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Biomedical subjects

J Hahn

Publications and source records attributed to J Hahn.

At least 109 records · Page 6Linked to original sources
PubMed1990

A model for occupational injury surveillance by occupational health centers.

Injuries account for more than 90% of the reported work-related health problems in the United States. However, a complete and standardized reporting system for occupational injuries does not exist in this country. This paper describes the first year's experience of a clinic-based occupational injury surveillance system involving occupational medicine clinics. During 1988, health and hazard information was collected on 14,156 work-related admissions. An analysis of these cases showed that most patients received care for minor trauma, with 78.4% of the cases classified as cuts or lacerations, sprains or strains, or contusions. Overall, 53.8% of the cases were caused by metal items, boxes, machines, or working surfaces. These preliminary results support the feasibility of conducting clinic-based occupational injury surveillance as a means of assisting employers with the control of work-related conditions.

Adult↗
PubMed1989

[Evaluation of inflammatory reactions following cataract surgery].

Following cataract extraction 179 patients were examined with a slit-lamp using focal and specular illumination. 163 of them had received an intraocular lens (IOL). The cells (granulocytes) and flare-up in the anterior chamber decreased during the first postoperative days, while the cellular growth on the IOLs (macrophages) did not decrease in the same period. No correlations could be found between the cells, the flare-up in the anterior chamber, and the cellular growth on the IOLs. All three seem to be independent inflammatory reactions that occur following cataract extraction.

Anterior Chamber↗
PubMed1989

[Preservation by deep freezing of oocytes and embryos].

Although cryopreservation experiments with mammalian embryos have been performed for more than 30 years, definite progress was only achieved in the seventies. Investigations with mouse embryos have mainly contributed to the establishment of cryopreservation procedures for livestock embryos. Today the freezing of sheep and cattle embryos is applied to practice, but still transfer results range about 10% to 15% below comparable results obtained from transfer with fresh embryos. Procedures for the cryopreservation of mammalian oocytes and subsequent in-vitro fertilization of frozen/thawed oocytes are just being developed. Until now, only in the mouse a reproducable method for this purpose has been found. Meanwhile children were born from human in-vitro fertilization programs after cryopreservation of oocytes as well as embryos, although the cryopreservation of human embryos is facing major ethical objections.

Animals↗
PubMed1989

[Gene transfer in laboratory animals].

Describing purpose and method of genetransfer by pronuclear microinjection comprehensively application on laboratory animals are reviewed. Experiments on the production of rabbits and mice transgenic for several uteroglobin-hybrid-genes (B2B3UG CAT; H/B/72/CAT; UG TAg; UG 11.8) were performed and resulted in four rabbit fetuses and one stillborne rabbit transgenic for UG TAg and one mouse transgenic for UG 11.8. These experiments are part of investigations on uteroglobin as a model of geneexpression regulated by steroid hormones.

Animals↗
PubMed1989

[Limits and risks of biotechnology in veterinary medicine from the viewpoint of the reproductive biologist].

New biotechnical methods in reproduction have been introduced in animal breeding via embryo transfer. There are no serious objections against these methods as long as the variety of species is reassured and the animal protection law is considered. More substantial objections exist against genetic engineering methods which alter the genome of animals. Beside for legal protection there is a strong public demand for the adequete awareness and responsibility of scientists who are active in this field. Comprehensive information on such research projects can lead to a better understanding of the aims and methods and might, therefore, help to reduce inadequate apprehensions.

Animals↗
PubMed1988

Laboratory and clinical variables to predict outcome in hemolytic-uremic syndrome.

To develop a guide to the prognosis of children with hemolytic-uremic syndrome, we reviewed the medical records of 78 patients with this diagnosis seen at The Children's Hospital, Boston, from 1976 through 1986. Two outcome groups were defined as follows: a "good outcome" group, which contained 6 patients with no serious sequelae at hospital discharge, and a "bad outcome" group, which contained 12 patients who died, had chronic renal failure, or had central nervous system sequelae at hospital discharge. Differences between the two groups in routine laboratory tests available within 48 hours of admission were identified by bivariate analysis. Using serum calcium (less than or equal to 2 mmol/L) plus urine output (less than 0.4 mL/kg/h) over a 24-hour period as a test to predict outcome, we identified patients who died, had chronic renal failure, or had serious central nervous system sequelae, with 75% sensitivity, 98% specificity, and 90% positive predictive value.

Adolescent↗
PubMed1988

Subdural electrodes in the evaluation for epilepsy surgery in children and adults.

To evaluate the utility and safety of chronic extraoperative subdural EEG and functional localization studies in children compared to adults, we studied 61 patients each of whom had similar evaluations for epilepsy surgery, regardless of age. The 23 children and adolescents (3 to 18 years old) and the 38 adults (20 to 41 years old) each had several days and nights of extraoperative EEG from scalp and chronically-implanted subdural electrodes, and the same percentage of children and adults also had functional localization studies including cortical electrical stimulation. The methods and results of these studies and of the subsequent resections did not differ between the two groups, and they both had similar rate of complications and similar incidence of good outcome. The subdural technique was as effective and well-tolerated in children and adolescents as in adults. Other invasive EEG techniques have not yet been systematically compared between children and adults, but the subdural technique, at least, appears to be suitable for patients over a wide age range.

Adolescent↗
PubMed1988

ENG-MRI correlates in cerebellar oculomotor dysfunction.

This study correlates ENG and MRI findings in six patients with cerebellar eye movements. For each subject, both tests independently support the presence of a cerebellar tract abnormality. In two patients, MRI studies confirmed the site of cerebellar dysfunction previously demonstrated by ENG. Although the number of patients is small, the strong correlation (100%) indicates that ENG remains a sensitive method for detection and localization of the origin of cerebellar eye movements. The physiologic information provided by ENG is supported anatomically by MRI. The cerebellar eye movement abnormalities are briefly reviewed.

Adolescent↗
PubMed1987

Electrophysiologic pathologic correlations in patients with complex partial seizures.

We studied interictal activity and site of ictal onset in 26 patients with complex partial seizures of temporal lobe origin. All patients had prolonged electrocorticographic recordings from subdural electrode arrays placed both over the convexity and beneath the temporal lobe. We found a significant correlation between the epileptogenic focus and the type of pathologic lesion found at time of surgery. Macroscopic lesions strongly tended to have an epileptogenic focus on the lateral surface of the temporal lobe; patients with only microscopic abnormalities tended to have an epileptogenic focus in the mesial/basal region of the temporal lobe.

Brain Mapping↗
PubMed1987

Isolation and characterization of Tn917lac-generated competence mutants of Bacillus subtilis.

We isolated 28 mutants of Bacillus subtilis deficient in the development of competence by using the transposon Tn917lacZ as a mutagen. The mutant strains were poorly transformable with plasmid and chromosomal DNAs but were normally transducible and exhibited wild-type resistance to DNA-damaging agents. The mutations were genetically mapped, and the mutants were characterized with respect to their abilities to bind and take up radiolabeled DNA. All were defective in uptake, and some failed to bind significant amounts of DNA. The abilities of the mutant strains to resolve into two buoyant density classes on Renografin gradients were studied. Most resolved normally, but several banded in Renografin only at the buoyant density of noncompetent cells. The genetic mapping studies and the other analyses suggested that the mutations define a minimum of seven distinct com genes.

Bacillus subtilis↗
PubMed1987

Expression of competence genes in Bacillus subtilis.

A set of competence (com) mutants of Bacillus subtilis was constructed by using Tn917lacZ as a mutagen. In about half of the mutants, the promoterless lacZ element on the transposon was placed under control of putative com promoters. Expression of the mutant com genes was studied by using the beta-galactosidase tag. Two of the mutant genes (those represented by com-124 and com-138) were expressed early in the growth cycle in all of the media tested and were not dependent on the spo0A or spo0H product for expression. The remaining mutants, which represented a minimum of four additional genes, expressed beta-galactosidase in stationary phase during the period in which competence developed. We conclude that expression of com genes is probably regulated transcriptionally and in a growth stage-specific manner. Expression of these genes was also dependent on growth in competence medium and, like competence development, required the presence of glucose and was dependent on the spo0H products. The dependence on the spo0A gene product was partially bypassed by the abrB703 mutation. These effects were qualitatively equivalent to those on competence development. The latter was dependent on spo0A and spo0H, and the spo0A dependency was partially suppressed by abrB703. Several of the mutants were still capable of resolution into light and heavy buoyant density cell fractions when grown in competence medium. All of these expressed beta-galactosidase to a greater extent in the light fraction, showing that expression of these com genes was cell type specific. Development of competence was not markedly affected by mutations in spo0B, spo0E, spo0F, spo0J, or sigB, the structural gene of sigma 37.

Bacillus subtilis↗
PubMed1987

The source of 'paradoxical lateralization' of cortical evoked potentials to posterior tibial nerve stimulation.

We report the potentials elicited by posterior tibial nerve stimulation and recorded simultaneously from the scalp and from electrodes within the interhemispheric fissure. The primary cortical potential was recorded from cortex contralateral but from scalp ipsilateral to the stimulated nerve. The scalp recordings thus demonstrated "paradoxical lateralization" as reported previously, and the similar morphology of the scalp and contralateral cortical recordings confirm that this "paradoxical lateralization" is most likely the result of a horizontal dipole located within the interhemispheric fissure.

Adolescent↗
PubMed1987

Clinical outcome after complete or partial cortical resection for intractable epilepsy.

This is the first epilepsy surgery series to analyze the definition of "completeness" of resection, based solely on results of chronic scalp and subdural EEG recording. When patients had complete removal of all cortical areas with ictal and interictal epileptiform discharges, the clinical outcome was usually good. When areas with epileptiform discharges were left behind, good outcome was significantly less frequent. This correlation between complete resection and good outcome was independent of the presence or absence of CT-detected structural lesions or sharp waves on post-resection electrocorticography. These results support completeness of resection, defined by prolonged extraoperative EEG, as an important factor in seizure surgery.

Adolescent↗