of increasing follicular diameters and changes in the size of the uterus have been recorded. The rate of the increase of the diameter of dominant follicles in LHRH induced cycles is identical to that observed in women undergoing spontaneous cycles. An interesting correlation was observed between follicular diameter and uterine size. The correlation suggests that uterine size measured ultrasonically can be used as a bio-assay of follicular oestradiol production. Uterine growth continues throughout the luteal phase of conception cycles and can be used as a very early sign of pregnancy.

Adult↗