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Biomedical subjects

B Kramer

Publications and source records attributed to B Kramer.

At least 19 recordsLinked to original sources
PubMed1992

Does the AHA/ACC task force grading system predict outcome in multivessel coronary angioplasty?

To assess the ACC/AHA task force grading system as a predictor of outcome in patients undergoing multivessel percutaneous transluminal coronary angioplasty we analyzed all failures (residual stenosis > 50%, Q-wave myocardial infarction, coronary artery bypass grafting during hospitalization, or death) in 97 patients with 328 stenoses. There were 70 males and 27 females; 60 patients had stable angina, and 37 had unstable angina. The mean number of lesions dilated per patient was 3.4 (range 2-8). The mean preangioplasty percent luminal diameter narrowing was 80 +/- 14%. Thirty-eight stenoses were AHA/ACC classification type A, 192 type B, and 98 type C. One hundred twenty-eight lesions were located in the left anterior descending artery or its distribution, 89 in the left circumflex, 96 in the right coronary artery, and 15 in other vessels. Procedural success (< 50% residual diameter narrowing and no major ischemic complications) was achieved in 266 lesions (81.1%). Major ischemic complications (death, myocardial infarction, or emergency bypass surgery) occurred in 8 patients (8.2%) and in-hospital mortality was 2%. Analysis on a per stenosis basis demonstrated 84% success in type A, 89% in type B, and 64% in type C (p < 0.0001). When type B was divided into type B1 (1 type B characteristic) and type B2 (two or more type B characteristics) the success rate was 90% vs. 88% and the complication rate was 1% vs. 2%, respectively (p = n.s.). Logistic regression analysis showed that the best single predictor of failed angioplasty was total occlusion > 3 months, followed by total occlusion < 3 months and severely angulated (> 90 degrees) segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Assessing operability in squamous carcinoma of the oesophagus. Are pre-operative investigations unreliable?

Pre-operative investigations, although providing useful information, were unreliable in predicting resectability in patients with malignant oesophageal lesions. Chest radiographs excluded metastasis and active tuberculosis. The barium swallow examination determined the length of the lesion and displayed various displacements, none of which excluded resectability. Tumour infiltration of the airways was the only change visible at bronchoscopy that contraindicated resection. Computed axial tomography was unreliable in excluding extra-oesophageal tumour extension and operability. As all these pre-operative investigations have their limitations in assessing operability, exploration of the lesion is essential to determine resectability for squamous carcinoma of the oesophagus, provided there is prior histological confirmation of a malignant oesophageal lesion.

Carcinoma, Squamous Cell↗
PubMed1990

Calcium-dependent distance changes in binary and ternary complexes of troponin.

Calcium-dependent distance changes have been determined by resonance energy transfer in binary and ternary troponin complexes in order to collect evidence for the structural rearrangements which are part of the hypothetical trigger mechanism of skeletal muscle contraction. Donor and acceptor fluorophores were either intrinsic tryptophans in subunits with a favourable sequence from different species, quasi-intrinsic Tb3+ ions bound to troponin C or extrinsic labels attached to specific cysteine or methionine residues. All chemically modified subunits proved fully active in conferring calcium sensitivity onto myosin ATPase. Nine distances were determined between five sites which allowed construction of a three-dimensional lattice representing the spatial distribution of four sites in the ternary complex of troponin C, I and T. Distances in binary complexes were nearly unaltered upon addition of the third subunit. Regulatory calcium binding caused distance changes of the order of 0.7-1.1 nm. In view of the large displacements of the hypothetical mechanism, they turned out to be smaller than anticipated. The fluorophoric sites selected may be localized in a zone of the troponin complex which happens to be relatively little affected by the mechanism. Alternatively, amplification of the moderate changes seen here would require the complete set of thin filament proteins.

Animals↗
PubMed1990

Comparative analysis of coronary angiographic morphology following restenosis.

The site and angiographic morphology of restenotic lesions following initially successful coronary angioplasty (PTCA) were compared to the original pre-PTCA stenosis and the immediate post-PTCA result. Forty-seven patients with 55 restenoses were analyzed. All patients with repeat angiography for recurrent ischemia 1 to 12 months post-PTCA documenting restenosis were included. Two orthogonal angiographic views best showing the initial lesion, immediate post-PTCA result, and the restenosis lesion, were selected and matched for angulation and cardiac cycle phase. Individual frames were traced and magnified. Restenosis lesions were similar in morphology to the pre-PTCA lesions in 29 of 55 (53%) and to the post-PTCA lesions in only 25 of 55 (46%) (p = NS). However, when the lesions with residual post-PTCA stenosis of greater than 25% luminal diameter narrowing were excluded from the analysis, the post-PTCA lesion morphology was similar to restenosis morphology in 25 of 30 (83%), whereas pre-PTCA and restenosis morphology was similar in only 15 of 30 (50%) lesions (p less than 0.01). Subgroup analysis revealed that when the restenosis occurred at the same site as the original lesion (group 1), post-PTCA morphology was significantly better (p = 0.01) in predicting restenosis morphology, 15 of 17 (88%), than was pre-PTCA morphology, 8 of 17 (47%). When the restenosis occurred greater than 5 mm distant from the original site (group 2), there was no significant difference in the association between pre-PTCA versus post-PTCA morphology and restenosis morphology. Thus restenosis morphology is usually dissimilar to the pre-PTCA stenosis morphology.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Mismatch repair-induced meiotic recombination requires the pms1 gene product.

The presence of multiple heterologies in a 9-kilobase (kb) interval results in a decrease in meiotic crossovers from 26.0% to 10.1%. There is also an increase from 3.5% to 11.1% in gene conversions and ectopic recombinations between the flanking homologous MAT loci. The hypothesis that mismatch repair of heteroduplex DNA containing several heterologies would lead to a second round of recombination has now been tested by examining the effect of a mutation that reduces mismatch correction. The repair-defective pms1-1 allele restores the pattern of recombination to nearly that seen in congenic diploids without the heterologies. Mismatch repair-induced recombination causes a significant increase in MAT conversions and ectopic recombination events with as few as two heterozygosities separated by 0.3-0.7 kb, but not when the mismatches are separated by greater than 1 kb. The frequency of these events depends on both the number and position of the heterozygosities relative to the flanking homologous MAT loci used to detect the events. The creation of recombinogenic lesions by mismatch repair in yeast could be analogous to the creation of recombinogenic lesions in dam- Escherichia coli. We suggest that the repair of heteroduplex DNA containing multiple mismatches may produce chromosomal rearrangements and gamete inviability when naturally polymorphic chromosomes undergo meiotic recombination.

Alleles↗
PubMed1990

Exogenous gonadotropins--serum oestrogen and progesterone and the effect on endometrial morphology in the rat.

The serum levels of oestrogen and progesterone in hyperstimulated, pregnant rats were compared with those of normal pregnant animals. The endometrial morphology was studied before (4.5 days), at the time of (5.5 days) and after (6.5 days) implantation. In the hyperstimulated group serum oestradiol levels were significantly higher than in the controls at 2.5 and 4.5 days, while progesterone levels were similar in the two groups. Consequently the progesterone:oestradiol ratio was significantly lower in the experimental groups prior to implantation. Significant changes in the endometrium caused by the raised oestradiol levels, included an early increase in gland epithelial height, increased surface epithelial height, increased number and length of microvilli, deficiencies in the glycocalyx and decreased mitotic activity in the surface epithelium and stromal cells. In addition, epithelial cell degeneration and failure of decidualisation of stromal cells was observed. These morphological changes adversely affect embryo attachment and implantation. Similar pathological changes in the endometrium may occur in human in vitro fertilisation utilising superovulation and may be an important factor in the low success rate of these programmes.

Animals↗
PubMed1990

[Thermal effects in the dental pulp caused by laser radiation from various laser types].

In this in vitro study the temperature rises occurring in the dental pulp during laser irradiation were measured. Infrared laser radiation (CO2 and Nd: YAG) had great thermal effects on the pulp tissues. At an average power output level of 5 W temperature rises of approx. 40 degrees C within 100 s were observed. The effect of a cooling system was negligible. Radiation from an ArF excimer laser (193 nm) at an average output of 5 W caused only slight thermal changes, when an airstream was used to remove the fragments of photoablative decomposition of the dental tissues. The temperature in the pulp chamber increased by approx. 5 degrees C after 6 min. This result leads to the conclusion that only ArF excimer lasers may be effectively used in the mouth without producing inacceptable thermal effects in the dental pulp.

Dental Pulp↗
PubMed1989

The effect of exogenous gonadotropic hormones on the endometrium of the rat.

This investigation examined the effects of hyperstimulation on the uterine endometrium of rats. Female rats were injected, out of cycle, with FSH followed by hCG and mated. Control rats were mated during oestrus. Animals were killed at 5.5 days of pregnancy. The endometrium was examined by light and electron microscopy. Hyperstimulation resulted in an increase in the length and number of microvilli and a deficiency of the glycocalyx of surface epithelial cells. Stromal cells failed to undergo decidualization. These alterations in morphology may interfere with attachment and implantation of the embryo.

Animals↗
PubMed1989

Cyclopia-synotia: an unusual presentation.

An infant showing an unusual combination of craniofacial abnormalities is described. Synotia, astomia, a rudimentary proboscis, and a central placode in the hairline were observed. Serial sections of the head were examined microscopically. The proboscis contained a mass of striated muscle, but no bony or nervous tissue. Cyclopia was suggested by the central placode, the latter consisting of a thin, stratified, squamous nonkeratinized epithelium attached to an incomplete orbit by a strand of connective tissue. The orbit consisted of a bony shelf with bundles of nerves, striated muscle, and degenerate retinal tissue. The central nervous system cranial to the hindbrain was poorly developed. The midbrain and diencephalon were rudimentary, and there was poor separation of the small cerebral hemispheres. The auditory system was well represented. The maxilla and mandible were present, but there was no evidence of tooth formation. The wide range of midline abnormalities and anodontia suggest that this is a case of cranial neural crest deficiency.

Anodontia↗
PubMed1979

An experimental investigation into the possible origin of pancreatic islet cells from rhombencephalic neurectoderm.

To determine whether or not any pancreatic islet cell type arises from rhombencephalic levels of neurectoderm, lengths of presumptive rhombencephalon (containing potential neural crest) of Black Australorp chick embryos at 6- to 9-somite stages were replaced isotopically and isochronically by neural tube of Japanese quail embryos. Some transplants included mesencephalic regions. In some cases various levels of the rhombencephalon were deleted and not replaced. The quail nuclear marker was detected in cranial ganglia in operated embryos sacrificed at 3 3/4 days of incubation and in enteric ganglia and cells accompanying some pancreatic nerves, in embryos killed at 7 days of incubation. This provided evidence of normal migration of crest cells from the grafts. Dopa was administered to the younger embryos, which were submitted to the formaldehyde-induced fluorescence procedure to demonstrate APUD (Amine Precursor Uptake and Decarboxylation) cells. No pancreatic APUD cells exhibited the quail nuclear marker. In 9- to 11-day embryos, A and B cells were identified by specific light and electron microscopic features. None showed the quail marker. The marker was also absent from those D cells seen and from cells of an as yet unidentified type, but not enough of these were found to warrant a conclusion. All islet cell types were found in embryos from which various levels of the rhombencephalon had been deleted. It is concluded that at least A and B islet cells are not derived from the rhombencephalic neurectoderm and probably not from mesencephalic levels. Their most likely origin remains the endoderm, which was the accepted source until recently.

APUD Cells↗
PubMed1978

An unusual case of persistent renal collar in a human adult male.

There are relatively few reports in the literature on accessory renal veins, and particularly that anomaly described as a persistent renal collar. The present paper describes a case in which a left renal vein is encountered in a human adult, both anterior and posterior to the abdominal aorta, though without a persistent left inferior vena cava.

Adult↗