Induction and rejoining of DNA double-strand breaks in V79-4 mammalian cells following gamma- and alpha-irradiation

The induction and rejoining of DNA double-strand breaks (dsbs) in V79-4 mammalian cells following irradiation by 60Co gamma-rays and 238Pu alpha-particles (average LET 120 keV microns-1) under aerobic conditions have been determined using both the sucrose sedimentation and filter elution techniques under non-denaturing conditions. Cellular inactivation was also determined. The dependence of the initial yield of dsbs at 277 K on dose under aerobic conditions is linear with a relative biological effectiveness (RBE) for alpha-particles of 0.85 +/- 0.14 (sedimentation) and 0.68 +/- 0.12 (elution) compared with 60Co gamma-rays. The ability of the cells to rejoin dsbs at 310K is significantly reduced for alpha-irradiations with only 30-50% rejoined for a 3-h incubation period. With low LET radiation, > 90% of the dsbs are rejoined within 3 h at a dose of 20 Gy. The RBE for cellular inactivation was determined to be 4.0 at the 1% survival level. From the cellular dimensions and the D0-value for cellular inactivation by alpha-particles, it is determined that, on average, 4.7 tracks traverse the cell nucleus per lethal lesion. Under hypoxic conditions, the RBE values for induction of dsbs and cellular inactivation (10% level) by alpha-particles are approximately 3.0 and approximately 11.8 respectively. From these findings, it is suggested that the residual DNA damage and not the initial damage is reflected in the cellular inactivation. It is inferred that the difference in repair of the various lesions is a reflection of the differences in the complexity of the clustered damage produced by these radiations.

Evaluation of therapy with hyperbaric oxygen for experimental infection with Clostridium perfringens

The effects of inoculum size and treatment delays on the efficacy of hyperbaric oxygen (HBO) were evaluated in a murine model of Clostridium perfringens myositis in which the infection was treated with an HBO regimen identical to that used for humans. The efficacies of treatment with penicillin, metronidazole, or clindamycin--alone or in combination with HBO--were also assessed. Survival was inversely related to the size of the bacterial inoculum used for challenge, and delays in treatment markedly reduced the efficacies of all single and combination regimens. When animals were challenged with > 10(8) colony-forming units, survival was significantly higher among those treated with clindamycin or metronidazole than among those treated with penicillin. HBO alone did not improve survival at any inoculum tested. However, when administered early, HBO plus metronidazole or penicillin demonstrated significant additive efficacies in animals challenged with > or = 10(9) organisms. Clindamycin was more effective at the higher inocula than penicillin, metronidazole, or HBO, and its superior efficacy was not further enhanced by adjunctive therapy with HBO.

The in vitro antibacterial activity of ceftriaxone against Streptococcus pyogenes is unrelated to penicillin-binding protein 4

The in vitro activities of penicillin and ceftriaxone were compared against 29 strains of Streptococcus pyogenes with the result that ceftriaxone showed greater activity than penicillin. The morphological changes induced by 1/2 and 1x MIC concentrations of penicillin and ceftriaxone, respectively, were very similar using scanning electron microscopy. Competitive binding studies using 'cold' penicillin or ceftriaxone as inhibitors of radiolabeled penicillin binding demonstrated that ceftriaxone had a very low affinity for penicillin binding protein (PBP) 4 compared to that of penicillin. Since ceftriaxone had greater antibacterial activity, this suggests that PBP 4 may not be important to the in vitro activity of ceftriaxone. In contrast, the IC50 for ceftriaxone was much lower (> 200 fold) for PBPs 2 and 3 compared to PBP 4, suggesting greater avidity of these high molecular mass PBPs for ceftriaxone. These data may at least in part explain the superior in vitro activity of ceftriaxone compared to penicillin against S. pyogenes. These data, together with the observation that PBP 1 was saturated at a lower concentration of penicillin than any of the other PBPs, suggest that the inhibition of PBPs 1, 2, and 3 mediates the bactericidal activity of beta-lactam antibiotics against group A streptococci.

Superantigens associated with staphylococcal and streptococcal toxic shock syndrome are potent inducers of tumor necrosis factor-beta synthesis

The role of tumor necrosis factor-alpha (TNF alpha) in the pathogenesis of severe bacterial infections has been studied extensively. However, the role of TNF beta, a lymphokine with biologic activities similar to those of TNF alpha, has received little attention. Therefore, the purpose of this study was to examine the production of TNF beta by peripheral blood mononuclear cells in response to lipopolysaccharide (LPS) and the superantigens staphylococcal toxic shock syndrome toxin 1 (TSST-1) and streptococcal pyrogenic exotoxin A (SPEA). Though LPS was a more potent inducer of TNF alpha than was TSST-1 or SPEA, TSST-1 and SPEA were both more potent inducers of TNF beta. The superantigens TSST-1 and SPEA were more potent inducers of total TNF (TNF alpha and TNF beta) than was LPS. These data suggest that the induction of TNF beta synthesis may be a unique pathway by which superantigens associated with severe streptococcal and staphylococcal infections mediate shock and multiorgan failure characteristic of toxic shock syndrome.

Role of theta toxin, a sulfhydryl-activated cytolysin, in the pathogenesis of clostridial gas gangrene

Clostridial infections cause a wide variety of dramatic infections and intoxications. In each case the major virulence factors are extracellular toxins. Clostridium perfringens produces potent exotoxins, which are its major virulence factors. theta Toxin, a thiol-activated cytolysin, causes the clear zone of hemolysis around colonies on blood-agar plates, suppresses myocardial contractility ex vivo, and induces shock within 1 to 2 hours in vivo. Low concentrations of theta toxin induce priming and degranulation of polymorphonuclear leukocytes (PMNs) and functional up-regulation of PMN-dependent adherence molecules such as the integrin CD11/CD18, whereas higher concentrations are cytotoxic. Similarly, theta toxin causes concentration- and time-dependent induction of endothelial cell synthesis of platelet-activating factor, a potent proinflammatory lipid autocoid that mediates endothelial cell-dependent adherence of PMNs. These data suggest that theta toxin in high concentrations is a potent cytolysin and promotes direct vascular injury at the site of infection. At lower concentrations theta toxin activates PMNs and endothelial cells, and in so doing promotes vascular injury distally by activating adherence mechanisms. The rapid tissue necrosis associated with C. perfringens infection may be related to progressive vascular compromise orchestrated by dysregulated host-cell responses induced by theta toxin.

Penicillin-binding protein expression at different growth stages determines penicillin efficacy in vitro and in vivo: an explanation for the inoculum effect

Mechanisms to explain the "inoculum effect" have not been elucidated in gram-positive infections. A mouse model of group A streptococcal myositis was used to compare the efficacies of two beta-lactams, penicillin and ceftriaxone, and a protein synthesis inhibitor, clindamycin, at three different inoculum sizes. beta-lactams were more susceptible to inoculum effects than was clindamycin both in vivo and in vitro (P < .05). The large inocula were hypothesized to reach stationary phase of growth sooner than smaller inocula both in vitro and in vivo. The penicillin-binding protein (PBP) patterns from membrane proteins isolated from mid-log-phase and stationary-phase cultures of Streptococcus pyogenes were compared. Binding of radiolabeled penicillin by all PBPs was decreased in stationary cells; however, PBPs 1 and 4 were undetectable at 36 h. Thus, the loss of certain PBPs during stationary-phase growth in vitro may be responsible for the inoculum effect observed in vivo and may account for the failure of penicillin in both experimental and human cases of severe streptococcal infection.

Comparison of oral cefpodoxime proxetil and cefaclor in the treatment of skin and soft tissue infections

This multicenter, randomized, double-blind study was designed to compare the safety and efficacy of cefpodoxime proxetil and cefaclor in the treatment of skin and soft tissue infections. Patients were aged > or = 12 years with acute (< or = 7 days duration), single-site skin or skin-structure infections. The 7- to 10-day treatment regimens were cefpodoxime proxetil (400 mg cefpodoxime) orally with food twice a day with cefaclor-matched placebo (orally, fasting, three times a day); or cefaclor (Ceclor; 500 mg anhydrous equivalent) orally, fasting, three times a day, with cefpodoxime-matched placebo (orally with food twice a day). Clinical progress and cultures were evaluated upon admission to the study; on study days 7-10 and 15-18; and 2-3 weeks after treatment. Cefpodoxime had lower minimum inhibitory concentrations against the majority of Staphylococcus species than did cefaclor. Both treatments were highly effective (99% pathogen eradication and 86% cure rate). These high eradication rates were not unexpected in this study of minor infections in which patients with resistant pathogens were excluded. Cefaclor had a higher failure rate [2 (4%) of 57], than did cefpodoxime [2 (1%) of 139; p not significant]. Most patients in both groups completed treatment as planned: 185 (74%) of 249 cefpodoxime-treated patients and 91 (75%) of 122 cefaclor-treated patients. Both treatments were well tolerated and considered safe and effective in the treatment of skin and skin structure infections. However, the twice-a-day dosing regimen for cefpodoxime proxetil compared with the three-times-a-day regimen for cefaclor may result in better patient compliance.

Rapid screening for deletion mutations in the hprt gene using the polymerase chain reaction: X-ray and alpha-particle mutant spectra

Conditions were devised for the isolation of DNA from single-mutant colonies on dishes, to give reproducible results in the polymerase chain reaction (PCR). Primers for 3 exons of the hamster hprt gene were used in a multiplex reaction to show rapidly whether the mutants carried deletions at these sites. 138 independent mutants were screened in total, some spontaneous and others induced by X-rays or by alpha-particles from plutonium-238. Few deletions were found among the spontaneous set, while 'total' gene deletions formed about half the mutants found after irradiation. At equitoxic doses, little difference in mutant spectrum was found for the X-ray set compared to the alpha-particle set. This rapid technique should be applicable to many instances of comparative mutagenesis.

Epidemiologic analysis of group A streptococcal serotypes associated with severe systemic infections, rheumatic fever, or uncomplicated pharyngitis

More than 1100 group A streptococcal isolates collected in the United States (1988-1990) were examined to document an association of individual serotypes with specific clinical infections during the recent resurgence of group A infections and their sequelae. The most commonly isolated strains from patients with only uncomplicated streptococcal pharyngitis ("control" strains) were M serotypes 1, 2, 4, and 12. M1, M3, and M18 were statistically significantly more frequently isolated from patients with serious invasive infections and M3 and M18 from patients with rheumatic fever compared with the distribution of serotypes from the 866 control strains. An unexpected and important finding indicated that isolation rates of M1 streptococci varied geographically within the United States by year. The propensity for M1 streptococci to be statistically associated with severe systemic infections appeared unrelated to the M1 isolation rates from patients with only uncomplicated pharyngitis, thus offering additional support for the concept of strain-associated virulence rather than virulence broadly related to a given serotype.

Streptococcal Pyrogenic Exotoxin A and Streptolysin O Enhance Polymorphonuclear Leukocyte Binding to Gelatin Matrixes

Autopsy data from cases of streptococcal toxic shock demonstrate accumulation of polymorphonuclear leukocytes (PMNL) within lung and soft tissue microvasculature. Because of the increased prevalence of streptococcal pyrogenic exotoxin A (SPEA)-producing strains associated with streptococcal toxic shock syndrome, experiments were done to determine whether SPEA or streptolysin O (SLO, a thiol-activated cytolysin produced by all group A streptococci) could stimulate PMNL-dependent adherence mechanisms in vitro. SPEA (0.01-10 micrograms/5.5 x 10(6) PMNL) only modestly enhanced PMNL adherence over the entire range of concentrations tested. In contrast, SLO-induced PMNL binding was highly dose dependent (maximal binding, 55.1 +/- 1.6% at 0.5 hemolytic units/5.5 x 10(6) PMNL) and was mediated by CD11/CD18 adherence glycoprotein.

Antinociceptive activity of intrathecally administered cannabinoids alone, and in combination with morphine, in mice

The antinociceptive effects of various cannabinoids, alone and in combination with opiates, were evaluated in antinociceptive tests in mice. The cannabinoids tested produce marked antinociceptive effects after i.t. administration to mice. The rank order of potency for the drugs using the tail-flick test was levonantradol greater than CP-55,940 = CP-56,667 greater than 11-hydroxy-delta 9-THC greater than delta 9-THC greater than delta 8-THC; dextronantradol was inactive at a dose of 25 micrograms/mouse. Respective ED50 values in the tail-flick test were 0.4, 12.3, 4.2, 15, 45 and 72 micrograms/mouse. Although pretreatment with morphine somewhat enhanced the effects of delta 9-THC, pretreatment of the mice with naloxone (1 mg/kg s.c. or 1 micrograms/mouse i.t.) failed to block the antinociceptive effects of the cannabinoids, indicating that the cannabinoid-induced antinociception does not occur due to direct interaction with the opiate receptor. Pretreatment of mice with 3.13 micrograms/mouse and 6.25 micrograms/mouse of delta 9-THC shifted the ED50 of morphine to 0.15 and 0.05 micrograms/mouse, respectively (a 4-and a 12-fold shift). The shifts in the dose-response curve of the morphine were parallel. Naloxone administration (1 mg/kg s.c.) completely blocked the antinociceptive effects of the combination of 6.25 micrograms of delta 9-THC with morphine. The AD50 for naloxone blockade of the drug combination was 0.24 (0.06-0.94) mg/kg s.c. and the pA2 was 7.7 (6.7-8.9). The pA2 for naloxone blockade of the dimethylsulfoxide-morphine combination was 6.9 (5.7-8.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Streptococcal toxic shock syndrome: synthesis of tumor necrosis factor and interleukin-1 by monocytes stimulated with pyrogenic exotoxin A and streptolysin O

Previous studies have found that 80% of strains isolated from patients with the streptococcal toxic shock syndrome produce pyrogenic exotoxin A (SPEA) and 100% produced streptolysin O (SLO). To elucidate the cellular mechanisms contributing to shock, human monocytes were stimulated with SPEA (0.1-10 micrograms/10(6) monocytes) or SLO (0.2-2.5 hemolytic units/10(6) monocytes), and production of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 beta was measured at 24, 48, and 72 h. SPEA and SLO were potent inducers of TNF alpha, with maximum production occurring at 72 h for SPEA and at 48 h for SLO (1067 and 687 pg/ml, respectively). In contrast, IL-1 beta production was greater for SLO than for SPEA (557 vs. 258 pg/ml). In addition, the effects of SPEA and SLO together were synergistic in terms of monocyte IL-1 beta production: SPEA, 193 pg/ml; SLO, 452 pg/ml; SPEA plus SLO, 799 pg/ml. These findings suggest TNF alpha and IL-1 beta are important candidates for mediating shock in severe streptococcal infections.

A proposed mechanism of action for the antinociceptive effect of intrathecally administered calcium in the mouse

Administration of i.t. calcium has been shown to produce effects which are opposite to those observed when calcium is injected into the brain. The purpose of this study was to elucidate the mechanism of the antinociceptive action of calcium (i.t.). Injection of calcium (i.t.) produced antinociceptive effects in the tail-flick and p-phenylquinone (PPQ) stretching tests. The ED50 value for calcium (i.t.) in the PPQ test was 4.8 (4.2-5.5) nmol per mouse vs. 344 (251-469) nmol per mouse for calcium (i.t.) in the tail-flick test. The antinociceptive effects of calcium (i.t.) were attenuated significantly in the tail-flick test by pretreatment with naloxone (i.t.) (AD50 value = 200 pmol/mouse) and ICI-174,864 (i.t.) (AD50 value = 20 nmol/mouse), but not by the kappa receptor-selective antagonist nor-BNI. The antinociceptive effects of calcium (i.t.) were attenuated significantly in the PPQ test by pretreatment with naloxone (i.t.) (AD50 value = 50 pmol/mouse) and norbinaltorphimine (i.t.) (AD50 value = 110 pmol/mouse), but not by the delta receptor-selective antagonists naltrindole and ICI-174, 864. Administration of calcium (i.t.) significantly enhanced the antinociceptive effects of mu [D-Ala2,N-Me-Phe4,Gly-ol]enkephalin, delta [D-Pen2,D-Pen5]enkephalin and kappa (U50,488H) opioid receptor-selective peptides. The injection of the dibutyryl derivative of cyclic AMP (i.t.), as well as forskolin (i.t.), blocked the antinociceptive effects of calcium (i.t.) (AD50 values = 39 nmol and 1.7 nmol/mouse, respectively). Injection of apamin (AD50 value = 2.9 pmol/mouse) and charybodotoxin (58 fmol/mouse), blockers of calcium-gated potassium channels, significantly blocked calcium (i.t.). The antinociceptive effects of calcium (i.t.) were also blocked by verapamil (30 and 60 nmol/mouse), theophylline (275 nmol/mouse) and substance P (7.4 nmol/mouse, i.t.). Thus, the data indicate that the mechanism underlying the antinociceptive effect of calcium (i.t.) involves mediation, at least in part, by opioid peptides, alterations in intraneuronal cyclic AMP and/or neuronal hyperpolarization, and decreased release of substance P. The administration of calcium (i.t.) may also enhance the release of adenosine as a significant factor in the antinociceptive effects of the calcium.

Invasive group A streptococcus infections

The late 1980s have witnessed the emergence of severe group A streptococcus (GAS) infection; shock, bacteremia, and acute respiratory distress syndrome are common features, and death has been associated with this infection in 30% of patients. Such infections have now been described in all parts of the United States, Europe, and Australia and have occurred predominantly in otherwise healthy adolescents and adults. The characteristic clinical and laboratory features of the streptococcal toxic shock syndrome include deep-seated infection associated with shock and multiorgan failure. Strains of GAS isolated from patients with invasive disease have been predominantly M types 1 and 3, which produce pyrogenic exotoxin A or B or both. In this report, the clinical and demographic features of streptococcal bacteremia, myositis, and necrotizing fasciitis will be presented and compared with those of streptococcal toxic shock syndrome. Current concepts of the pathogenesis of invasive streptococcal infection will also be presented in terms of the interaction between virulence factors of GAS and host defense mechanisms. Finally, new concepts for future treatment of serious streptococcal infections will be proposed.

Aspergillar myocarditis and acute coronary artery occlusion in an immunocompromised patient

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Molecular analysis of pyrogenic exotoxins from Streptococcus pyogenes isolates associated with toxic shock-like syndrome

Toxic shock-like syndrome (TSLS) is characterized by hypotension or shock, fever, multiorgan system involvement, and a concurrent group A streptococcal infection. We analyzed 34 streptococcal strains isolated from patients with clinically well-documented TSLS for their pyrogenic toxin profiles and M-protein types. Although strains of nine different M types were represented in the sample, 74% of the isolates were of either M type 1 or 3. It was determined that 53% produced streptococcal pyrogenic exotoxin type A under in vitro growth conditions and that 85% contained the gene encoding this toxin. These values are in contrast to the published value of 15% for the incidence of this gene in a sample of general group A streptococcal isolates. As has been found with all group A streptococci examined to date, regardless of disease association, 100% of TSLS-associated isolates contained the gene encoding pyrogenic exotoxin type B. This toxin was detectably produced by 59% of isolates. The gene encoding pyrogenic toxin type C was found in only 21% of isolates. We conclude that the pyrogenic exotoxin type A gene is associated with group A streptococcal strains isolated from patients with TSLS and may play a causative role in this illness. However, other factors are also likely to be important, since not all strains from patients with TSLS contained the A toxin gene.

Thickness measurements on V79-4 cells: a comparison between laser scanning confocal microscopy and electron microscopy

A quantitative comparison has been carried out between laser scanning confocal microscopy on living cells and standard electron microscope methods on fixed samples. It was estimated from these measurements that there was about 10-20% reduction in thickness in fixed samples of monolayer V79-4 hamster cells. Precise information on the true thickness of living cells, as irradiated, is required for full interpretation of radiobiological data with poorly penetrating radiations, including ultrasoft X-rays. The confocal microscope allows rapid measurements on unperturbed living samples.

Pulmonary carcinogenesis in rats given implants of shale oil in beeswax pellets

Pellets of crude shale oil, neutral, basic, or polynuclear aromatic fractions of shale oil, or crude petroleum were implanted in the lungs of rats through a thoracotomy. The pellets had a beeswax-tricaprylin vehicle that allowed the slow release of material into the surrounding parenchyma. A dose-related incidence of lung cancer was observed with each of the materials studies. A greater risk for lung cancer was not demonstrated for crude shale oil compared to crude petroleum.

Spontaneous, nontraumatic gangrene due to Clostridium septicum

Clostridium septicum is a major cause of spontaneous, nontraumatic gas gangrene. Unlike Clostridium perfringens, C. septicum is relatively aerotolerant and thus appears to be more capable of initiating infection in the absence of obvious damage to tissues. Six cases illustrate the clinical setting and fulminant nature of spontaneous gangrene caused by C. septicum. A lesion in the colon such as carcinoma is often present and is presumed to serve as a portal of entry to the bloodstream. Diabetes and leukopenia are also common predisposing conditions; compromise of vital host responses may facilitate proliferation of those organisms that settle out in the tissues. Acute lymphoma or leukemia during a course of chemotherapy is accompanied by damage to bowel mucosa and granulocytopenia, thus predisposing to spontaneous clostridial gangrene. Infection progresses in a fulminating manner; the majority of patients die within 24 hours of onset. Characteristic symptoms and signs include excruciating pain (although a sense of heaviness may be the only early symptom), swelling of tissues, crepitance, and bulla formation. A hallmark of C. septicum infection is the absence of acute inflammatory cells in involved tissues or in bulla fluid. A series of laboratory investigations demonstrated that fluid obtained from a bulla adversely affected the viability, morphology, and function of polymorphonuclear leukocytes (PMNs), which may explain the paucity of PMNs in involved tissues and may in part contribute to the fulminant progression observed in infection due to this organism.

Primary sternal osteomyelitis

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Severe group A streptococcal infections associated with a toxic shock-like syndrome and scarlet fever toxin A

There is concern that group A streptococci, which have caused less serious infections in developed countries in recent decades, may be acquiring greater virulence. We describe 20 patients from the Rocky Mountain region who had group A streptococcal infections from 1986 to 1988 that were remarkable for the severity of local tissue destruction and life-threatening systemic toxicity. Among the 20 patients (median age, 36), necrotizing fasciitis with or without myositis was the most common soft-tissue infection (55 percent). Nineteen patients (95 percent) had shock, 16 (80 percent) had renal impairment, and 11 (55 percent) had acute respiratory distress syndrome. The mortality rate was 30 percent. All patients but 1 had positive tissue cultures for Streptococcus pyogenes; 12 had positive blood cultures. Most of the patients had no underlying disease; 2 used intravenous drugs. Strains of group A beta-hemolytic streptococci isolated from 10 patients were not of a single M or T type; however, 8 of the 10 strains produced pyrogenic exotoxin A (scarlet fever toxin A, a classic erythrogenic toxin), which has rarely been observed in recent years. From our study of this cluster of severe streptococcal infections with a toxic shock-like syndrome, we conclude that in our region, more virulent group A streptococci have reappeared that produce the pyrogenic toxin A associated with scarlet fever.

The regulation of platelet-activating factor production in endothelial cells. The role of calcium and protein kinase C

Endothelial cells (EC) synthesize platelet-activating factor (PAF) when stimulated with agonists that bind to cell-surface receptors. We examined events that link receptor binding to synthesis of PAF by EC. Bovine EC stimulated with agonists that interact with specific cell-surface receptors accumulated PAF only in the presence of extracellular calcium. Hormonal stimulation of EC resulted in Ca2+ entry characteristic of that seen with receptor-operated calcium channels; Indo-1 measurements demonstrated that this inward flux of Ca2+ caused prolonged elevated levels of intracellular Ca2+. EC were exposed to melittin or theta toxin from Clostridium perfringens (pore-forming peptides that increase the permeability of the plasma membrane for small molecules) resulting in an inward flux of Ca2+ and accumulation of PAF. Ca2+ appears to be regulatory for PAF production at the level of phospholipase A2-mediated production of the PAF precursor 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine, as Ca2+ was required for the stimulated hydrolysis of 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine. PAF accumulation in EC is also regulated by protein kinase C. Pretreatment of EC with phorbol esters that activate protein kinase C or with dioctanoylglycerol, followed by stimulation, resulted in a 2-fold increase in stimulated PAF production. The regulatory effect of protein kinase C also appears to be at a phospholipase A2-mediated hydrolysis of 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine.

Neurology in Gloucestershire: the clinical workload of an English neurologist

Attempts to determine the ideal number of consultant neurologists that will be required in the United Kingdom in the future are hampered by a lack of information on a variety of topics, one of which concerns the workload of the average neurologist at the present time. This paper attempts to correct this deficiency by examining the clinical workload of a single handed neurologist practising in the south west of England. Diagnostic information is given on the 3020 new patients seen during 1984-1986 and is compared with similar data on 836 new patients seen in 1975. The pattern of diagnoses on these patients varies little from year to year, indicating a constancy of referral habit of those who seek neurological advice. However, the referral rates for different conditions do not correspond with what would be expected from epidemiological data, for when the incidence of particular conditions in the neurology clinic is compared with the calculated incidence in the community, very wide variations are noted. The implications of these data are discussed and it is suggested that further studies should be performed before detailed predictions are made on how many neurologists will be needed in this country in the future.