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Biomedical subjects

A Berkowitz

Publications and source records attributed to A Berkowitz.

At least 19 recordsLinked to original sources
PubMed2006

Prognostic value of FDG-PET scan imaging in lymphoma patients undergoing autologous stem cell transplantation.

We conducted a retrospective analysis of 50 lymphoma patients (Hodgkin's disease and non-Hodgkin's lymphoma) who had an 18F-fluoro-deoxyglucose positron emission tomography (FDG-PET) scan after at least two cycles of salvage chemotherapy and before autologous stem cell transplantation (ASCT) at our institution. The patients were categorized into FDG-PET negative (N = 32) and positive (N = 18) groups. The median follow-up after ASCT was 19 months (range: 3-59). In the FDG-PET-negative group, the median progression-free survival (PFS) was 19 months (range: 2-59) with 15 (54%) patients without progression at 12 months after ASCT. The median overall survival (OS) for this group was not reached. In the FDG-PET-positive group, the median PFS was 5 months (range: 1-19) with only one (7%) patient without progression at 12 months after ASCT. The median OS was 19 months (range: 1-34). In the FDG-PET-negative group, chemotherapy-resistant patients by CT-based criteria had a comparable outcome to those with chemotherapy-sensitive disease. A positive FDG-PET scan after salvage chemotherapy and prior ASCT indicates an extremely poor chance of durable response after ASCT.

Adult↗
PubMed2001

Sensitivity of prefrontal cortex to changes in target probability: a functional MRI study.

Electrophysiological studies suggest sensitivity of the prefrontal cortex to changes in the probability of an event. The purpose of this study was to determine if subregions of the prefrontal cortex respond differentially to changes in target probabilities using functional magnetic resonance imaging (fMRI). Ten right-handed adults were scanned using a gradient-echo, echo planar imaging sequence during performance of an oddball paradigm. Subjects were instructed to respond to any letter but "X". The frequency of targets (i.e., any letter but X) varied across trials. The results showed that dorsal prefrontal regions were active during infrequent events and ventral prefrontal regions were active during frequent events. Further, we observed an inverse relation between the dorsal and ventral prefrontal regions such that when activity in dorsal prefrontal regions increased, activity in ventral prefrontal regions decreased, and vice versa. This finding may index competing cognitive processes or capacity limitations. Most importantly, these findings taken as a whole suggest that any simple theory of prefrontal cortex function must take into account the sensitivity of this region to changes in target probability.

Adolescent↗
PubMed2001

Broadly tuned spinal neurons for each form of fictive scratching in spinal turtles.

Behavioral choice can be mediated either by a small number of sharply tuned neurons or by large populations of broadly tuned neurons. This issue can be conveniently examined in the turtle spinal cord, which generates each of three forms of scratching-rostral, pocket, and caudal-in response to mechanical stimulation in each of three adjacent regions of the body surface. Previous research showed that many propriospinal neurons are broadly tuned to either the rostral scratch region or the pocket scratch region, but responses to caudal scratch stimulation could not be examined in that reduced preparation. In the current study, individual spinal neurons were recorded extracellularly from the gray matter of the turtle spinal cord hindlimb enlargement, while sites in the rostral, pocket, and caudal scratch regions were mechanically stimulated. Many neurons were broadly tuned to the caudal scratch region; other neurons were broadly tuned to either the pocket scratch or rostral scratch region. All three types were typically found within a single animal. These data are consistent with the hypothesis that the turtle spinal cord relies on large populations of broadly tuned neurons to select each of the three forms of scratching. In addition, neurons that were broadly tuned to each of the scratch regions were typically found in each spinal cord segment and within the same range of mediolateral and dorsoventral locations. Providing that these neurons are related to the selection and generation of the three forms of scratching, this would indicate that cells of this type are not segregated into distinct regions of the spinal cord gray matter.

Animals↗
PubMed2001

Rhythmicity of spinal neurons activated during each form of fictive scratching in spinal turtles.

Are behaviors that rely on common muscles and motoneurons generated by separate or overlapping groups of pattern-generating neurons? This question was investigated for the three forms of scratching in immobilized, spinal turtles. Individual neurons were recorded extracellularly from the gray matter through most of the spinal cord hindlimb enlargement gray matter, but were avoided in the region of motoneuron cell bodies. Each form of fictive scratching was elicited by mechanical stimulation of the body surface. The rhythmic modulation of spinal neurons was assessed using phase histograms and circular statistics. The degree of rhythmic modulation and the phase preference of each rhythmically active neuron were measured with respect to the activity cycle of the ipsilateral hip flexor nerve. The action potentials of rhythmic neurons tended to be concentrated in a particular phase of the ipsilateral hip flexor activity cycle no matter which form of fictive scratching was elicited. This consistent phase preference suggests that some of these neurons may contribute to generation of the hip rhythm for all three forms of scratching, strengthening the case that vertebrate pattern-generating circuitry for distinct behaviors can be overlapping. The degree of rhythmic modulation of each unit during fictive scratching was consistently correlated with the dorsoventral location of the recording, but not with the mediolateral or rostrocaudal location; neurons located more ventrally tended to be more rhythmic. The phase preferences of units were related to the region of the body surface to which each neuron responded maximally (i.e., the region to which each unit was broadly tuned). Units tuned to the rostral scratch or pocket scratch region tended to have a phase preference during ipsilateral hip flexor activity, whereas units tuned to the caudal scratch region did not. This suggests the hypothesis that the hip flexes further during rostral and pocket scratching, and extends further during caudal scratching, due to the net effects of a population of spinal interneurons that are both broadly tuned and rhythmically active.

Action Potentials↗
PubMed1997

Postexcitatory inhibition of the crayfish lateral giant neuron: a mechanism for sensory temporal filtering.

Crayfish escape from threats by either giant neuron-mediated "reflex" tail flexions that occur with very little delay but do not allow for much sensory guidance of trajectory or by "nongiant" tail flexion responses that allow for sensory guidance but occur much less promptly. Thus, when a stimulus occurs, the nervous system must make a rapid assessment of whether to use the faster reflex system or the slower nongiant one. It does this on the basis of the abruptness of stimulus onset; only stimuli of very abrupt onset trigger giant-mediated responses. We report here that stimuli which excite the lateral giant (LG) command neurons for one form of reflex escape also produce a slightly delayed postexcitatory inhibition (PEI) of the command neurons. As a result, only stimuli that become strong enough to excite the command neurons to firing threshold before the onset of PEI, within a few milliseconds of stimulus onset, can cause giant-mediated responses. This inhibition is directed to distal dendrites of the LG neurons, which allows for some location specificity of PEI within the sensory field of a single hemisegment.

Animals↗
PubMed1996

Local control of leg movements and motor patterns during grooming in locusts.

This study demonstrates that the thoracic and abdominal nervous system of locusts is sufficient to mediate several site-specific and distinct grooming leg movements. Locusts can use a hindleg or middle leg to groom at least four ipsilateral thoracic and abdominal sites, without input from the brain, subesophageal ganglion, or prothoracic ganglion. The hindleg is used to groom the posterior abdomen, the ventral or posterior hindleg coxa, and the ear; the middle leg is used to groom the anterior hindleg coxa. Grooming movements are often rhythmic and display site-specific intralimb coordination patterns. During grooming of the posterior abdomen or ventral hindleg coxa, for example, hindleg tibial extension occurs nearly simultaneously with femur elevation, in contrast with locust hindleg movements during walking. Electromyographic (EMG) recordings during these movements show that rhythmic bursts of tibial extensor activity occur nearly in-phase with those of trochanteral levators, in contrast to hindleg EMGs during walking. During grooming of the ear, hindleg tibial extension/flexion and tibial extensor/flexor muscle bursts can occur independently of the femur elevation/depression and trochanteral levator/depressor muscle bursts, suggesting that the neural modules controlling tibial and femoral movements can be uncoupled during this behavior. Tibial extension can occur before, or even in the absence of, tibial extensor muscle activity, suggesting that spring-like properties of the leg and energy transfer from femur motion may play important roles in such leg movements. Adjacent legs sometime show coordinated femur movement during grooming with one hindleg, suggesting that grooming may also involve interlimb coordination.

Animals↗
PubMed1996

Central generation of grooming motor patterns and interlimb coordination in locusts.

Coordinated bursts of leg motoneuron activity were evoked in locusts with deefferented legs by tactile stimulation of sites that evoke grooming behavior. This suggests that insect thoracic ganglia contain central pattern generators for directed leg movements. Motoneuron recordings were made from metathoracic and mesothoracic nerves, after eliminating all leg motor innervation, as well as all input from the brain, subesophageal ganglion, and prothoracic ganglion. Strong, brief trochanteral levator motoneuron bursts occurred, together with silence of the slow and fast trochanteral depressor motoneurons and activation of the common inhibitor motoneuron. The metathoracic slow tibial extensor motoneuron was active in a pattern distinct from its activity during walking or during rhythms evoked by the muscarinic agonist pilocarpine. Preparations in which the metathoracic ganglion was isolated from all other ganglia could still produce fictive motor patterns in response to tactile stimulation of metathoracic locations. Bursts of trochanteral levator and depressor motoneurons were clearly coordinated between the left and right metathoracic hemiganglia and also between the mesothoracic and the ipsilateral metathoracic ganglia. These data provide clear evidence for centrally generated interlimb coordination in an insect.

Animals↗
PubMed1994

Descending propriospinal axons in the hindlimb enlargement of the red-eared turtle: cells of origin and funicular courses.

Spinal neurons with descending axons are important components of spinal sensorimotor networks. We used an anatomical tracing technique to study the distribution of descending propriospinal axons and cell bodies in red-eared turtles. We injected horseradish peroxidase into a portion of one funiculus in the middle of the hindlimb enlargement and examined six spinal segments rostral to the injection site (dorsal 3 through dorsal 8) for labeled neuronal cell bodies. Injections into each region of the white matter labeled substantial numbers of descending propriospinal neurons. Each injection labeled cell bodies over most of the six spinal segments examined. Each injection also labeled cell bodies in the ipsilateral dorsal horn, intermediate zone, and ventral horn as well as the contralateral intermediate zone and ventral horn. Injections into each of four regions of the white matter, the dorsal funiculus, the medial part of the lateral funiculus, the lateral part of the lateral funiculus, and the ventral funiculus reliably gave rise to a distinct distribution of labeled cell bodies. These experiments establish that descending propriospinal axons in red-eared turtles are found in all regions of the spinal white matter. This finding contrasts with a popular contemporary view of the organization of descending propriospinal axons in mammals. These experiments also demonstrate that neurons in each region of the gray matter give rise to a different distribution of descending, funicular axons, although these distributions are widely overlapping. Different funicular axon distributions could be associated with different sets of synaptic contacts with the white-matter dendrites of spinal neurons.

Animals↗
PubMed1994

Activity of descending propriospinal axons in the turtle hindlimb enlargement during two forms of fictive scratching: broad tuning to regions of the body surface.

We recorded the activity of descending propriospinal axons at the caudal end of a seven-segment (D3-D9) turtle spinal cord preparation. These seven spinal segments contain sufficient neural circuitry to select and generate fictive rostral scratching or fictive pocket scratching in response to tactile stimulation in the appropriate region of the body surface. Each turtle received two spinal transections, one just caudal to the forelimb enlargement and one in the middle of the hindlimb enlargement. Descending propriospinal axons were recorded extracellularly from the hindlimb enlargement on one side of the body, while the ipsilateral or contralateral body surface was stimulated. Concurrent recordings were made from ipsilateral and contralateral hindlimb muscle nerves to monitor fictive scratch motor patterns. We found that most tactilely responsive descending propriospinal axons were excited by stimulation anywhere within the rostral scratch or pocket scratch receptive fields on at least one side of the body, and often on both sides. The activity of these neurons was usually rhythmically modulated during fictive rostral scratching and fictive pocket scratching. Many neurons with large excitatory receptive fields generated action potentials at their highest rate during stimulation of a particular region of the body surface on one side, and generated action potentials at progressively lower rates during stimulation of sites progressively farther away. Thus, these units were broadly tuned to a region of the body surface. Some were tuned to a region of the rostral scratch receptive field and others were tuned to a region of the pocket scratch receptive field. These data suggest that selection of the appropriate form of scratching, rostral or pocket, may be mediated by populations of broadly tuned neurons rather than by highly specialized neurons.

Action Potentials↗
PubMed1994

Activity of descending propriospinal axons in the turtle hindlimb enlargement during two forms of fictive scratching: phase analyses.

In the preceding companion article (Berkowitz and Stein, 1994b), we showed that many descending propriospinal neurons in the turtle were rhythmically activated during two different motor patterns, fictive rostral scratching and fictive pocket scratching. In this article, we present phase analyses of the activity of each such neuron during fictive scratching. Each neuron's activity was concentrated in a particular phase of the ipsilateral hip flexor muscle nerve (VP-HP) activity cycle; each had a distinct "preferred phase." Each neuron's preferred phase during fictive rostral scratching was similar to its preferred phase during fictive pocket scratching. This result is consistent with the idea that some descending propriospinal neurons may contribute to the generation of both rostral scratching and pocket scratching. Many descending propriospinal neurons were rhythmically activated during fictive scratching evoked on either side of the body. This activity may contribute to production of bilateral hindlimb movements during scratching. It is also possible that synaptic interactions between the two sides of the spinal cord may be important in generating the motor patterns for movement of a single hindlimb. In addition, we present a model which illustrates that a population of propriospinal neurons, each of which is broadly tuned to a region of the body surface and is rhythmically activated in a constant phase of the hip control cycle, could mediate the selection and generation of rostral scratching and pocket scratching. Thus, the selection of an appropriate motor pattern and the production of the required knee-hip synergy may each be distributed over a diverse population of spinal cord neurons. This model requires that each such neuron project to both knee muscle and hip muscle motoneurons. According to this model, the process of selecting a motor pattern would not be completed until knee muscle motoneurons integrate overlapping excitatory and inhibitory inputs.

Animals↗
PubMed1992

College men as perpetrators of acquaintance rape and sexual assault: a review of recent research.

This article reviews literature since 1980 on college men as perpetrators of acquaintance rape and other forms of sexual assault. Topics include (1) the definition and incidence of acquaintance rape and sexual assault; (2) perpetrator characteristics; (3) situations associated with sexual assault; and (4) men's misperception of women's sexual intent. An integrated theory of sexual assault is proposed, along with implications for the development of effective rape-prevention programs for men.

Adult↗
PubMed1991

Comparison of two enzyme-linked immunosorbent assays for detection of herpes simplex virus antigen.

Two enzyme-linked immunosorbent assays (ELISAs) for herpes simplex virus (HSV) detection were compared with culture in a prospective, blinded study with 153 patients with suspected recurrent oral or genital HSV. A subset of 15 of these subjects were studied daily until symptom resolution during a single episode of recurrent HSV. Direct-site specimens were collected and either placed in viral transport media (for Ortho ELISA and fresh inoculation into primary rabbit kidney cells) or frozen in ELISA collection media (DuPont). One hundred eighty-six culture-ELISA comparisons were analyzed. On the basis of culture positivity, the DuPont and Ortho ELISAs differed substantially with regard to sensitivity (93 versus 35%) but had similar specificities (95 versus 100%) and positive (85 versus 100%) and negative (98 versus 85%) predictive values. There were seven DuPont ELISA-positive, culture-negative samples which were confirmed positive for HSV by blocking antibody test (revised specificity, 100%; positive predictive value, 100%). Six of these discrepant samples were from previously culture-positive subjects. These results demonstrate that currently available ELISA kits vary substantially as to their sensitivities in detecting HSV antigen from direct-site specimens. In addition, antigen detection, by ELISA technology, is not always synonymous with state of viral infectivity as judged by tissue culture cytopathic effect.

Antigens, Viral↗
PubMed1990

Multicenter clinical evaluation of the Du Pont Herpchek HSV ELISA, a new rapid diagnostic test for the direct detection of herpes simplex virus.

A new 4h rapid enzyme-immunoassay for direct detection of herpes simplex virus (HSV) antigen (Du Pont Herpchek) was evaluated with 743 clinical samples collected at obstetrics and gynecology (OB/GYN), sexually transmitted diseases (STD), and ophthalmology clinics. The sensitivity and specificity of Herpchek was 98.0% and 98.4% respectively compared to virus isolation in cell culture. Confirmatory blocking ELISA tests, clinical history and follow up indicate that the true specificity of the test is 100%.

Adult↗
PubMed1990

Pilocarpine, an orally active muscarinic cholinergic agonist, induces REM sleep and reduces delta sleep in normal volunteers.

The effect of oral pilocarpine, a direct-acting muscarinic, cholinergic agonist, on polygraphic sleep parameters was studied in 13 healthy male volunteers. Subjects received placebo and oral pilocarpine (25 mg) in a double-blind, counterbalanced, crossover design. Pilocarpine shortened the latency of rapid eye movement (REM) sleep and increased total REM time, REM%, and the duration of the first REM period. In addition, it reduced Stage 4 sleep and Delta sleep. Pulse rate was not significantly changed during the first hour of darkness after administration of pilocarpine. Subjective sleep experience and the subjects' condition in the morning were not altered. These results suggest that pilocarpine has central effects (i.e., induction of REM sleep) that are similar to those of other centrally acting muscarinic cholinomimetic agents.

Administration, Oral↗