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Biomedical subjects

M Meyer

Publications and source records attributed to M Meyer.

At least 397 records · Page 22Linked to original sources
PubMed1993

Ultrastructure of the trabecular meshwork in untreated cases of primary open-angle glaucoma (POAG).

Thirty-one trabeculectomy specimens of patients suffering from primary open-angle glaucoma (POAG) who had received no, or only minor, medication prior to surgery were ultrastructurally and quantitatively analysed. Most of the specimens revealed thickened trabeculae, increased amounts of plaque-material deposited within the cribriform layer and an abundance of long spacing (lattice) collagen. The uveal meshwork was partly deprived of cells whereas the cribriform layer often contained numerous enlarged, light cells with many small mitochondria and lysosomes but no prominent endoplasmic reticulum or Golgi complexes. The quantitation of sheath-deprived plaque material (SD plaques) in a defined area of inner and outer wall of Schlemm's canal showed no significant difference between the untreated cases studied here and the treated ones studied previously. However, both groups had significantly higher amounts of SD plaque material in the inner wall than normal controls of a similar age range.

Adult↗
PubMed1993

Participation of the SOS system in producing deletions in E. coli plasmids.

The participation of the SOS response in the deletion of palindromic and non-palindromic inserts of about 66 and 100 bp cloned within the EcoR1 site of the chloramphenicol acetyl transferase (cat) gene of plasmid pBR325 was tested after introducing the derived plasmids into strains containing different combinations of lexA, recA and umuC alleles and the auxotrophic mutation trpE65. This allowed for a comparison of deletion frequency in the plasmids, measured as the reversion of chloramphenicol sensitivity to resistance (Cms-->Cmr), to point-mutation frequency measured from the reversion of trpE65 to tryptophan independence (Trp(-)-->Trp+). We found that the spontaneous deletion frequency of palindromic inserts was increased by the overproduction of activated RecA* and UmuC+ in lexA (Def) backgrounds but the deletion of the non-palindromic inserts was unaltered. Overproduction of RecA+ had no significant effect on deletion incidence but it did increase Trp(-)-->Trp+ reversions. The SOS stimulation of palindrome deletions paralleled the SOS mutator effect of certain recA and umuC alleles on Trp(-)-->Trp+ reversions, suggesting that some form of SOS processing was responsible for the observed increases. The results further suggest that the SOS effect on deletions depends on the distinction between palindromy vs. non-palindromy, rather than on the sizes or sequences of the inserts or those of the terminal homologies bracketing them.

Base Sequence↗
PubMed1993

Ventilatory response to exercise after heart and lung denervation in humans.

This study, aimed at investigating some aspects of breathing control at work, was conducted on 8 heart and lung transplant recipients (HLTR) (age 33 +/- 13 years, mean +/- SD; 10 +/- 6 months post-transplantation) and on two control groups, i.e. 11 heart transplant recipients (HTR) and 11 healthy untrained subjects (C). The patients performed a series of 2 to 6 1-min exercise bouts (at 25 or 50 W, corresponding to about 50% of their VO2max) on a bicycle ergometer, followed by a 5 min 25 or 50 W constant load. C exercised both at 50 W (C1) and at 50% of their VO2max (C2). Inspiratory (VI) and expiratory (VE) ventilation, tidal volume (VT), respiratory frequency (fR), end-tidal O2 and CO2 partial pressures (PETO2 and PETCO2 and gas exchange (VO2 and VCO) were measured breath-by-breath. "Phase I" ventilatory response (ph I) was determined as the mean changes of VI, VE, VT, fR, PETO2 and PETCO2, compared to rest, during the first two respiratory cycles following exercise onset. In HLTR ph I did not significantly differ from that of C1 and C2, whereas the response was lower in HTR. VE, VO2 and VCO2 responses during "phase II" (t 1/2 on-) and "phase III" (steady state exercise) were similar in HLTR and in HTR. t 1/2 on- were longer in HLTR and in HTR compared to C1. In 3 HLTR the ventilatory pattern during the 5 min constant loads was similar to that of HTR and C, whereas 4 HLTR presented higher VT and lower fR values. It is concluded that: 1) The ventilatory response to exercise, in all its phases, is substantially preserved despite lung denervation. When slight alterations are found (i.e. the slower phase II), they are presumably of peripheral origin. 2) The normal ph I in HLTR indicates that cardiac and/or pulmonary inputs to the respiratory centers are not involved in its regulation, or that their role can be subserved by other ventilatory control mechanisms.

Adolescent↗
PubMed1993

Treatment of homozygous familial hypercholesterolemia by plasma exchange and LDL-apheresis.

Two girls with familial hypercholesterolemia were treated for 7 years by plasma exchanges (PE) or LDL-apheresis (LA). We compared different methods of treatment; PE with or without reuse of the plasma separator, LA of varying frequency, and LA with or without oral administration of simvastatin. We assessed the long-term results by measuring the blood levels of the biochemical parameters before sessions, and determined the effectiveness of each session by the percentage of decrease in the blood levels between the beginning and the end of the sessions. LA led to a more selective treatment (lowering of LDL cholesterol and maintenance of HDL cholesterol), but the blood levels of total cholesterol before sessions were the same as those obtained by PE. IgG and haemoglobin levels decreased little with LA. The rhythm of one session a week gave better results in LA. Although reuse of the plasma separator represents a financial saving it produced poorer results. The oral administration of simvastatin improved the results of LA.

Adolescent↗
PubMed1993

Noninvasive cardiac output measurement by arterial pulse analysis compared with inert gas rebreathing.

Noninvasive cardiac output (CO) measured by arterial pulse analysis was compared with that measured by inert gas rebreathing in six healthy male volunteers. Pulse contour analysis was applied to the pressure wave output of a Finapres, which noninvasively measures continuous arterial pressure in a finger. Data were collected before, during, and after a 10-day 6 degrees head-down tilt experiment. Intravenous saline loading and lower body negative pressure stimuli varied CO over 2.8-9.6 l/min, as measured by the rebreathing technique. Because pulse contour provides only relative changes in CO, to obtain absolute values it must be calibrated against another measurement. Pulse contour data were calibrated every measurement day against the mean of two to four control rebreathing CO measurements before the lower body negative pressure or intravenous saline loading stimuli. Using one averaged calibration factor per subject for a total of 27 days, we compared the results of both methods. The linear regression between pulse contour (Pc CO) and rebreathing CO (Rebr CO) was Pc CO = 0.15 + 0.98(Rebr CO) (r = 0.96). The standard deviation of the difference of the two methods was 0.5 l/min (n = 205), excluding data used for calibration. By monitoring pulse contour CO before and during rebreathing, the rebreathing maneuver itself was shown to produce a substantial increase in CO that was mainly related to an increase in heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[Immunological principles of polysaccharide-protein conjugate vaccination].

Haemophilus influenzae and Streptococcus pneumoniae are bacteria with a polysaccharide capsule. The production of specific antibodies against capsular polysaccharide plays a pivotal role in the defence against these organisms. However, children under the age of two years do not at all or only poorly respond to an infection with encapsulated bacteria or after vaccination with purified capsular polysaccharide antigen. In contrast, protein antigens, e.g. tetanus- and diphtheriae-toxoid, are good immunogens in this age group. The difference between polysaccharide antigen and protein antigen is that the former are T-dependent antigens whereas the latter are T-independent. The reason for this age dependent "immunodeficiency" is not clear. A functional immaturity of a B-cell population seems to be the reason for the unresponsiveness of young children against Ti-2 antigens. The Haemophilus conjugate vaccine contains the capsular polysaccharide chemically conjugated to a carrier protein. This results in an immune response against the polysaccharide with characteristics of a T dependent antigen, giving high immunogenicity even in children under the age of two years, resulting in high antibody-production and the induction of immunological memory.

Antibodies, Bacterial↗
PubMed1993

The humoral immune response to p53 in patients with hepatocellular carcinoma is specific for malignancy and independent of the alpha-fetoprotein status.

Recently, p53 gene aberrations have been recognized as a relevant factor in hepatocarcinogenesis, in tumors from both high-risk and low-risk areas. Because p53 gene mutations typically result in increased p53 levels in tumor cells, this cellular protein might become immunogenic during tumor development. To test this hypothesis, we have analyzed sera from 80 European patients with hepatocellular carcinoma for the presence of p53 antibodies. For this purpose we developed an immunoblot assay using recombinant p53 as antigen. Sixty-seven sera from patients with different acute and chronic liver diseases were used as controls. In addition, serum alpha-fetoprotein assays were performed. Circulating antibodies against p53 were found in 25% (20 of 80) of the sera from patients with hepatocellular carcinoma but not in various nonmalignant liver diseases. The association of p53 antibodies with malignancy was highly significant (p < 0.00003). In 73.8% (59 of 80) of the hepatocellular carcinoma sera the alpha-fetoprotein levels were elevated. Among the 21 alpha-fetoprotein-negative hepatocellular carcinoma sera, 5 were found to contain p53 antibodies (23.8%). In conclusion, an antibody response against p53 developed in a significant proportion of patients with hepatocellular carcinoma but not in those with nonmalignant liver diseases. Serological testing for p53 antibodies gives the opportunity to identify a subgroup of patients with hepatocellular carcinoma not detected by conventional tests for serum alpha-fetoprotein.

Adult↗
PubMed1993

[Rapid efficacy of preoperative chemotherapy in nephroblastoma involving cardiac cavities].

BACKGROUND: Tumors involving the inferior vena cava and cardiac cavities are rare in nephroblastoma. When they do occur, the standard treatment is primary surgery; but this is often technically difficult. CASE REPORT: A 3 year-7-month-old girl was admitted because of an abdominal mass and signs of heart failure. Ultrasonography showed that this mass involved the right renal vein and the inferior vena cava including the right atrium. A CT scan showed no metastases. Echocardiography showed that the mass occupied two thirds of the right atrium and had blocked the tricuspid valve. The patient was given heparin (2 mg/kg/day), vincristine (1.5 mg/m2 on day 1) and actinomycin D (15 micrograms/kg on day 1 to 3). The heart failure disappeared and the abdominal mass decreased in volume. This improvement was confirmed by successive ultrasonographies. Chemotherapy was then completed and the patient was operated on six weeks later: right nephrectomy and removal of the cavoatrial tumoral thrombus. Pathological examination confirmed the nephroblastoma and the patient was given radiotherapy and chemotherapy for 28 weeks. She was also given aspirin for 17 weeks. Pulmonary metastases were detected 1 year after onset and were treated by a combination of surgery and chemotherapy. The patient is well 20 months after the onset of the disease. CONCLUSION: Preoperative chemotherapy seems to be effective in nephroblastoma extending to cardiac cavities; it allows subsequent surgery and facilitates postoperative radiotherapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

[Bipolar luxation of the 5th metacarpal bone].

A case of post-traumatic double dislocation of the fifth metacarpal is reported. No reference has been found in the literature. Both were dorsal dislocations, mechanism appears as an axial compression on the metacarpal distal extremity, as first phalanx is hyperextended. Only the carpo-metacarpal-joint was reduced by close technic with percutaneous fixation; the metacarpo-phalangeal dislocation required surgery using a palmar approach. Normal function of the joint was recovered three months later.

Adult↗
PubMed1993

Age and indices of adequacy and nutrition in CAPD patients.

We have examined the correlations of age with 95 demographic, clinical, and laboratory parameters in a continuous ambulatory peritoneal dialysis (CAPD) population. Significant inverse correlations were found with lean body mass, dialysate creatinine concentration, serum creatinine concentration, and dialysate creatinine nitrogen output in grams per week; all these findings are compatible with the well-known decrease in muscle mass with aging. Urea nitrogen output in dialysate and urine predicts Kjeldahl nitrogen output in urine and dialysate applying the Randerson equation similarly in older and younger CAPD patients. The relationship of normalized net protein catabolic rate to weekly urea clearance normalized to total body water is similar for older and younger CAPD patients. Older and younger patients have similar values for serum albumin concentration. In conclusion, the findings suggest that comparable weekly creatinine clearances should yield much lower serum creatinine concentrations in older patients. Poor protein intakes in the elderly should not be attributed to age if weekly urea clearances are low. Increases in protein intake in response to increases in urea clearances are similar in older and younger CAPD patients.

Adult↗
PubMed1993

Corticosterone metabolism and membrane transport.

The mammalian kidney metabolizes virtually all of the steroid hormones. Corticosterone receptors have been found in the cortical collecting tubule, and at least four metabolites of the hormone have been identified in rat renal tissue and urine. The biologic activity of these metabolites is not completely known. In this study, we examined the functional effects of three of the metabolites of corticosterone on membrane transport in toad and turtle bladders; we also analyzed the oxidoreductase pathways for corticosterone metabolism. In the toad bladder, maximal water flow (vasopressin- and cyclic AMP-stimulated) was unaffected by corticosterone, 11-dehydro-20-dihydrocorticosterone (metabolite I) and 11-dehydrocorticosterone (metabolite IV); maximal water flow was significantly inhibited by 20-dihydrocorticosterone (metabolite II). Sodium transport in the toad bladder was stimulated by corticosterone, 11-dehydrocorticosterone and 20-dihydrocorticosterone. Analysis of the oxidoreductase pathways in this tissue revealed that most of the corticosterone was oxidized to 11-dehydrocorticosterone, a biologically active compound; 11-dehydrocorticosterone was further metabolized to 11-dehydro-20-dihydrocorticosterone, a biologically inactive compound. Only 6% of the parent compound was converted to 20-dihydrocorticosterone. In the turtle bladder, none of the metabolites tested altered hydrogen ion secretion over the time period studied; no significant biotransformation of corticosterone occurred in this tissue. As the metabolites of corticosterone found in toad bladder are the same as those identified in mammalian tissues, our studies suggest that some of them may be important modulators of sodium and water transport in the distal nephron. Our data further suggest that these compounds are likely not involved in the regulation of urinary acidification.

Animals↗
PubMed1993

[Quality management in the hospital--methodological comments on quality effects of two aspects of a real case].

In this article two aspects of a clinical case, known in Germany as the Marion P. case, are adapted to fit into Donabedians systematic of factors of influence on health care quality. These aspects, case-related communication between doctors on the one hand and between doctors and directly affected persons on the other, are also viewed as specific problems of decision making. It turns out that in either situation the probability theory based medical decision analysis could have been an important contribution to improve problem transparency, i.e. medical decision analysis could have been used as a tool for quality management in hospitals.

Adult↗
PubMed1993

Cross sectional assessment of weekly urea and creatinine clearances and indices of nutrition in continuous ambulatory peritoneal dialysis patients.

OBJECTIVE: To perform a cross sectional analysis in 71 patients on continuous ambulatory peritoneal dialysis (CAPD) to identify significant correlations of weekly small solute clearances and indices of nutritional status with each other and with patient demographics and other commonly monitored clinical and laboratory parameters. DESIGN: This was a retrospective, cross sectional analysis in 71 patients on CAPD from less than 1 to 105 patient-months (average, 20 months). SETTING: An outpatient CAPD program. PATIENTS: All patients on CAPD in our program at the time of the study willing to undergo the clearance and nutritional status measurements. INTERVENTIONS: No interventions other than the monitoring of their status. MAIN OUTCOME MEASURES: Weekly small solute clearances, dietary protein intake, serum albumin, lean body mass, net protein catabolic rate, and urinary and dialysate nitrogen. RESULTS: Weekly Kt/V urea (weekly urea clearance normalized to total body water) of at least 1.7 and weekly total creatinine clearances (liter/week/1.7 m2) of at least 50 are associated with net protein catabolic rates (PCR) greater than 0.9 g/kg of normalized body weight in average CAPD patients. Kt/V urea and net PCR correlate significantly with serum albumin. High transporters identified by the peritoneal equilibration test have greater albumin losses and lower serum albumin concentrations. Estimates of lean body mass correlate significantly with serum albumin and net PCR; lean body mass correlates significantly and inversely with age. CONCLUSIONS: Greater small solute clearances are associated with better nutritional status.

Adult↗