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Biomedical subjects

R Berg

Publications and source records attributed to R Berg.

At least 37 records · Page 2Linked to original sources
PubMed1998

Knowledge and attitudes of Arizona high-school coaches regarding oral-facial injuries and mouthguard use among athletes.

The authors assessed high-school athletic coaches' perceptions about oral-facial injuries and mouthguard use in sports that do not mandate mouthguard use. About 72 percent of the coaches said that their athletes sustained oral-facial injuries, 28 percent that some athletes used mouthguards regularly, 48 percent that athletes had sustained injuries and did not use mouthguards regularly, and 31 percent said they would not encourage mouthguard use. Advocacy for mouthguard use should focus on coaches, coaches' associations and rule-making organizations.

Adolescent↗
PubMed1997

xid affects events leading to B cell cycle entry.

X-linked agammaglobulinemia patients and X-linked immunodeficient (xid) mice possess mutations in the Bruton's tyrosine kinase (Btk kinase) gene and display defects in B cell development and activation by sIg cross-linking. Btk is an early activation kinase in sIg-cross-linked B cells. xid does not ablate Btk protein kinase activity, and immediate signal transduction events, such as tyrosine phosphorylation, occur in sIg-activated xid B cells. These cells do not subsequently progress into cell division and have a high rate of apoptosis, which has been shown to correlate with an absence of sIg-mediated induction of the bcl-xL protein. To establish the point where Btk activity is critical for progression beyond immediate signaling, we examined early and late events in sIg-cross-linked xid B cells. Induction of proto-oncogenes and nuclear factors occurred normally in xid cells. However, induction of cyclins and increased GAPDH mRNA was not observed in xid cells. Degradation of the cyclin inhibitor p27Kip1 occurred normally in xid cells. After 24 h of culture with anti-mu, the remaining live, nonapoptotic xid cells were enlarged, viable, and primed for subsequent stimulation by LPS. Our data suggest that the Btk kinase is not essential for several G1 events and that the failure of sIg-activated xid B cells to enter cell cycle correlates with a defect of cyclin induction. Moreover, these data suggest that Btk is important not only for immediate events following B cell activation and control of apoptosis but also for subsequent events leading to cyclin activation.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1997

Pharmacokinetic studies on 5-aminolevulinic acid-induced protoporphyrin IX accumulation in tumours and normal tissues.

Laser-induced fluorescence (LIF) for in vivo point monitoring and fluorescence microscopy incorporating a CCD camera were used to study the fluorescence distribution of 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) in tumours. Fluorescence in a chemically-induced adenocarcinoma in the liver of rats and in an aggressive basal cell carcinoma in a patient were studied after intravenous injection of ALA at a dose of 30 mg/kg body weight. The LIF technique demonstrated slightly more ALA-induced PpIX fluorescence in the tumour than in the surrounding normal liver and abdominal muscle of rats. The visible parts of the human basal cell carcinoma exhibited strong ALA-induced fluorescence, while this fluorescence was much weaker in the necrotic areas of the tumour and in the surrounding normal skin.

Adenocarcinoma↗
PubMed1997

Laser-induced fluorescence studies of normal and malignant tumour tissue of rat following intravenous injection of delta-amino levulinic acid.

BACKGROUND AND OBJECTIVE: Laser-induced fluorescence was studied in normal and tumour tissue of rat after intravenous injection of delta-amino levulinic acid (ALA). The aim of the study was to investigate the protoporphyrin IX accumulation in different tissue types in rat after systemically administered ALA. STUDY DESIGN/MATERIAL AND METHODS: A malignant rat tumour and normal tissue from 13 different organs were investigated in eight rats. The rats were injected with two different ALA doses, 30 and 90 mg/kg b.w., and the investigations were performed at 10, 30 and 240 min after the injection. The fluorescence was recorded utilising an optical fibre based fluorosensor at 405 nm excitation. RESULTS: Fluorescence spectra were recorded in the 400-750 nm wavelength region including the dual-peaked PpIX fluorescence at about 635 and 705 nm, and the tissue autofluorescence peaking at about 500 nm. The maximum tumour build-up of PpIX was achieved already in less than 1 hr after ALA injection. The fluorescence demarcation between tumour and surrounding tissue was a factor of 7-8:1 after 30 min and decreased for longer retention times. The accumulation in 13 different organs was investigated and a particularly high PpIX build-up was found in stomach and intestine. CONCLUSIONS: Fluorescence detection following i.v. injection of ALA provides attractive diagnostics for the experimental tumour used, indicating clinical usefulness.

Aminolevulinic Acid↗
PubMed1997

Time-resolved white light transillumination for optical imaging.

PURPOSE: To describe a new breast-imaging method with the potential of multi-spectral optical transillumination based on a time-resolved technique. MATERIAL AND METHODS: A breast phantom was irradiated with ultra-short laser pulses of white light generated by self-phase modulation of an incident high-power laser pulse in water. Time-resolved detection of the transmitted light was performed. Contrast resolution was studied using different absorbers located inside the breast phantom. RESULTS AND CONCLUSION: The results showed that simultaneous, multi-spectral transillumination is possible. The technique can also be used for measurements of optical properties in tissue.

Breast↗
PubMed1997

Morphometry of the small intestine in pigs with ileo-rectal anastomosis.

Ileo-rectal anastomosis (IRA), which is frequently used to measure prececal digestibility in pigs, could induce some disturbances of the normal absorptive function. Our aim was to investigate the effects of different IRA surgical procedures on the main histologic characteristics of the small intestine in pigs. The 4 different IRA procedures compared to intact pigs (INT) were the following: either end to end (EE) or end to side (ES) with or without preservation of the ileocecal valve (EEV, EE, ESV, ES respectively). At 147 d after surgery, samples of the wall of the duodenum, jejunum and ileum were taken under anesthesia and histometric examinations were performed on HE- and PAS-colored sections to estimate changes mainly of mucosa and muscle layers. The values recorded for villus length, crypt depth, and whole thickness of the mucosa suggested that the EE procedures disturb the small intestine less than the ES models. A new parameter, called epithelial quotient and calculated as [(villus length/crypt depth)/mitotic index], was proposed to improve the comparisons. According to this quotient, EE procedures did not significantly affect the mucosa of the whole small intestine. An increased density of goblet cells was recorded in all operated pigs along the small intestine, but mainly in the ileum after EE-IRA. The lymphatic follicle area was reduced. These findings, which were in agreement with a reduced mitotic index in the ileum of EE-pigs, indicated a decreased effect of noxious factors on the small intestinal mucosa in IRA-pigs, especially after the EE-IRA procedure. Some atrophic or hypertrophic effects on the muscle layers were related to the absence or preservation of the ileo-cecal valve. Finally it was concluded that i) there was no major disturbance after IRA, and ii) the end to end procedure was most beneficial for the structural integrity of the small intestine.

Anastomosis, Surgical↗
PubMed1997

Physiologic changes in the elderly.

A variety of age-related changes in the oral cavity and throughout the aging body can affect dental care and treatment plans. Some of these changes may be unavoidable features of senescence. Others, previously thought to be part of "normal aging," may be modifiable with lifestyle choices or may represent subclinical pathological processes. The ability to compensate for losses in system capacity varies among individuals and may result in functional changes ranging from substantial to unmeasurable. An appreciation of the intricacy of these relationships, and coordinated treatment with the primary care physician, can enhance the dental care of the aged patient.

Aged↗
PubMed1996

Hybrid antibody mediated veto of cytotoxic T lymphocyte responses.

Strategies are being sought that allow the induction of specific tolerance to allogeneic transplants without affecting other immune functions. The so-called veto effect has been described as one such technology where CD8+ cells suppress responses of class I MHC-restricted T-lymphocyte precursors to antigens expressed by those CD8+ veto cells. Yet, veto inhibition will not be able to provide complete tolerance to allogeneic grafts since it only operates on cell populations that express CD8. Other types of cells prevalent in most organs express different tissue-specific antigens that are recognized by alloreactive T-cells. Therefore, complete tolerance to an allogeneic transplant can only be achieved if all cellular components within the graft acquire the immune-inhibitory function. Here, we studied whether the veto effect could be exploited for this purpose nevertheless. We produced a hybrid antibody (HAb) combining a mAb specific for a class I MHC molecule with a soluble CD8 molecule. We found that this HAb specifically and effectively transferred veto inhibition to different stimulator cell populations. Thus, we have developed a strategy that promises to selectively and completely tolerize graft-specific CTLs without affecting normal immune responses.

Animals↗
PubMed1996

Permissive recognition during positive selection.

In the periphery alpha beta T lymphocytes recognize antigens in conjunction with major histocompatibility complex (MHC) molecules. In the thymus immature T cells are positively selected on MHC molecules in the apparent absence of cognate peptides. Thus, at different developmental stages a T cell responds to different epitopes, yet uses the identical alpha beta T cell antigen receptor (TcR). To explain this paradox it has been hypothesized that during positive selection immature T cells see peptides/ligands unique to the thymus, are selected by specific antagonists related to their cognate peptides, or are driven by lowered affinity thresholds of their TcR. Though different in detail, these theories rely on defined peptides uniquely matched to select certain TcR. However, we find that in a TcR-transgenic (TcR(trans +)) mouse severely limiting the diversity of peptides does not impair positive selection. We show that many unrelated peptides, including some naturally occurring on the cell surface, induce maturation of CD4-CD8+TcR(high) thymocytes. The same peptides when presented in conjunction with the selecting MHC molecule, are not recognized by peripheral T cells expressing the same TcR(trans). Therefore, these findings point to a promiscuous rather than discriminate recognition mode used by immature T cells.

Amino Acid Sequence↗
PubMed1996

Laser transillumination of breast tissue phantoms using time-resolved techniques.

The objective of this study was to evaluate a pulsed laser transillumination technique based on time-resolved detection on breast-tissue-like phantoms. Experiments have been performed on tissue-like plastic phantoms with different scattering characteristics. The effects of time-gate width, size, localisation and refractive index of hidden objects have been scrutinised. Our study showed that the shorter the time-gate the higher the contrast. The contrast is very dependent on the size of the hole, whereas the full width half maximum is not. Furthermore, the investigation showed that the changes of early detected light in an experimental setting is due to scattering, and not to a higher speed of the transmitted light.

Breast↗
PubMed1996

Quo vadis?

Explore the source record for details and available documents.

Germany↗
PubMed1996

The influence of extraction versus non-extraction orthodontic treatment on the soft tissue profile.

The aim of the present study was to study profile changes following orthodontic harmonization of enlarged overjet and to attempt to trace predictive aspects regarding prognosis of the soft tissue changes. Lateral cephalograms and study models of 40 female patients, at least 12 years old at the start of treatment, with an overjet of > or = 6 mm were analyzed before (T1) and after treatment (T2). Twenty patients were treated without extractions, while in the remaining 20 patients extractions of premolars were carried out bilaterally in both jaws. The 2 groups were found to be highly homogeneous as regards overjet, cephalometric characteristics, space condition in the upper arch at T1 and both at T1 and T2 as regards age. The most striking aspect of the findings was the considerable amount of variability of the soft tissue changes. These changes were found to be rather unpredictable for the individual patient, since the regression models employed could give only a very wide individual prediction range. The relatively small changes registered, using superimposition methods, in both groups as regards the sagittal position of the lips in comparison to the very strong changes observed in relation to the esthetic line shows that the influence of the growth of the chin and/or the nose on the facial profile might be more important than the influence of the orthodontic treatment. The interpretation of the findings in the present study suggests that, apart from marked cases of skeletal convexity or concavity, the extraction versus non-extraction decision should be based primarily upon current knowledge of long-term stability of orthodontic treatment results.

Adolescent↗
PubMed1996

Magnetic resonance lymphography in rats: effects of muscular activity and hyperthermia on the lymph node uptake of intravenously injected superparamagnetic iron oxide particles.

RATIONALE AND OBJECTIVES: We investigated the influence of muscular activity and regional body temperature changes on the accumulation of intravenously (i.v.) administered, dextran-coated superparamagnetic iron oxide (SPIO) particles in the lymph nodes of rats. METHODS: Four groups of rats (N = 21) were used. Five rats were allowed to move freely after i.v. contrast administration (group 1). In another five rats, muscular inactivity (group 2) was induced during i.v. injection of SPIO particles and for up to 2 hr thereafter by anesthesia. In seven rats (likewise anesthetized), the contrast agent was administered while the extremities of one side of the body were warmed in a water bath for 2 hr (group 3). The rats in groups 1-3 received 100 mumol Fe/kg of the contrast agent. Four rats not given SPIO particles served as the control group (group 4). The lymph nodes of all animals were removed 24 hr after SPIO administration and were embedded in an agar matrix for magnetic resonance imaging at 1.5 T using a proton-density-weighted spin-echo (PD-SE) sequence and a T2*-weighted gradient-recalled echo (T2* GRE) sequence. RESULTS: Signal loss varied widely among the different lymph nodes in group 1. A pronounced signal reduction was observed in the mesenteric (PD-SE = 20 +/- 6%, T2* GRE = 55 +/- 19%), iliac (PD-SE = 13 +/- 13%, T2* GRE = 44 +/- 24%), and popliteal (PD-SE = 24 +/- 7%, T2* GRE = 70 +/- 11%) lymph nodes and only a moderate reduction in the mandibular (PD-SE = 4 +/- 7%, T2* GRE = 42 +/- 15%), axillary (PD-SE = 0 +/- 4%, T2* GRE = 8 +/- 7%), and inguinal (PD-SE = 5 +/- 5%, T2* GRE = 34 +/- 18%) lymph nodes. The least pronounced signal loss occurred in the peripheral lymph nodes of group 2, ranging from 0 +/- 3% for PD-SE sequences and 10 +/- 11% for T2* GRE sequences to 13 +/- 15% for PD-SE sequences and 41 +/- 19% for T2* GRE sequences. In group 3, the uptake of contrast material in the peripheral lymph nodes of the hyperthermal side was significantly more pronounced than on the contralateral side (p < .01), and the contrast agent was distributed more evenly to the different lymph node groups than in group 1. CONCLUSION: Muscular activity and regional hyperthermia markedly influence the accumulation of SPIO particles in different lymph node groups in rats. These findings must be considered in preclinical studies and in the clinical administration of MR lymphography.

Anesthesia↗