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M J Rowe

Publications and source records attributed to M J Rowe.

At least 55 records · Page 3Linked to original sources
PubMed1988

Neural mechanisms in vibrotactile adaptation.

1. Peripheral and central neural contributions to vibrotactile adaptation were investigated in decerebrate or anesthetized cats by recording from sensory nerve fibers associated with Pacinian corpuscle (PC) receptors and from central neurons of the dorsal column nuclei that receive their input from vibration-sensitive receptors of the forelimb footpads. Responsiveness of units was assessed using 1-s duration, test vibration stimuli delivered with 1- to 2-mm-diam probes at different times following adapting trains of vibration (usually 300 Hz) that lasted from less than 1 min up to 50 min. 2. Cuneate neuron responsiveness underwent marked depression following prior vibration. The extent of the depression and the time course of recovery in responsiveness were dependent on the intensity and duration of the adapting vibratory stimulus. The recovery time course (often several minutes) was approximately exponential and resembled the reported time course of subjective vibrotactile adaptation obtained in psychophysical experiments. 3. Response depression in PC fibers was only seen at low amplitudes of the test vibration and displayed a brief time course of recovery in comparison with that seen in cuneate neurons. It is therefore unlikely to account for the adaptation time course either in cuneate neurons or at a subjective level. Furthermore, as the adaptation seen in PC fiber responses had a similar time course in both cutaneous and mesenteric PC fibers it is unlikely that mechanical changes in the skin contribute significantly to the adaptation in PC fiber responses to vibration. 4. The time course of afferent-induced inhibition following long periods of prior vibration was too brief to account for the response adaptation in cuneate neurons. 5. As the long-term response depression in cuneate neurons following their prior activation was seen for inputs from unconditioned sites within the neuron's excitatory receptive field, as well as from the conditioned site, it appears that the response adaptation is attributable to changes in the central neuron or in synaptic processes associated with the central neuron. It is proposed that this adaptation may be due to an increase in extracellular potassium ion concentration that alters the responsiveness of the central neurons.

Adaptation, Physiological↗
PubMed1988

Comparing state-only expenditures for AIDS.

The State AIDS Policy Center at the Inter-governmental Health Policy Project (IHPP) at George Washington University surveyed all 50 states to determine state AIDS (acquired immunodeficiency syndrome) expenditures, without Medicaid or federal funds, for fiscal 1984-88. During this period, state-only expenditures increased 15-fold, to $156.3 million. Between fiscal 1986-1988, the distribution of state funding for AIDS patient care and support services doubled from 16 to 35 per cent and the number of states supplementing federal funds for testing and counseling increased from eight to 20. Five states continue to account for the largest AIDS appropriations. Of these, California leads in funding research; New York, Florida, and New Jersey have directed funds to provide care and services to IV (intravenous) drug users, prisoners, and children. The average state expenditure per diagnosed AIDS case is $3,323 and an increasing number of states with relatively low case loads are appropriating funds beyond this level. Across states, AIDS expenditures per person average $.65 and $.21 for education, testing and counseling--below the level recommended by the Institute of Medicine for AIDS prevention activities. Some jurisdictions support AIDS activities indirectly by shifting resources, often from their STD (sexually transmitted disease) programs--this trend deserves continuing review given the rise in STD cases and their relationship to diagnosed AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1988

AIDS: legal and ethical issues.

The AIDS crisis challenges social workers to reaffirm their profession's traditional values of advocacy, community service, respect for differences, and commitment to social change. The authors discuss current and future legal and ethical issues with respect to the AIDS crisis.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Phase coherence in vibration-induced responses of tactile fibres associated with Pacinian corpuscle receptors in the cat.

1. In pentobarbitone-anaesthetized cats, responses were recorded in peripheral nerves or cervical dorsal columns from sensory fibres associated with Pacinian corpuscle (P.c.) receptors in the forelimb footpads. Factors affecting the phase of response to cutaneous vibration in individual P.c. fibres, and the extent of phase coherence in the responses of different P.c. fibres were examined when sinusoidal vibratory stimuli at 100-400 Hz were delivered using a 1 mm diameter probe. 2. Increases in vibration amplitude from the absolute to the 1:1 threshold for the P.c. fibre led to phase advances in the response, often of about 60 deg, in over 85% of fibres tested at 200 and 300 Hz, but further increases had little effect. 3. Variations in stimulus position within the receptive field led to unpredictable changes in the response phase that ranged from minimal change to shifts of 180 deg. As the response phase was unrelated to the distance from the point of peak sensitivity it is likely that at high vibration frequencies (greater than or equal to 100 Hz) the recruited population of P.c. fibres will respond over the whole range of phase angles. 4. The calculated phase of spike initiation in different pairs of P.c. fibres that shared coincident points of best sensitivity on the skin ranged from near synchrony to maximum asynchrony indicating that there is little phase coherence even in the subpopulation of somatotopically related P.c. fibres recruited by high-frequency cutaneous vibration. 5. Paired recordings from P.c. fibres within the cervical dorsal columns revealed a broad range of phase discrepancies in the responses of P.c. fibres to vibration at 200 and 300 Hz. 6. Several hypotheses are considered to explain the known presence of phase-locked responses to high-frequency (greater than or equal to 100 Hz) vibration in the central neurones of dorsal column nuclei.

Action Potentials↗
PubMed1987

Temporal patterning in the responses of gracile and cuneate neurones in the cat to cutaneous vibration.

1. Recordings were made in decerebrate cats from gracile and cuneate neurones responding to vibration-induced inputs from Pacinian corpuscle (P.c.) receptors of the hind-limb and forelimb footpads. The two groups of neurones were compared, in particular for their capacities for responding to cutaneous vibration with phase-locked impulse patterns. 2. In both nuclei the P.c. neurones were most sensitive to vibration in the range 80 to greater than 600 Hz. Stimulus-response relations were similar for the two groups, as were measures derived from these relations such as response levels, absolute thresholds and the dynamic range (defined as the vibration amplitude range over which responses were graded). 3. At frequencies up to 300-400 Hz, responses for some neurones in both nuclei remained well phase locked to the vibration; however, quantitative analysis using a factorial analysis of variance indicated that the phase locking was poorer in gracile than cuneate neurones. 4. In both nuclei there was marked variability from neurone to neurone in measures of phase locking which may reflect variations in the extent of convergence of P.c. fibres upon different target neurones. For neurones in either nucleus that had comparatively tight phase locking of responses to vibration it is proposed that their output is functionally dominated by one or a few of their convergent P.c. input fibres.

Action Potentials↗
PubMed1987

Actions of single sensory fibres on cat dorsal column nuclei neurones: vibratory signalling in a one-to-one linkage.

1. The synaptic linkage between single, identified sensory fibres associated with Pacinian corpuscle (P.c.) receptors and central neurones of the dorsal column nuclei was examined in decerebrate or anaesthetized cats. Paired recordings were made from individual neurones in the gracile division of the dorsal column nuclei and from the hind-limb interosseous nerve in which it is possible to identify and monitor the activity of each P.c. fibre activated when recording from the intact nerve with a platinum hook electrode. Individual P.c. fibres were activated by vibration delivered with an 0.2 mm diameter probe to the interosseous P.c. receptors. 2. Thirty-five P.c. fibre-gracile neurone pairs were isolated in which activity in the single, identified P.c. fibre evoked suprathreshold responses (mean latency +/- S.D., 10.3 +/- 1.5 ms) in the gracile neurone. A single impulse arriving over one P.c. fibre could generate pairs or triplets of output spikes from several target neurones thus revealing a potent synaptic organization within the dorsal column nuclei for the transmission and amplification of weak sensory signals. 3. The potency of the linkage for some pairs resulted in post-synaptic response levels of up to 400 impulses s-1 when a single input fibre was discharging one impulse on each vibration cycle at 200-400 Hz. 4. Gracile neurones driven by single P.c. fibres had phase-locked responses to vibration at frequencies of up to 400-500 Hz. However, the responses displayed much greater phase dispersion than those of P.c. fibres, indicating that a major component of phase dispersion in the vibration-induced responses of dorsal column nuclei neurones is attributable to the properties of the synaptic linkage between an individual fibre and the target neurone. 5. The potent actions of single, identified P.c. fibres on their target neurones are consistent with the hypothesis that phase-locked responses in dorsal column nuclei neurones to vibration at 100-400 Hz may reflect the functional domination of the target neurone's output by one or a few of its converging fibres.

Action Potentials↗
PubMed1987

Integrative processing of vibratory information in cat dorsal column nuclei neurones driven by identified sensory fibres.

1. In decerebrate or anaesthetized cats, the vibration-induced responses of dorsal column nuclei neurones were examined, first, when their input came from simultaneously recorded pairs or other combinations of identified Pacinian corpuscle (P.c.) afferent fibres of the interosseous nerve, and secondly, when different convergent sets of P.c. fibres were engaged by footpad vibration. 2. Suprathreshold actions were observed on individual dorsal column nuclei neurones from two or more identified P.c. fibres. Recruitment of these convergent fibres usually led to summation in the dorsal column nuclei neurone as reflected in higher response levels compared with those evoked by single-fibre inputs. 3. When the input was increased from one to two or more identified P.c. fibres the dorsal column nuclei neurones could retain a single, dominant phase of response to high-frequency (greater than 100 Hz) vibration even though these fibres, in isolation, evoked responses in the target neurone at substantially different latencies. However, on average, phase locking was significantly tighter in response to single-fibre input than to multiple P.c.-fibre input. 4. Dorsal column nuclei neurones were also able to retain phase-locked responses to high-frequency vibration when phase differences between different convergent inputs were systematically introduced to alter the degree of synchrony in the activity arriving over convergent, identified P.c. fibres. 5. When the input to dorsal column nuclei neurones came from the skin it was found that with the recruitment of two converging sets of P.c. fibres the dorsal column nuclei neurones were able to retain phase-locked responses to high-frequency vibration even when phase shifts were introduced between the two sets of P.c. inputs. 6. In conclusion, the observed integrative processing by dorsal column nuclei neurones of vibration-induced inputs arriving over identified, convergent P.c. fibres, or sets of P.c. fibres, is consistent with our hypothesis that the retention of phase-locked responses to vibration at frequencies greater than or equal to 100 Hz may reflect the functional domination of the target neurone by just one or a few of its convergent input fibres.

Action Potentials↗
PubMed1986

High gain transmission of single impulses through dorsal column nuclei of the cat.

Paired recordings were made in the cat from neurones of dorsal column nuclei and from intact pacinian sensory fibres of the hindlimb interosseous nerve. Direct evidence is presented for central neurones being driven by single impulses arriving over just one sensory nerve fibre. Transmission through this sensory relay appears to be optimized for the detection of minimal sensory inputs. Two mechanisms operate for the amplification of such inputs. First, individual sensory fibres can exert divergent, suprathreshold actions on multiple target neurones, and second, a single impulse coming over one input fibre can induce pairs or bursts of output spikes from its target neurones.

Afferent Pathways↗
PubMed1986

Suppression of endocytosis in neutrophils by influenza A virus in vitro.

The effect of influenza A virus on the endocytic pathway in polymorphonuclear leukocytes (PMNLs) and the relationship of altered endocytic activity to virus-induced inhibition of other PMNL functions were examined with virus that caused decreased phagosomelysosome fusion and bacterial killing (depressing virus [DV]) and virus that did not (non-DV). Binding of both viruses to PMNL surface receptors was similar, but uptake of DV into PMNLs was decreased compared with that of non-DV. Both viruses were associated with the PMNL plasma membrane and were in endosomes. DV caused less stimulation of pinocytosis than did non-DV. The rate of exocytosis of fluoresceinated-dextran (FL-dextran) from cells stimulated with DV was significantly less than for non-DV. When PMNLs were pretreated with buffer, DV, or non-DV and then exposed to FL-dextran and N-formylmethionylleucylphenylalanine, the pinocytosis of FL-dextran was significantly less in cells pretreated with DV as compared with non-DV or buffer.

Endocytosis↗
PubMed1986

Luteinization-specific ovarian mitochondrial proteins.

Mitochondria isolated from porcine medium- and large-sized ovarian follicles and corpora lutea show progressive increases in specific proteins temporally associated with luteinization. These include 12-15, 16-17, 33, 47, 50, and 60 kDa proteins. Synthesis of these same mitochondrial proteins is stimulated by incubation of large ovarian follicles with luteinizing hormone (LH) (0.10 microgram/ml) but not by follicle-stimulating hormone (0.10 microgram/ml). A dose-response curve was generated indicating that synthesis of several mitochondrial proteins is stimulated in an LH-dependent manner, while synthesis of two appear to be repressed (70 and 94 kDa). Examination of mitochondrial translation products (cycloheximide-insensitive, chloramphenicol-sensitive protein synthesis) from isolated follicular and luteal mitochondria, by both one- and two-dimensional electrophoresis, demonstrated that two proteins (23 and 35 kDa) are synthesized within luteal but not follicular mitochondria. Further, synthesis of two proteins within follicular mitochondria are significantly reduced in luteal mitochondrial. Regulation of mitochondrial proteins necessary for the rate-limiting step in steroidogenesis is discussed.

Animals↗
PubMed1986

Receptive field profiles and integrative properties of spinocervical tract cells in the cat.

The receptive fields of sixteen spinocervical tract (s.c.t.) cells whose responses were recorded extracellularly were mapped using discrete and uniform jets of air given at equally spaced locations on the clipped fur of cats anaesthetized with chloralose. All the cells whose receptive fields were on the thigh or upper hind limb showed approximately unimodal gradients of sensitivity to stimulation within their excitatory receptive fields. The response magnitudes declined steadily as the stimuli were moved sequentially from the centres to the peripheries of the fields and abrupt edges were not found. Spatial summation from within the excitatory receptive field was studied in twelve s.c.t. cells. These cells showed a poor ability to summate the responses to two spatially separated air jets when these stimuli were applied simultaneously within their receptive fields. No significant summation was found in twenty-five out of thirty-one trials and in six of these trials (four cells) the responses were significantly reduced. Summation was found in six trials (four cells). Lack of summation or response reduction was more prevalent when the individual response levels were low (less than impulses stimulus-1). These results are discussed in relation to similar findings for cells of somatosensory relay nuclei and cortex.

Action Potentials↗
PubMed1984

Effects of hind limb nerve section on lumbosacral dorsal horn neurones in the cat.

The sciatic and saphenous nerves of one hind limb were sectioned in young adult cats anaesthetized with halothane. Between 19 and 55 days later, under chloralose anaesthesia, dorsal horn neurones in the L6 and L7 segments were recorded and their receptive field properties examined. In seven animals recordings were made from identified spinocervical tract, post-synaptic dorsal column and dorsolateral funicular neurones as well as from neurones that did not project through these pathways. Thirty-one neurones were intracellularly stained with horseradish peroxidase, and fifty-three were recorded extracellularly and located by reference to stained cells. In two animals (both 31 days after nerve section) no attempt was made to identify axonal projections of the dorsal horn neurones in order to avoid any effects of cervical cord search stimuli on the cells' properties, but all isolated extracellularly recorded units were examined. On the side ipsilateral to the nerve sections 143 units were recorded. In all experiments, neurones in the medial three-quarters of the dorsal horn had no discernible cutaneous, mechanosensitive receptive fields between 19 and 55 days after nerve section. There were only two exceptions to this generalization, one neurone being one of the most rostral cells in the sample (in caudal L5) and the other being one of the most caudal cells (in caudal L7). We present evidence to show that neither of these two neurones had inappropriate receptive fields in terms of the somatotopic organization of the dorsal horn. All other neurones with receptive fields on the skin were appropriately located in the somatotopic map laid out in the dorsal horn. There was no evidence for gross anatomical changes in the dendritic trees of dorsal horn neurones following sciatic and saphenous nerve sections. We have been unable to confirm that, following loss of cutaneous receptive fields by peripheral nerve section, dorsal horn neurones in adult cats acquire 'inappropriate' receptive fields. Possible reasons for this are discussed.

Animals↗
PubMed1984

Functional maturation of tactile sensory fibers in the kitten.

The maturation of tactile coding capacities was investigated in sensory fibers supplying the forelimb footpads in anesthetized kittens. Fibers were isolated by microdissection from the median or ulnar nerves of neonatal kittens (1st to 5th postnatal day) and kittens in the age categories 10-15, 25-30, 55-63, and 83-90 days. The use of quantitative, reproducible tactile stimuli, in particular, cutaneous vibration, and objective analytical procedures enabled response parameters to be quantified and compared at different ages with those of adult fibers. While three classes of myelinated tactile sensory fibers are associated with the footpads in adult cats, one of them slowly adapting (SA) and two, the rapidly adapting (RA) and pacinian corpuscle (PC) classes, showing pure dynamic sensitivity, this breakdown into three classes is not apparent until 10-15 days after birth. In all age groups, the SA fibers displayed responses that were graded depending on the magnitude of the skin indentation. However, in younger kittens (less than 25-30 days) plateau levels of response were sometimes attained over a narrow range (0.5 mm) of indentation. From 10-15 days, when RA fibers are identifiable, their sensitivity, as measured by absolute and 1:1 thresholds to cutaneous vibration, was independent of age at low vibration frequencies, less than or equal to 80 Hz. However, at high frequencies, e.g., 200 Hz, their thresholds appeared to decrease during the 1st postnatal month with a resulting expansion in their bandwidth of vibratory sensitivity. At their best frequency, around 30 Hz, RA fibers appear mature by 10-15 days in their capacity for encoding vibratory frequency information. The PC class of tactile afferents displayed the most striking functional changes with age. Their vibratory bandwidths, at 50-micron amplitude, expand from an upper limit of about 200-300 Hz in the neonate to mature values of about 800-1,000 Hz over a 2-mo postnatal period.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Factors↗
PubMed1984

Tactile sensory coding during development: signaling capacities of neurons in kitten dorsal column nuclei.

The functional maturation of cuneate neurons was studied using reproducible tactile stimulation procedures and quantitative assessment of coding capacities in anesthetized (N2O/O2 plus barbiturate infusion) or decerebrate cats from six different age groups; neonatal (1-5 days), 10-15, 25-30, 55-63, and 83-90 days, and an adult group. Cuneate neurons were distinguished from input fibers to the nucleus on criteria of spike configuration and time course and on response profiles. Extracellular spike durations underwent a progressive shortening with age, reaching the adult range at approximately 3 mo when background activity levels also reached maturity. Despite an increase in conduction-path length, response latencies decreased to adult values by 25-30 days of age, presumably reflecting the increased conduction velocity in the input fibers. In each age group three functional classes of neurons responsive to tactile stimulation of the footpads were identifiable. One consisted of slowly adapting neurons whose stimulus-response relations resembled those of the adult in responsiveness and dynamic range by 25-30 days postnatal age. The remaining neurons were purely dynamically sensitive, but among them two classes could be distinguished by their differential sensitivity to cutaneous vibration, one receiving rapidly adapting (RA) fiber input the other pacinian corpuscle (PC) input. The combined bandwidth of vibration sensitivity in dynamically sensitive cuneate neurons expands from approximately 5-300 Hz in the neonate to the mature range of 5-1,000 Hz by 1 mo of age. The PC class of cuneate neurons showed an upward shift in peak sensitivity from 30-200 Hz in the neonate to 100-300 Hz at 10-15 days, reaching adult values of 200-600 Hz by 25-30 days. Over this period absolute thresholds dropped by an order of magnitude at 200-500 Hz reflecting the threshold trends in primary PC fibers. During the first 1-2 postnatal months, the capacity of cuneate PC neurons to signal information in a pattern code about vibration frequencies around 300 Hz is restricted because of poor phase locking and low responsiveness, which preclude an impulse periodicity reflecting the vibratory frequency.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1983

Proprioceptive contributions to tactile identification of figures: dependence on figure size.

Studies on the recognition of objects or shapes explored by a hand or finger have concentrated on the relative merits of different methods of exploration--in particular, whether the exploring hand or finger is moved by the subject himself (active), is guided by an assistant (passive), or remains stationary with the shape being moved by an assistant (tactile). These factors, together with another variable--the size of the explored shape--were investigated in twelve normal adults whose task, without the aid of vision, was to explore and identify various shapes with the tip of the extended right index finger. Two series of shapes were used, a large (15 cm) and small (3 cm) series, both of which consisted of twelve shapes each being a variant of the letter 'S'. The shapes were outlined as rows of Braille-like dots on a flat surface. Exploration was also tested in the proprioceptive mode, in which the exploring hand was guided by an assistant around a shape which was simply drawn on the surface so as to give a minimum of tactile information. For neither large nor small shapes could we demonstrate differences between active, passive and proprioceptive exploration. For the small shapes, the active, passive and proprioceptive modes gave no advantage over purely tactile assessment. However, for the larger shapes, active, passive and proprioceptive modes allowed better identification than movement of the shape. Thus, purely cutaneous signals appear sufficient for optimal discrimination of small figures but proprioceptive signals, generated by movement, are needed for optimal discrimination of larger figures.

Humans↗
PubMed1983

Osteomalacia in the elderly: the value of radio-isotope bone scanning in patients with equivocal biochemistry.

Radio-isotope bone scanning was used to detect osteomalacia in 17 elderly subjects who had equivocal biochemical evidence of this condition. The scan was positive in 10 of the 17 subjects. Bone biopsy confirmed osteomalacia in all 10, but also identified a further two cases. Isotope bone scanning is a practical and relatively non-invasive method of detecting osteomalacia in elderly subjects.

Aged↗