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Biomedical subjects

J A Kahn

Publications and source records attributed to J A Kahn.

At least 55 records · Page 3Linked to original sources
PubMed1991

Casebook: a system for tracking clinical encounters.

Casebook is a clinically oriented database, written in MUMPS, and designed for recording the clinical encounters of medical students at Harvard Medical School. Its main goals are to 1) increase student use of computer technology, 2) help faculty evaluate the diversity of clinical experiences on their service, 3) provide data to the faculty on the "typical" experience of medical students on their service to aid in the evaluation of the curriculum and, 4) provide report-generation capabilities for the students to improve dialog with their preceptors. Students are able to enter information on "Problems" and "Procedures" selecting from a pop-up menu of medical terms or by entering free text. Casebook is currently in use in the Medicine, OB/GYN, Pediatric and Ambulatory rotations. At sites where the faculty take an active interest in the use of Casebook students perceive it to be valuable and subsequently use it more frequently. It is currently being expanded for use by medical students in their second, third, and fourth years of school.

Attitude to Computers↗
PubMed1990

[Freezing, thawing and transfer of human embryos].

We present our experience of cryopreservation of human embryos from 1 July 1987 to 1 July 1989. During this period, 667 in vitro fertilizing cycles were completed. In 173 (26%) of these cycles, a total of 805 surplus embryos were cryopreserved. 516 embryos were thawed and 247 of these were transferred to the uterine cavity in a total of 110 replacement cycles. This resulted in 22 (20%) pregnancies in which a total of 28 gestational sacs could be verified by ultrasound. Seven of the pregnancies aborted spontaneously in the first trimester and one pregnancy was ectopic. By 1 July 1989, five singleton pregnancies were in progress and 13 babies had been born from nine deliveries (one set of triplets and two sets of twins). 25% of the patients whose embryos were cryopreserved became pregnant in the in vitro fertilizing cycle after replacement of fresh embryos.

Adult↗
PubMed1990

IVF in the Nordic countries 1981-1987: a collaborative survey.

This report concerns the development of in-vitro fertilization (IVF) in the Nordic countries from the start of 1981 to January 1, 1988. All the 24 clinics in the Nordic countries which treat infertile couples with IVF participated in the study. The number of IVF clinics in the Nordic countries has increased from four in 1981 to 24 in 1987. In the same period, the number of people who spent some of their professional time as a part of an IVF team increased from 17 to 150. The majority of the clinics (19) based their activity mainly on governmental funding, while five of the clinics were private. During the period from 1981 to 1987, the Nordic clinic changed their methods of oocyte retrieval. In 1981, all oocyte retrievals were done using laparoscopy. Transvesical, ultrasound-guided follicular punctures domainated in 1985 and transvaginal ultrasound-guided punctures were used in 81.5% of the retrievals in 1987. A total of 852 pregnancies were reported. Of these, 313 (36.8%) were miscarriages, including 66 (7.7%) ectopic pregnancies. At January 1, 1988, 433 babies had been born, including 48 sets of twins, 14 sets of triplets and two sets of quadruplets. This gave a multiple birth rate of 18.2%. Premature births (less than 36 weeks of gestation) were reported in 14.6% of the births. Five babies (1.1%) died in the neonatal period and five (1.1%) were born with various types of malformation. One hundred and eight-eight pregnancies were in progress at January 1, 1988.

Adult↗
PubMed1989

[Chlamydia trachomatis and infertility in women].

Humoral IgG antibodies to Chlamydia trachomatis were determined in 131 infertile women, 102 with fallopian tube disorders and 29 with other infertility diagnosis and normal fallopian tubes. Chlamydia antibodies were identified significantly more often among women with abnormal fallopian tubes (89%) than among women with other infertility diagnosis (48%). Among Chlamydia antibody positive subjects the mean index was significantly higher among subjects with tubal disorders than among subjects with normal tubes (3,4 versus 2,2; p less than 0.01). This study indicates a close association between anti-bodies to Chlamydia trachomatis and tubal infertility.

Adult↗
PubMed1989

A spleen pregnancy.

Non-tubal ectopic pregnancy is very rare. We report a case of spleen pregnancy, difficult to recognize clinically. The tests and investigations which led to the diagnosis and treatment are described briefly.

Adult↗
PubMed1989

Cytoplasmic pH is regulated in isolated avian osteoclasts by a Cl-/HCO3- exchanger.

Osteoclast resorb bone in an acid compartment formed by the bone-attachment site. The low pH of the resorption compartment provides a lysosome-like milieu suitable for acid proteases to degrade collagen. Solubilization of the hydroxyapatite that makes up bone mineral consumes about 2 moles of protons per moles of calcium dissolved, requiring a massive proton flux to maintain a low pH in the resorption compartment. In order to determine how the osteoclast maintains a physiological cytoplasmic pH while secreting massive amounts of acid, we studied the intracellular pH of osteoclasts using esterified fluorescein derivatives while controlling the electrolyte composition of the medium. The principal finding is that osteoclasts have a high capacity for chloride/bicarbonate exchange which enables them to maintain normal intracellular pH in the face of a large loading of base equivalents. Thus, the overall process of proton secretion during bone resorption is similar to the polarized acid elimination by renal epithelia, involving a proton pump on one surface of the cell, and a Cl-/HCO3- exchange to maintain cytoplasmic pH.

Acid-Base Equilibrium↗
PubMed1988

Intrauterine insemination: a European collaborative report.

This report summarizes the data collected in the European Collaborative Report on intrauterine insemination (IUI) with pretreated sperm. A questionnaire concerning methods and results of IUI was sent to European infertility clinics and evaluable data were obtained from 29 of these clinics. A total of 196 pregnancies was reported from a total of 20 clinics. Pregnancy rates per treatment cycle were on average 7.4% of all male infertility, 10.8% for infertility due to hostile cervical mucus and 12.9% for idiopathic infertility, giving an overall pregnancy rate per treatment cycle of 8.4%. The clinical abortion rate was on average 12.2%. The mean number of years of primary infertility in the patient group of the clinics reporting pregnancies was 4.8 years and the mean number of years of primary infertility in the patient group conceiving was 5.2 years. A total of 127 births was reported with a sex ratio (male/female) of 0.512. One congenital malformation was reported. In many clinics, treatment of male infertility with IVF or IUI gave comparable results per treatment cycle. No single factor in the procedure for performing IUI was identified accounting for the different pregnancy rates obtained in the clinics included in this study.

Adult↗
PubMed1982

The neuromuscular basis of swimming movements in embryos of the amphibian Xenopus laevis.

When removed from their egg membranes, Xenopus embryos can swim. High-speed cinematography shows that, in swimming, lateral undulations pass rostro-caudally down the body. The swimming rhythm period is 40-100 ms. In swimming, electrical activity in myotomal muscles alternates on opposite sides of a segment and sweeps rostro-caudally in ipsilateral myotomes. Myotome muscle physiology was examined. Muscle fibres are electrically coupled to each other, and the fibres are able to spike. The possible role of a myotomal conduction pathway in swimming is discussed.

Animals↗
PubMed1982

The central nervous origin of the swimming motor pattern in embryos of Xenopus laevis.

Rhythmic motor nerve activity was recorded in stage 37/38 Xenopus embryos paralysed with curare. The activity was similar to the swimming motor pattern in the following ways: cycle period (40-125 ms), alternation of activity on either side of a segment, rostro-caudal phase lag. Episodes of rhythmic motor activity could be evoked by stimuli that evoke swimming and inhibited by stimuli that normally inhibit swimming. On this basis we conclude that the swimming motor pattern is generated by a central nervous mechanism and is not dependent on sensory feedback. In addition to the swimming pattern, another pattern of motor activity ('synchrony') was sometimes recorded in curarized embryos. In this, the rhythmic bursts on either side of a segment occurred in synchrony, and the rhythm period (20-50 ms) was half that in swimming. This was probably not an artifact of curarization as there were indications of a similar pattern in uncurarized embryos. Its function remains unclear.

Animals↗
PubMed1982

The neuromuscular basis of rhythmic struggling movements in embryos of Xenopus laevis.

Xenopus embryos struggle when restrained. Struggling involves rhythmic movements of large amplitude, in which waves of bending propagate from the tail to the head. Underlying this, electrical activity in myotomal muscles occurs in rhythmic bursts that alternate on either side of a segment. Bursts in ipsilateral segments occur in a caudo-rostral sequence. Curarized embryos can generate motor nerve activity in a struggling pattern in the absence of rhythmic sensory stimulation; the pattern is therefore produced by a central pattern generator.

Animals↗