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Biomedical subjects

R Hartung

Publications and source records attributed to R Hartung.

At least 109 records · Page 6Linked to original sources
PubMed1992

[Initial studies of the possibility of selective ablation of arteriosclerotic vascular changes using laser-induced shock waves].

We studied the effect of laser-induced shock waves in 94 arterial segments from freshly obtained autopsy material. In analogy to the well-established method of shock-wave based lithotripsy, the new principle of our treatment depends on an indirect interaction of the laser energy with the arterial wall via laser-induced mechanical shock waves (angiotripsy). We used a Nd:YAG laser, 1064 nm, 8-20 ns pulse-length to create shock waves that effected smooth craters in arteriosclerotically affected arteries. The histological examination found no thermal damage. Shock waves applied to the healthy and normal arterial wall only resulted in focal intimal ablation and in a minor loosening of the medial structures. The examination of the irrigation solution by means of a laser-guided, high-resolution analysis of the particles revealed that, in 97%, the particles created by our shock wave angiotripsy showed a diameter of less than 5 mm and an area of less than 25 mm2. Based on these first in vitro results, it seems possible to ablate arteriosclerotically affected tissue without significant damage to normal wall segments. Further in vitro and in vivo studies are required to evaluate the clinical implications of this new therapeutic approach.

Angioplasty, Laser↗
PubMed1990

Laser-induced shock wave lithotripsy. Influence of laser pulse energy and irrigation solutions on stone disintegration.

With a high intensity Q-switched Nd-YAG laser shock waves can be generated in a liquid close to the calculus. Up to 80 mJ single pulse energy with 8 nsec pulse duration can be transmitted through flexible quartz fibers. Energy conversion and enhancement can be accomplished at the fiber tip with optical focussing of the light at the quartz tip, with irrigation solutions and with high pulse energies. Iron-III-dextran solutions (1 mg Fe3+/1) and magnesium chloride (50 mmol/l) increased the pressure in the laser induced breakdown up to ten times (8,000-10,000 bar). Smaller stone particles and higher efficacy in stone fragmentation could be achieved.

Humans↗
PubMed1990

[Laser lithotripsy with the neodymium YAG laser].

Laser-induced shock wave lithotripsy (LISL) with a Q-switched neodymium-YAG laser depends on the generation of a laser-induced breakdown in the fluid surrounding the stone. An oscillating plasma bubble is created, directing shock waves towards the stone. These cavitational effects fragment the calculus into small particles. A new bifunctional laser is introduced: this allows both nanosecond pulses for shock wave generation and disintegration of urinary calculi and millisecond pulses for biliary stones and tissue coagulation. It can be supplied with 320-, 400-, and 600-micron fibers. We have treated 189 ureteric stones in 185 patients with laser lithotripsy utilizing flexible ureteroscopes (n = 26) or rigid ureteroscopes (n = 159). It proved possible to fragment 179 stones into small pieces. In eight patients LISL was not successful. A rigid cystoscope that can be dismantled into an upper and lower hemisheath for the introduction of flexible endoscopes into the ureter without prior dilatation of the ureteral orifice was used in 15 patients.

Cystoscopes↗
PubMed1989

First clinical experience with a Q-switched neodymium:YAG laser for urinary calculi.

Animal studies using a high intensity nanosecond pulsed neodymium:YAG laser did not reveal any serious tissue damage. Following these investigations patient treatment was begun in June 1987. Laser energy of a neodymium:YAG laser with an 8 nsec. pulse duration and a repetition rate of up to 50 Hz. was coupled into a flexible 600 resp. 400 micron. quartz fiber. Laser-induced breakdown was created with 35 to 50 mJ. at the fiber tip, resulting in a shock wave that disintegrated the calculus into tiny fragments. A total of 56 patients with 58 calculi (54 ureteral and 4 kidney stones) was treated from June 1987 to March 1988. Of the calculi 48 could be fragmented completely, while 6 others were reduced to a size small enough to be removed with forceps. Four stones composed of calcium oxalate monohydrate could not be disintegrated. The combination of laser stone disintegration with flexible ureterorenoscopy implies the possibility of an atraumatic, 1-step procedure for fragmentation of ureteral and kidney calculi.

Endoscopy↗
PubMed1988

Phosphatidylcholine-fatty acid membranes. I. Effects of protonation, salt concentration, temperature and chain-length on the colloidal and phase properties of mixed vesicles, bilayers and nonlamellar structures.

The phase and colloidal properties of phosphatidylcholine/fatty acid (PC/FA) mixed vesicles have been investigated by optical methods, acid-base titration, and theoretically as a function of temperature (5-80 degrees C), molar lipid ratio (0-1), lipid chain length (C14-C18), headgroup ionization (1.5 less than or equal to pH less than or equal to 10), vesicle concentration (0.05-32 mumol vesicle.dm-3, and ionic strength (0.005 less than or equal to J less than or equal to 0.25). Increasing the fatty acid concentration in PC bilayers causes the phase transition temperatures (at 4 less than or equal to pH less than or equal to 5) to rise until, for more than 2 FA molecules per PC molecule, the sample turbidity exhibits only two transitions corresponding to the chain-melting of the 1:2 stoichiometric complexes of PC/FA, and pure fatty acid. The former transition is into a nonlamellar phase and is accompanied by extremely rapid vesicle aggregation (with association rates on the order of Ca approximately 10(7) dm3.mol-1.s-1) and massive lipid precipitation. Fluid-phase vesicles with less than 2 FA per PC associate much more slowly (Ca approximately 10(3) dm3.mol-1.s-1), their aggregation being comparable to that of the ordered-phase liposomes. Under no conditions was the relation between the fatty acid concentration and the vesicle association rate for the fluid-phase vesicles linear. In contrast to the X-ray diffraction data, optical measurements reveal a 'pretransitional region' between the chain-melting temperature of the PC component and the temperature at which the gross transformation into a nonlamellar phase sets in. This is seen for all lipid mixtures investigated. On the relative temperature scale, lipids with different chain lengths behave qualitatively similarly; however, the effective association constants determined for samples of constant lipid concentration seem to decrease somewhat with the number of CH2 groups per chain. Fatty acid protonation, which yields electrically neutral bilayers, invariably increases the rate of vesicle association; we have measured, for example, Ca approximately 10(2) at pH approximately 7 and Ca approximately 10(7) dm3.mol-1.s-1 at pH approximately 4). Protonation of the phosphatidylcholine phosphate groups, which causes a net positive charge to accumulate on the lipid vesicles, initially increases (Ca approximately 10(8) dm3.mol-1.s-1) but ultimately decreases (Ca approximately 10(7) dm3.mol-1.s-1) the rate of association between PC/FA (1:2) mixed vesicles.(ABSTRACT TRUNCATED AT 400 WORDS)

Chemical Phenomena↗
PubMed1988

Laser induced shock wave lithotripsy--biologic effects of nanosecond pulses.

Laser energy of a Nd-YAG laser (1064 nm. wave length, 8 nsec pulse duration) was directed against various tissue cultures and the urothelium of the ureter, bladder and kidney parenchyma in pigs. Single pulse energy was 50 to 120 mJ with a repetition rate of 20 Hz. Urothelium and kidney parenchyma were irradiated in seven pigs. Tissue samples were examined histologically and electron microscopically directly, two, four, eight and 12 days after irradiation. No macroscopic lesion could be found. Maximum energy caused a small 'rupture cone' of 40 micron. depth. No thermic effects or necrosis resulted, so that no harm is to be expected with unintentional irradiation during laser stone disintegration.

Animals↗
PubMed1988

Use of pulsed Nd:YAG laser in the ureter.

An Nd-YAG laser of 1064-nm wavelength, 8-nanosecond pulse duration, and single-pulse energy of 20 to 80 mJ can create shock waves with a peak pressure of 1000 bar in less than 4 nanoseconds. The safety of this laser has been demonstrated in cultured cells, whole blood, and porcine urothelium. Clinically, ureteral calculi have been removed from 24 of 27 patients.

Animals↗
PubMed1987

[Special aspects of right colon cancer].

752 patients with colon carcinoma of the years 1966-1985 were studied retrospectively. 189 tumors were located in the right and 563 in the left colon. There was no difference in the 5-year survival rate, Dukes classification and operative mortality in both groups. Considering the higher median of tumor diameter, the three months longer diagnostic delay and the twice higher rate of undifferentiated carcinomas the prognosis of the right sided tumors is relatively better. In our opinion the cause of this more efficient local tumor defence is the better blood and lymph supply of the right colon and mucosal mechanisms. Expression of this better tumor defence is the distinct tumor colitis in the right colon. Improvement of the right colon carcinoma prognosis is to be expected of earlier tumor diagnosis. Routine endoscopic evaluation of hemoccult positive subjects is most helpful.

Adult↗
PubMed1987

Animal experiments on hemostasis with a collagen-fibrin tissue-adhesive sealant in the nephrostomy tract.

After a median laparatomy, nephrostomy was performed on 22 porcine kidneys: puncture, dilatation and introduction of a 26-French operating sheath through the parenchyma into the renal pelvis. At the end of the operation, an 8-French nephrostomy catheter prepared with a collagen-fibrin tissue-adhesive sealant was introduced through the operating sheath and the sheath was afterwards extracted. The hemostasis in the nephrostomy tract was very good in all 22 cases. There were no complications such as wound infection or stone formation during a post-operative period of between one and 95 days. Experimental investigations showed severe bleeding in nontamponade of the nephrostomy tract, in tamponade with an 8-French nephrostomy catheter and in tamponade of the nephrostomy tract with the collagen fleece wrapped around an 8-French nephrostomy catheter but not coated with the fibrin glue.

Animals↗
PubMed1987

Subcutaneous heparin injection in the upper arm as a method of avoiding lymphoceles after lymphadenectomies in the lower part of the body.

The authors have measured the concentration of biologically active heparin in the drainage fluid after ilioinguinal, pelvic and retroperitoneal lymphadenectomy. After s.c. heparin administration in the thighs high levels of heparin were found in the drainage fluid of all patients (up to 0.89 IU/ml). After s.c. heparin application in the upper arms, no measurable concentrations of heparin were detected. Lymph loss in these patients was considerably lower. According to this experience, subcutaneous application of heparin into the upper arms is to be recommended in patients who undergo lymphatic surgery of the lower part of the body.

Heparin↗
PubMed1987

[Morphologic examination of the urothelium after irradiation with laser energy].

The energy of a Nd-YAG laser (1,064 nm wave length, 8 ns pulse duration) was used to irradiate the urothelium of the ureter or bladder and kidney parenchyma in pigs. Single pulse energy was 50-120 mJ with a 20-Hz repetition rate. The horizontal laser beam was reflected 90 degrees down by a 100% mirror and with a specially designed apparatus focussed on the surface of the tissue. Laser light from a quartz glass fiber was also focussed directly onto the tissue. Urothelium and kidney parenchyma were irradiated in 7 pigs. Tissue samples were examined histologically and raster electron microscopically 2, 4, 8 and 12 days after irradiation. No macroscopic lesion could be found. Maximum energy caused a small cone of 40 micron depth. No thermic effects or necrosis resulted, so that no harm is to be expected with unintentional irradiation.

Animals↗
PubMed1987

Local hemostasis of nephrostomy tract with fibrin adhesive sealing in percutaneous nephrolithotomy.

In 26 patients percutaneous nephrolithotomy was carried out under local anesthesia with systemic sedation. Instead of the 25-French nephrostomy catheter used so far, a 5- or 10-French nephrostomy catheter prepared with a collagen-fibrin adhesive sealant was introduced into the nephrostomy tract. In all cases, excellent hemostasis was attained with the fibrin glue. In applying a fibrin glue, the danger of protracted venous or arterial hemorrhage from the parenchymal canal can be markedly reduced; the large-lumen nephrostomy catheter can also be dispensed with.

Aprotinin↗
PubMed1986

[Preoperative staging and follow-up in rectal cancer using endorectal sonography].

32 patients suffering from rectal carcinoma were examined by endorectal sonography. The preoperative staging by sonography was compared with digital palpation, colon enema and computertomography of the pelvis. In 90% of the cases the sonographic determination of the grade of invasion was identical to the histopathological examination. The efficiency of local destruction methods of rectal carcinoma (cryotherapy) can be controlled by this method.

Biopsy↗
PubMed1985

Changes in height velocity of obese preadolescents during weight reduction.

Height velocities prior to and during weight reduction were determined retrospectively in 19 obese children selected because of a 10% or greater fall in weight for height. Mean duration of the weight reduction period was 9.7 months. All children were treated with a balanced calorie-deficit diet containing 1.5 to 2.0 g of protein per kilogram of ideal body weight per day. Height velocities were normalized by calculating the Z score for each one. Prior to weight reduction, the mean (+/- SD) Z score for height velocity was 2.32 +/- 2.47 units. Eleven patients were 2 SDs or more above the mean height velocity for age and sex. During weight reduction, the mean Z score for height velocity decreased significantly to 0.62 +/- 2.37 units. The change in Z score before and during weight reduction was significantly correlated with the change in weight but not with the change in weight for height. These data indicate that even mildly restrictive diets may be associated with a reduction in linear growth velocity. The implications of these observations for the risk of other adverse consequences of weight reduction are not clear. Nonetheless, our observations emphasize the importance of careful monitoring of obese children during mildly restrictive dietary therapy.

Child↗
PubMed1985

Novel methods for the estimation of acceptable daily intake.

This paper describes two general methods for estimating ADIs that circumvent some of the limitations inherent in current approaches. The first method is based on a graphic presentation of toxicity data and is also shown to be useful for estimating acceptable intakes for durations of toxicant exposure other than the entire lifetime. The second method uses dose-response or dose-effect data to calculate lower CLs on the dose rate associated with specified response or effect levels. These approaches should lead to firmer, better established ADIs through increased use of the entire spectrum of toxicity data.

Animals↗
PubMed1985

[Dissociation of testis and epididymis in incomplete descent].

Failure of fusion between testis and epididymis will usually be encountered during operations for undescended testis in children and for infertility in adults. In 325 groin dissections for undescended testis monorchism was diagnosed in 3.7% and nonfusion of testis and epididymis in 1.2%. Case reports of three unilateral and one bilateral conditions are presented. Intraoperative misjudgement of this condition is likely to occur if the blind ending epididymis is mistaken for an atrophic testis. Careful search for the missing testis is mandatory.

Adolescent↗