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Biomedical subjects

B Kruger

Publications and source records attributed to B Kruger.

At least 19 recordsLinked to original sources
PubMed2004

Pancreas graft thrombosis: is there a role for trypsin.

PURPOSE: Thrombosis of the pancreas graft is the main cause of early graft loss in pancreas transplantation. We investigated whether hypercoagulability develops locally in the pancreas and contributes to thrombosis formation because of ischemia or reperfusion injury. It was further hypothesized that this might be induced by excessive intravascular trypsin activity. METHODS: Ten Patients undergoing pancreas transplantation were studied. In addition to the standard operation a 14 French catheter was inserted in the distal part of the splenic vein of the pancreas graft. After reperfusion blood samples were drawn simultaneously from the splenic vein of the pancreas graft (local samples) and the radial artery (systemic samples) at 0,1,2,5,10,30, and 60 minutes after reperfusion. RESULTS: After reperfusion a progressive hypercoagulability developed locally in the pancreas as seen by an increase of thrombin-antithrombin complexes and only a transient increase of plasmin-antiplasmin complexes. In addition antithrombin 3 and protein c decreased systemically. The alterations seem not to be triggered by trypsin because trypsin activity locally remained low despite trypsinogen release and activation as assessed by trypsinogen activation peptides. CONCLUSION: Local hypercoagulability might contribute to the development of graft thrombosis, however, the mechanism seems not to be related to ectopic trypsin activation.

Antithrombins↗
PubMed2000

RLR1 (THO2), required for expressing lacZ fusions in yeast, is conserved from yeast to humans and is a suppressor of SIN4.

We isolated a mutation (rlr1-1; required for lacZ RNA) in the Saccharomyces cerevisiae (Sc) RLR1 gene as a suppressor of sin4, a component of the Mediator subcomplex of the RNA polymerase II holoenzyme and a determinant of chromatin structure. RLR1 encodes a deduced protein found also in fission yeast, nematode worms, and humans. The presence of these orthologs suggests that Rlr1 family members comprise a class of putative KEKE motif-containing proteins, characteristic of certain chaperones as well as regulators and subunits of the mammalian 20S proteasome. A role for RLR1 (THO2) in transcription appears to occur at a step subsequent to transcription initiation (see also Piruat, J.I. and Aguilera, A., 1998. EMBO J. 17, 4859-4872); Sc genes fused to the reporter gene lacZ were expressed at a very low level, while the corresponding native chromosomal genes were expressed at approximately normal levels in rlr1 mutants. Our studies show that rlr1 mutations cause a wide range of growth defects in addition to their novel affect on lacZ.

Amino Acid Sequence↗
PubMed1999

Three-dimensional guidance system for implant insertion: Part II. Dual axes table--problem solving.

The three-dimensional guidance system for implant insertion is a technique for placing a radiopaque vertical orientation pin over the crest of the alveolar ridge on the stone cast during fabrication of the radiographic guide. The cross-sectional and panoramic reformatted images were reproduced on a Polaroid or 35-mm print. The true vertical orientation pin facilitates (1) identification and the exact planned location of each implant in the reformatted images of the CT scan, (2) establishment of the internal starting point for the osteotomy on a photographic print, (3) optimum implant orientation, and (4) measurement of the angulation between the true vertical orientation line and optimum implant orientation. With the aid of a newly developed dual-axes base and transfer of the internal starting point of each implant to the stone cast, the buccolingual and mesiodistal implant inclinations for each implant were transferred to a surgical guide in the form of surgical steel drill guide tubes. The resulting pilot osteotomy transfers to the alveolar bone the exact starting point and the buccolingual and mesiodistal inclination for each implant. The technique provides a three-dimensional guidance system for implant insertion that is extremely accurate and yet practical.

Anatomy, Cross-Sectional↗
PubMed1998

Three-dimensional guidance system for implant insertion: Part I.

A technique is presented, with two sets of newly designed drills, that facilitates three-dimensional guided insertion of implants. A radiographic guide has been fabricated with titanium markers that are transferred into the CT scan reformatted images. The resulting cross-sectional and panoramic reformatted images provide the precise location for each implant. The buccolingual and mesiodistal inclinations of each implant are measured and transferred to a surgical guide that contains steel drill guide tubes. The starting point and three-dimensional orientation of each implant is then transferred to a pilot osteotomy. The widening of an osteotomy, with end-cutting drills of the usual design, can lead to the loss of orientation because a wider drill cannot be effectively guided by a smaller diameter osteotomy. A newly designed set of drills has been developed that maintains tracking of the original orientation as the incremental increase in width proceeds. The three-dimensional guidance system for implant insertion was first accomplished in vitro and then on patients.

Anatomy, Cross-Sectional↗
PubMed1996

An evaluation of torque (moment) on implant/prosthesis with staggered buccal and lingual offset.

The supposition that staggered buccal and lingual implant offset is biomechanically advantageous was examined mathematically. The method of evaluation utilized a standard hypothetical geometric configuration from which implants could be staggered buccally and/or lingually in both arches. Torque (moment) values were calculated at the gold screw, abutment screw, and 3.5 mm apical to the head of the implant. Comparisons were made in percentages of change from the hypothetical standard to the buccal and/or lingual implant offset. In the maxillary arch, buccal offset decreased the torque (moment) while lingual offset increased it. If more lingually offset implants were present in the maxillary restoration, the total torque would be greater than if they were all in a straight line. Staggered buccolingual implant alignment often requires abutment reangulation. The resultant line of force produced by occlusal anatomy usually results in buccal inclination in the maxillary arch and lingual inclination in the mandibular arch. As a result, mandibular implant/prostheses are greatly favored over similar maxillary configurations because the mandibular resultant line of force usually passes lingually, closer to the components and supporting bone and considerably less torque is produced. Therefore, the concept of staggered offset for multiple implant-supported prostheses can be utilized on the mandible but is not recommended for the maxilla where maximum uniform buccal implant orientation is advised.

Algorithms↗
PubMed1994

Biomechanical considerations when combining tooth-supported and implant-supported prostheses.

The force distribution of multiple tooth-supported and implant-supported prostheses is completely different. A direct correlation exists between the degree of flexion at the site of loading and the amount of force distribution to other members of the prosthesis. Micromovement produced by the periodontal fibers facilitates force distribution to all the root surfaces of the natural tooth abutments. The rigidity of the implant/abutment/prosthesis configuration concentrates the force at the crestal bone at the site of loading with limited distribution to the remaining implants. Differential mobility concentrates the force distribution to the bone support of the most rigid members of splinted natural teeth or to the implants when they are united with natural teeth in a combined prosthesis. Implants always support the natural teeth and never the other way around. Therefore a nonrigid attachment is recommended between a tooth-supported prosthesis and an implant-supported prosthesis when they are combined. However, when implants are interspersed with natural teeth in the same prosthesis, the restoration will be implant borne. This requires special force distribution analysis to prevent implant overload.

Alveolar Process↗
PubMed1993

TSF3, a global regulatory protein that silences transcription of yeast GAL genes, also mediates repression by alpha 2 repressor and is identical to SIN4.

TSF3 encodes one of six (TSF1 to TSF6) recently identified global negative regulators of transcription in Saccharomyces cerevisiae. Mutant tsf3 strains exhibit defects in transcriptional silencing of the GAL1 promoter, allow expression from upstream activation sequence-less promoters, and exhibit pleiotropic defects in cell growth and development. Here we show that TSF3 is involved in transcriptional silencing mediated by the alpha 2 repressor and demonstrate that specific systems of transcriptional silencing may depend on the more global role of TSF3. Cloning and sequencing of TSF3 allowed us to predict a 974-amino-acid gene product identical to SIN4, a negative regulator of transcription of the HO (homothallism) mating type switching endonuclease. TSF3 disruptions are not lethal but result in phenotypes similar to those of the originally isolated alleles. Our results, together with those of Y. W. Jiang and D. J. Stillman (Mol. Cell. Biol. 12:4503-4514, 1992), suggest that TSF3 (SIN4) affects the function of the basal transcription apparatus, and this effect in turn alters the manner in which the latter responds to upstream regulatory proteins.

Amino Acid Sequence↗
PubMed1988

Reference thresholds for the ER-3A insert earphone.

Several recent studies have demonstrated that the ER-3A insert earphone may sometimes be directly substituted, without recalibrating, for a TDH-39/MX-41AR earphone. However, most available data have not been reduced to a form suitable for establishing a revised estimate of the reference threshold levels. This article reports such a data analysis performed on the results of five recent studies. The mean data from the five studies are typically within 1 dB of the provisional reference threshold SPLs given by the ER-3A manufacturer for calibration in a (HA-1) 2-cc coupler. After converting the mean data to equivalent Zwislocki-coupler-type ear simulator SPLs at each of the reported audiometric frequencies (125, 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz), agreement within 1.5 dB was seen with the revised estimate of minimum audible pressures given by Killion [J. Acoust. Soc. Am. 63, 1501-1508 (1978)]. Either the manufacturer's provisional SPLs or the average results from this study may be used with little noticeable difference for most purposes.

Auditory Threshold↗
PubMed1987

An update on the external ear resonance in infants and young children.

The diffuse field to ear canal sound pressure transformations determined for 26 children (34 ears) from birth to 3 years old, confirm the earlier findings [Kruger B. Ruben RJ. Acta Otolaryngol (Stockh) 1987; 103:578-85] that the external ear fundamental resonance frequency is significantly higher at birth (about 6 kHz), and decreases with age to adult values (2.7 kHz) by the second year. The transformations were measured with either single or double probe tubes (coupled to miniature microphones) that were placed in the ear canal of sleeping infants. The accuracy of the magnitude of the transformations is discussed. Previously reported implications for hearing aid selection are supported.

Acoustic Stimulation↗
PubMed1985

Accuracy of the Welch Allyn AudioScope and traditional hearing screening for children with known hearing loss.

The Welch Allyn AudioScope is a new screening instrument that allows both audiometric testing at 500, 1000, 2000, and 4000 Hz at 25 dB hearing level and otoscopic examination. Sixty-eight patients between 3 and 9 years of age with normal hearing or a variety of hearing losses comprised the study population. Immediately after receiving an audiologic evaluation the subjects were screened with a traditional screening audiometer and two examinations with the AudioScope, performed in a clinic examining room by pediatricians and nurse practitioners unaware of the children's hearing status. The AudioScope was as accurate as traditional hearing screening in identifying children with normal hearing and those with hearing loss. Log-linear modeling demonstrated that the results of AudioScope testing were similar to those of traditional hearing screening. However, the false positive rate was higher at 500 Hz for the first AudioScope examination, suggesting the need for two AudioScope tests. The AudioScope was quick and easy to use, nonthreatening to the subjects, less expensive than a pure-tone screening audiometer, and does not require a sound-treated room.

Audiometry↗
PubMed1978

Tympanic membrane perforations in cats: configurations of losses with and without ear canal extensions.

In cat, a small tympanic membrane (TM) perforation produces a low-frequency loss--in terms of sound pressure changes (deltaSP) in front of the TM re a 10-micronV round window cochlear microphonic (RW CM)--that varies inversely with frequency at a rate of 12dB/octave with a surgically shortened external auditory meatus (EAM). Losses were determined at the outer opening (deltaSP00) and at the TM (deltaSPTM) of four artificial EAM's of various lengths, volumes, and leakiness. In the low-frequency region, a leaky EAM produced a flat loss. In the midfrequency region, the flatness of losses was attributable to (1) the length of the EAM and (2) the location at which the loss was determined. EAM volume was not related to the configuration of the loss. Losses, under all conditions, were always identical in shape and magnitude for the open and closed systems. Clinically, hearing losses due to TM perforations are essentially frequency independent, especially in the low frequencies. The relation between voltage changes (deltaV) across the transducer and losses with different EAM's suggests that the discrepency between audiometric results and CM losses--at least in the high and midfrequencies--may be due to the use of precalibrated SPL's in clinical audiometry.

Acoustic Impedance Tests↗
PubMedDate not supplied

Middle ear transmission losses caused by tympanic membrane perforations in cats.

Losses (determined by measuring microphonic responses) were essentially identical, regardless of whether produced by admittance of sound into the middle ear via perforations in the tympanic membrane (TM) or in the bulla. With SPLs monitored directly at the TM, losses increased at 12 dB/oct with inverse frequency for f less than 1 kHz, a pattern determined by the changes in the (calculated) net sound pressure acting from front and back on the TM. Clinically, hearing losses due to TM perforations are frequency-independent. The difference between the two situations has mainly to do with the use of precalibrated SPLs in Clinical Audiometry.

Acoustic Stimulation↗