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Biomedical subjects

P Hofmann

Publications and source records attributed to P Hofmann.

At least 55 records · Page 3Linked to original sources
PubMed1998

Parasympathetic receptor blockade and the heart rate performance curve.

Parasympathetic receptor blockade and the heart rate performance curve. Med. Sci Sports Sci., Vol. 30. No. 2, pp. 229-233, 1998. The aim of the present study was to investigate the influence of parasympathetic receptor blockade on the heart rate performance curve (HRPC). Twenty healthy male subjects performed a first cycle ergometer test (F), showing a HRPC deflection of varying degree and direction. Subjects then in random order performed two additional cycle ergometer tests, one with atropine (A) and the other with placebo (P). Two lactate turn points (LTP1, and LTP2) were determined by means of linear regression turn point analysis. The degree and direction of the deflection of the HRPC was calculated mathematically as factor kHR (kHR>0 = downsloping of HPRC; kHR<0 = upsloping of HRPC). In comparison with that in F and P, HR in A was significantly higher at rest, LTP1, LTP2, and during recovery, but not at Power(max). An upsloping deflection of the HRPC was seen in only five cases in F and P, whereas in A 10 cases were observed (P < 0.05). In A, kHR was significantly lower than in F and P. A significant correlation for kHR was found among F, P, and A. Independent from parasympathetic receptor blockade and the HR at Power(max), the HR at LTP2 was lower in cases with negative kHR (upsloping). In A as well as in P a significant correlation was observed between kHR and HR at LTP2. The individual time course of HRPC is reproducible and may be independent of parasympathetic activity.

Adult↗
PubMed1998

The heart rate performance curve and left ventricular function during exercise in patients after myocardial infarction.

PURPOSE: The aim of the study was to investigate the heart rate turn point (HRTP) in the time course of the heart rate performance curve (HRPC) in patients after myocardial infarction, and the relationship between the HRTP, the left ventricular function, and the second lactate turn point (LTP2). METHODS: We studied the degree and the direction of the HRPC and the left ventricular ejection fraction (LVEF) in 49 male patients 57 +/- 8 d after their first posterior wall infarction (MI). An incremental cycle ergometer test was performed and three phases of energy supply were defined (I: aerobic; II: aerobic-anaerobic transition; III: anaerobic) via blood lactate LA concentration. HRTP and LVEF-turn points (LVEFTP) were assessed by linear turn point analysis. The degree and direction of the deflection of HRPC were described as factor k (k > 0.1: downward deflection; -0.1 < k < 0.1: linear time curse; k < -0.1: upward deflection). The LVEF was determined by RNA. The difference between Pmax and LTP2 was calculated for LVEF (delta LVEF). RESULTS: An HRTP could be found in 44 and a LVEFTP in 47 cases. The HRTP occurred at 85 +/- 17 Watt (W), which correlated (r = 0.95; P < 0.001) with the LTP2 (84 +/- 17 W) and the LVEFTP (84 +/- 17 W, r = 0.93; P < 0.001). From LTP2 to Pmax a significant decrease in LVEF was found. There was a correlation between the percentage of HRmax at the HRTP and k (r = 0.70), as well as delta LVEF (r = 0.56). CONCLUSIONS: To prevent myocardial overloading, it seems to be useful to determine the HRTP, which indicate the workload where LVEF decreases.

Anaerobic Threshold↗
PubMed1998

[Total hysteroscopic endometrium resection: a critical analysis of indications, technique and results].

130 total hysteroscopic resections of the endometrium (RE) were performed at the Department of Gynecology and Obstetrics of the Deutschlandsberg Hospital from August 1, 1992 to May 31, 1997. 115 patients (88.5%) suffered from distinctive therapy-resistant uterine bleeding in terms of hypermenorrhea and menorrhagia, frequently combined with poly- and dysmenorrhea. 15 (11.5%) women who had previously been operated for breast cancer developed--during continuous treatment with tamoxifen--endometrial hyperplasia or polyps on which RE was performed after a hysteroscopic biopsy or resection had been carried out in a second setting. The operation showed that 98 out of 115 patients (85.2%) had pathologic anomalous uteri which were the organic cause of the uterine bleeding. Only 17 women (14.8%) suffered from dysfunctional uterine bleeding (12 cases) or from iatrogenically reduced coagulability (5 cases). The majority of the women (106 cases = 81.5%) were older than 40 (average 46.9 +/- 6.21 years). All RE were performed under inhalation anesthesia whereby the complete uterine cavity up to the inner orifice of the uterus was resected with the resectoscope loop. 92 out of 130 patients (70.8%) underwent a hysteroscopy or a dilatation and curettage before the RE. 77 patients (66.9%) received pretreatment with drugs to reduce the endometrium. 15 women (13.0%) underwent a laparoscopic tubal sterilization in the same setting. Finally, the results of 107 patients were analyzed excluding dropouts and patients who had undergone continuous treatment with tamoxifen and those who had an observation time of less than 6 months. After an observation period of 6-58 months, the success rate was 84.1%. For treatment of relapses 7 second resections were performed, whereby in 1 patient with a further uterine bleeding the uterus had to be extirpated. Nine of the 10 remaining patients had a hysterectomy, 1 patient refused any further treatment. The total hysterectomy rate was 12.2%. Basically, RE is absolutely practicable as far as the treatment of abnormal uterine bleeding is concerned, since hysterectomy can be avoided in a number of cases. Satisfactory long-term results, however, can only be achieved if indication and operation technique are of high quality. A problem which has not yet been solved is the indication and treatment of proliferating adenomyosis uteri interna.

Adult↗
PubMed1997

Synthesis of ganglioside GM1 containing a thioglycosidic bond to its labeled ceramide(s). A facile synthesis starting from natural gangliosides.

Capitalizing on the readily available ganglioside, GM1, we have devised a simple synthesis of labeled GM1 analogues with sulfur in place of oxygen in their linkage to the ceramide residue (SGM1). The sugar moiety of ganglioside GM1 was released by ozonolysis and subsequent alkaline fragmentation in good yield. During acetylation of the ganglioside sugar, the carboxyl group of the sialic acid residue lactonized with the 2-hydroxyl group of the inner galactose moiety (galactose II). The resulting sialoyl-II2-lactone of pentadeca-O-acetyl-monosialogangliotetraose could be readily transformed into the alpha-glycosyl bromide. Subsequent treatment of this glycosyl bromide with potassium thioacetate afforded the sialoyl-II2-lactone of tetradeca-O-acetyl-1-S-acetyl-1-thio-beta-monosialogangliotetra ose. The latter could be condensed with (2R, 3R, 4E)-3-O-benzoyl-2-dichloroacetamido-1-iodo-4-octadecen -3-ol in methanolic sodium acetate to afford a protected lyso-SGM1 derivative. One-step removal of the protecting groups under alkaline conditions gave beta-monosialogangliotetraosyl thiosphingosine. This lyso-SGM1 was converted into labeled analogues of SGM1 using the N-succinimidoyl derivative of radiocarbon-labeled octanoic and octadecanoic acid, respectively. Subsequent actions of GM1-beta-galactosidase, beta-hexosaminidase A, sialidase and again GM1-beta-galactosidase on these labeled analogues of SGM1 in the presence of taurodeoxycholate produced the respective analogues of GM2, GM3, lactosylceramide and glucosylceramide, respectively.

Carbohydrate Conformation↗
PubMed1997

Susceptibility of mononuclear phagocytes to influenza A virus infection and possible role in the antiviral response.

Among leukocytes, only monocytes and macrophages were found to be highly susceptible to an infection by influenza A virus. After infection, de novo viral protein synthesis was initiated but then interrupted after 4-6 h. Most macrophages died by apoptosis within 25-30 h. Before cell death, however, macrophages responded to influenza A virus with a high cytokine gene transcription and subsequent release of tumor necrosis factor alpha (TNF-alpha), interleukin-1 (IL-1), IL-6, interferon (IFN)-alpha/beta, and CC-chemokines. The basic mechanisms of virus-induced cytokine expression are still unknown and appear to involve transcription factors such as nuclear factor-kappaB and AP-1 which, however, were only activated for 2 h and declined below control values thereafter. After influenza A virus infection, only the mononuclear cell attracting CC-chemokines macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-1beta, and RANTES were produced while the prototype neutrophil CXC-chemoattractants IL-8 and GRO-alpha were entirely suppressed. This selective induction of CC-chemokines may explain the preferential influx of mononuclear leukocytes into virus-infected tissue. Our data show that monocytes and macrophages represent a primary target for an influenza A virus infection. Thus, the mononuclear phagocyte response leads to a rapid proinflammatory reaction and an enhanced immigration of mononuclear leukocytes, which may condition the infected host for the subsequent virus antigen-specific defense.

Apoptosis↗
PubMed1997

Respiratory comfort of automatic tube compensation and inspiratory pressure support in conscious humans.

OBJECTIVE: To compare the new mode of ventilatory support, which we call automatic tube compensation (ATC), with inspiratory pressure support (IPS) with respect to perception of respiratory comfort. ATC unloads the resistance of the endotracheal tube (ETT) in inspiration by increasing the airway pressure, and in expiration by decreasing the airway pressure according to the non-linear pressure-flow relationship of the ETT. DESIGN: Prospective randomized single blind cross-over study. SETTING: Laboratory of the Section of Experimental Anaesthesiology (Clinic of Anaesthesiology; University of Freiburg). SUBJECTS: Ten healthy volunteers. INTERVENTIONS: The subjects breathed spontaneously through an ETT of 7.5 mm i.d. Three different ventilatory modes, each with a PEEP of 5 cmH2O, were presented in random order using the Dräger Evita 2 ventilator with prototype software: (1) IPS (10 cmH2O, 1 s ramp), (2) inspiratory ATC (ATC-in), (3) inspiratory and expiratory ATC (ATC-in-ex). MEASUREMENTS AND MAIN RESULTS: Immediately following a mode transition, the volunteers answered with a hand sign to show how they perceived the new mode compared with the preceding mode in terms of gain or loss in subjective respiratory comfort: "better", "unchanged" or "worse". Inspiration and expiration were investigated separately analyzing 60 mode transitions each. Flow rates were continuously measured. The transition from IPS to either type of ATC was perceived positively, i.e. as increased comfort, whereas the opposite transition from ATC to IPS was perceived negatively, i.e. as decreased comfort. The transition from ATC-in to ATC-in-ex was perceived positively whereas the opposite mode transition was perceived negatively in expiration only. Tidal volume was 1220 +/- 404 ml during IPS and 1017 +/- 362 ml during ATC. The inspiratory peak flow rate was 959 +/- 78 ml/s during IPS and 1048 +/- 197 ml/s during ATC. CONCLUSIONS: ATC provides an increase in respiratory comfort compared with IPS. The predominant cause for respiratory discomfort in the IPS mode seems to be lung over-inflation.

Adult↗
PubMed1997

The Conconi test.

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Anaerobic Threshold↗
PubMed1997

Heart rate performance curve during incremental cycle ergometer exercise in healthy young male subjects.

In 1992 Conconi et al. (20) presented an indirect and noninvasive method for the determination of anaerobic threshold (AnT) in an incremental field test for runners. This noninvasive method for the determination of anaerobic threshold is dependent on the occurrence of a deflection of the heart rate performance curve (HRPC). The aim of our study was to evaluate the degree and direction of the deflection of the HRPC and the relationship of the heart rate threshold (HRT) to the lactate turn point in a group of 227 healthy young subjects (age: 23 +/- 4 yr). The subjects were divided into three groups by means of second degree polynomial fitting (GI: regular deflection, kHR > 0.1; G II: no deflection, 0 < kHR < 0.1; G II: inverse deflection, k < -0.1). No significant differences between the groups were found in the anthropometric data or in the power output and the blood lactate concentration at both the first (LTP1) and second (LTP2) lactate turn points and at maximum performance (Pmax). Using the method of Conconi et al. (20), 85.9% of the subjects showed a "regular" deflection, 6.2% showed no deflection at all, and 7.9% showed even an inverted deflection of the HRPC. An HRT could be obtained in both G I and G III, and power output at HRT was not significantly different in comparison to that at the LTP2. No HRT could be assessed in G II. The heart rate at HRT and the LTP2 were significantly lower in G III compared with G I. The phenomenon of heart rate break point may be attractive in training regulation, but its application is limited because a heart rate deflection cannot be found even in young subjects in some cases.

Exercise↗
PubMed1997

Left ventricular function in response to the transition from aerobic to anaerobic metabolism.

The purpose of this investigation was to study myocardial function at rest, during three phases of energy supply, and during recovery. Radionuclide angiography was performed during the aerobic phase (phase I, rest-first lactate increase), the aerobic-anaerobic transition phase (phase II, first lactate increase-second lactate increase), the anaerobic phase (phase III, second lactate increase-maximal work performance (Pmax)), and during recovery. Thirty-eight male patients (59 +/- 7 d after myocardial infarction) were compared with 19 healthy control subjects and 21 sport students of comparable age. Left ventricular ejection fraction (LVEF) increased from rest to phase I and from phase I to phase II in sports students and control subjects. During phase III, LVEF did not change significantly in sports students, but it decreased significantly in control subjects. This is in contrast to the patients, who showed an increase of LVEF from resting values (47 +/- 3%) to phase I (50 +/- 1%), no change during phase II (51 +/- 2%), and a decrease to resting values (45 +/- 2) during phase III. All subjects showed an increase in stroke volume (SV) during phase I and II, reaching a maximum at phase II. This was evidenced by an improvement of the systolic function with a constant left ventricular end-diastolic volume (EDV) in control subjects and sports students. In contrast, an improved SV in patients was achieved through an increase in EDV and a less distinct increase in the left ventricular end-systolic volume (ESV). Maximal LVEF values were measured during the first 90 s of recovery in all subjects. Values during recovery are not representative of load dependent myocardial function. This increase in LVEF does not cause an increase in cardiac output but is a consequence of changes in the EDV and ESV, which decrease again immediately after the end of exercise performance.

Adult↗
PubMed1996

[Clinical relevance of changes in serum prolactin level caused by electroconvulsive therapy].

In this study 15 (4 males, 11 females) depressive patients (according to DSM-III-R criteria), who were refractory to psychopharmacological treatment were referred for electroconvulsive therapy (ECT). Six ECTs were administered within a period of 3 weeks. Before the first, third and fifth ECT and 15, 30, and 60 minutes after each of these 3 treatments serum levels of prolactin were determined. After six ECTs eight patients showed significant symptomatic improvement, whilst the depressive symptoms in the other seven patients remained more or less unchanged. There was no statistically significant difference with respect to prolactin response following the three ECTs between the symptomatically improved and the unchanged group. There was no correlation of severity of depression and prolactin baseline levels before the first ECT. Neither baseline prolactin levels prior to the first ECT nor prolactin response predicted therapeutic outcome. From this point of view changes in serum prolactin levels do not reflect therapeutic pathways in depression or mechanisms of action of ECT.

Adult↗
PubMed1995

Demonstration of direct glycosylation of nondegradable glucosylceramide analogs in cultured cells.

After uptake by various cells (human skin fibroblasts, rat neuroblastoma B 104, human neuroblastoma SHSY5Y, murine cerebellar cells), a radioactive and a fluorescent analog of a nondegradable glucosylceramide with sulfur in the glycosidic link were glycosylated to a cell-specific pattern of glycolipid analogs. These results, for the first time, show that a glucosylceramide analog can be conveyed from the plasma membrane of cultured cells to those Golgi compartments that function in the early glycosylation steps of glycolipids. This observation is further confirmed by the fact that the cationic ionophore monensin, known to impede membrane flow from proximal to distal Golgi cisternae, inhibited the formation of complex ganglioside analogs but not those of lactosylceramide, sialyl lactosylceramide (GM3), and disialyl lactosylceramide (GD3).

Animals↗
PubMed1995

Volunteer low-risk outpatient surgery for uninsured patients in San Francisco. The Ambulatory Surgery Access Coalition.

OBJECTIVE: To provide uncompensated elective low-risk outpatient surgery for uninsured patients through a coalition of volunteer physicians, nurses, and hospitals. DESIGN: Description of the process of establishing the Ambulatory Surgery Access Coalition (ASAC), the political and administrative obstacles encountered, and the clinical results of treatment of the first 25 patients in the pilot project. SETTING: The ASAC includes the Kaiser Foundation Hospital, San Francisco, Calif, the University of California, San Francisco, the San Francisco General Hospital (SFGH), the San Francisco Department of Public Health, the San Francisco Consortium of Community Clinics, the Northern California Chapter of the American College of Surgeons, and the San Francisco Medical Society. A pilot program of uncompensated outpatient surgery was performed at the Kaiser Foundation Hospital. PATIENTS: Twenty-nine patients were referred to the ASAC between January 1 and November 1, 1994. Twenty-six patients were judged to be candidates for surgery, and 25 patients met the criteria for the ASAC program. One patient was referred to SFGH for treatment because of a perceived increased risk for hospitalization after surgery. RESULTS: Twenty-one patients underwent herniorrhaphy; three, excision of large inclusion cysts; and one, anal fistulotomy. Seventeen procedures were done under local anesthesia, seven under general anesthesia, and one under spinal anesthesia. None of the patients required hospital admission. No wound infections occurred. CONCLUSION: The ASAC successfully provided uncompensated low-risk outpatient surgery to 25 low-income uninsured patients in San Francisco. The coalition hopes, first, to include other San Francisco hospitals and surgical specialties, and second, to serve as a model for other communities throughout the country.

Ambulatory Surgical Procedures↗