Behavioural deviance and maternal depressive symptoms in paediatric outpatients

A consecutive series of 95 3 to 4 year old and 43 7 to 11 year old children attending surgical, and medical outpatient clinics was studied, using questionnaires that measured behavioural deviance and had adequate reliability and validity for screening populations of children. A control group was also studied in the 7 to 11 year old sample. Depressive symptoms in the mothers of the children were determined using the Wakefield depression inventory. There was considerable behavioural deviance in children attending the outpatient clinics; 44% of the 7 to 11 year olds who were surgical outpatients had deviant scores. Thirty two per cent of mothers of medical outpatients had deviant scores on the depression inventory. These findings have relevance for the approach paediatricians take to their outpatients.

Nerve growth factor counteracts the neurophysiological and neurochemical effects of chronic sciatic nerve section

The sciatic nerve was sectioned unilaterally in rats and nerve growth factor (NGF) applied locally to the nerve stump for the following 10-14 days using an indwelling osmotic pump. The aim of the experiment was to test whether NGF had any effect on the previously reported neurophysiological and neurochemical events that occur central to a peripheral nerve lesion. The method of application allowed the sciatic nerve on the other side to be used as a control. Primary afferent depolarization fell, as expected, to 13% of its control value after chronic nerve section but if NGF was administered it fell to only 43.5% of control. Chronic nerve section is also known to result in expansion of the receptive fields of deafferented dorsal horn cells. NGF treatment reduced the number of such large receptive fields by 50%. The normal depletion of fluoride resistant acid phosphatase from the cut nerve terminals in the dorsal horn did not occur following NGF treatment. Radioimmunoassay of substance P revealed that the 30% reduction in dorsal horn levels that follows chronic sciatic nerve section did not occur when NGF was applied and that the accompanying 60% decrease in dorsal root ganglion levels was changed to a 64% increase by NGF. The results show that chronic NGF treatment of a cut sciatic nerve does partially reverse the central changes that normally follow deafferentation.

Pulp capping of dental pulp mechanically exposed to oral microflora: a 1-2 year observation of wound healing in the monkey

Four adult Rhesus monkeys provided 120 teeth for buccal Class V cavities. Twenty-nine were non-exposed controls and 91 were exposed for 3 intervals. All 120 teeth were capped with a hard set Ca(OH)2 medicament, restored with amalgam, 57 evaluated after 1 year and 63 after 2 years. Of the 91 exposed pulps, 45 showed complete healing, 25 showed pulpal inflammation varying from acute to chronic, 12 showed severe pulpal breakdown and abscess formation and 9 were necrotic. No difference was observed in the healing response between the 3 exposure times. New hard tissue formed at, or subjacent to, the medicament in 77 of 91 exposed pulps with a tunnel defect frequently present, running from the medicament interface to the pulp. This study demonstrates that recurring pulp inflammation observed after 1 & 2 year direct pulp capping, is associated with bacterial contamination.

The postnatal physiological and neurochemical development of peripheral sensory C fibres

The postnatal development of sensory C fibre function was investigated in neonatal rats aged 1-21 days. From birth, flexor-withdrawal reflexes (measured from the hamstring electromyograph) to pinching and heating the skin of the hindfoot were easily recorded under light anaesthesia and in fact were exaggerated in amplitude and duration compared to adult responses. Flexor reflexes to irritant chemicals, however, were not present until day 10-11 of life. In parallel with this late development of specific chemical sensitivity, neurogenic oedema, a C fibre-mediated inflammatory reaction, also did not occur until day 11. Substance P and fluoride-resistant acid phosphatase histochemistry were used to investigate the neurochemical development of sensory C fibres. Substance P was present in the skin, nerve, dorsal root ganglion and spinal cord from birth and fluoride-resistant acid phosphate within 12 h of birth. The adult neurochemical appearance of C-fibre terminals in the dorsal horn was established in a few days. The results show that despite the apparent early anatomical and neurochemical maturity of C fibres, physiological function is not fully established until the second week of life.

Alterations in the structure, function, and chemistry of C fibers following local application of vinblastine to the sciatic nerve of the rat

Vinblastine, a transport blocker, was applied locally to the sciatic nerve in rats. It was found to be a powerful neurotoxin with a dose-dependent action, destroying all afferents at doses of 5 X 10(-4)M, primarily C fibers at intermediate doses of 2.5 X 10(-4)M, and only at a critically low dose of 10(-4)M was a degeneration-free axon transport blockade, lasting for 4 to 5 days, produced. Such transport block failed to alter thermal responsiveness of the rats as measured behaviorally, by the flexor reflex, or by dorsal horn cell responses. It did, however, significantly reduce both the chemical sensitivity of the C afferents and their ability to produce neurogenic edema. This began 24 hr after treatment and lasted 4 to 5 days. Therefore, it is likely that these functions are dependent on the continuous transport of some compound to the axon terminals from the cell body. This low concentration of local vinblastine treatment also resulted in depletion of fluoride-resistant acid phosphatase from C fiber terminals in the dorsal horn of the spinal cord. Transmission from C fibers to second-order neurons in the spinal cord, however, was totally unaffected. Substance P levels in the spinal terminals was largely unaffected, although in 1 of 5 cases there was depletion. It appears, therefore, that some, but not all, retrograde changes in sensory neurons following peripheral nerve damage can be mimicked by blockade of axon transport. The effects following vinblastine treatment are compared to other peripheral nerve manipulations, such as cut, crush, and application of local capsaicin.

The termination pattern of sciatic nerve afferents in the substantia gelatinosa of neonatal rats

A study was carried out to determine at what stage of development the adult pattern of primary afferent projections to the substantia gelatinosa (SG) is first established. Horseradish peroxidase conjugated wheat-germ agglutinin (WGA-HRP) was applied to cut ends of sciatic nerves at mid-thigh level in adult and neonatal rats aged 1-16 days. The distribution of transganglionically transported label in primary afferent terminals in SG was reconstructed from transverse sections of spinal cord segments L1 to S1. The distinctive U-shaped projection field of the sciatic nerve in SG of the adult was found to exist in miniature form already in the second postnatal day 24 h after WGA-HRP had been applied. The highly specific somatotopic projections of primary afferents to SG are probably established before birth. Any delay in the maturation of functional specificity in the dorsal horn of the neonate cannot be attributed to the absence or disorganization of anatomical projections to SG of primary afferent inputs.

The properties of neurones recorded in the superficial dorsal horn of the rat spinal cord

The physiological properties of neurones in the superficial laminae of the dorsal horn of the fourth and fifth lumbar segments of the rat spinal cord have been investigated in decerebrate spinal animals. Both extracellular recordings with platinum-plated tungsten microelectrodes (n = 72) and intracellular recordings with glass microelectrodes (N = 79) were made. Attempts were made to fill cells intracellularly with horseradish peroxidase or Lucifer Yellow. Thirty-seven percent of the intracellularly injected neurones were recovered after histological processing and their cell bodies found to be in lamina 1 or 2 and in the dorsal white matter overlying lamina 1. The dendritic spread of the stained neurones was maximal in the rostrocaudal plane with a restricted mediolateral spread. The physiological properties of the extracellularly recorded units, the intracellularly unidentified units, and the intracellularly stained units were the same. The neurones were characterized by low background activity and all had excitatory receptive fields on the lower limb. Some neurones responded only to low-threshold mechanical stimulation of the skin or only to noxious skin stimulation but the majority of units (58%) were wide-dynamic-range cells responding to both types of stimuli. Receptive field classification was made questionable, however, by the existence of cells (9%) that exhibited a spontaneous shift in the size of their receptive fields and in the type of stimulus that elicited a response. The neurones in the superficial dorsal horn commonly showed a marked inhibition to repeated cutaneous stimuli (27%) or a prolonged afterdischarge followed a single stimulus (20%). Afferent input from the sural nerve was found to be from A and C fibres in both extra-and intracellular recordings. A delta- and C-mediated excitations were most common although convergent inputs from A beta-fibres occurred in 40% of units. No correlation was found between cell structure or distribution of dendritic fields and physiological properties in our small sample of intracellularly stained cells. The morphology of the cells was highly diverse, as were the different receptive fields. There was, however, some correlation between the location of cell bodies and their responses. Neurones responding only to low-threshold stimuli were distributed either in the dorsal white matter or in inner lamina 2. Wide-dynamic-range cells were distributed throughout the superficial dorsal horn. These results suggest that neurones of different shapes and positions may subserve the same function and, conversely, that neurones of the same shape and position may subserve different functions.

Cognitive and physiologic responses to EMG biofeedback and three types of pseudofeedback during a muscular relaxation task

Four groups of normal human subjects were tested for their ability to reduce frontal muscle tension levels during presentation of veridical auditory biofeedback or auditory pseudofeedback. A double-blind methodology was used. Three groups of subjects assigned to the pseudofeedback conditions received a feedback signal that was not contingent on EMG activity but that followed one of three different patterns. One group received a truly random signal, the second received a signal that gradually increased in frequency (apparent failure), and the third received a signal that gradually decreased in frequency (apparent success). Dependent measures included both physiologic (frontal and neck EMG) and subjective reactions to the relaxation task. The different patterns of pseudofeedback did produce reliably different subjective responses, suggesting that the manipulations succeeded in producing unequal nonspecific effects that were unrelated to the feedback contingency specifically. However, these differential subjective effects were not strongly reflected in the physiologic responses since the differences in EMG levels among the four groups did not differ significantly at any stage of training. An analysis of the integrity of the double-blind procedure showed that although experimenters were effectively kept blind to group assignment, subjects' responding suggested a response bias as well as the possibility that the double-blind was breached. The utility of the double-blind methodology in biofeedback experiments is discussed and suggestions for future research are offered.

Influences of contralateral nerve and skin stimulation on neurones in the substantia gelatinosa of the rat spinal cord

Stimulation of high threshold A delta and C fibre peripheral afferents inhibits dorsal horn cells on the other side of the spinal cord. The substantia gelatinosa (SG) is an area full of interneurones known to have commissural connections across the spinal cord. The role of SG in this contralateral inhibitory pathway is investigated here. Forty-three SG cells were recorded in the lumbar dorsal horn of decerebrate spinal rats. Their ipsilateral excitatory receptive fields and responses to sciatic nerve stimulation were recorded. Repetitive electrical stimulation was then applied to the contralateral sciatic nerve. Eight (19%) units were excited by such stimulation. A brief tetanus was followed by an increase of ongoing activity lasting 30 s to 10 min. These cells did not, however, have excitatory contralateral fields. A small separate group of 4 cells (9%) were mildly inhibited by heating or pinching the contralateral limb. The significance of contralateral excitation of some SG cells is discussed in the light of the predominantly inhibitory contralateral effect on dorsal horn cells in laminae 4 and 5. It is suggested that some SG cells may be inhibitory interneurones in their effect on deeper cells.

Alterations in the ipsi- and contralateral afferent inputs of dorsal horn cells produced by capsaicin treatment of one sciatic nerve in the rat

Dorsal horn cells in the lumbar spinal cord of decerebrate spinal rats were examined 7-21 days following local application of capsaicin to the sciatic nerve. Such local capsaicin treatment is known not to influence the size of the incoming A and C fibre afferent volley. The receptive field properties and primary afferent input of cells on both sides of the cord, that is ipsi and contralateral to the treated nerve, were examined. On the treated side, the percentage of cells excited by C fibres from the capsaicin treated nerve was 30% of normal and the number of cells responding to noxious heating of the cutaneous receptive field was reduced by 50%. A fibre input and low and high threshold mechanical input were normal. The receptive field size was larger in many cells innervated by the treated nerve. On the side opposite to the treated nerve, responses to noxious and non-noxious stimulation of the untreated limb were unaffected as was the input from the untreated sciatic nerve. Receptive fields were somewhat larger than normal. Effects were also observed from contralateral stimuli. Cells on both sides of the cord were found with excitatory contralateral receptive fields and excitatory responses to trains of high intensity stimulation to the contralateral sciatic nerve. In untreated animals the effect of such contralateral stimulation is inhibitory. The results show that peripheral nerve capsaicin treatment causes long lasting reduction of the C fibre input to dorsal horn cells on the treated side. However, it also results in changes in the inhibitory and excitatory receptive fields of cells on both sides of the cord.

The time course and specificity of the changes in the behavioural and dorsal horn cell responses to noxious stimuli following peripheral nerve capsaicin treatment in the rat

Capsaicin, a neurotoxin which acts specifically on sensory primary afferent C-fibres was applied locally to one sciatic nerve of a group of rats. One to sixteen days following this a series of behavioural and electrophysiological studies were performed. The latency of foot withdrawal of the rats to a controlled thermal noxious stimuli was significantly elevated (200%). The peak increase occurred on day 1 after treatment; the response then fell to a steady but elevated level for up to 16 days. Responses to noxious mechanical stimuli were unaffected by capsaicin treatment. Single unit analysis of the dorsal horn of the spinal cord showed that the number of neurones in deep laminae (4, 5 and 6) responding to a C peripheral volley was normal (60%) for the first 2 days after treatment. On day 3 post treatment, the number of cells with a C input began to fall reaching a maximal decrease on day 7 (25%), where it remained up to day 16. In contrast to this delayed effect on C-evoked responses, the number of cells responding to noxious heating of the skin fell from control levels of 60% down to 20% on day 1 and remained decreased for up to 16 days. The onset of thermal analgesia following local, capsaicin treatment, therefore, closely parallels the time course of the decrease of noxious heat-evoked responses in the dorsal horn. Since at early pretreatment times, the electrically C-evoked activity is normal these effects are likely to be due to action on peripheral C-fibre nociceptors in the skin. At a later stage capsaicin also appears to act on the central terminals of fibres reducing transmission to second order dorsal horn neurones.

Capping of the dental pulp mechanically exposed to the oral microflora -- a 5 week observation of wound healing in the monkey

The healing capacity of mechanically exposed and bacterially contaminated dental pulps was assessed in monkeys after capping with 2 commercial Ca(OH)2 containing compounds. One hundred eighty teeth in 7 monkeys were employed, 45 as untreated controls and 135 as treated exposures. Class V buccal cavity preparations resulting in pulpal exposure were prepared, left open to the oral cavity for 0, 1, 24 h or 7 days and employed as controls, or debrided, capped, restored with amalgam and left undisturbed for 5 weeks as treated exposures. Zero and 1 h untreated exposures presented damage from the mechanical trauma only, whereas 24 h and 7 day pulp wounds exhibited pronounced infiltrations of polymorphonuclear and mononuclear leukocytes. In addition, the 7 day exposures demonstrated several teeth with partial and total necrosis. Treated 0, 1 and 24 h exposures demonstrated wound healing, minimal pulp tissue inflammation, reorganization of soft tissue and formation of new hard tissue at the exposure site in 86 of 99 teeth. Treated 7 day exposures healed less frequently, showing signs of dentin bridging in 15 of 27 teeth. This study indicated that mechanically exposed and orally contaminated dental pulps in monkeys have a high capacity to resolve inflammation and initiate healing with new dentin formation at the exposure site when treated as described.

Chronic blockade of sciatic nerve transmission by tetrodotoxin does not produce central changes in the dorsal horn of the spinal cord of the rat

Rat sciatic nerves were treated with tetrodotoxin (TTX) for 4--10 days, by implanting a glass capillary tube filled with TTX into the nerve through the epineurium. Following this treatment the somatotopic organization of receptive fields in the L4 dorsal horn, an area of cord normally responding only to foot stimulation. The map was normal in animals treated with TTX. Dorsal horn levels of fluoride-resistant acid phosphatase, substance P, somatostatin, cholecystokinin-like peptide, neurotensin and neurophysin were also normal as assessed from density of staining. These results are discussed in the light of the positive changes that are seen following chronic sciatic nerve section.

The contralateral input to the dorsal horn of the spinal cord in the decerebrate spinal rat

Input from the contralateral limb and tail was examined in the lumbar dorsal horn of decerebrate spinal rats. Fifty-three cells were recorded from laminae 4, 5 and 6 and classified according to their ipsilateral response to natural and electrical stimulation. Twenty-nine (54%) of these cells were found to have inhibitory contralateral fields. This inhibition was evoked by noxious pinching or heating of the skin. In most cases the inhibitory field was a mirror image of the excitatory ipsilateral field although it also often included the tail. Activity evoked by natural and electrical stimulation as well as spontaneous activity was inhibited by contralateral skin stimulation. Noxious specific and wide dynamic range cells displayed these fields but low threshold mechanoreceptive cells did not. Twenty-six cells (49%) received direct short-latency excitatory input from the contralateral sciatic nerve; this correlated well with the presence of contralateral fields. Trains of stimuli applied to the contralateral sciatic nerve at A delta- and C-fibre strength resulted in inhibition of the cell whereas trains of A beta strength had no effect. The results demonstrate the existence of segmental contralateral control over dorsal horn cell activity, not involving supraspinal pathways.

Do opioid peptides mediate a presynaptic control of C-fibre transmission in the rat spinal cord?

A presynaptic inhibitory role for opioid peptides in the control of C-fibre-evoked activity in the dorsal horn has been investigated. The excitability of C-fibre terminals in the dorsal horn of decerebrate spinal rats was tested using intraspinal terminal stimulation and recording the size of the antidromic C wave from the dorsal roots. Naloxone (1-2 mg/kg) failed to alter the baseline terminal excitability of the C-fibres, but reduced the increase in terminal excitability produced by A-fibre afferent conditioning stimuli. The inhibition of postsynaptic C-evoked activity in lamina 5 cells produced by A-afferent fibre conditioning stimuli was also reduced by naloxone. This effect may reflect the reversal of an opioid-mediated presynaptic inhibition, although blockade of a direct postsynaptic inhibitory action could also be involved.

Effects of capsaicin applied locally to adult peripheral nerve. I. Physiology of peripheral nerve and spinal cord

(1) Systemic capsaicin treatment of neonatal and adult rats is known to affect unmyelinated afferents. However, the systemic route of administration presents several disadvantages and in order to overcome these a method was explored where a single nerve in adult rats was locally treated. (2) Sciatic nerves were exposed and a 10 mm length was soaked for 15 min in 1.5% capsaicin in vehicle or in the vehicle alone (10% Tween 80, 10% ethyl alcohol in saline). (3) Both the capsaicin solution and the vehicle caused acute block of the C compound action potential while in contact with the nerve. Removal of the solutions, however, resulted in substantial recovery of C fibre conduction. The A fibre volley was totally unaffected. (4) 13-21 days after treatment, the size of the myelinated and unmyelinated volleys evoked by maximal stimulation of the capsaicin treated nerve were unchanged but there was a 20% decrease of conduction velocity in the C fibres. (5) The ability of the maximal C volley from the treated nerve to excite cells in the spinal cord was substantially decreased (by 50%) 13-21 days after local capsaicin.

Nuclear bodies as structural indicators of estrogenic stimulation in uterine luminal epithelial cells

Preliminary evidence has indicated that the number of nuclear bodies in uterine luminal epithelial cells of the immature rat may be related to the duration of nuclear retention of the estrogen receptor complex (Clark et al., 1978). To test this hypothesis, an ultrastructural analysis of nuclear and cytoplasmic differentiation was performed at 4, 12, 24, 48, and 72 hr after a single injection of estradiol or nafoxidine (synthetic estrogen agonist/antagonist) into 21 day female rats. Variations in nuclear and cytoplasmic differentiation and in the frequency of occurrence of nuclear bodies (simple and complex) were determined and compared with established biochemical changes in the concentration of nuclear estrogen receptor and RNA polymerase activity (Clark et al., 1978). Following nafoxidine there is sustained elevation of the nuclear concentration of the estrogen receptor as well as RNA polymerase I and II activities over the entire 72-hr period. From 4 to 72 hr the height of the luminal epithelial cell as well as the frequency of nuclear bodies increase at linear rates. Through steady expansion of the cytoplasmic membrane system (RER) and Golgi) the relatively undifferentiated epithelial cells of the control uterus are converted progressively into ones equipped for protein secretion. At 72 hr the effects of an estradiol implant resemble closely those observed after a single injection of nafoxidine; these include sustained nuclear receptor occupancy, elevated RNA polymerase activity, epithelial hypertrophy, and high frequency of nuclear bodies. However, after a single injection of estradiol, the luminal epithelial cells become slightly but significantly taller than the control cells and remain close to this size from 24 to 72 hr.; the frequency of nuclear bodies decreases linearly from 4 to 72 hr to fall below the control level. In addition, limited cytoplasmic autolysis is evident from 24 to 72 hr. A single injection of estradiol results in short-term nuclear receptor occupancy and elevated RNA polymerase activities which return to control levels by 24 hr. This collective evidence offers further support to the hypothesis that the duration of nuclear occupancy by the estrogen receptor is reflected in the size of the nuclear body populations in these epithelial target cells. Also during hyperestrogenization, epithelial hypertrophy is accompanied by steady formation of nuclear bodies.

Effects of cutaneous nerve and intraspinal conditioning of C-fibre afferent terminal excitability in decerebrate spinal rats

1. Changes in the threshold for antidromic activation of C-fibre afferent terminals in the lumbar spinal cord of the decerebrate-spinalized rat have been examined. 2. The antidromic compound action potential elicited by stimulation in the dorsal horn was recorded in a sectioned dorsal root. 3. The antidromic C wave had conduction velocities and strength-duration properties similar to that described for other unmyelinated fibres. 4. The optimal position of the stimulating electrode within the spinal cord for eliciting the antidromic C wave was found to correlate with the site of entry and termination of C-afferent fibres. 5. Local stimulation within the dorsal grey of the spinal cord was shown to produce prolonged increased excitability of the C-afferent terminals in that segment. This effect was restricted to the terminals and could not be demonstrated in the stem axons of the C fibres. 6. Cutaneous afferent conditioning volleys from the sural nerve produced marked increases in the excitability of the C-afferent terminals. This effect was present at A-fibre strength sural stimulation, with no significant alteration when C-fibre strength stimulation was used. The alteration in the threshold for antidromic stimulation produced by the sural conditioning stimuli only occurred at the C-afferent terminals and not at their axons. 7. The results are discussed in terms of presynaptic inhibition of C-fibre input at a segmental level.

Lamina-specific alteration of C-fibre evoked activity by morphine in the dorsal horn of the rat spinal cord

The effect of systemic morphine (5 mg/kg) on the C-fibre evoked activity in the dorsal horn of decerebrate spinalized rats has been investigated. Activity in units recorded from lamina 5 was inhibited in a naloxone-reversible fashion by morphine. However, morphine produced variable changes in the C-evoked activity of units recorded within the substantia gelatinosa, some units showing excitation, some inhibition and some an alteration in the timing and pattern of the C-evoked activity.

The sequence 5'-AAUAAA-3'forms parts of the recognition site for polyadenylation of late SV40 mRNAs

We have observed three effects of deletion mutations on polyadenylation of late SV40 mRNAs. The first class of mutants lack segments (-3 to -14 bp) between the 5-AAUAAA-3' and normal poly(A) site. These mutants produce mRNas polyadenylated at new sites, downstream from the wild-type site. The poly(A) site is moved farther downstream as the deletions become larger; as a result, polyadenylation always occurs within an 11-19 nucleotide range from the AAUAAA sequence. The second class of mutants lack segments (-12 to -30 bp) between the AAUAAA sequence and the coding region of the mRNA. The poly(A) site for only one of these mutants was studied (dl1457, -12 bp). In this case, the spatial relationship between AAUAAA and poly(A) site is altered. dl1457 produces a class of mRNAs polyadenylated at the first Ca following the AAUAAA sequence, as well as other mRNAs polyadenylated farther downstream. Finally, a 16 bp deletion that includes the AAUAAA sequence prevents poly(A) addition.

Mammographic practice and dosimetry in Britain

A survey of mammographic techniques and dosimetry in 61 NHS centres in Britain has been completed. Physical parameters measured at each centre included tube output, half-value thickness, peak kilovoltage, surface dose and percentage depth dose. Ionisation and thermoluminescence dosimetry were employed and image quality was assessed subjectively using a test phantom. Absorbed doses are given at the plane surface of an average-sized, 5 cm thick homogenous breast composed of 50% fat and 50% water. The doses fall naturally into the four combinations of molybdenum (Mo) and tungsten (W) targets and film (F) and xerox (X) receptors. The Mo/X group produced the best images of the phantom but also the highest mean dose of 3.26 cGy (rad) for a cranio-caudad (c-c) view and its use does not seem justified for asymptomatic screening. The Mo/Lo-Dose or MIN-R film combination gave a mean dose of 0.95 cGy(rad) for a c-c view whereas the W/X group gave 0.89 cGy(rad) and superior image quality. The W/F group gave the poorest image quality and its continued use for mammography is questionable.

Haemodynamic effects of increasing extracellular potassium concentration in ACTH-induced hypertension in sheep

1. ACTH administration (20 microgram day-1 kg-1) to sheep produces hypertension associated with a raised cardiac output and hypokalaemia. 2. The aim of the present experiments was to detail the haemodynamic changes associated with restoration of the extracellular potassium concentration in sheep with ACTH-induced hypertension. 3. After 7 days of ACTH treatment potassium chloride (10 mmol/h) was infused for 3 days to restore plasma [K+] to the pre-ACTH value. 4. ACTH reduced plasma [K+] from 4.4 +/- 0.1 to 3.2 +/- 0.2 mmol/l but 3 days of potassium chloride infusion returned plasma [K+] to 4.3 +/- 0.2 mmol/l. 5. ACTH increased mean arterial pressure from 67 +/- 2 to 88 +/- 1 mmHg in the first 7 days and it remained elevated during potassium chloride infusion (91 +/- 5 mmHg on day 10). 6. Cardiac output rose with 7 days ACTH treatment from 4.9 +/- 0.2 to 6.0 +/- 0.6 l/min but fell progressively with potassium chloride infusion to 4.9 +/- 0.3 l/min on day 10. 7. These studies suggest that potassium status or extracellular [K+] may play a role in determining the haemodynamic profile associated with steroid-induced hypertension.

The laminar organization of dorsal horn cells responding to peripheral C fibre stimulation

Cat dorsal horn was searched for all detectable units that responded to peripheral C fibre input. Fifty-seven such units were examined in detail. They were located in two main areas. One group was in the superficial laminae 1, 2, and possibly dorsal 3 (n = 29), and the other group was much deeper in laminae 5 and 6 (n = 24). Only four units were situated in the region of lamina 4. Differences were found in the responses to C fibre stimulation of these two groups, both in the optimum stimulus and in the timing of responses to repeated stimulation. Superficial units often did not respond to C fibre stimulation unless a train of two or more stimuli (10 ms apart) were applied, but when responses did occur they were usually very even and regular, with precise onset latencies on repeated stimulation. Deep units tended to need only one peripheral C fibre stimulus for excitation, but the responses were irregular with latencies fluctuating with each stimulus. Some superficial and deep units showed a steady increase in latency of the late C response on repeated stimulation. Increases of up to 80 ms after 30 s of stimulation at 1 Hz were observed. The results are discussed in terms of the neuronal connections in the dorsal horn.

The stereospecific effect of naloxone on rat dorsal horn neurones; inhibition in superficial laminae and excitation in deeper laminae

The effect of systemic naloxone on the activity evoked by C-fibre stimulation in dorsal horn neurones of the rat spinal cord has been investigated. Recordings were made in unanaesthetized, decerebrate spinalized rats. Fifteen units were recorded from laminae 4 and 5 of the dorsal horn, 11 of these units were excited by naloxone (0.2--1.0 mg/kg). The onset of this excitation was after 20 sec to 5 min and recovery to control levels occurred within 15--40 min. Of 17 units recorded in substantia gelatinosa of the dorsal horn, 13 were inhibited by the naloxone. The latency of onset of this inhibition was short (2--10 sec) and the effect persisted for 5--10 min. The effects were largely restricted to C-fibre evoked activity although sometimes A delta responses were similarly altered. Neurones stimulated by A beta-fibre threshold, or whose sole afferent input were A beta-fibres, were unaffected by the naloxone. The stereoisomer of naloxone, (+)naloxone which is inactive in opiate receptor binding tests, failed to produce the same changes found with (-)naloxone in 17 units. These results show a differential effect of naloxone on neurones in the dorsal horn which respond to C-fibre input. Units in the substantia gelatinosa are inhibited while units in deeper laminae are excited by naloxone. These effects are likely to be mediated by the blockade of endogenous opioids in the spinal cord.

The spread of sensitization of polymodal nociceptors in the rabbit from nearby injury and by antidromic nerve stimulation

1. Ninety-three polymodal nociceptor units with unmyelinated axons were isolated from rabbit sural nerves. Twenty-three were used for control data. These showed normal sensitization on repeated heating of their receptive fields, measured here as a drop in mean heat threshold. 2. Small injuries were made 5 (n = 15) or 10 (n = 12) mm outside the receptive fields of some polymodal nociceptors. This resulted in the development of spontaneous firing and lowered thresholds to heating of the receptive field. 3. Local anaesthetic previously injected into the site of injury blocked this spread of heat sensitization. Previous injection of saline had no effect. 4. Antidromic stimulation of the sural nerve, proximal to the recording site, also resulted in heat sensitization of polymodal nociceptors (n = 10). 5. Possible mechanisms for the spread of sensitization of polymodal nociceptors from nearby injury are discussed. Analogies are drawn between these results and those of Lewis (1935--36) on the spread of cutaneous ;yperalgesia around a skin injury in man.

Cellular mechanics of dentinal bridge repair using 3H-thymidine

Cellular reorganization in the pulp following mechanical pulp exposure involves three steps: First, lysis and macrophage resolution of the clot form; second, there is an invasion of the clot area by fibroblasts and endothelial cells, i.e., formation of granulation tissue; third, an organization and differentiation of these cells into functional odontoblasts occurs as early as 9 days after exposure. Autoradiographic results showed an increased DNA synthesis in the fibroblast and endothelial cell populations which coincided with a histologically-observed increase in those populations. A relative increase in fibroblastic activity, as compared to endothelial cell activity, suggested that fibroblasts may be the cells that replace odontoblasts.