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Biomedical subjects

D B Tillman

Publications and source records attributed to D B Tillman.

8 recordsLinked to original sources
PubMed1995

Response of C fibre nociceptors in the anaesthetized monkey to heat stimuli: estimates of receptor depth and threshold.

1. Responses to ramped or stepped temperature stimuli were obtained from fifty-three cutaneous C fibre mechano-heat nociceptors (CMHs) in the hairy skin of the pentobarbitone-morphine anaesthetized monkey. A three-layer heat transfer model was developed to describe the temperature distribution within the skin and to estimate receptor depth and heat threshold. 2. Surface heat threshold, defined as the surface temperature when the first action potential occurs, increased as: (a) the rate of temperature rise for the ramped stimuli increased from 0.095 to 5.8 degrees C s-1; (b) the duration of stepped heat stimuli decreased from 30 to 1 s; and (c) the base temperature of stepped heat stimuli decreased from 38 to 35 degrees C. These results suggest that the heat threshold for CMHs is determined by the temperature at the depth of the receptor. 3. Receptor depth estimates from responses to ramped stimuli ranged from 20 to 570 microns with a mean of 201 microns. The estimated mean receptor heat threshold was 40.4 +/- 2.2 degrees C (+/- S.D.). No correlation was observed between depth and thermal or mechanical threshold. The average receptor depth and threshold, estimated from the responses to stepped heat stimuli, were 150 microns and 40.2 degrees C, respectively. 4. We conclude that: (a) the receptor endings of CMHs occur in the epidermis and dermis; (b) temperature at the level of the receptor determines threshold; (c) temperature at the receptor ending is much lower than skin surface temperature at threshold; and (d) the tight distribution of receptor heat thresholds suggests a uniform transducer mechanism for heat in CMHs.

Animals↗
PubMed1995

Response of C fibre nociceptors in the anaesthetized monkey to heat stimuli: correlation with pain threshold in humans.

1. Ramped heat stimuli were used to compare the effects of rate of temperature change on the responses of monkey nociceptors and on heat pain threshold in human subjects. Recordings were made from twenty-five cutaneous C fibre mechano-heat nociceptors (CMHs) innervating the hairy skin in the anaesthetized monkey. Heat pain thresholds were determined on the volar forearm of eight human subjects using a converging staircase technique. 2. The heat pain threshold decreased as stimulus ramp rate increased. In contrast, the CMH heat threshold, defined as the surface temperature at which the first action potential occurred, increased as stimulus ramp rate increased. Thus, the properties of the heat stimulus that dictate heat pain threshold are different from the properties of the heat stimulus that govern the initiation of a response in nociceptors. 3. Peak discharge frequency of CMHs during the heat ramp increased with stimulus ramp rate. Heat pain threshold was correlated with achievement of a minimum discharge rate in nociceptors (0.5 Hz), rather than with the threshold for action potential initiation.

Action Potentials↗
PubMed1991

Ectopic excitability of injured nerves in monkey: entrained responses to vibratory stimuli.

1. The responses to mechanical stimulation of myelinated fibers that originate from an acutely cut nerve or a neuroma were studied in the anesthetized monkey. The superficial radial or sural nerve was tightly ligated and cut. Either immediately (acute experiment) or 2-6 wk later (chronic experiment), single-unit recording techniques were used to record the evoked neural activity after vibratory mechanical stimulation (5-100 Hz; 50-800 microns) near the injury site. 2. The 30 myelinated afferents studied in the chronic experiments displayed an entrained response (1 action potential for each stimulus cycle) to vibratory stimuli applied at or near the nerve injury site. For 19 fibers, the minimum amplitude for entrainment was determined as a function of frequency (tuning curve). For 11 others, complete tuning curves were not obtained, although the frequency range over which they were most sensitive could be estimated. The afferents could be classified into three groups on the basis of the frequency range over which they were most sensitive: 1) a low-frequency group that was most sensitive to frequencies less than or equal to 5 Hz (n = 7), 2) a mid-frequency group that was most sensitive to a broad range of frequencies (i.e., 20-75 Hz, n = 13), and 3) a high-frequency group that was most sensitive to frequencies greater than or equal to 100 Hz (n = 10). These three response classes are similar to the three classes of response associated with the different low-threshold mechanoreceptors (i.e., slowly and rapidly adapting and Pacinian-like mechanoreceptors).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

Clinical value of teichoic acid antibody titers in the diagnosis and management of the staphylococcemias.

Differentiation of endocarditic from nonendocarditic Staphylococcus aureus (SA) septicemia is prognostically and therapeutically important. A study of 68 cases of either SA or streptococcal sepsis, including 50 cases of SA sepsis of both cardiac and noncardiac origin, was done to determine the presence and titer of serum teichoic acid antibodies (TAA's) by double immunodiffusion. Thirty-seven uninfected controls were also examined. There was no statistical difference in either incidence or peak TAA titers in endocardial versus deepseated, extracardiac SA sepsis. However, in both of these groups, incidence and peak titers were significantly higher than in intravascular catheter-related SA sepsis, streptococcal endocarditis and controls (P<0.05). Peak TAA titers in SA sepsis develop on admission or shortly thereafter (6 to 11 days) and permit early decisions on degree of tissue infection, likelihood of metastatic seeding and necessity for higher-dose, longer-term antibiotic therapy. Cases of catheter-related SA sepsis with no clinical evidence of metastatic SA seeding and with negative or low-titered (1:1) TAA's were classified as superficial sepsis. Treatment consisted of short-term, low-dose antistaphylococcal regimens and catheter removal. In posttherapy follow-up after 6 to 12 weeks, all of the patients were cured and no signs of endocarditis or deepseated SA infection developed.

Anti-Bacterial Agents↗
PubMed1980

Oxacillin nephritis.

Acute interstitial nephritis secondary to administration of antibiotics is a well-described entity. Oxacillin, however, has never been directly implicated. An 80-year-old man had a rising creatinine level and eosinophiluria while receiving oxacillin sodium. These findings disappeared when use of the drug was discontinued. We conclude that oxacillin is an additional penicillin that can cause interstitial nephritis.

Aged↗
PubMed1979

Use of circulating immune complex levels in the serodifferentiation of endocarditic and nonendocarditic septicemias.

Distinguishing endocarditic from nonendocarditic septicemias is prognostically and therapeutically important. One hundred two patients with both valvular and nonvalvular sepsis were studied for the presence and quantitation of circulating immune complexes. Ninety per cent of the patients with infective endocarditis versus 50 per cent of septic patients without infective endocarditis had circulating immune complex levels (p less than 0.005). Mean circulating immune complex levels in patients with infective endocarditis were significantly higher than in those without infective endocarditis, 106 +/- 18.58 microgram/ml versus 31 +/- 7.4 microgram/ml (p less than 0.005). Only three of 52 patients without infective endocarditis had circulating immune complex levels greater than 100 microgram/ml, as opposed to 16 of 50 patients with infective endocarditis (p less than 0.005). Similarly, one of 52 patients without infective endocarditis has circulating immune complex levels greater than 200 microgram/ml, as opposed to eight of 50 patients with infective endocarditis (p less than 0.05). In 92 per cent of the patients without infective endocarditis and 76 per cent of those with infective endocarditis peak circulating immune complex levels developed within 14 days after their entry into the study, often on the initial sampling. In febrile, septicemic patients with clinical symdromes nonclassic for endocarditis, measurements of serial circulating immune complex levels may be of adjunctive diagnosis importance. If circulating immune complex levels are undetectable, endocarditis would appear less likely; alternatively, levels above 100 to 200 microgram/ml would suggest a valvular rather than nonvalvular septic focus.

Antigen-Antibody Complex↗