Spatial restriction of light adaptation and mutation-induced inactivation in fly photoreceptors

The spatial spread within fly photoreceptors of 2 forms of desensitization by bright light have been investigated: the natural process of light adaptation in normal Musca photoreceptors and a receptor-potential inactivation in the no-steady-state (nss) mutant of the sheep blowfly Lucilia. The suction-electrode method used for recording from vertebrate rods was applied to fly ommatidia. A single ommatidium in vitro was partially sucked into a recording pipette. Illumination of the portion of the ommatidium within the pipette resulted in a flow of current having a wave form similar to that of the receptor potential and polarity consistent with current flow into the illuminated region of the photoreceptors. Two 5-microns slits of light, positioned at right angles to the ommatidial axis, were employed to determine the spread of light adaptation or inactivation along the ommatidium. The intensity of a flash of light delivered to one (adapting) slit was adjusted until it produced a criterion fractional reduction in the response to the other (test) slit. The reciprocal of this intensity of the adapting slit was taken as a measure of the effectiveness of the slit in causing light adaptation or inactivation. The effectiveness of the slit in causing light adaptation in normal Musca ommatidia fell as the adapting and test slits were moved farther apart along the ommatidial axis, declining to half its maximal value at a distance of 13 +/- 2 microns. Similar measurements of the effectiveness of a slit in causing light-induced inactivation in the nss mutant of Lucilia also demonstrated localization, declining to half its maximal value at a distance between the slits of 9 +/- 1 microns. Neither light adaptation nor inactivation by the nss mutation, therefore, appear to be mediated by voltage or by a highly diffusible agent. The results are consistent with the idea that inactivation by the nss mutation replaces adaptation in the mutant photoreceptors.

Motor functions in rat hindlimb muscles following neonatal sciatic nerve crush

The sciatic nerve was crushed in the right hindlimb in newborn (3-8 h old) rats. Two to four months later, electromyographic activity was recorded from both the control and reinnervated ankle extensor muscles soleus or lateral gastrocnemius and from the ankle flexor muscle tibialis anterior. Tonic postural activity was present in the extensor muscles on both sides during quiet stance. The control flexor muscles were usually silent in this situation, but the reinnervated flexors exhibited abnormal sustained activity. During locomotion, the control extensors were activated during the stance phase and their mean burst made up 61.5% of the step cycle. The control tibialis anterior muscle fired only during the swing phase, with the burst lasting 18.1% of the step cycle. In the reinnervated extensor muscles, the mean burst duration was decreased (46% of the cycle) but the basic locomotor pattern was not impaired. The reinnervated tibialis muscle, however, was activated abnormally, with one appropriate flexor burst during the swing phase and an "extensor-like" burst during the stance phase of the step. Reflex responses to stretch were weak or absent on the operated side. Histological examination showed that the reinnervated soleus and tibialis muscles were almost devoid of muscle spindles. The motor unit mean firing rates in the reinnervated soleus (22 imp/s) and lateral gastrocnemius (45 imp/s) matched those of the control muscles (25 and 42 imp/s, respectively). In contrast to the phasic, high-frequency firing (52-80 imp/s) in the control tibialis, the reinnervated tibialis motor units fired at significantly lower rates (22-56 imp/s).(ABSTRACT TRUNCATED AT 250 WORDS)

Medication-induced performance deficits: analgesics and narcotics

Pain is the most common medical complaint, and analgesic drugs are often used for its management. Seven out of 10 Americans took nonprescription pain relievers in the last year. Analgesics are classified as nonnarcotics (acetaminophen, aspirin, and nonsteroidal anti-inflammatory drugs), narcotics (which include the morphine-like drugs), and analgesic adjuvants (a heterogeneous group of drugs, including antihistamines, phenothiazines, anticonvulsants, calcium channel blockers, and tricyclic antidepressants), which may have intrinsic analgesic efficacy for specific pain syndromes or may be used as co-analgesics in combination with the traditional nonnarcotic and narcotic agents. Although these agents can be used safely most of the time by patients with acute or chronic pain, all classes of analgesics may impair cardiovascular and neuropsychiatric functioning, which may influence job performance in specific instances.

Feedback inhibition by calcium limits the release of calcium by inositol trisphosphate in Limulus ventral photoreceptors

Injection of inositol 1,4,5 trisphosphate (InsP3) into Limulus ventral photoreceptors elevates the concentration of intracellular calcium ions and as a consequence depolarizes the photoreceptor. This InsP3-induced elevation can be inhibited by a prior injection of calcium or InsP3 delivered 1 s earlier. Recovery from this inhibition has a half-time of between 1.5 and 5 s at 20 degrees C. Calcium released by InsP3 therefore inhibits further release of calcium from InsP3-sensitive calcium stores. This feedback inhibition may protect the calcium stores from depletion during prolonged bright illumination. Feedback inhibition, rather than periodic depletion of calcium stores, may also underlie the oscillatory bursts of InsP3-induced calcium release that have been observed in many cell types.

On the dissociation constants of BAPTA-type calcium buffers

We have determined or redetermined the calcium dissociation constants of seven BAPTA-type buffers with KD's in the range from 0.4 microM to about 20 mM in 300 mM KCl. These include four newly synthesized ones: 5-nitro BAPTA; 5,5'-dinitro BAPTA; 5-methyl-5'-nitro BAPTA; and 5-methyl-5'-formyl BAPTA. Moreover, we tabulate dissociation constants or KD's for BAPTA and eleven BAPTA-type buffers, compare most of them with an empirical curve based upon so-called Hammett values, and predict KD's for several still unsynthesized but potentially valuable buffers.

Cancer pain. Anatomy, physiology, and pharmacology

Cancer pain can be divided into three classes: somatic, visceral, and deafferentation. Somatic and visceral pain result from activation of nociceptors by tumor infiltration of tissues and from secondary inflammatory changes with release of algesic chemicals that act to sensitize nociceptors. Pain may be experienced locally (somatic and visceral) or referred to remote cutaneous sites (visceral). Deafferentation pain results from injury to the nervous system due to tumor infiltration or cancer therapy and may persist even after the cause of the injury has been removed. Somatic, visceral, and deafferentation pain may be complicated by sympathetically maintained pain, in which efferent sympathetic activity promotes persistent pain, hyperpathia, and vasomotor and sudomotor changes after tissue injury from cancer or its therapy. The neurobiology of cancer pain is complex and incompletely understood. This article summarizes current knowledge in this area and briefly discusses approaches to cancer pain management that are based on this knowledge.

Pharmacologic management of bone pain in the cancer patient

Cancer patients may experience acute or chronic pain caused by tumor infiltration of pain-sensitive structures or related to surgery, radiation, and chemotherapy. Acute bone pain, with or without associated neurologic deficits resulting from tumor metastasis to bone and contiguous neural structures (e.g., large peripheral nerve trunks or the spinal cord), is a common cause of intractable pain in cancer patients. Most often, treatment of bone pain involves the concomitant use of focal radiation therapy and analgesic drugs, especially steroids, nonsteroidal anti-inflammatory drugs (usually in combination with opioids), and adjuvant analgesic agents such as levodopa and calcitonin. However, pharmacologic therapy is not always efficacious and may have significant side effects. Less commonly, invasive therapies, such as resection of vertebral body tumor with spinal reconstruction or pituitary ablation and intraventricular opioid administration (for diffuse bone pain), are offered. In this article I discuss current approaches to the management of pain in cancer patients, emphasizing current hypotheses on the pathogenesis of bone pain and the rationale for its pharmacologic treatment.

Leukemic relapse presenting as sciatic nerve involvement by chloroma (granulocytic sarcoma)

A relapse of acute nonlymphocytic leukemia in a child presented as subacute mononeuropathy involving the sciatic nerve. Surgical exploration showed a chloroma (granulocytic sarcoma) of the distal sciatic nerve, but resection and irradiation did not lead to recovery of nerve function or complete resolution of the patient's symptomatic neuropathic pain. This case represents a rare neurologic complication of what is currently an uncommon presentation for leukemic relapse, and may be the only reported case of chloromatous involvement of the peripheral nervous system (PNS) without coexisting epidural or leptomeningeal leukemia.

The concentration of cytosolic free calcium in vertebrate rod outer segments measured with fura-2

The use of fluorescent indicators such as fura-2 (Grynkiewicz et al., 1985) to measure the cytosolic free calcium activity in retinal rods is complicated by the rods' sensitivity both to the fluorescence and to the light that excites it. By stimulating fluorescence from large numbers of rods in whole, loaded retinas and averaging repeated measurements, however, we have been able to monitor changes in free [Ca2+]i during exposure to nonsaturating lights under physiological conditions. Retinas, isolated from the bullfrog Rana catesbeiana, were loaded with fura-2 by incubation and mounted, receptor-side up, in a perfusion chamber placed on the stage of a specially designed apparatus. A step of light delivered from above, whose wavelength alternated between 340 and 380 nm every 110 msec, excited fluorescence from 24 mm2 of retina and evoked a light response (the aspartate-isolated pIII component of the electroretinogram--ERG). By comparing the fluorescence intensities excited by the 2 wavelengths (corrected for background and dark-noise), the free [Ca2+]i of the rod outer segment was determined. In darkness, the [Ca2+]i of the outer segment was found to be approximately 220 nM. A bright light caused it to fall exponentially to approximately 140 nM, with a time constant of approximately 1.6 sec. The value of [Ca2+]i at the onset of illumination was independent of stimulus intensity over a 2 log-unit range, and in all cases the fall was monotonic. After terminating the illumination, [Ca2+]i rose again to its time-zero value.(ABSTRACT TRUNCATED AT 250 WORDS)

The localization of calcium release by inositol trisphosphate in Limulus photoreceptors and its control by negative feedback

Microvillar photoreceptors of invertebrates exhibit a light-induced rise in the intracellular concentration of free calcium (Cai) that results in part from release of calcium from an intracellular compartment. This light-induced release of calcium appears to result from a cascade of reactions that involve rhodopsin, a GTP-binding protein and a phospholipase-C which releases inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) from the plasma membrane; the Ins(1,4,5)P3 acts to release calcium from smooth endoplasmic reticulum. In the ventral photoreceptor of the horseshoe crab Limulus polyphemus not all of the endoplasmic reticulum is subject to calcium release by Ins(1,4,5)P3. Only endoplasmic reticulum in the light-sensitive region of the cell is competent to release calcium in response to Ins(1,4,5)P3. The release of calcium by Ins(1,4,5)P3 in ventral photoreceptors appears to be subject to feedback inhibition through elevated Cai. We suggest that this feedback inhibition contributes to sensory adaptation in the photoreceptor and may account for oscillatory membrane responses sometimes observed with large injections of Ins(1,4,5)P3.

CSF distribution of opioids in animals and man

The CSF distribution of opioids after subarachnoid administration is important in determining therapeutic and undesirable side-effects. There are many factors which influence CSF distribution of opioids including the age, position, anatomy of the spinal column of the patient or animal, and the physico-chemical properties of the opioid solution and of the CSF. Opioids are cleared from their site of administration in CSF by three mechanisms: 1) uptake into the spinal cord, 2) diffusion through the dura and uptake into the blood, and 3) rostral-caudal CSF distribution. Physico-chemical factors such as lipid solubility, degree of ionization in the CSF and the baricity of the opioid solution are important in determining the rate of clearance by these three routes. Opioids which are highly lipid soluble, have high affinity for delta and/or kappa opiate receptor subtypes, and are largely non-ionized at physiologic CSF pH, would have optimal pharmacokinetic properties for subarachnoid administration. These properties would allow administration of a small dose of opioid which would be rapidly taken up into the spinal cord, thereby limiting CSF and vascular distribution to supraspinal brain regions.

Inositol 1,4,5 trisphosphate releases calcium from specialized sites within Limulus photoreceptors

We have investigated the subcellular distribution and identity of inositol trisphosphate (InsP3)-sensitive calcium stores in living Limulus ventral photoreceptor cells, where light and InsP3 are known to raise intracellular calcium. We injected ventral photoreceptor cells with the photoprotein aequorin and viewed its luminescence with an image intensifier. InsP3 only elicited detectable aequorin luminescence when injected into the light-sensitive rhabdomeral (R)-lobe where aequorin luminescence induced by light was also confined. Calcium stores released by light and InsP3 are therefore localized to the R-lobe. Within the R-lobe, InsP3-induced aequorin luminescence was further confined around the injection site, due to rapid dilution and/or degradation of injected InsP3. Prominent cisternae of smooth endoplasmic reticulum are uniquely localized within the cell beneath the microvillar surface of the R-lobe (Calman, B., and S. Chamberlain, 1982, J. Gen. Physiol., 80:839-862). These cisternae are the probable site of InsP3 action.

Novel routes of opioid administration in the management of cancer pain

Administration of opioids by less conventional routes may produce pain relief of more rapid onset, of longer duration, and fewer side effects in comparison with conventional oral or parenteral administration. This review will discuss the indications, efficacy, complications and potential advantages of these novel routes of administration.

Role of epidural and intrathecal narcotics and peptides in the management of cancer pain

The spinal administration of opioids may provide analgesia of long duration to patients with bilateral or midline lower abdominal or pelvic cancer pain. However, cross-tolerance to orally and parenterally administered narcotics and the rapid development of tolerance to spinal narcotics have limited their usefulness. Opioids have extensive distribution in the CSF and plasma when administered into the epidural or intrathecal space, and delivery of drug to brain stem sites may account for many of the toxic and therapeutic effects of spinal opioids. Further clinical and pharmacokinetic studies are required to provide the information regarding: the optimal opioids for use as spinal analgesics; equieffective dose ratios of spinal opioids in comparison to parenteral or oral opioids; strategies useful to forestall the development of tolerance of spinally administered opioids; the analgesic efficacy of this therapy in opioid-tolerant patients; and the role of spinally administered nonopioid analgesics in the management of cancer pain in the tolerant patient. These questions will need resolution before this therapy can be recommended for routine use in the management of cancer pain.

Anatomy, physiology, and neuropharmacology of cancer pain

The anatomy, physiology, and pharmacology of nociception and its modification by analgesic drugs have been studied extensively in the past decade. Although the neural mechanisms of nociceptors and the stimuli that activate them are much better understood, it must be emphasized that the perception of pain, as well as the meaning of pain to the individual, is a complex behavioral phenomenon and involves psychologic and emotional processes in addition to activation of nociceptive pathways. Pain related to malignant disease can be classified as somatic, visceral, and deafferentation in type. Somatic pain and visceral pain involve direct activation of nociceptors and are often a complication of tumor infiltration of tissues or injury of tissues as a consequence of cancer therapy. The management of this type of pain is typically accomplished by treating the tumor (with surgery, chemotherapy, and/or radiation therapy) and by using the appropriate non-narcotic, narcotic, and adjuvant analgesic agents. Neuroablative therapies may be helpful in specific circumstances. For example, cordotomy may be helpful for unilateral pain below the waist in patients with somatic and visceral pain. This procedure may also be helpful for early deafferentiation pain (i.e., lumbosacral plexopathy) in which peripheral nerves are compressed but not infiltrated or destroyed by metastatic tumor growth. Deafferentiation pain may be a complication of tumor infiltration of peripheral nerve or of cancer therapy that injures neural tissue. This type of pain is often poorly tolerated and difficult to control, particularly if not treated early and aggressively. Although incompletely understood, the pathophysiology of deafferentation pain appears to be different from that of somatic or visceral pain, and the treatment approaches may be different. Management approaches to deafferentation pain usually emphasize treatment of the pain, because injury to the nervous system may be difficult to reverse, even if one can successfully treat the underlying malignancy, and many deafferentation pain syndromes occur as a complication of cancer therapy. The role of narcotic analgesics in the management of deafferentation pain is not clear, although the published experience suggests that they are less useful than in somatic or visceral pain.

Neck pain in the elderly: a management review. Part II

Rheumatoid arthritis and metastatic cancer occur commonly in the elderly, and may cause neck pain. Rheumatoid arthritis may produce cervical radiculopathy and myelopathy resulting from vertebral body subluxation, although radiological manifestations of subluxation are much more common than neurological dysfunction. Cervical spinal cord compression is a neurological emergency and may produce cervical radiculopathy as well as myelopathy. Careful neurological and radiological assessments are required to minimize pain and preserve neurological function in elderly patients suffering from neck pain complicating rheumatoid arthritis or cervical spinal metastasis.

Neck pain in the elderly: a management review. Part I

Degenerative disease of the cervical spine is a common cause of neck pain in the elderly. This article reviews the pathogenesis, clinical features, and management of cervical spondylitic radiculopathy and myelopathy in the elderly.

Back pain in the elderly: updated diagnosis and management

CT of compression fractures is a useful adjunct to the plain x-ray in excluding signs of metastasis. However, increased bone density on CT may not distinguish osteoporotic fractures from neoplastic disease, in which case radioiodine scan, bone and marrow biopsies, or myelography may be necessary. Surgery for painful osteoarthritic spinal disease is controversial. The potential advantages of surgery must be weighted against the risk of anesthesia, the length and tolerance of postoperative immobility, and the effect of laminectomy and fusion on the biomechanics of the spine. Furthermore, the elderly are at increased risk for postoperative complications.

A chronic sheep preparation for the study of drug pharmacokinetics in spinal and ventricular CSF

We describe a sheep preparation utilizing chronic vascular and subarachnoid catheterization and ventriculocisternal perfusion. This preparation allows simultaneous, atraumatic sampling of plasma and CSF after drug administration by the intravenous, intracerebroventricular, or lumbar intrathecal (i.t.) routes in an unanesthesized animal. This sheep preparation provides a convenient means of studying the CSF distribution of exogenous and/or endogenous substances. During intravenous infusion at a rate of 2.2 micrograms/kg/min, morphine appears in cisternal CSF within 15 min. The steady-state plasma concentration and CSF flux (or appearance rate) of morphine was 0.037 and 0.009 micrograms/min, respectively. At steady state, 0.008% of the administered dose appears in CSF/min. The coadministration of morphine, methadone, and [14C]sucrose into the fifth lumbar subarachnoid space is associated with the simultaneous appearance of morphine and [14C]sucrose, but not methadone, in cisternal CSF. The ratio of [14C]sucrose to morphine increased by nearly sevenfold in cisternal CSF, indicating clearance of morphine relative to [14C]sucrose as the compounds ascend in the CSF axis. The simultaneous appearance of morphine and [14C]sucrose in cisternal CSF after lumbar subarachnoid administration indicates that morphine, like sucrose, is distributed within the CSF by bulk flow. This sheep preparation can be used to provide the quantitative data necessary for the development of pharmacokinetic-pharmacodynamic models that relate plasma and CSF concentrations of opiates to their pharmacological effects. These studies will help to provide the pharmacological rationale for the administration of opiates by novel routes for pain management in man.

Pressure injection of calcium both excites and adapts Limulus ventral photoreceptors

Single pressure injections of 1-2 mM calcium aspartate into the light-sensitive region of Limulus ventral photoreceptors resulted in a rapid, 20-40-mV depolarization lasting approximately 2 s. The depolarization closely followed the rise in intracellular free calcium caused by the injection, as indicated by aequorin luminescence. The depolarization was followed by reversible desensitization (adaptation) of responses to both light and inositol 1,4,5 trisphosphate. Similar single injections of calcium into the light-insensitive region of the receptor were essentially without effect, even though aequorin luminescence indicated a large, rapid rise in intracellular free calcium. The depolarization caused by injection of calcium arose from the activation of an inward current with rectification characteristics and a reversal potential between +10 and +20 mV that were similar to those of the light-activated conductance, which suggests that the same channels were activated by light and by calcium. The reversal potentials of the light- and calcium-activated currents shifted similarly when three-fourths of the extracellular sodium was replaced by sucrose, but were not affected by a similar replacement of sodium by lithium. The current activated by calcium was abolished by prior injection of a calcium buffer solution containing EGTA. The responses of the same cells to brief light flashes were slowed and diminished in amplitude, but were not abolished after the injection of calcium buffer. Light adaptation and prior injection of calcium diminished the calcium-activated current much less than they diminished the light-activated current.

Excitation and adaptation of Limulus ventral photoreceptors by inositol 1,4,5 triphosphate result from a rise in intracellular calcium

Single pressure injections of 1-10 pl of inositol 1,4,5 triphosphate (IP3) or inositol 4,5 bisphosphate [I(4,5)P2] excite Limulus ventral photoreceptors by inducing rapid bursts of inward current. After excitation by IP3, responses to subsequent injections of IP3 or light flashes are often reversibly diminished (adapted). Single injections of IP3 and I(4,5)P2 are effective at concentrations in the injecting pipette of 20 microM to 1 mM. Single injections of inositol 1,4 bisphosphate are ineffective at concentrations of 100-500 microM. Excitation by IP3 or I(4,5)P2 is accompanied by a rise in intracellular free calcium, as indicated by aequorin luminescence. Prior injection of calcium buffer solutions containing 100 mM EGTA greatly diminishes the total charge transferred across the plasma membrane during excitation by IP3 or I(4,5)P2, which suggests that a rise in Cai is necessary for excitation by the inositol polyphosphates. Adaptation of the response to light by IP3 is also abolished by prior injection of EGTA. In the same cells, the response to brief light flashes is slowed and diminished in amplitude by the injection of calcium buffer, but the charge transferred during the response is not significantly diminished. This suggests that light has access to a pathway of excitation in the presence of EGTA that is not accessible to intracellularly injected IP3.

Localization of the photocurrent of Limulus ventral photoreceptors using a vibrating probe

We have used a vibrating probe to determine the profile of electrical current density around ventral photoreceptors of the horseshoe crab following flashes of light that uniformly illuminated the entire surface of the photoreceptor's cell body. The vibrating probe signal indicated that the density of inward current was greatest at the distal region of the cell, the region that is expected to contain the light-sensitive rhabdom. The density of inward current typically declined at the midpoint of the cell body and then reversed to an outward current flow in the proximal region of the cell body, close to the axon. The profile of local sensitivity of the photoreceptor to light closely matched the profile of inward current density, suggesting that the light-activated conductance is localized to the light-sensitive region of the cell.

Paraneoplastic opsoclonus-myoclonus. Association with medullary thyroid carcinoma and review of the literature

The syndrome of opsoclonus-myoclonus (OM) is an infrequent but well-known "remote effect" of neuroblastoma in children. The OM syndrome is even less frequent in adults. A few cases of adult paraneoplastic OM have been described in association with several systemic neoplasms. We report the unique case of a 29-year-old man with metastatic medullary thyroid carcinoma in whom OM developed as part of a generalized transient encephalopathy. We outline the postulated anatomic lesions and pathophysiologic mechanisms underlying the OM syndrome, as well as examine the possible connections between the neuroendocrine derivation of medullary thyroid carcinoma and the neurotoxic and/or autoimmune theories of the causation of the OM syndrome in patients with systemic neoplasms.

The initial response of Limulus ventral photoreceptors to bright flashes. Released calcium as a synergist to excitation

The leading edge of the response of Limulus ventral photoreceptors to brief flashes was investigated using a voltage clamp. The leading edge of responses increases linearly with flash intensity when dim flashes produce less than one photoisomerization per square micron of cell surface. Brighter flashes accelerate the initial portion of the response, resulting in a fourth-power relationship between the magnitude of the response at brief times after the flash and the flash intensity. The onset of this nonlinearity with increasing flash intensity is determined by the local density of photoisomerizations within the receptor. Responses to bright 10-15-mum-diam spots therefore rise faster than responses to diffuse flashes producing the same number of photoisomerizations within the receptor. Background illumination shortens the response latency and suppresses the initial nonlinearity. These phenomena can be explained by a model of transduction in which light activates two parallel cascades of reactions. Particles released by the first of these cascades open ionic channels, while the second produces an agent that accelerates the rate of production of particles by the first. Injection of the calcium buffer EGTA slows the initial portion of the response to bright flashes and suppresses its nonlinearity, which suggests that the accelerating agent released by the second cascade is calcium.

C-13 NMR Investigation of the Ph-Dependence of Copper(II) Complexation to Glucuronic-Acid

The interaction of paramagnetic copper(II) ions with glucuronic acid in aqueous solution was studied by differential line broadening analysis of carbon-13 n.m.r. spectra. Evidence is presented for pH-dependent complexation behaviour, with simple carboxylate complexation dominating below pH 4.5, and a more complicated bidentate coordination mode involving O 3 above pH 4.5.

CSF distribution of morphine, methadone and sucrose after intrathecal injection

The lumbar to cisternal CSF distribution of morphine and methadone were compared to C-14 sucrose, a standard marker of CSF bulk flow, after lumbar subarachnoid injections in a sheep preparation. Morphine appeared and peaked simultaneously with C-14 sucrose in cisternal CSF at 90 to 190 minutes. The mean peak cisternal CSF morphine concentrations were sustained for 30-40 minutes, and averaged 148 ng/ml, representing 0.3% of the administered dose. Methadone was not detectable in cisternal CSF up to 240-300 minutes after lumbar subarachnoid administration. The C-14 sucrose/morphine ratio was increased an average of 6.7 times in cisternal CSF as compared to the ratio of the two compounds injected into the lumbar subarachnoid space. These studies demonstrate that morphine, a hydrophilic opioid, given intrathecally moves rostrally and appears in cisternal CSF by bulk flow. Furthermore the rostral redistribution of morphine is associated with the clearance of morphine from CSF. Methadone, a lipophilic opioid, appears to be completely cleared from CSF before it reaches the cisterna magna. These pharmacokinetic studies support a contribution of supraspinal sites to the analgesic and adverse effects produced by morphine given by spinal routes of administration. In contrast methadone appears to exert its effects predominantly at spinal sites.

The postnatal functional development of muscle stretch receptors in the rat

The response to a 5-sec stretch of the triceps muscle was studied in dorsal root filaments L5 of 72 infant rats (1-19 days old) under urethane anesthesia. More than 50% of all units in 1-day-old rats responded by repetitive firing until the end of the 5-sec stretch (slowly adapting or SA receptors), while the rest ceased to fire earlier (relatively rapidly adapting or 1/2 SA receptors), or gave an "on" response only. The number of units exhibiting an SA response increased with age and attained 80% in 5-day-old rats. By the 10th day of life, almost 90% of endings behaved as SA receptors. During development, the maximal discharge frequencies at the peak of stretch increased markedly, and their values in 18-day-old rats were comparable to those in adult rats. The phasic component of the response to stretch, although less well defined in the younger animals, was already present even in 1-day-old rats. Adaptation of the static response during maintained stretch was relatively steep in all the age groups studied. The results indicate that, in the rat, large numbers of muscle stretch receptors are capable of responding to sustained stretch as SA receptors, even at an age when their morphological and ultrastructural maturation is not yet fully accomplished.

Photoreceptor excitation and adaptation by inositol 1,4,5-trisphosphate

A central question concerning vision is the identity of the biochemical pathway that underlies phototransduction. The large size of the ventral photoreceptors of Limulus polyphemus renders them a favourite preparation for investigating this problem. The fact that a single photon opens approximately 1,000 ionic channels in these photoreceptors suggests the need for an internal transmitter. We have investigated whether inositol 1,4,5-trisphosphate (InsP3) functions as such an internal transmitter, given that InsP3 may act as an intracellular messenger in other cellular processes. Here we report that in Limulus, intracellular pressure injection of InsP3 both excites and adapts ventral photoreceptors in a manner similar to light.

Aetiology of pneumonia in children in Goroka Hospital, Papua New Guinea

To determine the aetiology of pneumonia in 83 children admitted to Goroka Hospital, Papua New Guinea, lung aspirates and blood were cultured for bacteria. Haemophilus infuenzae, Streptococcus pneumoniae, or both, were isolated from 43 (52%) of the children, other bacteria from 8 (10%), and no bacteria from 32 (39%). Of the 32 strains of H influenzae tested, 18 (56%) were non-serotypable, 8 (25%) were serotypes other than type b, and only 6 (19%) were type b. Viruses were isolated from lung or nasopharyngeal aspirates from 18 (29%) of the 62 children for whom viral cultures were done. It seems that, although viruses may initiate infection, death from pneumonia in children in developing countries is often due to H influenzae, S pneumoniae, or both. Antibiotic therapy would prevent many of these deaths. There is an urgent need for vaccines, effective in children less than 6 months old, that protect against all strains of H influenzae, and S pneumoniae.

Social class and psychological ill-health during unemployment

This study explores psychological health and the experience of being unemployed for between 6 and 11 months in two social class groups: unskilled and semi-skilled workers v. white-collar, managerial and professional workers. The respondents were British married men aged between 25 and 39. Information was obtained through interviews about financial and other problems, perceived threats associated with unemployment, anxiety, depression, general psychological distress and ratings of general health. It was expected that the working-class sample would exhibit poorer psychological health than the middle-class, but this was not confirmed. Medium-term unemployment appeared to have a homogenizing effect, with similarly poor health in both social class samples, although working-class respondents reported significantly greater financial problems and difficulties in filling the time.

The use of methylmethacrylate cement as an instantaneous fusion mass in posterior cervical fusions: a canine in vivo experimental model

The authors previously predicted the failure of posterior cervical fusions utilizing methylmethacrylate cement as an instantaneous "fusion" mass, based on research using an in vitro canine experimental model. This report describes the results of in vivo canine studies on the same subject. Three groups of dogs had application of a posterior C4-C5 20-gauge cerclage wire and autologous iliac crest bone graft; application of a posterior C4-C5 20-gauge cerclage wire and methylmethacrylate cement; or application of a C4-C5 20-gauge cerclage wire only. This group represented the control group. The dogs were allowed to live for 3 months postoperatively, at which time they were killed and their spine fusions studied radiologically, mechanically, and histologically. Five of the bone fusions united solidly radiologically. Their flexion stability was statistically superior to the others. Histologic studies confirmed solid union of the fusion mass to the underlying bone. Four of the six methylmethacrylate fusions demonstrated cerclage wire fracture and methacrylate-bone separation by the second postoperative month. At the time the dogs were killed, their flexion stability was statistically inferior to the bone fusions and tended to be inferior to the controls as well. Histologically, fibrous tissue was noted to have grown between the methacrylate "fusion" mass and the underlying bone. This work provides a mechanical explanation for the well-known success of the traditional bony fusion. It further supports our original prediction regarding the failure of methylmethacrylate "fusions."

Reconstruction of the cervical spine following anterior vertebral body resection: a mechanical analysis of a canine experimental model

In some quadriplegic patients whose acute spinal injury consists of a vertebral body fracture with bony retropulsion anteriorly and ligamentous damage posteriorly, it is appropriate to perform a decompression of the injured spinal cord by excision of the fractured body. Reconstruction of such a spine to achieve immediate and ultimate stability can be quite difficult. This is a report of mechanical testing using a canine in vitro experimental model to simulate different general types of reconstruction systems applicable to the spine destabilized as above. The results explain some of the previously noted failures of the traditional anterior strut grafting procedures. In addition, one of the reconstruction systems tested (anterior and posterior tension bands compressing an anterior strut graft into place) appeared to have sufficient immediate stability to eliminate the need for a halo-vest in the postoperative period. If such a reconstruction system were to prove clinically applicable, it would be quite beneficial to the quadriplegic patient in his rehabilitation.

Advances in the management of cancer pain

The study of pain in the cancer patient offers a unique opportunity to use clinical observations to advance biologic knowledge. The cancer patient unfortunately represents the experimental model of pain. This group of heroic patients can help teach us the physiologic and psychologic differences between acute and chronic pain, the importance and evolution of psychologic factors, the difference between pain and suffering, the clinical pharmacology of analgesic drugs, and the behavioral mechanisms humans use to suppress pain. They are a rich resource of research potential which should not go untapped. The development of better methods of pain control will benefit all patients with pain. There is a pressing need to develop innovative approaches based on sound, scientific principles, and advances in research technology offer us the opportunity to understand the complex phenomenon of pain.

Alpha adrenergic receptor subtype associated with receptor binding, Ca++ influx, Ca++ release and contractile events in the rabbit aorta

The alpha-adrenergic receptor mechanism in rabbit aorta was examined for the involvement of alpha-1 or alpha-2 receptor subtypes. Agonists (phenylephrine, norepinephrine and clonidine) and antagonists (prazosin and yohimbine) with known receptor subtype selectivity were used to define the contribution of alpha-1 or alpha-2 receptors to receptor-initiated cellular Ca++ influx, intracellular release of Ca++ and overall contraction. The receptor content of isolated membranes was also measured in [3H]prazosin and [3H]yohimbine radioligand binding studies. Contraction-derived KB values for prazosin (3 nM) or yohimbine (1 microM) were similar for all three agonists, indicating that each acted on the same alpha-1 receptor. Prazosin (10(-7) M) was effective in causing inhibition of cellular Ca++ influx initiated by agonists whereas yohimbine (10(-6) M) had no effect. Prazosin but not yohimbine caused a partial reduction in phenylephrine or norepinephrine-induced stimulation of 45Ca efflux rate whereas the smaller clonidine-induced stimulation was totally inhibited by prazosin and partially inhibited by yohimbine. Alpha-1 specific binding of [3H]prazosin was observed with a KD of 3.5 nM and maximum binding site (Bmax) of 73 fmol/mg of protein. Although no alpha-2 specific binding of [3H]yohimbine was observed, binding to a low-affinity/high-capacity class of sites was found. The results indicate the sole presence and contribution of alpha-1 receptors to Ca++ flux and contractile events in the rabbit aorta.

"Bare lymphocytes" without immunodeficiency

"Bare lymphocytes," which cannot be typed for the HLA-A,B, and C antigens were observed in two siblings, nine and six years of age. The elder child presented with aplastic anemia and was being considered for bone marrow transplantation. The younger child was healthy. The inability to phenotype both children for these three gene products persisted throughout the 21-month period of observation. The DR antigens were demonstrable which rendered it possible to deduce their A, B, and C genotype from the typing of the other four family members. Although alloantisera failed to detect the antigens on peripheral blood lymphocytes, monoclonal antibodies demonstrated reduced amounts of the HLA-A,B, and C antigens on the cells. The reduced level was confirmed following EBV transformation of the cells. After prolonged culture, HLA antigens immunoprecipitated from the cell extracts were normal in amount, molecular weight, and polypeptide composition. Southern blot analysis did not reveal gross genomic rearrangements. A regulatory defect leading to the expression of these Class I antigens is postulated.

HLA-DR antigens in Chinese-American families

This paper contains results of a study on HLA-DR antigens in Chinese-American families. DR2, DR4, DRw9, and DRw6Y were the most common DR specificities encountered, and DR1 occurred with the lowest frequency. All recognized DR antigens were observed. The frequency of a blank allele was 6.4-12.8%. Weak serologic reactions with sera primarily of Caucasian origin were not infrequently observed. These findings suggested that ethnic-related antigens were present in this population. Two families showed segregation of a new serologic pattern based on polyspecific sera. The gene frequencies of the BfF allele and the GLO1 allele were low as compared to Caucasians. A method is described for improving the yield of viable B cells from frozen B-lymphocyte preparations.