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Biomedical subjects

D Schaefer

Publications and source records attributed to D Schaefer.

At least 37 records · Page 2Linked to original sources
PubMed1995

Catechol interferes with TGF-beta-induced elimination of transformed cells by normal cells: implications for the survival of transformed cells during carcinogenesis.

We have recently shown that TGF-beta-treated normal fibroblasts are able to induce apoptosis of transformed fibroblasts, leading to their elimination. Here we describe a test system that allows the quantitative analysis of the elimination of G418-resistant transformed cells by TGF-beta-treated normal cells. This assay system was used to screen for substances that interfere with the elimination of transformed cells. Catechol and hydroquinone, but not resorcinol, were found to represent potent antagonists of TGF-beta-induced elimination of transformed cells by normal cells. Protection of transformed cells from negative effects derived from their cellular environment defines a hitherto unrecognized crucial mechanism for the survival of transformed cells. The protective effect of catechol as seen in this experimental system may act in concert with its co-carcinogenic and promoting activities during carcinogenesis.

Animals↗
PubMed1994

Stereotactic microresection of small cerebral vascular malformations (SCVM).

Between 1988-1993 we performed CT-stereotactic guided microsurgical resection as a one-session-procedure in 46 patients bearing small (< 30 mm) cerebral vascular malformations (SCVM). The location of the SCVM was deep subcortical in 38 patients, temporal medio- basal in 3 and brainstem in 5. The surgical technique intended to minimise invasiveness by reducing the operative approach to a size less than the diameter of the lesion concerned. The mean diameter of our SCVM's was 20 mm ranging from 10 to 30 mm. Histologically we found 23 arteriovenous malformations, 22 cavernous malformations and 1 capillary telangiectasia (capillary malformation). Clinical symptomatology consisted mainly of seizures, (progressive) neurological deficit and (minute) acute intracerebral bleeding. The SCVMs could be demonstrated by contrast-enhanced CT as well as by MRI. 15 of the AVM's revealed as angiographically occult. Complete microsurgical resection of the SCVM was accomplished in all cases with a surgical morbidity of 6.5% and no operative mortality. In 14 patients, most of them with initial acute intracerebral haemorrhage, the pronounced focal neurological deficit improved. During the follow-up period (1/2-5 years) no rebleeding occurred. As far as epileptic seizures were concerned 13 patients became seizure-free without anticonvulsants and 11 patients seizure-free with anticonvulsant, in the remaining 4 patients seizures were reduced in frequency.

Adolescent↗
PubMed1993

The economic effect of estrus synchronization in beef heifers on average weaning weight of calves.

Prostaglandin was used to induce estrus in 129 Hereford x Holstein heifers for artificial insemination. At the start of the breeding season heifers were observed twice daily and inseminated 12 hours after first being observed in estrus. On the morning of the sixth day of the breeding season all heifers not yet observed in estrus or inseminated were treated with prostaglandin (25 mg Lutalyse(R)). Observation was continued and heifers were bred 12 hours after first observed in estrus. Of the 129 heifers 33 were inseminated before prostaglandin treatment, the remainder of the heifers were bred within 4 days of treatment. Two heifers developed cysts and did not express estrus. First service pregnancy rates were 70% before treatment and 79% after treatment. All heifers were inseminated the first time within the first 10 days of the breeding season and 100 pregnancies occurred in the first 10 days of the season. As a result median days to pregnancy was 8. Calves were all weaned and weighed at approximately 150 days of age. These results were then used to model the economic impact of estrus synchronization of beef heifers on the increased weaning weights of their calves. Prostaglandin treatment altered the distribution of pregnancies and resulted in a cluster of conceptions from Day 7 to 10 of the breeding season with no conceptions from Day 11 to 19. In order to study the influence of estrus synchronization on weaning weights a simulation model was constructed. All heifers that conceived on the first service after prostaglandin were assigned an alternate date of conception from Day 7 to 21 of the breeding season with a random number generator. In this way a uniform random distribution of pregnancies over the first 21 days of the breeding season was constructed. An alternate calving date was then estimated using the known gestation length and this date was used to calculate the weaning weight of the calf using the known weight per day of age. The average weaning weight of the uniform random distribution was then compared to the synchronized distribution with Student's t -test. The simulation model was repeated 10 times and each time weaning weights of the uniform random distribution were significantly less than with the synchronization program (p<.01). At a value of $4.00 for prostaglandin and $1.76 for each kilogram of calf the average increase of 3.8 kgs in weaning weight per calf resulted in a return on investment of $1.92 for every dollar invested in prostaglandin.

Journal Article↗
PubMed1991

Stable transformation of the moss Physcomitrella patens.

We report the stable transformation of Physcomitrella patens to either G418 or hygromycin B resistance following polyethylene glycol-mediated direct DNA uptake by protoplasts. The method described in this paper was used successfully in independent experiments carried out in our two laboratories. Transformation was assessed by the following criteria: selection of antibiotic-resistant plants, mitotic and meiotic stability of phenotypes after removal of selective pressure and stable transmission of the character to the offspring; Southern hybridisation analysis of genomic DNA to show integration of the plasmid DNA; segregation of the resistance gene following crosses with antibiotic-sensitive strains; and finally Southern hybridisation analysis of both resistant and sensitive progeny. In addition to stable transformants, a heterogeneous class of unstable transformants was obtained.

Blotting, Southern↗
PubMed1991

Ossified mucin-secreting choroid plexus adenoma: case report.

This is the first report of a fully documented case of an ossified mucin-producing benign choroid plexus tumor. This was a chance finding in a man who complained only of posttraumatic low back discomfort. The ossification of the tumor appears to have been therapeutic. Mucin production may be a defense mechanism.

Adenoma↗
PubMed1991

Intervertebral disc injury complicating cervical spine trauma.

The incidence of acute herniated nucleus pulposus was determined in 55 patients with cervical spine trauma. A standardized protocol and a 1.5-T magnetic resonance image scanner was used to document a 42% incidence of acute herniated nucleus pulposus in patients studied within 72 hours of injury. The incidence of herniated nucleus pulposus was correlated with the patients' presenting neurologic status and mechanism of injury. The incidence of herniated nucleus pulposus was highest in patients with bilateral facet dislocations (80%) and anterior cord syndromes (100%). There was no statistically significant correlation between the incidence of herniated nucleus pulposus and patients' age or sex.

Adult↗
PubMed1991

Recurrent spinal cord tethering by sacral nerve root following lipomyelomeningocele surgery. Case report.

A 21-year-old woman had recurrent progressive weakness/hypesthesia and pain in both lower extremities. At the age of 5 and 19 years, she had undergone surgical resection of a lipomyelomeningocele at L5-S1. Surgical exploration revealed that the cord was tethered and pulled over to the side by an excessively short right S-1 nerve root. The contralateral L-5 and S-1 nerve roots were markedly stretched. Division of the right S-1 nerve root resulted in prompt disappearance of pain in the lower extremities and improvement in neurological function.

Adult↗
PubMed1991

[Fluoride accumulation of the surface enamel of primary tooth after supervised brushing with a low dose-fluoridated dentifrice].

The fluoride accumulation on the surface enamel of primary incisive using a low dosed fluoridated dentifrice (0.085% F) was determined in vivo in comparison with a placebo dentifrice within a longitudinal study. After 12 months supervised brushing the superior incisive of the preschool children used the fluoridated dentifrice show a fluoride concentration of 609 ppm, after 20 months 612 ppm fluoride. The fluoride concentration of the surface enamel of the placebo group was 380 (after 12 months) and 385 ppm fluoride (after 20 months). Presume the optimal caries prevention should not reach by only using the low dosed fluoridated dentifrice.

Child, Preschool↗
PubMed1991

[Caries protective effect of a NaF containing toothpaste with and without calcium carbonate polishing agent].

A caries preventive effect depending on the free fluoride concentration was registrated on rats using dentifrices with NaF or MFP (alone or in combination) despite the presence of CaCO3 as abrasive material because the composition of these dentifrices was changed. The free fluoride concentration of dentifrices had induced the accumulation of fluoride into enamel. The ionized fluoride content of NaF-dentifrices was unchanged for 3 years. MFP was hydrolized and had continuously released fluoride ions. The caries preventive effect which was increased by HCO3- was reproducible in correspondence with the fluoride concentration after the storage for two years.

Animals↗
PubMed1989

Evaluation of antibacterial sensitivity testing methods for methicillin-resistant Staphylococcus aureus in a dermatology outpatient population.

Over a period of one year, 1986-1987, 116 strains of Staphylococcus aureus were isolated from patients attending two outpatient dermatology clinics in Houston, Texas. The purpose of this study was to evaluate the adequacy of routine antibiotic sensitivity testing methods for detecting methicillin-resistant Staphylococcus aureus (MRSA). The Kirby-Bauer disk diffusion method was compared with a commercially available screening medium containing 6 micrograms/ml of oxacillin and 4% NaCl. The minimal inhibitory concentration (MIC) of methicillin, oxacillin, and oxacillin with 4% NaCl to S aureus using the agar dilution method was also determined. Approximately 90% of S aureus strains produced beta-lactamase and were resistant to penicillin and ampicillin. By disk diffusion, no strains were resistant to methicillin, though diameters of zones of inhibition were between 10 and 14 mm in seven strains. All strains proved to be sensitive to methicillin by MIC determinations and on the oxacillin-NaCl screening medium. The MIC of methicillin was 2.5 micrograms/ml for the majority of strains of S aureus, between 0.16 and 0.31 microgram/ml for oxacillin, and 0.08 to 0.16 microgram for oxacillin with 4% NaCl. We concluded that the incidence of MRSA in an outpatient dermatology population is low, and a combination of disk diffusion and oxacillin-NaCl screening is adequate for testing sensitivity.

Adolescent↗
PubMed1988

[Analysis of the periodical Strahlentherapie from 1920 to 1984].

The part of medical science, radiotherapy and radiology, and its outstanding publication organ, Strahlentherapie, in its development in the last sixty years is evaluated in form of a publication analysis. From every decennium the first five years from 1920 to 1984 are taken to analyse the articles by formal facts and contents. Especially the habit of citing is evaluated in detail. Dependences among the factors (especially time dependences) are worked out in detail.

Germany, West↗
PubMed1987

Basal cell epithelioma in black patients.

The occurrence of cutaneous carcinoma in black patients is an unusual phenomenon, with basal cell carcinoma being particularly uncommon. We present five cases of basal cell epithelioma in black patients collected from the Texas Medical Center to graphically illustrate the varied and often atypical clinical presentations of such tumors. This report supports recent series of basal cell epithelioma in black patients derived from retrospective chart reviews.

Adult↗
PubMed1985

Characterization of west nile virus persistent infections in genetically resistant and susceptible mouse cells. II. Generation of temperature-sensitive mutants.

Long-term persistent infections were established with the flavivirus, West Nile virus (WNV), strain E101, in embryofibroblast cultures derived from susceptible C3H/HE and congenic-resistant C3H/RV mice. Cultures were initially maintained by weekly subculture at 37 degrees, but at passage 6 sister cultures were shifted to 32 degrees. Virus progeny titers were observed to increase after the shift to 32 degrees indicating the possible presence of temperature-sensitive mutants. Temperature-sensitive mutants were found to arise in cultures of both susceptible and resistant cells. However, only in the resistant cultures did temperature-sensitive virus become the majority population. Temperature-sensitive mutants did not appear to be essential for either initiation or maintenance of WNV-persistant infections. The resistant cells appear to provide an environment which is advantageous for the amplification of temperature-sensitive mutants.

Animals↗
PubMed1985

Ultrastructural and immunofluorescent studies of acute and chronic lactate dehydrogenase elevating virus-induced nonparalytic poliomyelitis in mice.

Light microscopic, electron microscopic, and immunofluorescent studies have been performed on young C58/J mice following administration of cyclophosphamide and peripheral inoculation of the C strain of lactate dehydrogenase-elevating virus (LDV-C). Using special fixation techniques, all three types of studies were performed on the spinal cord tissues obtained from the same mice. LDV-C infection-specific immunofluorescence was detected in anterior horn neurons. Ultrastructurally, anterior horn neurons during the acute inflammatory phase of the disease were characterized by various degrees of chromatolysis, an increase in the number of lamellar inclusion bodies, and extensive membrane proliferation of perinuclear endocytoplasmic reticulum. A chronic vacuolar appearance of the anterior horn was due to intraneuronal vacuolation as well as vacuolation of the neuropil; these changes may have been due to expansion of proliferated intracytoplasmic membranes and/or focal ischemia secondary to the acute inflammatory response. Direct evidence was obtained that indicated the cytopathology was not immune mediated in that highly poliomyelitis-susceptible 18-month-old C58/J mice developed severe paralysis without inflammation of the spinal cord when treated with cyclophosphamide before infection.

Animals↗
PubMed1984

Etiology of deafness in Robarts School for the Deaf.

A survey of the children at the Robarts School for the Deaf was performed in order to determine the etiology of hearing loss, the reading ability as related to the degree of hearing loss, and the incidence of middle ear disease. The largest category for etiology was idiopathic at 31%, followed by hereditary at 22.5%, and maternal rubella at 19%. The incidence of serous otitis media was found to be 11%.

Adolescent↗