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At least 19 recordsLinked to original sources
PubMed1992

The effect of femoral stem geometry on interface motion in uncemented porous-coated total hip prostheses. Comparison of straight-stem and curved-stem designs.

We compared the magnitudes of motion between the prosthesis and bone during axial and torsional loading in seven matched pairs of fresh-frozen femora of cadavera in which an uncemented, collarless, isthmus-filling, straight-stem (Harris-Galante) prosthesis had been placed in one femur and an uncemented, collarless, proximal-filling, curved-stem (anatomic) prosthesis had been placed in the other femur. The comparison was performed in order to determine the effect of the geometry of the stem on the magnitude of motion. Single-limb-stance loads and combined axial and torsional loads were applied to the implanted femoral prostheses with the use of a jig that simulated acetabular and trochanteric loading. Extensometers were used to measure motion at the prosthesis-bone interface. The prostheses were then removed and were reinserted, with cement applied to the proximal porous coating to simulate ingrowth of bone. The single-limb-stance and combined axial and torsional loads were reapplied and the magnitude of motion was recorded again. No significant differences in the magnitudes of the motion were found between the femora in which the straight stem had been implanted and the femora in which the curved stem had been implanted, during either simulated single-limb-stance or low-intensity torsional loading. When large torsional moments (twenty-two newton-meters) were applied, significantly less motion occurred at the bone-prosthesis interface, both proximally (p = 0.019) and distally (p = 0.0013), in the femora with the curved-stem implant than in the femora with the straight-stem implant. When cement had been applied proximally, proximal and distal motion between the prosthesis and the femur was decreased during simulated single-limb-stance and during torsional loading in the femora with the straight stem and the femora with the curved stem.

Adolescent↗
PubMed1979

Acute intracranial hypertension and auditory brain-stem responses. Part 2: The effects of brain-stem movement on the auditory brain-stem responses due to transtentorial herniation.

Movement of the upper brain stem (inferior colliculus) was correlated with the alterations in the amplitude of wave V of the auditory brain-stem responses (BER's) during supratentorial brain compression in cats. In vivo observation of the brain stem and postmortem inspection show that suppression of the amplitude of BER wave V reflects the extent of caudal displacement of the inferior colliculus. Marked suppression of the amplitude of BER wave V (approximately 30% of control) correlates with the beginning of transtentorial herniation, and complete suppression of the wave V indicates complete transtentorial herniation of the brain-stem and supratentorial structures. The BER wave V is thought to be a sensitive index of caudal movement of the upper brain stem due to transtentorial herniation.

Animals↗
PubMed1992

The effect of central stem and stem length on micromovement of the tibial tray.

The effects of a central stem and its length on cementless tibial tray micromovement were investigated using preserved cadaver tibial specimens. For axial loading tests, cyclical compressive loads ranging 50-1000 N were applied to the anterolateral portion of the implanted tray. With subsidence on the loaded side and lift-off on the contralateral side, micromotions on both sides and bending of the tray were measured. The three groups consisted of a stemless group, a 7.5 cm (short) central stem group, and a 15 cm (long) central stem group. For shear loading tests, shear loads ranging 20-250 N were applied to the central portion of the posterior rim of the tray anteriorly for 1,000 cycles. Displacement values for subsidence and micromotion were measured on the medial and lateral side of the trays and compared for each group. For axial tests, the long stem minimized subsidence and lift-off (P < .05) when compared to the stemless group. Although the short stem also tended to prevent contralateral lift-off, no significant difference was shown when compared to the stemless group. However for shear loading, both central stem lengths significantly reduced subsidence and micromotion (P < .05). The authors conclude that the tibial tray with a long stem can achieve better initiation fixation of the implant to bone when compared to the short stem and no stem groups.

Humans↗
PubMed1986

Proliferation of purified murine hemopoietic stem cells in serum-free cultures stimulated with purified stem-cell-activating factor.

Under conditions of steady-state hemopoiesis in normal mice, the majority of hemopoietic stem cells in the bone marrow are in the quiescent state of the cell cycle. These cells can be stimulated to proliferate in vitro by the addition of a factor termed the "stem-cell-activating factor" (SAF), which is present in medium conditioned by various cell types. This factor is indistinguishable in antigenic and molecular properties from the lymphokine interleukin 3 (IL-3). The action of SAF on the stem cell cycle was studied by examination of the survival of the spleen colony-forming unit(s) (CFU-S) after four days of serum-free culture in the presence of purified SAF. CFU-S subtypes were distinguished on the basis of the day of colony counting (i.e., days 7, 9, and 12 after transplantation). The results indicate that SAF selectively induces an increase of the day-7 CFU-S: the CFU-S number increased 2.7-fold on day 7 and 1.2-fold on day 9, and decreased fivefold for day-12 CFU-S. Similar results were obtained in SAF culture of partially and highly purified stem cells. The proliferation of day-9 CFU-S in cultures of low-density bone marrow cells was found to be similar to that of unfractionated bone marrow cells until day 4 of culture. However, in the culture of partially purified stem cells, this proliferation stopped between days 4 and 10, whereas it continued with unfractionated cells. This indicates that cocultured bone marrow cells affect the proliferation of stem cells upon induction by SAF; day-4 cultures of highly purified resting stem cells with purified SAF resulted in a similar decrease in day-12 CFU-S and an increase in day-7 CFU-S, as was observed with unfractionated bone marrow cells. The DNA histogram of the stimulated sorted cells clearly revealed an actively DNA-synthesizing population. The results are in agreement with those of a selective induction of proliferation by SAF of resting pluripotent hemopoietic stem cells.

Animals↗
PubMed1989

Abnormal brain-stem function (brain-stem auditory evoked response) correlates with acoustic cry features in term infants with hyperbilirubinemia.

We hypothesized that changes in brain-stem auditory evoked responses related to bilirubin would be associated with changes in cry because of the anatomic proximity in the brain stem of cranial nerves 8 (auditory) and 9 to 12 (vagal complex, which controls cry). Brain-stem auditory evoked responses and computerized cry analysis were used to study the concurrent effects of moderate hyperbilirubinemia on auditory function and cry. Fifty term infants were divided equally into two groups on the basis of serum bilirubin concentrations: low (less than 8 mg/dl; 136) mumol/L and moderate (10 to 20 mg/dl, 170 to 342 mumol/L). Forty-three infants had successful tracings of brain-stem auditory evoked responses recorded with a Cadwell model 5200A evoked response unit during two successive trials, and a cry recording of each infant was analyzed by computer. The moderate serum bilirubin group had an increase in percent cry phonation (p less than 0.02) and an increase in the variability of the first formant (p less than 0.04) in comparison with the low serum bilirubin group. Serum bilirubin values correlated positively with brain-stem conduction time (r = 0.36, p less than 0.01), percent phonation (r = 0.42, p less than 0.004), and variability of the first formant (r = 0.39, p less than 0.02). Percent phonation, the voiced component produced by increased neural control, correlated with the interpeak of waves latencies I to III (r = 0.32, p less than 0.03) and brain-stem conduction time (wave I to V) (r = 0.35, p less than 0.01). We conclude that hyperbilirubinemia affects adjoining areas of the brain stem that control hearing and cry production.

Brain Stem↗
PubMed1988

Dynamic axial brain stem distortion as a mechanism in the production of brain stem hemorrhages: role of the carotid arteries.

Dynamic axial distortion of the brain stem has long been recognized as occurring in the presence of supratentorial mass lesions. Although brain stem hemorrhages occur under these circumstances, the pathophysiology of these hemorrhages is still a matter of controversy. In the present study, the role of the carotid arteries in tethering the brain stem was evaluated during dynamic axial distortion of the neuraxis of the dog. Brain stem hemorrhages occurred in 32 of 48 dogs in which the carotid arteries were left intact (67%) and in only 9 of 46 animals in which the carotid arteries were sectioned (20%). The difference between the two groups is statistically significant (chi 2 = 19.3; P less than 0.001). In this study, we can eliminate intracranial pressure as the primary cause of the lesions because a single variable is present in one series and absent in the other, whereas intracranial pressure and its duration are kept constant. It is concluded that the tethering effect of the carotid arteries is a significant factor in the production of brain stem hemorrhages in the dog by dynamic axial distortion of the brain stem. A selective review of the literature on production of brain stem lesions is provided to support these findings.

Animals↗
PubMed1991

[The role of stem cell mobilization in the scope of autologous blood stem cell transplantation].

It is widely believed that hemopoietic stem cells have to be mobilized from extravascular sites into the circulation to guarantee a sufficient and safe blood stem cell autograft. The question of using mobilized or non-mobilized stem cells for transplantation purposes addresses the quality of hemopoietic engraftment rather than its feasibility. Two aspects are of clinical relevance: 1. The increment of peripheral cell concentration per time, and 2. shortening the duration of total aplasia following myeloablation and stem cell transplantation. When comparing the various stem cell mobilization techniques the CFU-GM yield per apheresis was highest during rh GM-CSF application (250 micrograms/m2/day continuous i.v. infusion), whereas the MNC yield was not greatly affected. More severe side effects were seen during rh GM-CSF infusion: One patient experienced an axillary phlebothrombosis. In a series of 15 advanced stage Hodgkin's lymphoma patients the reconstitutive ability of the various stem cell autografts, whether chemotherapy-, cytokine-, or non-mobilized, did not vary. Particularly in acute leukemias, mobilization of hemopoietic precursor cells does not necessarily exclude a concomitant mobilization of clonogenic tumor cells, and, therefore, the probability of disease-free survival after ABSCT might be lower when using mobilized stem cells for transplant.

Blood Component Transfusion↗
PubMed1982

Surface antigens of murine hemopoietic stem cells. IV. Characteristics of antisera exhibiting cell-lineage specificity, and differentiating ability of stem cells surviving treatment with antisera against cell-lineage antigens.

Hemopoietic stem cells express cell-lineage antigens in common with platelets, thymocytes and macrophages. Further evidence for the cell-lineage antigen model is presented. Erythrocyte-absorbed antiserum against purified mouse neutrophils cross-reacts with the hemopoietic stem cell in a lineage-specific manner. Thus, most of the anti-stem cell activity is absorbed out with neutrophils but not by other non-granulocytic hemopoietic cells. Of the four antisera tested for anti-stem cell activity, antiplatelet serum showed the highest degree of cell-lineage specificity (96% of the anti-stem cell activity satisfied cell-lineage criteria). To test predictions of the cell-lineage model of hemopoietic cell differentiation concerning the differentiating potential of stem cells selected for low concentration of cell-lineage antigen, bone marrow cells were treated with antiplatelet serum at a predetermined concentration required to produce 75-85% loss of spleen colonies. Stem cells surviving this treatment showed normal ability to form megakaryocytes and platelets. The results are consistent with postulates of the cell-lineage model.

Animals↗
PubMed2025

A Protocol for Detecting DNA Methylation Changes at CpG Sites of Stemness-Related Genes in Aging Stem Cells.

Aging adversely affects the self-renewal and differentiation capabilities of stem cells, which impairs tissue regeneration as well as the homeostasis. Epigenetic mechanisms, specifically DNA methylation, play a key role in the maintenance of pluripotency in stem cells and regulation of pluripotency-related gene expression. Age-related modifications in methylation patterns could influence the expression of genes critical for stem cell potency maintenance, including transcription factors Nanog and Sox2. The following chapter describes a step-by-step bisulfite sequencing protocol for detection of methylation changes in the aging stem cells and provides valuable insights into the stem cells epigenetic profile. Further, the methodology describes the steps of genomic DNA extraction, bisulfite conversion, real-time PCR amplification, and sequencing for an in-depth view of the epigenetic profile derived from aging stem cells.

DNA Methylation↗
PubMed1984

Expression of cell surface determinant(s) on murine myeloma stem cells and hematopoietic stem cells.

Murine B cell lymphomas and myelomas were examined for the expression of a determinant previously found exclusively on normal pluripotent stem cells colony-forming unit-spleen (CFU-s). This determinant(s), which is defined by a rabbit antimouse brain antiserum (R alpha MB), is present on the tumor stem cell population of some but not all B cell neoplasms examined. The determinant is not detected on tumor cells of the macrophage or T cell lineage. Absorption of the activity in R alpha MB with myeloma cells, concomitantly removed reactivity with the normal stem cell, CFU-s, and the myeloma stem cell, plasmacytoma CFU-s. Sorting analysis further showed that the antigen was diminished within a positive tumor population as cells acquired the capacity to secrete immunoglobulin. These studies suggest that this normal stem cell-associated antigen may also be an early differentiation antigen for the B cell lineage, and is expressed on some stem cells of B cell tumors.

Animals↗
PubMed1978

Compound impulse response for the brain stem derived through combinations of cochlear and brain stem recordings.

To overcome some of the problems involved in the application of brain stem evoked responses (BSER) in otoneurological diagnosis an approach is developed which combines cochlear and brain stem recordings. The activity of the cochlea and brain stem generators, as seen from the far-field recording electrode, is considered to be the output from a single system. The impulse response of this system can be derived through deconvolution of the brain stem evoked responses, BSER, with the compound action potential, AP, followed by appropriate filtering. This method is used on the recordings from 15 subjects with various degrees of cochlear hearing loss. The results show that the compound impulse response, CIR, for the brain stem consists of five recognizable peaks. From the individual subjects this response pattern is largely independent of intensity. By plotting the amplitude and latency of the individual peaks for all 15 subjects a set of normative data is retrieved. The variation in the data is small, probably because interfeerence from the periphery is eliminated and the separation of activity from the different brain stem generators is improved.

Audiometry↗
PubMed1979

Antibodies against pluripotent stem cells: their use in studying stem cell function.

The biologic characteristics and specificity of rabbit anti-mouse brain (RAMB) serum for pluripotent hemopoietic stem cells (CFU-s) is reviewed. The application of RAMB serum to the functional analysis of stem cell differentiation and self renewal characteristics is discussed. Preliminary data are presented which suggest the existence of two stem cell subcompartments. The majority of stem cells express membrane determinants that are detected by RAMB serum. A minor (5%-10%) stem cell subpopulation lacks the stem cell antigen and exhibits a greater self-renewal capacity than those cells expressing the antigen.

Animals↗
PubMedDate not supplied

Alterations in brain-stem auditory responses induced by head down tilting in hypertensives with supine brain-stem disorders.

The influence of head down (HD) tilting on brain-stem auditory evoked responses (BAER) was studied in hypertensives with supine brain-stem disorders (occipital headache, vertigo, nausea, diplopia, blurred vision occurring after night recumbency), in hypertensives without such phenomena and in normotensives. In the latter two categories of subjects HD tilting had no effect on BAER. On the contrary, in hypertensives with supine brain-stem disorders the manoeuvre induced a constant prolongation of I-V and III-V intervals and a depression in the amplitude of wave V; the alterations of BAER produced by HD tilting reveal probably a dysfunction of the superior brain-stem area and might be due to the impaired cerebral venous draining subsequent to the manoeuvre. The study of BAER after HD tilting seems to be a proper means to attest the supine brain-stem disorders displayed by some hypertensives.

Brain Ischemia↗
PubMed1985

Brain-stem auditory evoked potentials in children with brain-stem or cerebellar dysfunction.

Brain-stem auditory evoked potentials (BAEPs) were recorded in 23 children who had signs of brain-stem or cerebellar dysfunction. In patients with brain-stem gliomas, BAEPs were abnormal in all except one, in whom involvement of the brain-stem auditory pathway was limited to the midbrain tectum. The BAEPs were normal in neuronal ceroid lipofuscinosis, but abnormal bilaterally in inheritable leukoencephalopathies. All patients with Leigh's encephalopathy had BAEP abnormalities; in two, abnormalities occurred before the appearance of lesions on computed tomographic scan. Patients with Friedreich's ataxia and giant axonal dystrophy had abnormal BAEPs, but the test was normal in a child with similar neurologic findings with vitamin E deficiency. Patients with diffuse metabolic encephalopathies had variable findings. Thus, BAEP abnormalities are nonspecific for various disease processes but are frequently seen in neoplastic and neurodegenerative diseases, with primary white matter or extensive brain-stem involvement.

Adolescent↗
PubMed1984

Brain-stem involvement in multiple sclerosis: a comparison between brain-stem auditory evoked potentials and the acoustic stapedius reflex.

Brain-stem auditory evoked potentials (BAEPs) and the acoustic stapedius reflex (ASR) were recorded in 68 patients with definite, probable and possible multiple sclerosis (using the definitions of McAlpine). The high incidence of abnormal results, 68% and 60%, respectively, pointed to the diagnostic value of these two measures in detecting brain-stem dysfunction. Combination of the methods increased the diagnostic yield to 85%. Since in part the same brain-stem generator sites underlie BAEPs and the ASR, it was considered that a study of their correlation might serve to increase the reliability and validity of these techniques. There was 71% agreement overall between results from the two measures. Furthermore, 72% of the joint BAEP and ASR abnormalities corresponded in detection of the brain-stem lesion site. It was concluded that the combined approach may supply powerful, complementary information on brain-stem dysfunction, which may aid in establishing the diagnosis of multiple sclerosis.

Brain Stem↗
PubMed1978

Auditory brain-stem responses in comatose patients: relationship with brain-stem reflexes and levels of coma.

Auditory brain-stem responses (BSR) were recorded in 20 comatose patients in whom the level of brain-stem dysfunction was defined by clinical assessment of brain-stem reflexes and posture. No BSR abnormalities were found in the 10 cases with cortico-subcortical or diencephalic levels. The other 10 patients showed a clear relationship between alteration of the different components of the BSR and the clinical levels of brain-stem dysfunction caused by the rostro-caudal evolution. Alteration of wave P5 seems related to a midbrain dysfunction, of P3 to a pontine dysfunction and of P1 or P2 to a lower brain-stem dysfunction.

Brain Stem↗