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Biomedical subjects

W Jenkins

Publications and source records attributed to W Jenkins.

At least 19 recordsLinked to original sources
PubMed1998

Language learning impairments: integrating basic science, technology, and remediation.

One of the fundamental goals of the modern field of neuroscience is to understand how neuronal activity gives rise to higher cortical function. However, to bridge the gap between neurobiology and behavior, we must understand higher cortical functions at the behavioral level at least as well as we have come to understand neurobiological processes at the cellular and molecular levels. This is certainly the case in the study of speech processing, where critical studies of behavioral dysfunction have provided key insights into the basic neurobiological mechanisms relevant to speech perception and production. Much of this progress derives from a detailed analysis of the sensory, perceptual, cognitive, and motor abilities of children who fail to acquire speech, language, and reading skills normally within the context of otherwise normal development. Current research now shows that a dysfunction in normal phonological processing, which is critical to the development of oral and written language, may derive, at least in part, from difficulties in perceiving and producing basic sensory-motor information in rapid succession--within tens of ms (see Tallal et al. 1993a for a review). There is now substantial evidence supporting the hypothesis that basic temporal integration processes play a fundamental role in establishing neural representations for the units of speech (phonemes), which must be segmented from the (continuous) speech stream and combined to form words, in order for the normal development of oral and written language to proceed. Results from magnetic resonance imaging (MRI) and positron emission tomography (PET) studies, as well as studies of behavioral performance in normal and language impaired children and adults, will be reviewed to support the view that the integration of rapidly changing successive acoustic events plays a primary role in phonological development and disorders. Finally, remediation studies based on this research, coupled with neuroplasticity research, will be presented.

Dominance, Cerebral↗
PubMed1998

Remifentanil versus propofol as adjuncts to regional anesthesia. Remifentanil 3010 Study Group.

STUDY OBJECTIVE: To compare the safety and efficacy of remifentanil and propofol as adjuncts to regional anesthesia in patients undergoing orthopedic or urogenital surgery. DESIGN: Prospective, randomized study. SETTING: Multicenter university hospitals. PATIENTS: 107 ASA physical status I, II, and III adult patients who underwent orthopedic or urogenital surgery with axillary, ankle, or spinal block. INTERVENTIONS: Patients were randomized to receive either an infusion of remifentanil 0.2 microg/kg/min or propofol 100 microg/kg/min 5 minutes before nerve block placement. The infusions were decreased by 50% on block completion, increased by 50% for patient discomfort, and decreased by 50% for hypoventilation (< 8 breaths/min) or hemodynamic instability. MEASUREMENTS AND MAIN RESULTS: Pain, discomfort, anxiety, and sedation were assessed by both patient and investigator. Vital signs and adverse events were recorded. Fewer patients in the remifentanil group experienced pain during block placement (6%), and were oversedated (7%) than patients in the propofol group (23% and 26%, respectively; p < 0.05). Hypoventilation during and after block placement (21% and 25%, respectively) and nausea and vomiting during and after block placement (60% and 21%, respectively) were more common in the remifentanil group than in the propofol group (0% and 3%; 17% and 6%, respectively; p < 0.05). The incidence of hypoventilation in remifentanil-treated patients was higher in patients over 65 years of age (p < 0.05), but was transient, resolving within minutes of discontinuing the infusion. CONCLUSIONS: At the doses studied, remifentanil was more effective than propofol in minimizing pain without producing excessive sedation. Remifentanil was associated with more transient respiratory depression and short-term nausea. Our findings indicate that the initial remifentanil rate should be 0.1 microg/kg/min (50% lower than the study's initial rate) and should be further decreased an additional 50% in the elderly to minimize adverse effects.

Adult↗
PubMed1998

Language learning impairment: integrating research and remediation.

Timing cues present in the acoustic waveform of speech provide critical information for the recognition and segmentation of the ongoing speech signal. Research has demonstrated that deficient temporal perception rates, that have been shown to specifically disrupt acoustic processing of speech, are related to specific language-based learning impairments (LLI). Temporal processing deficits correlate highly with the phonological discrimination and processing deficits of these children. Electrophysiological single cell mapping studies of sensory cortex in brains of primates have shown that neural circuitry can be remapped after specific, temporally cohesive training regimens, demonstrating the dynamic plasticity of the brain. Recently, we combined these two lines of research in a series of studies that addressed whether the temporal processing deficits seen in LLIs can be significantly modified through adaptive training aimed at reducing temporal integration thresholds. Simultaneously, we developed a computer algorithm that expanded and enhanced the brief, rapidly changing acoustic segments within ongoing speech and used this to provide intensive speech and language training exercises to these children. Results to date from two independent laboratory experiments, as well as a large national clinical efficacy trial, demonstrate that dramatic improvements in temporal integration thresholds, together with speech and language comprehension abilities of LLI children, results from training with these new computer-based training procedures.

Autistic Disorder↗
PubMed1998

Plasticity of primary somatosensory cortex paralleling sensorimotor skill recovery from stroke in adult monkeys.

Adult owl and squirrel monkeys were trained to master a small-object retrieval sensorimotor skill. Behavioral observations along with positive changes in the cortical area 3b representations of specific skin surfaces implicated specific glabrous finger inputs as important contributors to skill acquisition. The area 3b zones over which behaviorally important surfaces were represented were destroyed by microlesions, which resulted in a degradation of movements that had been developed in the earlier skill acquisition. Monkeys were then retrained at the same behavioral task. They could initially perform it reasonably well using the stereotyped movements that they had learned in prelesion training, although they acted as if key finger surfaces were insensate. However, monkeys soon initiated alternative strategies for small object retrieval that resulted in a performance drop. Over several- to many-week-long period, monkeys again used the fingers for object retrieval that had been used successfully before the lesion, and reacquired the sensorimotor skill. Detailed maps of the representations of the hands in SI somatosensory cortical fields 3b, 3a, and 1 were derived after postlesion functional recovery. Control maps were derived in the same hemispheres before lesions, and in opposite hemispheres. Among other findings, these studies revealed the following 1) there was a postlesion reemergence of the representation of the fingertips engaged in the behavior in novel locations in area 3b in two of five monkeys and a less substantial change in the representation of the hand in the intact parts of area 3b in three of five monkeys. 2) There was a striking emergence of a new representation of the cutaneous fingertips in area 3a in four of five monkeys, predominantly within zones that had formerly been excited only by proprioceptive inputs. This new cutaneous fingertip representation disproportionately represented behaviorally crucial fingertips. 3) There was an approximately two times enlargement of the representation of the fingers recorded in cortical area 1 in postlesion monkeys. The specific finger surfaces employed in small-object retrieval were differentially enlarged in representation. 4) Multiple-digit receptive fields were recorded at a majority of emergent, cutaneous area 3a sites in all monkeys and at a substantial number of area 1 sites in three of five postlesion monkeys. Such fields were uncommon in area 1 in control maps. 5) Single receptive fields and the component fields of multiple-digit fields in postlesion representations were within normal receptive field size ranges. 6) No significant changes were recorded in the SI hand representations in the opposite (untrained, intact) control hemisphere. These findings are consistent with "substitution" and "vicariation" (adaptive plasticity) models of recovery from brain damage and stroke.

Analysis of Variance↗
PubMed1996

The relationship between static posture and ACL injury in female athletes.

Female participation in athletics has increased dramatically over the last decade. Accompanying the increase in participation in sports is the increase incidence of anterior cruciate ligament (ACL) injury. The purpose of this study was to examine the correlation between static postural faults in female athletes and the prevalence of noncontact ACL injury. Twenty ACL-injured females and 20 age-matched controls were evaluated. Seven variables were measured: standing pelvic position, hip position, standing sagittal knee position, standing frontal knee position, hamstring length, prone subtalar joint position, and navicular drop test. A conditional step-wise logistic regression analysis revealed the factors of knee recurvatum, an excessive navicular drop, and excessive subtalar joint pronation to be significant discriminators between the ACL-injured and noninjured groups. These findings may have implications regarding rehabilitation techniques in physical therapy.

Adolescent↗
PubMed1995

Epidemiology of minority health.

Collecting epidemiologic data by ethnicity and race is a highly useful undertaking; but "bench mark" comparisons relative to majority Americans should not take priority over defining the determinants of health status within a minority group. Thus, it is necessary to identify factors contributing to the measured health status and to modify the environment, lifestyles, and behaviors to diminish the likelihood of undesirable health outcomes. This article presents an overview of the health status of African Americans, Asians and Pacific Islanders, and Hispanics. The goals are to provide a framework for the rational interpretation of both health status data and its determinants both within and between minority groups. This approach recognizes the heterogeneity of health status that exists within a minority group and encourages investigators to place more emphasis on the within-group health status differentials as they search for modifiable factors that underlie the risk for undesirable health outcomes.

Adolescent↗
PubMed1981

Hepatic organelle pathology in primary biliary cirrhosis and the response to low-dose D-penicillamine therapy.

1. Analytical subcellular fractionation in combination with enzymic microanalysis has been used to investigate the hepatic organelle pathology of primary biliary cirrhosis. Activities of plasma membrane and lysosomal enzymes in hepatic needle biopsies were increased, but marker enzymes for other organelles were normal. 2. Seven patients were treated with a low dose of penicillamine, 250 mg daily, over a 3--6 month period. The initially raised serum alkaline phosphatase and IgM levels were significantly reduced. In four patients with markedly elevated hepatic copper there was a small decrease, but urinary copper excretion was unaltered. Hepatic organelle pathology was significantly improved. 3. No serious side-effects were noted and it is suggested that a controlled trial of low-dose D-penicillamine therapy is indicated in patients with primary biliary cirrhosis.

Adult↗
PubMed1980

Subcellular fractionation studies on hepatic tissue from a patient with Pompe's disease (type II glycogen-storage disease).

1. An homogenate of liver biopsy taken from a patient with Pompe's disease (type II glycogen-storage disease) was analysed by enzyme microassay and subcellular fractionation by sucrose-density-gradient centrifugation. 2. A strikingly low activity of lysosomal acid alpha-D-glucosidase was noted but there was also increased activity of neutral alpha-D-glucosidase (found in endoplasmic reticulum). 3. Activities of the acid hydrolases, acid phosphatase and beta-N-acetyl-D-glucosaminidase, were elevated compared with those of controls. Measurement of latent beta-N-acetyl-D-glucosaminidase activity and results of subcellular fractionation experiments, indicated a marked fragility of certain populations of lysosomes. Lysosomes containing predominantly acid phosphatase and beta-D-glucuronidase activities appeared to have normal integrity. 4. Assessment of organelle pathology by enzyme microassay indicated low mitochondrial and peroxisomal enzyme activities. In addition there was evidence of mitochondrial damage as reflected by increased sucrose permeability and by ultrastructural studies.

Acetylglucosaminidase↗
PubMedDate not supplied

Remifentanil versus alfentanil as analgesic adjuncts during placement of ophthalmologic nerve blocks.

BACKGROUND AND OBJECTIVES: Short-acting opioids are often used prior to the placement of ophthalmologic nerve blocks. This study examines whether remifentanil would provide superior analgesia compared with alfentanil, without oversedation or prolonged recovery when given either as a single dose over 30 seconds or as a single dose followed by a continuous infusion, in a dose ratio of 1:7 (remifentanil:alfentanil). METHODS: Seventy-nine ASA I-III patients scheduled for elective ophthalmologic surgery participated in this multicenter, double-blind study. Patients were randomized into three groups: remifentanil (remifentanil 1 microg/kg and placebo infusion); remifentanil infusion (remifentanil 1 microg/kg and infusion of 0.2 microg/kg/min); and alfentanil (alfentanil 7 microg/kg and placebo infusion). Supplemental doses of the respective opioid were given as needed. RESULTS: Seventy-seven percent of patients in the remifentanil group were pain-free at the time of the block placement compared with 44% in the alfentanil group (P < .05). Eighty percent of patients in the remifentanil infusion group were pain-free. Although the occurrence of respiratory depression (14%) was higher in the remifentanil infusion group, it was short-lived (< or = 5 minutes) and resolved spontaneously. More than 89% of patients were awake and alert prior to surgery, and > or = 85% bypassed the phase I recovery area. Nausea and vomiting were rare. CONCLUSIONS: Remifentanil 1 microg/kg results in superior analgesia compared with alfentanil 7 microg/kg when used during the placement of ophthalmologic nerve blocks. The combination of a single dose of remifentanil followed by a continuous infusion was equally effective but resulted in a higher incidence of respiratory depression.

Aged↗
PubMedDate not supplied

Representational plasticity in cortical area 3b paralleling tactual-motor skill acquisition in adult monkeys.

The representations of the surfaces of the hand in the primary somatosensory cortical field, area 3b, were reconstructed in detail in seven owl monkeys and two squirrel monkeys trained to pick up food pellets from five wells of different sizes. From an early clumsy performance in which several to many retrieval attempts were required for each successful pellet retrieval, the monkeys exhibited a gradual improvement in digital dexterity as shown by significant decreases in mean numbers of grasp attempts/successful retrieval and corresponding standard deviations (e.g. 5.8 +/- 4.5 and 4.8 +/- 3.1 respectively, for the smallest well) between the first and last training sessions. All monkeys commonly used alternative, specific retrieval strategies involving various combinations of digits for significant time epochs before developing a highly successful strategy, which, once achieved, was rapidly stereotyped. For example, the numbers of digit combinations used during the first five versus the last five training sessions decreased from 3.3 +/- 0.7 to 1.8 +/- 0.6 for the smallest well. In both owl and squirrel monkeys, as the behavior came to be stereotyped, monkeys reliably engaged limited surfaces of the glabrous tips of two digits (in eight monkeys), or of three digits (in one monkey) in the palpation and manipulation of these small pellets for their location, capture, and transportation to the mouth. In cortical area 3b, the magnification of representation of these differentially engaged glabrous fingertip surfaces was nearly 2x larger than for the corresponding surfaces of other hand digits, or for the contralateral cortical representations of the same digit surfaces on the opposite hand. In parallel, cutaneous receptive field for area 3b neurons representing crucial digital tip surfaces were less than half as large as were those representing the corresponding surfaces of control digits. Receptive field overlaps were smaller on the trained fingertips than on control fingers. Moreover, the proportion of small overlaps was greater for the trained digits (76 +/- 7%) than for the other digits of the same hand (49 +/- 5.4%). There was still a simple, single--but apparently topologically expanded--representation of these differentially engaged skin surfaces in these monkeys. Thus, with very limited manual exercise over a total period of a few hours of practice at a skill played out in brief daily sessions over a several week long training period, the representations of skin surfaces providing information crucial for successfully performing a small-object retrieval behavior appeared to be substantially remodeled in the most 'primary' of the SI somatosensory cortical fields, cortical area 3b. By that remodeling, behaviorally important skin surfaces were represented in a much finer representational grain than normal. Some implications of these findings for motor skill acquisition are discussed.

Animals↗