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Biomedical subjects

H Gruber

Publications and source records attributed to H Gruber.

At least 37 records · Page 2Linked to original sources
PubMed1999

Chemical stability of silicone oil in the human eye after prolonged clinical use.

OBJECTIVE: To investigate the assumption that silicone oil is chemically stable in the human eye after prolonged clinical use as a vitreous substitute. DESIGN: Experimental study. MATERIAL: Samples of silicone oil recovered from the vitreous cavities of 25 consecutive patients up to 26 months (mean, 9.2 months) after implantation and 4 different batches of original highly purified silicone oil with a kinematic viscosity of 5000 mPa.s were analyzed. Visible silicone oil emulsification was present in 18 of the 25 eyes. INTERVENTION: Gas chromatography/mass spectroscopy (GC/MS) was used to detect and characterize low-molecular weight components (LMWC). Gel permeation chromatography (GPC) was used to determine the molecular weight distribution of the silicone oils. Functional groups of the silicone oils were quantified and characterized by infrared (IR) spectroscopy and 1H nuclear magnetic resonance (1H NMR) spectroscopy. MAIN OUTCOME MEASURES: The sample oils explanted from the eyes were compared to the original oils with regard to LMWC, molecular weight distribution, and type and amount of functional groups. RESULTS: The GC/MS chromatograms showed no peaks indicative of LMWC in any of the 25 sample oils explanted from the eyes or any of the original oils. In the GPC chromatograms, the peak position occurred at the same retention times with identical signal shape in all original and sample oils, indicating that the molecular weight and the molecular weight distribution did not change after prolonged implantation. The IR spectroscopy and 1H NMR spectroscopy showed characteristic absorption bands at 1260 cm(-1) related to symmetric deformation vibration of the Si-CH3 group and at 800 cm(-1) related to the Si-(CH3)2 group. This was identical for all sample and original oils. CONCLUSIONS: Highly purified 5000-mPa.s silicone oils, used as prolonged retinal tamponades in patients with proliferative vitreoretinopathy, proliferative diabetic retinopathy, and tractional retinal detachment after central retinal vein occlusion, are chemically stable in the human eye and do not undergo chemical modification. The LMWC do not play a substantial role in the variations of oil emulsification.

Adult↗
PubMed1999

The nerve of Henle: an anatomic and immunohistochemical study.

The topography of the nerve of Henle was reviewed. Fifty-two human cadaveric upper extremities were studied. In 30 (58%) the nerve was well defined; in 22 (42%) its origin from the ulnar nerve was unidentifiable. The palmar cutaneous branch of the ulnar nerve separated from the ulnar nerve 5 to 11 cm distal to the medial epicondyle of the humerus to divide into its terminal branches in the distal forearm. Four patterns were detected: ulnar, radioulnar, vessel-related, and radial. These shared a consistent vascular branch, which sent 2 branches to the ulnar artery just proximal to the distal ulnar tunnel. Using a tyrosine hydroxylase antibody-based immunohistochemistry technique the nerve was shown to carry sympathetic fibers. Motor fibers were ruled out with Karnovsky's stain, which was used in combination with the tyrosine hydroxylase method in 10 specimens.

Adult↗
PubMed1999

regA, a Volvox gene that plays a central role in germ-soma differentiation, encodes a novel regulatory protein.

Volvox has two cell types: mortal somatic cells and immortal germ cells. Here we describe the transposon-tagging, cloning and characterization of regA, which plays a central role as a master regulatory gene in Volvox germ-soma differentiation by suppressing reproductive activities in somatic cells. The 12.5 kb regA transcription unit generates a 6,725 nucleotide mRNA that appears at the beginning of somatic cell differentiation, and that encodes a 111 kDa RegA protein that localizes to the nucleus, and has an unusual abundance of alanine, glutamine and proline. This is a compositional feature shared by functional domains of many 'active' repressors. These findings are consistent with the hypothesis that RegA acts in somatic cells to repress transcription of genes required for growth and reproduction, including 13 genes whose products are required for chloroplast biogenesis.

Algal Proteins↗
PubMed1999

Value of transrectal ultrasound in preoperative staging of prostate cancer.

BACKGROUND: The aim of the study was to compare preoperative transrectal ultrasound findings with final histopathological stage after radical prostatectomy to determine the value of TRUS in preoperative staging of prostate cancer. METHODS: The evaluation was performed as a retrospective study. In 114 radical prostatectomy specimens the histopathological, ultrasound and rectal digital findings were correlated. Mean age of patients was 63 years and in all patients a radical retropubic prostatectomy was performed. RESULTS: Organ confined PC was found correctly with TRUS in 68% and capsular penetration in 32%. Corresponding findings with digital rectal examination (DRE) were 68% and 17% respectively. Sensitivity of TRUS in organ confined PC (T1-2) was 66.1% (DRE 68.5%), specificity 32.6% (DRE 20%) and positive predictive value 55.7% (DRE 49.3%). Sensitivity, specificity and positive predictive value of TRUS for stage T3 (a,b,c) were 32.6%, 68.4% and 45.5% respectively. A separate evaluation of stage T3c revealed for TRUS: sensitivity 41.2%, specificity 81.8% and positive predictive value 36.8%. CONCLUSION: On the basis of this retrospective analysis, and due to the low sensitivity and specificity, TRUS is not suitable for adequate preoperative staging of prostatic cancer.

Adult↗
PubMed1998

Fast to slow transformation of denervated and electrically stimulated rat muscle.

1. Denervated fast extensor digitorum longus (EDL) muscles of adult rats were stimulated electrically for up to 4 months with a slow pattern resembling the activity in soleus (Sol) motor units and examined with antibodies against myosin heavy chains (MHCs). 2. The normal EDL contained, on average, 45% type IIB, 29% type IIX, 23% type IIA and 3% type I fibres. All type IIB and almost all type IIX fibres disappeared during the first 3 weeks of stimulation. They were replaced by type IIA and type I fibres, whose percentages increased to about 75 and 15, respectively. Type IIA fibres remained at 75% for nearly 2 months and were then gradually replaced by type I fibres during the next 2 months. The transformation occurred sequentially in the order IIB/IIX-->IIA-->I, the first step (IIB/IIX-->IIA) occurring after a short delay (2 weeks) and the last step (IIA-->I in originally IIB or IIX fibres) after a long delay (> 2 months). During the transformation coexpression of MHCs occurred. 3. It appears that the transformation to type I fibres occurred in pre-existing type II fibres since no signs of fibre damage or regeneration were observed. 4. Normal EDL was also stimulated through an intact nerve with the same pattern for up to 37 days. The effects on fibre type distributions were identical to those observed in the denervated EDL. The result indicated that the Sol-like pattern of evoked muscle activity, rather than nerve-derived trophic influences or denervation per se, was primarily responsible for the fast to slow transformation.

Animals↗
PubMed1998

The impact of a muscle target organ on nerve grafts with different lengths--a histomorphological analysis.

The present study was done in order to evaluate the influence of a target muscle on the regenerative processes in long nerve grafts. In 21 rabbits the saphenous nerve was used as a nerve graft and coapted to the cut motor nerve of vastus medialis. The animals were separated into three groups with different graft lengths, namely 3, 5, and 7 cm. In a second stage the distal end of the graft (Graft.dist.) was coapted to the motor branch of rectus femoris. Cross sections of the normal vastus nerve and the Graft.dist. before and 7 months after the connection to rectus femoris were analyzed histomorphometrically. Before coaptation to the target organ mean fiber number in the Graft.dist. of the 3-cm-long grafts was 3380 and decreased to 2413 in the 7-cm-long grafts. Seven months after coaptation the results showed a statistically significant decrease of fibers in the Graft.dist. of group two and three and a distinct decrease of the fibers in group one. Summarizing, in a two-stage nerve grafting procedure the reinnervation of the muscle target organ leads to a down-regulation of fibers in the distal end of short and long nerve grafts.

Animals↗
PubMed1998

Learning from Worked-Out Examples: The Effects of Example Variability and Elicited Self-Explanations

It was investigated to what extent example variability and the elicitation of sophisticated self-explanations foster the acquisition of transferable knowledge by learning from worked-out examples. In addition, it was asked whether the effects of these factors are moderated by the learners' levels of prior topic knowledge. To this end, we had 56 apprentices from a bank learn calculation of compound interest and real interest. They were randomly assigned to the four conditions of a 2 x 2-factorial design (factor 1: uniform vs. multiple examples; factor 2: spontaneous vs. elicited self-explanations). The learning results were measured by a post-test comprising near-transfer problems and far-transfer problems. It was found that the acquisition of transferable knowledge can be supported by eliciting self-explanations. In the case of near transfer, especially learners with low levels of prior topic knowledge profited from the elicitation procedure. On the whole, the findings underline the "causal" relevance of the quality of self-explanations for knowledge acquisition by learning from worked-out examples. The assumption that multiple examples foster transfer performance, at least when sophisticated self-explanations are elicited, was not supported. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Considerations on stimulated anal neosphincter formation: an anatomic investigation in search of alternatives to the gracilis muscle.

Electrically stimulated anal neosphincter formation with transposed gracilis is performed clinically in an increasing number of patients. The use of a stimulated gluteus maximus in this application has been reported also. The question arises whether or not an optimal design for such a procedure has already been ascertained. An anatomic study was performed on 30 human cadavers to evaluate the semitendinosus muscle and its suitability for construction of a stimulated anal neosphincter. Semitendinosus fulfilled requirements for transposition around the anal canal in all cases. The muscle length was found adequate for transposition; nerve and vascular supply provided a suitable arc of rotation. The pattern of innervation might allow selective stimulation of that particular part of the muscle, which is intended to restore sphincter function. For clinical application, a vascular delay procedure is strongly recommended.

Anal Canal↗
PubMed1998

[Nerve coaptation using CO2 milliwatt laser].

The technique of laser tissue welding with a low-output CO2 laser has become popular due to the minimal amount of nerve tissue damage caused. The purpose of this study was to ascertain the efficacy of nerve coaptation by laser tissue welding in comparison to micro-sutures. In a first series of 15 rats, peripheral nerves were transsected. 24 nerves were coaptated by laser welding (LW) with different parameters in order to evaluate the optimal laser settings. For comparison, six nerves were coapted (NS) with four 10/0 nylon sutures. Finally, the nerves were removed and the tensile strength of the different coaptations determined. The best results of the laser welds were obtained at laser settings of 40 to 60 mW in the continuous mode resulting in a tensile strength of 9.5 +/- 2.2 g. The tensile strength was 39.3 +/- 7.3 g for the sutured coaptation. In a second series, one sciatic nerve was coapted in thirteen rats by laser welding (LW) (60 mW, cont. mode) and in eleven rats using four 10/0 nylon sutures (NS). After six months, the Sciatic Function Index (SFI) was evaluated and the nerves were harvested for histological examination of transverse and longitudinal sections. All animals showed good regeneration and none of the 24 nerve coaptations showed dehiscence. The SFI was for the NS-group -94 +/- 23 and for the LW-group -77 +/- 20. The mean number of myelinated nerve fibres (NS 10,170 +/- 2512 vs. LW 11,902 +/- 1649) and the fibre diameter (NS 4.30 +/- 0.14 um vs. LW 4.02 +/- 0.59 microns) of the nerves distal to the coaptation were similar in both groups and showed no statistical difference. We conclude that nerve coaptation by CO2-laser welds are as successful as the 10/0 nylon sutures in the animal model. Improvements of welding techniques may in the future reduce nerve damage even further and so yield even better functional results.

Animals↗
PubMed1997

Human facial muscles: dimensions, motor endplate distribution, and presence of muscle fibers with multiple motor endplates.

BACKGROUND: Extrafusal muscle fibers of human striated skeletal muscles are known to have a uniform innervation pattern. Motor endplates (MEP) of the "en plaque" type are located near the center of muscle fibers and distributed within the muscles in a narrow band. The aim of this study was to evaluate the innervation pattern of human facial muscles and compare it with that of skeletal muscles. METHODS: Ten facial muscles from 11 human cadavers were dissected, the nerve entrance points located, and the dimensions measured. All muscles were stained in toto for MEPs using Acetylcholinesterase (AChE) and examined under the microscope to determine their location. Single muscle fibers were teased to evaluate the stained MEPs. RESULTS: The length of the different facial muscles varied from 29 to 65 mm, which correlated to the length of the corresponding muscle fibers. MEP zones were found on the muscles in the immediate vicinity of the nerves' entrance points and located eccentrically. Numbers and locations varied from muscle to muscle. Three MEP zone distribution patterns were differentiated: numerous small MEP zones were evenly spread over the muscle, a predominant MEP zone and two to three small zones were spread at random, and two to four MEP zones of equal size were randomly scattered. One MEP of the "en plaque" type was found in 73.8% of the muscle fibers and two to five MEPs were found in 26.2%. The distances between the multiple MEPs on one muscle fiber varied from 10 to 500 microm. CONCLUSIONS: This study suggests that facial muscles differ from skeletal muscles regarding distribution and number of MEPs. The eccentric location of MEP zones and multiple MEPs suggests there is an independent mechanism of neural regulation in the facial muscle system.

Acetylcholinesterase↗
PubMed1997

Basic anatomical investigation of semitendinosus and the long head of biceps femoris muscle for their possible use in electrically stimulated neosphincter formation.

Anal neosphincter formation with electrically stimulated gracilis muscle is used increasingly for the surgical treatment of fecal incontinence. An alternative to gracilis might be of interest if this muscle is not available. 30 semitendinosus muscles and 15 long heads of biceps femoris were investigated on human cadavers. In particular, the nerve and vascular supply of these muscles was studied, both representing basic factors for muscle transposition. The long head of biceps femoris m. was found to receive its dominant vascular supply from the first and second perforating artery and its nerve supply from one motor branch out of the sciatic nerve, both as described in literature. The examination of semitendinosus m., however, revealed new anatomical aspects in its vascular supply. In all cases semitendinosus m. was found to receive dominant vascular pedicles from the medial circumflex femoral artery close to the ischial tuberosity and the second perforating artery. The nerve supply consisted of two motor branches out of the sciatic nerve. Both muscles fulfilled several basic criterias for transposition to the anus. However, regarding these requirements, semitendinosus offered distinct advantages in comparison with the long head of biceps femoris. Due to its vascular and nerve topography, semitendinosus seems suitable to serve as an alternative to gracilis.

Anal Canal↗
PubMed1997

Three-dimensional representations of corneal deformations from keratotopography data.

PURPOSE: To improve the perception of corneal shape from the data measured by a corneal topography system. METHODS: A computer program to illustrate the deformation of the cornea measured by corneal topography is described. The deviations from a regular corneal curvature are presented in a three-dimensional (3-D) map. Elimination of the basic curvature in the individual cornea allows the small deformations of the cornea to be seen as shapes and not as power maps. CONCLUSION: The images obtained with the 3-D maps are different from the keratotopographic images. The latter show the deformation of the cornea on a micro-metric scale and are understandable in terms of shape or surgical planning. Using our inborn 3-D perception mechanism provides a better understanding of corneal shape. A shape reconstruction from the keratotopographic image alone is nearly impossible.

Cornea↗
PubMed1997

The external oblique muscle free flap.

To date, the external oblique muscle has been considered to have a purely segmental vascular supply and therefore has been used surgically only as a pedicled flap. To better define the vascular anatomy and nerve supply of the muscle, we performed arterial injection studies and dissected the nerves that entered the muscle in 35 human cadavers. We found that in addition to the segmental arteries, one or two large branches of the deep circumflex iliac artery contributed significantly to the blood supply of the external oblique muscle in 33 of the 35 cadavers. We also found that the lateral cutaneous branches of the intercostal nerves entered and supplied the muscle near its origin from the rib in a strictly segmental pattern. These anatomic findings enabled us to transplant the external oblique muscle successfully as a free flap based on the deep circumflex iliac vessels in six patients. The muscle flap is thin, pliable, and can be combined with an iliac bone or an abdominal skin transplant. Its vascular pedicle is long (mean 12 cm) and of adequate diameter for microvascular repair. The donor scar of the flap is inconspicuously situated along the inguinal ligament and the iliac crest. Finally, since the muscle has a multiple nerve supply, it has the potential to provide several functional units at the recipient site when transplanted as a functional free flap.

Abdominal Muscles↗
PubMed1997

Hypertrophy and transformation of muscle fibers in paraplegic patients.

Transcutaneous electrical stimulation of the quadriceps femoris muscle was applied in 14 paraplegic patients (10 spastic patients with spinal cord lesions and 4 patients with conus-cauda lesions with denervation atrophy). In both the spastic and the denervated group, the vastus lateralis muscle was biopsied and computed tomography (CT) images of the entire upper leg were made both at the onset and termination of the 8-month training period. The stimulation was carried out twice a day for 20 min. The increase in muscle tissue was significant in the CT images. The biopsies showed that the fiber diameter of both fiber types increased during the training period in the spastic group from 47 to 67 microns and in the denervated group from 22 to 38 microns. In both groups, the differences were significant between the first and second biopsies. Both groups showed a marked Type 2 fiber predominance. The histological and CT findings correlated with the clinical improvement of muscle function.

Biopsy↗
PubMed1997

[Comparative studies of morphometric and functional results following reconstruction of motor nerves].

In order to determine the value of a reconstructive procedure in the peripheral nerve, experimental studies often evaluate the number and the diameter of myelinated nerve fibers as a parameter for the quality of regeneration. This study addresses the correlation between the number of fibers in a peripheral motor nerve after microsurgical reconstruction and the functional result, expressed as the force of the reinnervated muscle. In a total number of 24 sheep, the motor branch to the rectus femoris muscle was severed. The muscle was reinnervated either by direct neurorrhaphy or by nerve grafting, performed in three different ways (free grafting to the ipsilateral muscle, free grafting to the contralateral muscle, vascularized grafting to the ipsilateral muscle). In the final experiments, the muscle force in the reinnervated muscle was determined by supramaximal electrical stimulation. Number and diameter of myelinated nerve fibers were evaluated by computer-assisted morphometric analysis. Regression analysis of morphometric data and the muscle forces was calculated. No correlation was found between fiber numbers in the nerve graft and the maximal force. However, a positive correlation between the number of myelinated fibers in the motor branch distal to the site of coaptation and the functional result was observed in some cases. The diameter of myelinated fibers had no influence on the functional outcome.

Animals↗
PubMed1996

Effect of the CO2 milliwatt laser on neuroma formation in rats.

BACKGROUND AND OBJECTIVE: The purpose of this study was to determine whether the milliwatt laser can suppress neuroma formation at the end of a divided nerve. STUDY DESIGN/MATERIALS AND METHODS: The peripheral nerves of eight rats were transected with microscissors and the cross-sectional area of their proximal ends was irradiated using the CO2 milliwatt laser. The power ranges used were similar to those applied to weld neural tissue. RESULTS: None of the eight irradiated nerve ends formed a neuromatous bulb and only one of them regenerated into the surrounding tissues. Histologically, these nerve ends did not show the disorganized picture of classic neuromas. On morphometric measurements, they contained less connective tissue than the control nerve ends (P < 0.001) and their nerve fibers were larger in diameter (P < 0.001) and better myelinated (P < 0.001). CONCLUSION: These findings in rats show that the CO2 milliwatt laser has the ability to suppress neuroma formation at the end of a divided nerve.

Animals↗
PubMed1996

Role of a muscle target organ on the regeneration of motor nerve fibres in long nerve grafts: a synopsis of experimental and clinical data.

The importance of the muscle target organ as a promoting factor for nerve fibre regeneration in nerve grafts is still a subject of controversial discussion. In the last few years we published uniform results of experimental series in sheep and rabbits in which we investigated the biology of nerve fibre regeneration in long nerve autografts without connection to a target organ. Surprisingly, we found excellent regeneration of myelinated nerve fibres without the influence of a target organ through the whole length of the nerve graft, with an increase in the number of nerve fibres up to fourfold at the distal end. In the sheep series the additional contact with a muscle target organ for 6 months had a variable effect on the fibre population in the distal end of the nerve graft. The results of our planimetric analyses of nerve biopsies in patients with facial paralysis, who were treated by cross-face nerve grafting and free muscle transplantation, are extremely divergent from the results of our experimental series. Instead of an increase, we found a decrease in number of regenerating nerve fibres arriving at the distal end of the cross-face nerve graft down to 20%. Species-specific differences in the biology of nerve regeneration are discussed, together with their implications for the complex clinical situation of nerve grafting with or without the influence of a target organ.

Anastomosis, Surgical↗