Biomedical subjects
Publications and source records attributed to J Weissmüller.
We report a macroscopic shrinkage by up to 30 vol % during electrochemical dealloying of Ag-Au. Since the original crystal lattice is maintained during the process, we suggest that the formation of nanoporous gold in our experiments is accompanied by the creation of a large number of lattice defects and by local plastic deformation.
We report an experimental study of the variation of surface stress with surface charge density for nanoporous Pt immersed in aqueous solutions of NaF of various concentration. As the concentration is reduced, we find initially an increase in the magnitude of the surface stress-charge coefficient, followed by saturation at a value of -1.9 V. Since specific adsorption is expected to be reduced as the solution becomes more dilute, the results support the notion that changes in the bonding at the metal surface play a decisive role in determining the change in the surface stress during double-layer charging.
We analyze the simultaneous mechanical and chemical equilibrium at the interface between a fluid electrolyte and a solid conductor in terms of a continuum theory, with attention to surfaces of varying orientation and of arbitrary curvature. On top of the variable which is conjugate to the surface stress, the tangential strain, we introduce an additional degree of freedom for the surface deformation, the surface stretch, to account for the observation of a reversible normal relaxation of the top atomic layer as a function of the electrochemical potential. We derive relations between the materials constants of the surface, for instance, the pressure dependence of the electric potential at constant superficial charge density, and discuss experiments-using cantilevers or porous solids-by which they can be measured.
We have obtained the magnetic field dependence of static ferromagnetic correlations in nanocrystalline electrodeposited Co and Ni by means of the correlation function of the spin misalignment, determined from small-angle neutron scattering data. The approach yields a correlation length l(C), which is a measure for the spatial extent of inhomogeneities in the magnetization distribution. The correlation length depends strongly on the applied magnetic field with values ranging from 94 nm in nanocrystalline Co at low fields to about 15 nm at saturation. The results for l(C) indicate that in Co the main source of nonuniformity in the spin system is the anisotropy field of each individual crystallite, whereas in nanocrystalline Ni the main sources of spin disorder originate from twin faults or from the defect cores of grain boundaries.
Dimension changes on the order of 0.1% or above in response to an applied voltage have been reported for many types of materials, including ceramics, polymers, and carbon nanostructures, but not, so far, for metals. We show that reversible strain amplitudes comparable to those of commercial piezoceramics can be induced in metals by introducing a continuous network of nanometer-sized pores with a high surface area and by controlling the surface electronic charge density through an applied potential relative to an electrolyte impregnating the pores.
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Among 29 evaluable patients with progressive metastatic renal cell cancer treated by interferon alpha 2b in combination with vindesine and ifosfamide, we have observed an objective (complete and partial) response rate of 24.1% and an overall (complete and partial response and stable disease) response rate of 58.6%. The median duration of remission has not yet been reached, but the survival of responding patients is considerably longer than that of non-responders. Because we could not find any differences (sex, age, WHO performance status, prior therapy, site of metastatic disease) between responding and non-responding patients, we believe that the treatment might modify intrinsic characteristics of the tumour growth and/or host-tumour relationship in the long term. Although the toxicity recorded is high, the results are sufficiently positive to justify further investigation of this approach.
The in vitro evaluation of a pulsed Nd:YAG laser, showed an effective and fine fragmentation of urinary calculi and showed only minimal subepithelial bleeding in the directly irradiated canine ureter. Since 1989 we have treated ureteral calculi in 30 patients. The laser pulses of 15-20 mJ (at fiber tip), 20 ns, 20-25 cps are transmitted by a 300-microns quartz fiber with a specially formed tip focusing the light. The fiber is passed through an 11.5-F ureteroscope within a guide tube, or, without a guide tube, through one of the new minimized ureteroscopies and is placed in front of the calculus. In 27 patients the procedure was successful, without any residual concretions after 1 day. In our opinion the advantages of this method are the very fine-grained, complete fragmentation of all sorts of calculi, the highly atraumatic procedure, and the absence of either optical or acoustic irritation to the operator.
The problems of adrenal surgery are discussed--especially those in malignant tumors. The results of 115 operated patients (1969-1987) are presented, and the most advantageous operative procedures are described. Radical adrenal surgery is nearly the only chance for the involved patients.
Nephrectomy was performed in 938 patients with renal carcinoma between the years 1960 and 1986. The cumulative survival rate was 78.7 +/- 2.7% after 1 year; 62.9 +/- 3.2% after 3 years; 52.4 +/- 3.5% after 5 years, and 38.0 +/- 4.1% after 10 years. Of this group, 39 patients with lung metastases underwent surgery of their metastases following radical surgical removal of their primary tumor. Using the so-called actuarial method of analysis, the cumulative survival rate of this group was 66.7 +/- 15.1% 1 year after the lung surgery; 47.6 +/- 16.3% after 3 years and 32.7 +/- 15.7% after 5 years. The survival rates were correlated with the number of metastases, the operative techniques employed, and with the time interval between primary tumor removal and the appearance of secondary lung metastases. A comparison was made between those patients who underwent curative lung surgery (R0 group) and those with residual tumor (R+ group). Follow-up of the tumor status at the end of the study of the 39 patients is presented.
As part of the tumor aftercare service afforded by our policlinic, 91 patients were examined one to six times in 18 months following radical orchiectomy for testicular germ cell tumors. The period of observation averaged 35 months (3-147) after the contralateral removal of the testicle. In addition to the usual routine checks, sonography of the residual testicle also formed part of the established followup protocol. Among these patients sonography identified in residual testicles 3 testicular tumors (3.3%) which had escaped detection on palpation. The existence of these second tumors was demonstrated 3, 25 and 38 months following contralateral orchiectomy. In all instances the second lesion differed from the first tumor in histology. In another patient a plum-sized malignancy was revealed within a large concurrent hydrocele by scrotal sonography carried out 18 months following preceding contralateral orchiectomy. Thus, our group of patients gave an incidence of 4.4% for second primary testicular tumors, a poor known incidence rate. Such malignancies can be spotted early by ultrasound, they are genetically obscure just as the increasing morbidity of the unilateral disease. These results urgently suggest that after semicastration for testicular germ cell tumor the residual testicles should be regularly scanned by ultrasonography at four-month intervals. Retrograde sonography has been shown to detect even those small occult testicular tumors which pass unnoticed until metastasizing.
The rare duplications of the male urethra--only 210 cases are described till now--are found as many different variations. Only few of these malformations are symptomatic. The embryology is not always clear. Several classifications have been proposed, often too complicated or incomplete. We think, that our classification avoids these disadvantages. Each duplication is systematically classified in a morphological way according to the type of orifice (epispadiac, normotopic on the glans, hypospadiac, perineo-anal), without urinary transport (distal abortive types) or with urinary transport. The latter type can be complete (if a channel exists between bladder and an external meatus) or incomplete (if a channel exists between bladder and any point of the normal urethra or between the normal urethra and any accessory meatus). Four cases are reported and therapeutical aspects are discussed.
As an aspect of the caudal regression syndrome the dysgenesis of the sacrum, the correlating neuro-urological pathology, and a classification are presented, based on the literature and a report of ten cases. The sacral osteological anomaly--as a numerical and as a structural anomaly--and the neuro-urological defect exist to different extents. Therefore the diagnosis is made at several ages. The type of neurogenic bladder disturbance is the "lower neuron lesion". Use of a proper diagnostic approach and conservative or surgical therapy according to the type of lesion improve the prognosis by protecting the upper urinary tract and also ameliorate the social hardships resulting from incontinence. Irregularly correlated are disturbances of the rectum and of the lower extremities.
Juvenile male rats received either 20 mg DDVP or 40 mg malathion/kg on the 4th and 5th day of life, and either 10 mg DDVP or 20 mg/kg malathion daily from the 4th to the 23rd day of life. The histological examination of the testes showed slight reductions of the spermatogentic cells and Leydig cells. Therefore, it is assumed that testosterone synthesis is reduced, followed by damage to spermatogentic cells. All disturbances return by normal by the 50th day of life.
Juvenile male rats of Wistar/Han strain were fed DDT suspended in olive oil. They received either 500 mg/kg at the 4th and 5th or 300 mg/kg daily at the 4th till 23rd day of life. After certain interval the testes were examined histologically, and at the 60th and 90th day of life fertility was proved. The spermatogenetic cells showed an increase of the physiological degeneration in the course of spermatogenesis and a decrease of their total number. The number of Leydig cells was diminished. In parallel, the litters of normal female rats mated to treated males were smaller than those of controls. The hypothesis is suggested that the damage of the seminiferous epithelium can be explained by a lack of local testosterone.
Immature male rats receive orally DDVP 20 mg/kg on the 4th and 5th resp. 10 mg/kg on the 4th to the 24th day of life or malathione 40 resp. 20 mg/kg. At defined days the testes are examined histologically. The body weight does not change. The testis weight, tubular diameter, number of Sertoli cells, and of A-spermatogonia per tubular cross section as well as the number of Leydig cells is diminished. Malathione produced more severe alterations, they disappear, however, until the 50th day of life. Refering to the metabolic mechanisms of both the phosphatic esters a local lack of testosterone causing the disturbances is discussed.