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H Rees

Publications and source records attributed to H Rees.

At least 19 recordsLinked to original sources
PubMed1995

The role of glutamate and GABA receptors in the generation of dorsal root reflexes by acute arthritis in the anaesthetized rat.

1. In rats anaesthetized with pentobarbitone sodium, a unilateral acute arthritis was produced by the injection of kaolin and carrageenan into one knee-joint cavity. Four hours after injection, the medial articular nerve (MAN) was sectioned distally and recordings obtained from the proximal stump of the nerve. 2. Centrifugally conducted action potentials were recorded from the cut MAN following the development of arthritis. Acute dorsal rhizotomy, but not sympathectomy, prevented the action potentials, and so it is concluded that the action potentials represent dorsal root reflexes. 3. Central administration of either the GABAA receptor antagonist, bicuculline, or the non-NMDA receptor antagonist, CNQX, also prevented dorsal root reflexes in the MAN. 4. Neither the GABAB receptor antagonist, CGP35348, nor the NMDA receptor antagonist, AP7, altered the dorsal root reflexes in the MAN. 5. It is concluded that arthritis causes excess primary afferent depolarization in the dorsal horn of the spinal cord leading to dorsal root reflexes. It is proposed that these dorsal root reflexes contribute to the inflammation.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1995

Fiber types contributing to dorsal root reflexes induced by joint inflammation in cats and monkeys.

1. Injection of kaolin and carrageenan into the knee joint of cats or monkeys resulted in an acute inflammation. Four hours after injection of the knee joint, efferent activity could be evoked in articular afferent fibers and in dorsal root filaments. We interpret this efferent activity to be dorsal root reflexes (DRRs). Under our experimental conditions, the DRRs were generally synchronized compound action potentials, although in some cases single-unit activity was also observed. 2. DRRs were not produced in animals with uninflamed knee joints and normal body temperatures. 3. Recordings from two different sites on cut dorsal root filaments ipsilateral to the inflamed knee joint allowed the determination of the conduction velocities of groups of afferent fibers carrying DRRs. The DRRs occurred in A beta-, A delta-, and C fibers. However, in these experiments the peripheral destination of the afferent fibers was unknown. 4. To prove that DRRs occurred in joint afferents, recordings were made from two different sites on the proximal stump of the medial articular nerve that innervated the inflamed knee. The DRRs were again found in all fiber types, i.e., group II, III, and IV (A beta, A delta, and C) articular afferent fibers. 5. Compound DRRs were recorded from the central end of a cut dorsal root filament after electrical stimulation at C fiber intensity of a dorsal root adjacent to the filament. This DRR activity was eliminated by extensive dorsal rhizotomies of the L2-S1 roots.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1995

Association of infantile neuroaxonal dystrophy and osteopetrosis: a rare autosomal recessive disorder.

The association of neuroaxonal dystrophy and osteopetrosis is reported in 2 siblings born to non-consanguineous parents. The 1st child was diagnosed as having infantile osteopetrosis shortly after delivery. A computed tomography scan of the head revealed agenesis of the corpus callosum. She died at the age of 9 months. Post-mortem examination showed pneumonia and bony sclerosis. Neuropathological examination revealed cerebral atrophy, ventricular dilation, absence of the corpus callosum, and a small hippocampus. Neuroaxonal spheroids were found in hippocampus, basal ganglia, pons, medulla, spinal cord, cranial nerves, cerebellum, and peripheral nerves. Ultrastructural examination revealed membranous cytoplasmic bodies and electron-dense granular deposits within the neuroaxonal spheroids as well as the soma of neurons. The 2nd child was delivered at 36 weeks of gestation because of intrauterine fetal distress. The diagnosis of osteopetrosis and partial agenesis of the corpus callosum was made shortly after delivery. The child died at 1 month without an autopsy. There are rare cases reported previously with the association of neuroaxonal dystrophy and osteopetrosis. We review these cases and compare them with ours.

Agenesis of Corpus Callosum↗
PubMed1994

Increase in enkephalin-like immunoreactivity in hippocampi of adults with generalized epilepsy.

The changes of opioid peptide reactivity in seizure activity have been well studied in animals. Increased enkephalin and dynorphin immunoreactivity in the hippocampi of animals are interpreted as the result of seizure induced mossy fibre sprouting. We studied the hippocampi of six patients with a history of long-standing grand mal seizures and six age-matched control patients with no history of epilepsy or neurologic disease, using frozen sections which were immunostained with antibodies against Leu-enkephalin and Met-enkephalin. The staining intensity in the CA3, CA4 and internal molecular layer of the dentate fascia in each case was quantified using optical densitometry image analysis. The CA3 and CA4 of the epileptic hippocampi showed highly significant increase in Leu-enkephalin-like immunoreactivity compared to the controls (P < 0.005) while the inner molecular layer showed only significant increase (P < 0.05). Met-Enkephalin-like immunoreactivity was only significantly increased in CA4 of the epileptic hippocampi (P < 0.05).

Adult↗
PubMed1994

Do dorsal root reflexes augment peripheral inflammation?

Efferent activity was recorded in knee joint afferents in response to mechanical stimulation of the hindlimb following induction of acute arthritis. The activity was abolished by application of lidocaine or crushing the nerve proximally and by dorsal rhizotomy but not by sympathectomy. It was concluded that this activity represents dorsal root reflexes in response to natural stimulation of the hindlimb. We propose that increased activity of articular afferents and of dorsal horn neurons during arthritis results in the pathological activation of the central terminals of primary afferents by enhancing primary afferent depolarization. Dorsal root reflexes could then release substances in the knee joint and thus contribute to the acute inflammatory response.

Action Potentials↗
PubMed1994

Proposed protocol for a multi-centre study to compare clinical and trade tests of colour vision in firefighters.

Fire-brigade recruits in the UK have their colour vision screened using the Ishihara test. This is unsatisfactory because it rejects subjects with minor deficiencies in colour vision and does not test for blue defects. The Home Office is currently reviewing its recommendations on visual standards. This paper summarizes defects in colour vision, discusses alternative clinical and trade tests for the fire-brigade, and proposes a multi-centre study to collect data on the performance of fire-brigade recruits in clinical and trade tests.

Clinical Protocols↗
PubMed1993

The anterior pretectal nucleus: a proposed role in sensory processing.

Four nuclei of the pretectal complex, the olivary pretectal nucleus, the medial pretectal nucleus, the nucleus of the optic tract and the posterior pretectal nucleus, all have a demonstrated role in visual function. In contrast, the anterior pretectal nucleus (APtN) has no inputs from retina and has few outputs to visual accessory nuclei. The APtN has connections with areas associated with sensory functions and it has been suggested that this nucleus may have a role to play in somatosensory processing. An increasing number of behavioural and electrophysiological studies support this view. Brief low-intensity electrical or chemical stimulation of the APtN causes antinociception in the tail flick test in both unanaesthetised and anaesthetised animals. This inhibition of the tail flick response is attenuated by naloxone, alpha-adrenoceptor antagonists and muscarinic cholinergic receptor antagonists. Electrical stimulation of the APtN is similarly effective in the paw pressure and formalin tests. APtN stimulation also causes a brief inhibition of the tooth pulp-evoked jaw opening reflex. studies with [C14]2-deoxyglucose indicate that peripheral noxious stimuli will cause an increase in metabolic activity within the APtN. Animals with electrodes placed in the APtN will self-administer electrical stimulation and this can reduce the aversive and autonomic effects of stimulating the ventromedial hypothalamus. Part of the antinociceptive effects of stimulating the APtN are due to a descending inhibition of spinal dorsal horn projection neurones. Multireceptive neurones deep in the dorsal horn are inhibited by APtN stimulation. In contrast, superficial projection neurones that respond to intense cutaneous stimuli are excited by APtN stimulation. The APtN receives an excitatory input from low-threshold afferents via the dorsal column pathway and a high-threshold excitatory drive from superficial cells projecting through the dorsolateral funiculus. The excitatory input from the dorsal columns may well participate in the long-term inhibition of spinal projection neurones evoked by dorsal column stimulation. These ascending excitatory pathways may also be important to the long-term activation of descending inhibition from the APtN.

Animals↗
PubMed1993

Delivering at the right price--the costs of primary maternity care at the Diepkloof Community Health Centre, Soweto.

This paper reports on a study of the costs of primary maternity care services at the Diepkloof Community Health Centre (DK) in Soweto. DK, the Soweto community health centre system as a whole and numerous other non-hospital settings provide a wide range of maternal health services to substantial numbers of women, and relieve hospitals of a major potential clinical burden. However, no research has been done in South Africa on the relative costs of the provision of these services in different settings and by different types of health worker. The cost structure of these services at DK is presented and the costs of antenatal care, deliveries in midwife-run labour wards, postnatal care (at the health centre and at home) and family planning services detailed. Some comparisons are made with existing data for another community health centre and with Baragwanath Hospital. These results are relevant to policy and planning of maternal health services. They are also shown to be of relevance to management and several areas of potential improvement of these services are noted.

Cost-Benefit Analysis↗
PubMed1993

What does primary health care cost and can we afford to find out? Rationale and methodology for a cost analysis of the Diepkloof Community Health Centre, Soweto.

Accurate information on the costs of providing primary health care (PHC) services is now an urgent priority for health policy makers and planners, if the Government's stated commitment to an adequate PHC system is to be realised. Cost information is also a critical management tool for both public and private sector providers. In this context, the inability of public sector PHC providers to generate accurate cost accounting information is a serious shortcoming. In an attempt to address this lack of local PHC cost data, a detailed analysis of the costs of PHC services was undertaken at the Diepkloof Community Health Centre (DK) in Soweto during 1990. The study aimed to assess the cost of each service provided at DK and where possible, to identify areas of inefficiency. This paper is the first of two that report the findings of this study. It briefly describes the methodology employed and presents the major results. These raise several important management issues. Most importantly, the study suggests that there is excess capacity in the administrative and in several of the clinical areas of this community health centre; this implies that the average cost per service could be reduced in several areas. Certain services, such as home visits, are particularly expensive and require careful evaluation. The policy implications of this analysis are also examined. The high cost of several services implies that extension of this type of PHC service to all urban and rural areas is likely to be unaffordable.(ABSTRACT TRUNCATED AT 250 WORDS)

Community Health Services↗
PubMed1992

The pontine parabrachial region mediates some of the descending inhibitory effects of stimulating the anterior pretectal nucleus.

Electrical stimulation of the anterior pretectal nucleus (APtN) elicits antinociception by inhibiting the responses of spinal multireceptive neurones to noxious stimuli. This descending inhibition is mediated, in part, by activating cells in the ventrolateral medulla. Neuronal tract tracing has previously shown that the APtN also projects directly to the pontine parabrachial region (PPR). The PPR, investigated by Katayama et al. (Brain Res., 296 (1984) 263-283), corresponds to the cholinergic cell group Ch5 of Mesulam et al. (Neuroscience, 10 (1983) 1185-1201). In this study, the pathway from APtN to PPR was investigated using urethane anaesthetised rats. Electrical stimulation (single square wave 0.2 ms pulses, 1-10 V, 5 Hz) of the APtN potently excites 40% of the cells recorded in the PPR. In the reverse experiment, stimulation of the PPR at the same parameters excited 36% of the cells recorded in the APtN. The contribution of this pathway to the spinal inhibitory effects of APtN stimulation was then examined. Unanaesthetised animals received electrical stimulation to the APtN (35 microA r.m.s., 15 s) and the increase in tail-flick latencies was measured. Bilateral electrolytic lesions of the PPR caused a 67% reduction of the antinociceptive effect of APtN stimulation. In urethane anaesthetised rats, microinjection of tetracaine into the PPR blocked the inhibition of multireceptive dorsal horn neurones caused by APtN stimulation (20 s train of 50 microA square wave 0.1 ms pulses, 100 Hz). In conclusion, these experiments strongly sugget that the PPR may be an important part of a descending antinociceptive pathway originating in the APtN.

Animals↗
PubMed1991

Immunisation coverage and reasons associated with non-immunisation in Alexandra township, September 1988.

Regular annual measles outbreaks in Alexandra prompted a revision of immunisation strategies at the Alexandra Health Centre and University Clinic (AHC) and an immunisation coverage survey in September 1988. Forty-five clusters of 7 children aged 12-23 months were studied. Eighty-two per cent of mothers were in possession of a 'Road to Health' card, 12% said they had the card elsewhere, 3% reported it lost and 3% had never had a card. Thirty-three per cent of the children completed the immunisation schedule on time, 50% by 1 year of age and 61% by the time of the interview. The influence of sociodemographic, immunisation knowledge, and health service access variables on immunisation rates were analysed. Those children with a non-AHC 'Road to Health' card (P less than 0.01), the squatters (P less than 0.05), and those living farthest away from the clinic (P less than 0.05) were the only groups with a statistically significant lower on-time immunisation rate. Those children with a non-AHC 'Road to Health' card (P less than 0.01) and those whose caregivers could not or had difficulty reading a simple message in English (P less than 0.01 and P less than 0.05, respectively) had a significantly lower immunisation rate by 1 year of age and by interview. A child health outreach programme, started immediately after the survey, has begun to address some of the determinants of immunisation uptake described in this survey.

Adult↗
PubMed1991

Central antiaversive and antinociceptive effects of anterior pretectal nucleus stimulation: attenuation of autonomic and aversive effects of medial hypothalamic stimulation.

Previous studies have shown that stimulation of the rat anterior pretectal nucleus (APtN) strongly depresses a spinal reflex to noxious heat without causing significant aversion or depression of other motor responses. It is not known if APtN stimulation can similarly reduce the aversiveness of electrical stimulation of the brain, nor is it known if APtN stimulation is itself rewarding or aversive. This study used a simple switch-off paradigm to examine the rewarding properties of APtN stimulation at different sites throughout the nucleus and also used the tail-flick test to determine if the stimulation produced antinociception. The effects of APtN stimulation on the behavioural and autonomic responses to electrical stimulation of the medial hypothalamus (MH) and the nucleus raphe magnus (NRM) were also examined. The results show that electrical stimulation of dorsal APtN was rewarding and also caused antinociception which lasted for 50 min. However, sites which gave the strongest reward were not necessarily those which gave the greatest antinociception, as these effects were not correlated. Electrical stimulation of ventral APtN induced only aversive effects. The aversive and autonomic effects of MH stimulation were significantly reduced by conditioning stimulation of dorsal APtN. However, the very similar escape and autonomic effects of NRM stimulation were unaffected by APtN stimulation. These results suggest that electrical stimulation of the dorsal parts of the APtN has positive rewarding properties as well as the well-known antinociceptive effects. The antiaversive effects of dorsal APtN stimulation may be due in part to the inhibition of central substrates of aversion as well as inhibition of sensory neurones.

Animals↗
PubMed1991

The antinociceptive effects of anterior pretectal stimulation in tests using thermal, mechanical and chemical noxious stimuli.

Four behavioural tests have been used to study the antinociceptive effects of electrical stimulation of the anterior pretectal nucleus (APtN) in the rat. The antinociceptive effects of stimulating this nucleus, which lies dorsally in the posterior diencephalon, have recently been studied extensively but always using briefly applied heat stimuli. It is reported here that APtN stimulation effectively inhibited responses to briefly applied noxious pressure and longer-lasting noxious chemical (formalin) stimuli. Although the tail-flick reflex to noxious heat was very potently depressed by APtN stimulation, responses to noxious heat in the hot-plate test were not. Three doses of morphine were also studied with each test and it was concluded that 15 sec of 35 microA r.m.s. current into the APtN was as effective as 3-5 mg/kg morphine s.c. in the rat.

Animals↗
PubMed1991

The antinociception evoked by anterior pretectal nucleus stimulation is partially dependent upon ventrolateral medullary neurones.

Electrical stimulation (35 microA rms/15 s) of the anterior pretectal nucleus (APtN) inhibits the spinal reflex of the tail-flick (TF) to noxious heat in unanaesthetised rats. APtN stimulation also reduces the nociceptive response of spinal dorsal horn neurones in halothane-anaesthetised rats. This study determined if the antinociceptive effects of APtN stimulation depended on neurones in the ventral medulla. Bilateral electrolytic lesions of the ventrolateral medulla, but not the nucleus raphe magnus, reduced by 70% the antinociceptive effect of APtN stimulation in the TF test. In rats anaesthetised with halothane, electrical stimulation of the APtN (single square wave 0.1 msec pulses, 2-20 microA, 1 Hz) excited cells in the ventrolateral medulla. These data suggest a connection between both areas. This connection is further confirmed by neuroanatomical tract tracing studies in which the retrograde dye Fast Blue was injected into the ventrolateral medulla. Fluorescent cell bodies were found in the APtN. We therefore conclude that the ventrolateral medulla is part of a descending antinociceptive pathway from the APtN.

Animals↗
PubMed1990

Gastric enterochromaffin-like (ECL) cells in hypergastrinaemic duodenal ulcer disease.

Patients with hypergastrinaemic duodenal ulcer disease were studied to determine whether chronic moderate hypergastrinaemia produces hyperplasia of gastric enterochromaffin-like cells in man. Eight patients had peak postprandial plasma gastrin concentrations greater than 200 pmol/l, which is the 92nd percentile for patients with duodenal ulcer disease in this laboratory. The control group was eight patients with duodenal ulcers whose peak postprandial gastrin concentrations were less than 200 pmol/l. Basal and peak postprandial plasma gastrin concentrations were 107 (37) and 306 (66) pmol/l (mean (SEM] respectively in the hypergastrinaemic patients compared with 26 (4) and 137 (14) pmol/l respectively in the controls. There was no significant difference in the density of gastrin enterochromaffin-like cells between the two groups. The number of enterochromaffin-like cells per high power field was 53 (8) in the hypergastrinaemic patients compared with 50 (8) in the controls. We conclude that chronic moderate hypergastrinaemia does not produce hyperplasia of enterochromaffin-like cells in man. Our hypergastrinaemic group had plasma gastrin concentrations similar to, or greater than those reported during treatment with drugs such as omeprazole and histamine H2 receptor blockers.

Adult↗
PubMed1989

Afferent projections to the rostral anterior pretectal nucleus of the rat: a possible role in the processing of noxious stimuli.

The afferent inputs to the rostral pole of the anterior pretectal nucleus have been examined by utilizing the retrograde axonal transport of a fluorescent dye, Fast Blue. After unilateral injection of the dye into the rostral anterior prectectal nucleus, large numbers of labelled neuronal somata were found in the somatosensory cortex, the ventrolateral geniculate nucleus, the zona incerta, the superior colliculus, the deep mesencephalic nuclei, the pedunculopontine tegmental nucleus and the medial vestibular nucleus. In addition, the contralateral parabigeminal nucleus provided a major input to the rostral part of the anterior pretectal nucleus. Smaller and sparser collections of stained cell bodies could be found in the ventromedial hypothalamus, the posterior pretectal nucleus, the nucleus of the posterior commissure, the peripeduncular nucleus, the periaqueductal central gray, the contralateral anterior pretectal nucleus, and the locus coeruleus. Many of the inputs originated in areas associated with nociceptive pathways. The regional distribution of neurons projecting to the rostral pole of the anterior pretectal nucleus differs substantially from that of the cells innervating the anterior pretectal nucleus proper, i.e. its more caudal parts. It is concluded from this that the rostral pole constitutes a separate nucleus, anatomically distinct from the rest of the anterior pretectal nucleus and other cell groups in the pretectal complex. The demonstration that many of the afferents to the rostral anterior pretectal nucleus arise in regions involved in nociception supports recent electrophysiological and behavioural evidence that this brain area plays a role in the processing of noxious stimuli, rather than as a component in the pretectal control of visual system reflexes.

Afferent Pathways↗
PubMed1989

Activation of cells in the anterior pretectal nucleus by dorsal column stimulation in the rat.

1. The responses of neurones in the anterior pretectal nucleus (APTN) to electrical stimulation of the dorsal columns at twice the threshold for A fibres were studied in the rat anaesthetized with urethane. 2. APTN cells were excited by dorsal column stimulation. Forty-six discharged phasically in response to a single stimulus. Sixteen cells did not respond phasically but slowly increased the discharge rate with repeated stimulation. 3. Electrical stimulation of the contralateral gracile fasciculus caused neurones in the APTN to discharge with a variable latency of 2-22 ms. Stimulations of the ipsilateral gracile and contralateral cuneate fasciculi had weaker effects. 4. Microinjection of DL-homocysteic acid into the contralateral gracile nucleus increased the discharge rate of APTN neurones. Microinjection of gamma-aminobutyric acid into the contralateral gracile nucleus blocked the gracile fasciculus evoked excitation of APTN neurones. 5. On thirteen occasions cells in the gracile nucleus were driven antidromically by electrical stimulation of the APTN. 6. It is concluded that electrical stimulation of the gracile fasciculus activates a monosynaptic excitatory input to the APTN.

Animals↗