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Biomedical subjects

B Brenner

Publications and source records attributed to B Brenner.

At least 289 records · Page 16Linked to original sources
PubMed1983

Technique for stabilizing the striation pattern in maximally calcium-activated skinned rabbit psoas fibers.

A procedure was developed for stabilizing the striation pattern of fully activated skinned rabbit psoas fibers. Inhomogeneities of the striation pattern that develop during the rise in tension and also during isometric steady state are completely reversible by this procedure. The striation pattern can be stabilized for approximately 2 h. During this period isometric tension and speed of isotonic shortening decrease less than 10-20% of their initial values.

Animals↗
PubMed1982

A new technique for securing a chest tube.

Most techniques described for securing a chest tube in position do not discuss closing the orifice in the chest wall after removal of the tube. An air tight closure of the chest wall and good approximation of the wound edges after removal of the chest tube must be done to prevent complications and obtain a cosmetically good scar. A technique for securing a chest tube is described that permits excellent approximation of the wound edges upon removal.

Humans↗
PubMed1982

Evidence for cross-bridge attachment in relaxed muscle at low ionic strength.

In vitro at low ionic strength (mu = 0.02 M) and 5 degrees C, myosin subfragment-1 shows significant binding to regulated actin in the presence of ATP, independent of the concentration of free Ca2+. Under the same conditions, single skinned rabbit psoas muscle fibers develop force only in the presence of Ca2+ and are relaxed in its absence. However, the stiffness, measured with very rapid stretches (0.5% of muscle length in 0.1 ms), is high even when the fibers are relaxed. This "rapid stiffness" of the resting muscle is sensitive to ionic strength, becoming small at normal ionic strength (mu = 0.17 M). At low ionic strength, the rapid stiffness is approximately proportional to the overlap between the actin and myosin filaments. At zero overlap (sarcomere length = 3.8 microns), the stiffness is less than 20% of the value measured at full overlap. This remaining 20% is relatively insensitive to ionic strength, like the passive resting tension, and it may in fact be due to the structures responsible for the resting tension. Thus, both in vitro binding and the effect of overlap on rapid stiffness measurements in fibers suggest that cross-bridges are attached to actin in relaxed muscle at low ionic strength.

Actins↗
PubMed1982

Incidence, prognostic significance and therapeutic modalities of central nervous system involvement in multiple myeloma.

In 114 patients with systemic malignant gammopathies followed during a 10-year period in the hematology clinic of the Rambam Medical Center, 23 episodes of CNS involvement were recorded. 19 cases with spinal cord compression and 4 cases of intracranial plasmacytomas. Early diagnosis followed by prompt laminectomy and subsequent radiotherapy resulted in complete recovery in 50% and partial improvement in 30% of the patients with spinal cord involvement. In good responders. overall survival was not affected by the neurological complication. In the 4 patients with intracranial involvement, external plasmacytomas of the skull preceded the neurological symptoms. 3 of them were diagnosed late, which led to delay and failure of accurate treatment. Only 1 patient was immediately operated and continued to be well for the past 2 years.

Aged↗
PubMed1979

Depressed affect as a cause of associated somatic problems.

Depressed affect as a cause of associated somatic problems is explored by means of data on affect, appetite, energy, and sleep collected from a community sample and from subsamples contacted after each of several time lags. The analysis of the data indicates that depressed affect is a cause of the major somatic problems associated with it. It is suspected that depressed affect involves continuing high density neural firing which, over a period of months, causes a reduction of post-synaptic biogenic amine receptor cell sensitivity in the brainstem, with the diencephalon as the major site. This results in a functional impairment responsible for the somatic problems.

Affect↗
PubMedDate not supplied

High prevalence of activated protein C resistance due to factor V leiden mutation in cases of intrauterine fetal death.

OBJECTIVE: To test a possible association between activated protein C resistance and intrauterine fetal death. METHODS: The activated protein C anticoagulant activity and factor V R506Q mutation were assessed in 14 nonpregnant women with a history of intrauterine fetal death and 14 healthy controls. RESULTS: Four women in the study group were heterozygotes for the factor V mutation and none of the controls. The mean activated protein C activity of the study group was statistically significantly lower than that of the controls (P = 0.013). CONCLUSION: Resistance to activated protein C activity may be of etiologic importance in some cases of intrauterine fetal death.

Activated Protein C Resistance↗
PubMedDate not supplied

The necessity of using two parameters to describe isotonic shortening velocity of muscle tissues: the effect of various interventions upon initial shortening velocity (vi) and curvature (b).

In skinned skeletal muscle fibers and skinned preparations of myocardium or smooth muscle, for all conditions studied, the length traces during isotonic shortening are always found to be significantly curved. It is demonstrated that the observed curvature is not simply due to inhomogeneities on the sarcomere level in striated muscle, damaged ends of the preparations, double overlap and collision of filaments, or depletion of MgATP during the period of isotonic shortening. It is shown that the velocity of shortening can be described by an exponential function: v = vi exp (-b[SLi-SL]) with SLi: sarcomere length at the start of the release; SL: sarcomere length during isotonic shortening. Thus, instantaneous shortening velocity (v) is determined by two parameters: vi, the initial shortening velocity for SL = SLi, and b, a constant characterizing the decrease in velocity during isotonic shortening. Factors which affect isotonic shortening can do this by affecting vi, or by changing b, or both. Therefore, when analysing the effects of interventions which affect instantaneous shortening velocity, these two possibilities have to be distinguished. Since curvature of the length traces might be caused by noncross-bridge components, only vi, the initial speed of shortening, is a parameter which directly reflects kinetics of the cross-bridge cycle while instantaneous speed of shortening might also be affected by noncross-bridge factors. Analysing isotonic shortening in terms of vi and b, the effects of ionic strength, free Ca++ concentration, MgATP/MgADP ratio and temperature on unloaded isotonic shortening have been studied. For the conditions used, it can be shown that ionic strength and free Ca++ concentration only affect b without significant effect on vi, whereas MgATP/MgADP ratio and temperature affect both vi and b. This means that of these factors only MgATP/MgADP ratio and temperature affect the cross-bridge kinetics which determine the maximum speed of shortening while ionic strength and free Ca++ concentration have no such effect within the experimental error.

Adenosine Triphosphate↗
PubMedDate not supplied

[An indirect proof of stretch-induced Ca++ release from the sarcoplasmic reticulum in glycerinated skeletal and heart muscle preparations (author's transl)].

The existence of still functioning vesicles of the sarcoplasmic reticulum (SR) in glycerinated rabbit psoas muscle fibers and cat myocardium is demonstrated by the use of activation (force development and shortening) of the contractile system as an indicator for "sarcoplasmic", free Ca++ concentration and by electron microscopic studies. Furthermore, the conditions for Ca++ release and uptake by the SR vesicles were analyzed. (1) As indicated by electron microscopic studies, glycerinated skeletal and heart muscle preparations contain SR vesicles (diameter 0.1--0.2 mu). Detergent treatment as used by Julian (1971) causes neither morphological change in the contractile system nor in the SR vesicles. (2) The delay in tension development of glycerinated preparations after an increase in free Ca++ concentration of the bathing medium is demonstrated to be caused at least partly by Ca++ uptake in these SR vesicles. (3) The SR vesicles of glycerinated preparations are able to accumulate Ca++ just at concentrations which are subthreshold for tension development. The accumulated Ca++ can be detected by a transient force development resulting from abolishment of the Ca++ storage capacity of the SR vesicles caused by high concentrations of detergents. (4) Ca++-induced Ca++ release is also demonstrated in glycerinated preparations. After Ca++ loading this release mechanism occurs at Ca++ concentrations in the bathing medium starting at about 10(-7,48) Mol/l both in skeletal and heart muscle preparations. (5) Quick stretch of Ca++-loaded, relaxed preparations caused local contractions of the myofibrils in both single fibers and fiber bundles of glycerinated rabbit psoas muscle. Skeletal fiber bundles and cat myocardium show a transient tension development parallel to these local contractions. These effects are demonstrated to be due to a stretch-induced Ca++ release from the SR vesicles. (6) Length-controlled quick stretches or quick releases of partly activated preparations cause sinusoidal tension oscillations superimposed on the well-known, delayed active tension development. In contrast, fully activated preparations do not show superimposed oscillations in tension. Force-controlled quick stretches or quick releases induce equivalent oscillations in length which are more distinct than the tension oscillations, however. These oscillations are also demonstrated to be due to stretch or release-induced changes in the Ca++ fluxes between SR vesicles and the "sarcoplasm". (7) This stretch induced release of Ca++ from the SR could be one reason for the multiple-phase course of active and passive isometric tension development in vivo following quick changes in length, and could also partly explain the prestretch dependence of tension development which cannot be explained from the degree of overlapping of the contractile filaments alone...

Animals↗
PubMedDate not supplied

Reluctance of paramedics and emergency medical technicians to perform mouth-to-mouth resuscitation.

Recently, a reluctance of lay and medical personnel to perform mouth-to-mouth resuscitation (MMR) in hospital and community settings has been documented, with 45% of respondents declining to perform MMR on a stranger. In the present study, we examined whether the perceived risk and fear of contracting infectious diseases diminishes the willingness of paramedics and emergency medical technicians (EMTs) to perform MMR. Seventy-seven EMTs and 27 paramedics responded to a questionnaire, administered by one of two physicians, containing mock cardiac arrest scenarios that were designed to assess willingness to perform MMR as a citizen responder. Faced with a situation in which an adult stranger required MMR, 57% of the participating EMTs and all of the paramedics stated that they would refuse to perform MMR. None of the paramedics and only 32.5% of the EMTs stated that they would perform MMR on a man in a gay neighborhood. In addition, 23% of the EMTs and 37% of the paramedics indicated that they would refuse to perform MMR on a child. White respondents were more willing than nonwhite respondents to perform MMR. Twenty-nine percent of the prehospital-care providers had been in situations requiring MMR in the community, and 40% either had walked away or did only external compression. Of those participating paramedics and EMTs who had performed MMR in emergency situations, only 45% indicated that they would do so again. The respondents indicated that they would not be willing to administer MMR because of the fear of contracting infectious agents, especially the human immunodeficiency virus. Despite the proven effectiveness of MMR in saving lives, paramedics and EMTs are highly reluctant to perform MMR as citizen responders. Their perceived risks of contracting infectious agents during MMR are high, despite the low actual risks. We recommend that instruction in cardiopulmonary resuscitation for providers of pre-hospital care, the medical community, and the general public should emphasize the benefits of providing MMR, the actual low risks of contracting infectious diseases during administration of MMR, and the use of widely available and effective barrier masks to minimize any risks due to administration of MMR.

Adult↗
PubMedDate not supplied

Toxicity of adjuvant high-dose interferon-alpha-2b in patients with cutaneous melanoma at high risk of recurrence.

Interferon-alpha-2b (INF-alpha-2b) has been approved by the FDA as adjuvant treatment for patients with melanoma at high risk of recurrence. INF-alpha-2b is administered at 20 MU/m2/day IV, 5 days per week for 4 weeks, and then 10 MU/m2/day SC, three times weekly for 48 weeks. We investigated the toxicity of this protocol in 30 patients between June 1996 and February 1998. An intensive toxicity evaluation program was developed to monitor side effects. During both induction and maintenance phases, 60% of patients required a dose delay and/or reduction. Twenty percent were unable to complete the treatment plan, and 53% tolerated at least 80% of the scheduled dose. The frequently reported toxicity during induction included constitutional symptoms, myelosuppression, and hepatotoxicity. All were reversible on cessation of treatment or dose modification. During maintenance, toxicity included thyroid dysfunction, hypertriglyceridemia, retinopathy and a combination of mood disturbances, memory loss, cognitive slowing and impaired executive function. Administration of high-dose INF-alpha-2b is feasible, with close patient monitoring.

Adolescent↗
PubMedDate not supplied

Laryngeal carcinoma--epidemiological and clinical features: experience of the Rabin Medical Center in Israel.

We sought to compare the epidemiological and clinical features of patients with carcinoma of the larynx treated at a major Israeli tertiary facility with other series in the literature. The charts of 361 consecutive patients from 1974 to 1995 were reviewed. Our population was distinguished from other series by a low rate of alcohol abuse (12%), high incidence of second malignancies in sites other than the upper aerodigestive tract (53%) and high rate of early-stage tumors (82%). Overall 5-year survival and local control rates were 88% and 85%, respectively. Our study suggests that the low alcohol consumption and high proportion of early-stage tumors at diagnosis, characteristic of the Israeli population of patients with laryngeal carcinoma, may explain, in part, the relatively high survival and local control rates.

Adolescent↗