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Biomedical subjects

S Kaiser

Publications and source records attributed to S Kaiser.

At least 73 records · Page 4Linked to original sources
PubMed1996

Communities, commodities, cultural space, and style.

This article explores the interconnections between queer communities and cultural space(s) in the context of style. Visibility issues and politics have become important to gay communities in the U.S. Gays and lesbians use clothing and appearance style to signal membership in or separation from specific cultures or communities. Within commodity capital, the heuristic categories of 'subculture' and 'target market' describe space or spaces that gays and lesbians occupy, and often occupy differently, based on self positionality within gay cultures, within commodity capital, and in relation to gender-specific discourse. Based on in-depth interviews with 60 lesbians and gays, this paper illuminates the ambivalences gays and lesbians express in embracing 'subculture' and 'target market' as categories to establish differences and fashion identities within the current cultural economy.

Culture↗
PubMed1996

Drosophila differentiation genes instrumental in tumor suppression.

Tumor suppressor genes of Drosophila are developmental genes which, in the homozygously mutated state, induce in one step malignant or benign neoplastic transformation of specific cell types. They act early in development and by this set the stage for cell specific differentiation of imaginal discs, adult optic neuroblasts, blood and gonial cells. The structure, expression and possible function of the following four tumor suppressor genes are discussed: tumorous imaginal disc, lethal (3) malignant brain tumor, lethal (3) malignant blood neoplasm-1 and benign (2) gonial cell neoplasm.

Animals↗
PubMed1995

Mathematical modelling of ventilation mechanics.

Routine application of 'rule of thumb' parameter sets in clinical practice pushes model visions to the background, including the complete framework of assumptions, simplifications, suppositions and conditions. But: models can be very strong tool, when applied selectively--that means, with a clear idea of destination, definition, parameter selection and verification. This article discusses universal issues of modelling--based on ventilation mechanics models in intensive care medicine.

Airway Resistance↗
PubMed1995

Simulation of mechanical respiration using a multicompartment model for ventilation mechanics and gas exchange.

The mechanical respiration of intubated patients is a process which is influenced by many parameters and, through its many interactions, is extremely complex. Taken by itself the logical analysis of this complexity is extraordinarily difficult and leads very often to false conclusions. For that reason computer simulation of complex systems by means of the computer is an important tool in the analysis of these processes. Required is a model which describes the actual behavior of the system. However, it should not be overlooked that a model always describes only a portion of reality. Models having exclusively to do with ventilation mechanics or with gas exchange cannot simulate the interactions between the two. To accomplish this purpose, an improved model is necessary, including both partial processes and thereby capturing the complexity of the system. Accordingly, both ventilation mechanics and gas exchange have been integrated equally into the newly developed model for the simulation program Simu Vent. The core of the program builds a functional multicompartment model of the lungs and considers the partial processes ventilation mechanics, gas transport, gas mixing and gas exchange. Further considered are the respirator, blood circulation and peripheral compartments. The program runs under a graphical user interface, allowing its easy use. Responsible for this ease is the user's ability to interact with the program while simulation is in progress and the specially designed graphic screen mask. Comparing measured with simulated values demonstrated that the measured curve can be simulated with minimal error. Furthermore, the multicompartment model describes disruptions in distribution. Simu Vent's application is especially well advised in the description and analysis of the theoretical fundamentals of mechanical respiration. This aspect is meaningful above all in education and research, rendering these two the model's main areas of use.

Computer Simulation↗
PubMed1995

Checklist self-evaluation in a standardized patient exercise.

BACKGROUND: Standardized patient (SP) exercises are expensive and time consuming. We hypothesized that self-evaluation would further the goals of teaching and evaluation for a group of medical students. METHODS: Students were given self-evaluation checklists (essentially identical to those filled out by the SPs) and completed them prior to reviewing the SP checklists. Agreement between student and SP checklists (whether each item was checked or not) and the extent of agreement on the interactional skills rating scales were assessed. RESULTS: Overall agreement was 93%, with 98% agreement on interactional items, 92% on physical examination items, and 89% on history items. Disagreements tended to be clustered on a few items in each scale. Scores on the interactional skills rating scales also showed strong agreement. CONCLUSION: The use of checklists and rating scales in this context is well established. At virtually no cost, a self-evaluation tool adds a valuable dimension to the exercise.

Clinical Clerkship↗
PubMed1995

Fusarium solani fungal infection of the lateral line canal system in captive scalloped hammerhead sharks (Sphyrna lewini) in Hawaii.

Two of five scalloped hammerhead sharks (Sphyrna lewini) captured May 1987 in Hawaii (USA) developed granulomatous exudative mycotic dermatitis localized in the lateral line canal system. The lesion initially was noted in the cephalic canals, but over a period of months extended into the lateral canal. Fusarium solani and Vibrio spp. were isolated from the canal exudate of both sharks. Bacterial colonies were not observed in the canal walls or surrounding tissues. Fusarium solani infection resulted in a chronic physical and behavioral deterioration of the two sharks; one shark was euthanized in September 1988 and the other in July 1989. This is the first report of Fusarium solani infection in the lateral line canal system and the third account in hammerhead sharks.

Animals↗
PubMed1994

Urokinase overproduction results in increased skeletal metastasis by prostate cancer cells in vivo.

We previously reported that urokinase (uPA) is produced by the human prostate cancer cell line, PC-3, and could function as a growth factor for cells of the osteoblast phenotype. To examine the role of uPA in metastasis to the skeleton and to extraskeletal sites, we have developed a homologous model of uPA overexpression in a rat prostate cancer cell line. Full length cDNA encoding rat (r) uPA was isolated and subcloned as a 1.4-kilobase XbaI-BspHI fragment in the sense and antisense orientation into the Moloney murine leukemia retroviral vector pYN. The control (pYN) and experimental (pYN-ruPA, pYN-ruPA-AS) plasmids were transfected into Dunning R 3227, Mat LyLu rat prostate carcinoma cells. Experimental clones expressing at least 5-fold higher (pYN-ruPA) or 3-fold lower (pYN-ruPA-AS) than controls were selected, and control and experimental cells were inoculated into the left ventricles of inbred male Copenhagen rats. Animals were sacrificed at timed intervals to examine the evolution of metastatic lesions. Control animals developed metastases to the lumbar vertebrae resulting in spinal cord compression and hind limb paralysis at 20-21 days postinoculation. Animals inoculated with cells overexpressing uPA developed hind limb paralysis significantly earlier (by day 14-15 postinoculation). Additionally, more widespread skeletal (ribs, scapula, and femora) metastases were seen. Serum from experimental animals showed a progressive elevation in alkaline phosphatase levels, and histological examination of lumbar metastases revealed markedly increased osteoblastic activity over that observed in control animals. In contrast to this, animals inoculated with cells underexpressing uPA developed hind limb paralysis significantly later (days 25-29 postinoculation) and displayed decreased tumor metastasis. These studies support a role for the catalytic domain of uPA in enhancing both skeletal and nonskeletal prostate cancer invasiveness and are consistent with a role for the growth factor domain of uPA in mediating an osteoblastic skeletal response.

Animals↗
PubMed1994

Early detection of subperiosteal abscesses by ultrasonography. A means for further successful treatment in pediatric osteomyelitis.

Subperiosteal abscess (SA) is a well-known complication of osteomyelitis (OM) in children. The efficiency of treatment of OM with this complication is dependent on early drainage of the abscess. We present a prospective study of 32 children with clinical suspicion of OM. Ultrasonography detected SA in 13 of these children. In nine cases OM with SA was confirmed surgically and in the remaining four other radiographic modalities and/or blood cultures supported the sonographic diagnosis. In the remaining 19 cases, OM without SA was the final diagnosis.

Abscess↗
PubMed1992

Effect of altered acid-base balance and of various agonists on levels of renal glutamate dehydrogenase mRNA.

Rat kidney contains 3.5-kb and 2.8-kb mRNAs that encode for glutamate dehydrogenase (GDH). The levels of both mRNAs are increased gradually after onset of chronic metabolic acidosis and reach a maximum induction of 2.5-fold after 7 days. In contrast, during recovery from chronic acidosis, the levels of the GDH mRNAs are returned to normal within 1 day. The development of an acute metabolic acidosis causes a more rapid induction of GDH mRNA. This increase occurs after a 7-h lag and plateaus after 18 h at a level that is threefold greater than normal. A very similar profile was observed after the transfer of LLC-PK-F+ cells from normal medium to an acidic medium containing 10 mM bicarbonate and adjusted to pH 6.9. However, the transfer of cells from acidic to normal medium caused an immediate and rapid [half-life (t) = 1 h] decrease in GDH mRNA. The apparent half-lives of GDH mRNA were measured by treating cells grown in normal (t = 4 h) and acidic media (t = 12 h) with actinomycin D. Thus, increased stability may account for the induction of GDH mRNA that occurs during growth in response to acidosis. The levels of GDH mRNA are independently affected by changes in medium pH or bicarbonate concentration. The levels of GDH mRNA are also increased by treating cells with adenosine 3',5'-cyclic monophosphate, epinephrine, triiodothyronine, or retinoic acid, whereas treatment with angiotensin II, vasopressin, phorbol 12-myristate 13-acetate, or cycloheximide did not produce an increase. The inductive effect of dexamethasone, which is observed in vivo, is not reproduced in the LLC-PK-F+ cells.

Acid-Base Equilibrium↗
PubMed1992

Studies of the molecular biology of parathyroid hormone-like peptide.

Molecular biology techniques have been used to examine alternative splicing of the PLP gene, interspecies homology of PLP, the genetic relationship of PLP and PTH. Molecular biology approaches can also be successfully employed to examine both the regulation of PLP production and its function both in emulating PTH and in non PTH-related actions.

Animals↗
PubMed1991

Effect of pH and bicarbonate on phosphoenolpyruvate carboxykinase and glutaminase mRNA levels in cultured renal epithelial cells.

A gluconeogenic strain of renal epithelial cells (LLC-PK1-F+) was used to characterize the effect of pH and bicarbonate concentration on the levels of phosphoenolpyruvate carboxykinase (PCK) and glutaminase (GA) mRNAs. The levels of both mRNAs are markedly dependent upon medium glucose concentration. The level of PCK mRNA is increased with increasing glucose concentration from 0 to 40 mM, whereas the level of GA mRNA is maximal between 3 and 5 mM glucose. When LLC-PK1-F+ cells are grown with 5 mM glucose and then subjected to an acute decrease in pH (from 7.4 to 6.9) and bicarbonate concentration (from 25 to 10 mM), the level of PCK mRNA exhibits a biphasic response. The PCK mRNA is initially increased 4-fold within 3 h, then decreases slightly and subsequently increases between 10 and 20 h to a level that is 17-fold greater than normal. Only the initial increase parallels the changes observed in vivo. In contrast, after onset of acidosis, the level of GA mRNA initially remains unchanged, is then increased 8-fold between 10 and 16 h, and then decreases slightly. This response closely mimics the results obtained in vivo. A decrease in media pH at constant bicarbonate causes a marked increase in both mRNAs. However, the levels of the two mRNAs are also elevated by decreasing bicarbonate at a constant pH. Thus, both parameters independently affect the level of the two mRNAs. The use of actinomycin D to measure the half-lives of PCK and GA mRNAs at pH 7.4 and 6.9 indicates that stabilization may fully account for the induction of GA mRNA and contributes to the inductive effects of decreased pH and/or bicarbonate on PCK mRNA. Following recovery from acidic conditions, the two mRNAs exhibit a rapid and coordinate decrease (t1/2 approximately 20 min). Dexamethasone had no effect on the level of either mRNA, whereas cAMP increased only PCK mRNA. The latter effect was additive with the increase caused by decreased pH and/or bicarbonate and was reversed by incubating in alkalotic media. Thus, the induction of PCK and GA mRNAs during acidosis is initiated in direct response to a decrease in extracellular pH and/or bicarbonate.

Acidosis↗
PubMed1991

Singlet oxygen induced single-strand breaks in plasmid pBR322 DNA: the enhancing effect of thiols.

The biologically occurring thiols, glutathione, cysteamine and cysteine, significantly enhance the single-strand breaks in plasmid pBR322 DNA induced by singlet molecular oxygen (1O2) generated by the thermodissociation of the endoperoxide of 3,3'-(1,4-naphthylidene)dipropionate. The enhancing effect was also observed with chemically related sulfhydryl compounds but not by disulfides. In contrast, dihydrolipoate and its disulfide lipoate protected the plasmid DNA. Metal chelators as well as superoxide dismutase or catalase had no effect, whereas mannitol or sodium azide, decreased the thiol-1O2-induced strand breaks. It is concluded that the observed effects are mediated by reactive oxidation products arising from the 1O2-oxidation of thiols.

Chelating Agents↗
PubMed1991

Activity of thiols as singlet molecular oxygen quenchers.

Singlet molecular oxygen O2(1 delta g) arising from the thermodissociation of the endoperoxide of 3,3'-(1,4-naphthylidene) dipropionate (NDPO2) was used to assess the quenching ability of various thiols and related compounds in sodium phosphate buffer in D2O at 37 degrees C. The overall quenching ability decreases in the sequence ergothioneine, methionine, cysteine, beta,beta-dimethyl cysteine (penicillamine), mercaptopropionylglycine, mesna, glutathione (GSH), dithiothreitol, N-acetyl cysteine and captopril. Cystine, glutathione disulphide, dimesna, methionine sulphone and methionine sulphoxide have no quenching effect. Comparison of the rate constants for physical (kq) with chemical (kr) quenching by thiols indicates that chemical reactivity accounts fully for their ability to quench O2(1 delta g), and pD dependence indicates that the thiolate anion reacts with O2(1 delta g). Loss of thiol groups, as exemplified by GSH, is not affected by the free radical scavengers superoxide dismutase and mannitol. However, sodium azide, a scavenger of O2(1 delta g), completely prevents NDPO2-induced thiol depletion. Depletion of GSH by NDPO2 is accompanied by the formation of its disulphide, sulphinate, sulphonate, sulphoxide and other products.

Glutathione↗
PubMed1991

Prevalence of renal artery stenosis in diabetes mellitus--an autopsy study.

The prevalence of renal artery stenosis in diabetic patients is unknown, since no noninvasive and valid screening procedures are available. We have therefore evaluated 5194 consecutive autopsy protocols from patients who died between 1980 and 1988. In addition, all available clinical records for patients with renal artery stenosis (RAS) and a random sample were evaluated. It was found that 73% of patients with RAS were hypertensive, and 53% had diabetes, all but one being Type 2 (non-insulin-dependent). Renal artery stenosis was present in 225 (4.3%) of all patients [95% confidence interval (95% CI), 3.8-4.9], and was not reported in the patients' clinical records in 93% of cases. RAS was present in 8.3% of all diabetic patients (95% CI, 6.8-9.8%), the odds ratio being 3.5 (95% CI, 2.6-4.6). The frequency of renal artery stenosis in diabetic patients with hypertension was 10.1%. Bilateral renal artery stenosis was found in 43% of patients with RAS and diabetes, and in 30% of non-diabetic patients with RAS (P = 0.059). Our results indicate that renal artery stenosis often goes undetected before autopsy. The presence of non-insulin-dependent diabetes mellitus increases the risk of renal artery stenosis. The risk of bilateral renal artery stenosis is greater in diabetic patients. These results may be of significance with regard to the diagnostic evaluation and choice of antihypertensive treatment in hypertensive non-insulin-dependent diabetic patients.

Aged↗
PubMed1990

Physical and chemical scavenging of singlet molecular oxygen by tocopherols.

Singlet molecular oxygen (1O2) arising from the thermal decomposition of the endoperoxide of 3,3'-(1,4-naphthylidene) dipropionate was used to assess the effectiveness of alpha-, beta-, gamma-, and delta-tocopherol in the physical quenching as well as the chemical reaction of 1O2. The relative physical quenching efficiencies of the tocopherol homologs were found to decrease in the order of alpha greater than or equal to beta greater than gamma greater than delta-tocopherol. The ability of physical quenching depends on a free hydroxyl group in position 6 of the chromane ring. Chemical reactivity of the tocopherol homologs with 1O2 was low, accounting for 0.1-1.5% of physical quenching with beta-tocopherol showing particularly low reactivity, resulting in the sequence alpha greater than gamma greater than delta greater than beta-tocopherol. Tocopheryl quinones were products of all tocopherol homologs, and in addition a quinone epoxide was a major product from gamma-tocopherol. This quinone epoxide was not cleaved by rat liver microsomal epoxide hydrolase; however, it reacted further with 1O2. It is concluded that methylation in position 5 of the chromane ring enhances physical quenching of 1O2, whereas chemical reactivity is favored by a methylated position 7. In view of the fact that beta-tocopherol is as effective as alpha-tocopherol in physical quenching of 1O2 but shows very low chemical reactivity, this tocopherol homolog might be particularly suitable for biological conditions in which an accumulation of oxidation products might weaken the antioxidant defense.

Kinetics↗