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Biomedical subjects

J Hahn

Publications and source records attributed to J Hahn.

At least 127 records · Page 7Linked to original sources
PubMed1986

In vitro fertilization and embryo transfer of pre-ovulatory rabbit oocytes.

The objective of this study was to develop an effective and successful technique of in vitro fertilization in rabbits that could lead us to start treatment of infertile couples by using extracorporal fertilization. Pre-ovulatory oocytes were harvested from follicles of virgin does 9 h after induction of ovulation by hCG injection, and incubated with in vivo capacitated sperm for 5 h. An 82% in vitro fertilization rate was achieved. The fertilized ova were cultivated for an additional 20, 44 and 68 h, and until they reached the hatched blastocyst stage. Most of these embryos (439) were transferred to 42 pseudopregnant recipients, asynchronous in the sense that they had been given hCG injections 0, 6, 12, 18, 24, 36 and 42 h later than the rabbits from which the ova had been obtained. With this type of synchronicity implantation rates of 31, 78, 52, 33, 52, 33, 51 and 10% were achieved, respectively. One hundred and twenty-eight embryos were not transferred to recipients but cultured in Ham's F-10 medium supplemented with 20% FCS. 77% of these embryos reached the stage of hatched blastocyst. A total of 143 young were born after 28-32 days of gestation and all are fertile till the third generation. Our results were obtained in a consecutive series of experiments, and demonstrated that in vitro fertilization can be made to work quite well in the rabbit, which in the early stages of embryogenesis has sufficient similarity to the human to make it a useful model for those wishing to acquire techniques applicable to human fertilization in vitro and embryo transfer.

Animals↗
PubMed1986

Basal temporal language area demonstrated by electrical stimulation.

We report on a 38-year-old patient with intractable complex partial seizures originating in the dominant left medial temporal region. In the work-up for seizure surgery, arrays of subdural electrodes were placed, and electrical stimulation revealed marked language interference in a 2 X 2-cm area in the left basal temporal fusiform gyrus (3.5 to 5.5 cm posterior to the temporal tip). Complete receptive and expressive aphasia, inability to repeat, agraphia, and alexia were elicited, but visual memory was preserved, and no constructional apraxia was noted. Stimulation of the basal temporal gyrus at lower stimulus intensities produced a relatively selective and severe anomia.

Adult↗
PubMed1986

Electrical stimulation of Wernicke's area interferes with comprehension.

Arrays of subdural electrodes were placed over the lateral convexity of the dominant hemisphere for propositional language in four patients with epilepsy as part of an evaluation prior to cortical resections. Stimulation was performed over several days. When we stimulated the posterior temporal language area, reading and comprehension of complex verbal information were impaired, but comprehension of nonverbal and simple verbal data was not affected. Impairment produced by stimulation seemed to be due to language comprehension difficulties, rather than impaired praxis or initial word storage.

Adolescent↗
PubMed1985

Analysis of plasmid deletional instability in Bacillus subtilis.

Using a model system, we have studied deletion formation in Bacillus subtilis. When the staphylococcal plasmids pSA2100 (7.1 kilobases) and pUB110 (4.5 kilobases) were ligated to one another at their unique XbaI sites and transformed into either rec+ or recE4 strains of B. subtilis, an intramolecular recombination event usually occurred. Two plasmids, one of 2.6 kilobases and the other of 9.0 kilobases, were consistently isolated and shown by restriction enzyme analysis to be derived by recombination occurring in the pSA2100-pUB110 cointegrate. Analysis of the sequence of the junctions of the recombinant plasmids and of the crossover regions of the parental plasmids suggested that a reciprocal, conservative, intramolecular recombination event had occurred between short 18-base-pair homologous sequences that were oriented as direct repeats and bounded by regions of dyad symmetry. Evidence is presented that the above illegitimate recombination event is biased to occur intramolecularly and that randomly chosen direct repeats of either 22 or 29 base pairs are not sufficient to support recombination. The recombination event occurs in recA1, recB2, recD3, recE5, recL16, recM13, polA59, polA13, uvr-22, uvr-13, and stb mutants of B. subtilis and does not require that the competent state be established.

Bacillus subtilis↗
PubMed1985

Ipsilateral trigeminal sensory responses to cortical stimulation by subdural electrodes.

Twelve patients with medically intractable epilepsy had plates of chronic subdural electrodes placed over the lateral and basal cortical hemispheres during evaluations for surgical therapy. During cortical stimulation, ipsilateral sensations involving any of the branches of the trigeminal nerve were noted in the eye, face, and mouth. Some responses could have been due to dural or direct trigeminal nerve trunk stimulation, but others were probably due to electrical stimulation of trigeminal fibers accompanying the pial-arachnoidal vessels. These fibers had been demonstrated in animals, but not in humans.

Adolescent↗
PubMed1984

Integrating library services and continuing education.

This paper presents an innovative integration of library services and continuing education (CE). While print material is an important continuing education information source for physicians, its volume is overwhelming. Librarians have developed the use of a variety of methods, including online data bases such as MEDLINE, to simplify and expedite access to printed information. Combining a library information delivery system with formal continuing education course activities can enhance the educational potential of two popular learning methods.

Data Collection↗
PubMed1984

In vitro fertilization and embryo transfer of rabbit oocytes collected at different times after P-LH injection.

No difficulties were encountered in the collection of preovulatory oocytes from the follicles of rabbits. A mean of 11.7 ova were recovered by follicle puncture. In vitro fertilization of the preovulatory oocytes was influenced by their stage of maturation. The highest fertilization rate (83%) was obtained using oocytes collected 9 h after injection of P-LH shortly before ovulation. Only after pretreatment with FSH-P was it possible to fertilize some preovulatory oocytes without administration of P-LH. In vitro fertilized preovulatory oocytes developed in culture. After 4-5 days 47-64% reached the blastocyst stage; the corresponding rate for in vivo fertilized oocytes was 48%. After transfer of in vitro fertilized preovulatory oocytes 19-28% implantations were achieved.

Animals↗
PubMed1984

Recording of auditory evoked potentials in man using chronic subdural electrodes.

With the aid of chronic subdural electrodes we have been able to record from the posterior banks of the sylvian fissure, auditory evoked potentials (AEPs) that had morphologies and peak latencies compatible with the primary AEPs described by Celesia and Puletti (1969). These AEPs had amplitudes that were not only affected by the side of stimulus presentation but were maximal in an area close to the primary auditory cortex. The AEPs also displayed an extremely steep spatial gradient and were not altered by pentobarbitone sodium and nitrous oxide anaesthesia. Together, these properties suggest that these subdurally recorded potentials are near-field evoked potentials from the primary auditory cortex. The focal nature of these potentials also allows them to be used as effective electrophysiological tools for localization of the primary auditory cortex in patients.

Adolescent↗
PubMed1984

The location of speech and writing functions in the frontal language area. Results of extraoperative cortical stimulation.

In three patients stimulation of the frontal speech area resulted in one or more of the following symptoms: speech arrest, writing arrest, or impaired rapid alternating movements of the tongue, fingers or toes. Speech arrest could be altered at individual points either with or without impairment of rapid movements or writing, but writing was not impaired without concomitant difficulties with either speech or rapid finger movements. Our data suggest that the frontal speech area may function to integrate complex motor functions, some speech related and others not. We also confirm previous conclusions that Exner's writing centre is not separate from Broca's area and that the writing defect in Broca's aphasia can occur without involvement of the motor strip.

Adult↗
PubMed1984

Cortical afterdischarge and functional response thresholds: results of extraoperative testing.

We have evaluated the afterdischarge thresholds and functional response thresholds in 21 patients with chronically implanted arrays of subdural electrodes. Afterdischarge thresholds varied from 2 to greater than 15 mA over the tested cortex, by as much as 12 mA in individual patients, and by as much as 12 mA between adjacent electrodes. Thresholds for functional alteration varied from 2 to 15 mA in tested cortex, by as much as 9.5 mA in individually tested patients, and by as much as 6.5 mA between adjacent electrodes. We conclude that the optimal localization of functional cortical areas requires different stimulation intensities at different points. The use of too high an intensity would produce afterdischarges at some positions. The use of too low an intensity would falsely make others appear functionally "silent."

Adolescent↗
PubMed1984

Transient neuropsychological abnormalities (including Gerstmann's syndrome) during cortical stimulation.

A patient with intractable partial seizures was intensively studied before surgical removal of the epileptogenic focus. A subdural electrode array was surgically placed over the left temporoparietal cortex to better localize the epileptogenic focus and localize cortical function. In addition to speech and sensory findings, acalculia, agraphia, right-left confusion, and finger agnosia were transiently produced by electrical stimulation in the perisylvian area. These findings and their relationship to the controversy surrounding Gerstmann's syndrome are discussed.

Adolescent↗
PubMed1983

Cortical somatosensory evoked potentials in response to hand stimulation.

Somatosensory evoked potentials were recorded from chronically implanted subdural electrodes in six patients with intractable seizures. The following conclusions were reached: 1) The initial cortical negativity-positivity (N1 with a latency of about 20 msec and P2 with a latency of about 24 msec) recorded in the postcentral area was an expression of the classical primary surface positivity, but N1 was generated by the posterior pole of an early horizontal dipole in area 3b, and P2 was generated by the positive pole of a slightly delayed vertical dipole in area 1 and 2.2) P2 permitted the most accurate localization of the primary somatosensory area. 3) No potentials were elicited in the primary somatosensory area by stimulation of the ipsilateral hand. 4) No cortical potentials were seen at stimulation intensities below the sensory threshold. The cortical distribution of evoked potentials evoked by weak and strong intensities had significantly different distribution. 5) The recovery function of cortical evoked potentials showed a U-curve with an early period of facilitation (10 to 30 msec) followed by a prolonged period of subnormality which peaked at about 50 msec. The recovery curve at different cortical loci differed.

Cerebral Cortex↗