The spatial organization of the cutaneous input to hindlimb withdrawal reflexes was studied in spinalized, decerebrated, unanesthetized rats. Reflex activity in plantar flexors of the digits, pronators of the foot, dorsiflexors of the digits, and/or the ankle and flexors of the knee was recorded with electromyographic techniques for up to 12 h after spinalization. Graded mechanical (pinch) and thermal stimulation (CO2 laser) of the skin were used. Reflexes were absent ("spinal shock") during approximately 10-20 min after spinalization. The reflex thresholds for pinch and CO2 laser stimulation then decreased considerably during the following 5-8 h. After this time, even mild pressure (less than 0.1 N/mm2) on the skin was sufficient to evoke a reflex in most muscles. During the period from about 0.5-3 h after spinalization, the nociceptive receptive field of each muscle usually corresponded to the area of the skin withdrawn by the muscle. Maximal responses were evoked from the area of the receptive field maximally withdrawn. During this period, responses to innocuous pinch were evoked mainly from the most sensitive area of the receptive fields. Concomitant with the decrease in reflex thresholds, the nociceptive receptive fields expanded for all muscles, often to include areas of the skin not withdrawn by the muscles. For most muscles, reflexes on tactile stimuli were eventually elicited from the entire receptive fields. The receptive fields for thermonociceptive and mechanonociceptive inputs were similar in most muscles. The interossei muscles were exceptional in that they responded very weakly to thermal stimulation. It is concluded that there are neuronal networks in the spinal cord that translate cutaneous nociceptive and tactile input into a withdrawal. However, the control exerted by descending pathways is necessary to maintain a functionally adequate excitability in these reflex pathways and an appropriate size for their receptive fields.
The withdrawal reflex pathways to hindlimb muscles have an elaborate spatial organization in the rat. In short, the distribution of sensitivity within the cutaneous receptive field of a single muscle has a spatial pattern that is a mirror image of the spatial pattern of the withdrawal of the skin surface ensuing on contraction in the respective muscle. In the present study, a search for neurones encoding the specific spatial input-output relationship of withdrawal reflexes to single muscles was made in the lumbosacral spinal cord in halothane/nitrous oxide-anaesthetized rats. The cutaneous receptive fields of 147 dorsal horn neurones in the L4-5 segments receiving a nociceptive input and a convergent input from A and C fibres from the hindpaw were studied. The spatial pattern of the response amplitude within the receptive fields of 118 neurones was quantitatively compared with those of withdrawal reflexes to single muscles. Response patterns exhibiting a high similarity to those of withdrawal reflexes to single muscles were found in 27 neurones located in the deep dorsal horn. Twenty-six of these belonged to class 2 (responding to tactile and nociceptive input) and one belonged to class 3 (responding only to nociceptive input). None of the neurones tested (n = 20) with reflex-like response patterns could be antidromically driven from the upper cervical cord, suggesting that they were spinal interneurones. With some overlap, putative interneurones of the withdrawal reflexes to the plantar flexors of the digits, the plantar flexors of the ankle, the pronators, the dorsiflexors of the ankle, and a flexor of the knee, were found in succession in a mediolateral direction.(ABSTRACT TRUNCATED AT 250 WORDS)
f We aimed to compare sputum and nasopharyngeal aspirate (NpA) samples and the PCR gene targets lytA and Spn9802 in quantitative PCR (qPCR) assays for rapid detection of pneumococcal etiology in community-acquired pneumonia (CAP). Seventyeight adult patients hospitalized for radiologically confirmed CAP had both good-quality sputum and NpA specimens collected at admission. These samples were subjected to lytA qPCR and Spn9802 qPCR assays with analytical times of <3 h. Thirty-two patients had CAP with a pneumococcal etiology, according to conventional diagnostic criteria. The following qPCR positivity rates were noted in CAP cases with and without pneumococcal etiology: 96% and 15% (sputum lytA assay), 96% and 17% (sputum Spn9802 assay), 81% and 11% (NpA lytA assay), and 81% and 20% (NpA Spn9802 assay), respectively. The mean lytA and Spn9802 DNA levels were significantly higher in qPCR-positive sputum samples from cases with pneumococcal etiology than in qPCR-positive sputum samples from CAP cases without pneumococcal etiology or qPCR-positive NpA samples from cases with pneumococcal etiology (P < 0.02 for all comparisons). For detection of pneumococcal etiology, receiver operating characteristic curve analysis showed that sputum specimens were superior to NpA specimens as the sample type (P < 0.02 for both gene targets) and lytA tended to be superior to Spn9802 as the gene target. The best-performing test, the sputum lytA qPCR assay, showed high sensitivity (94%) and specificity (96%) with a cutoff value of 10 5 DNA copies/ml. In CAP patients with good sputum production, this test has great potential to be used for the rapid detection of pneumococcal etiology and to target penicillin therapy.
1. The postnatal development of nociceptive withdrawal reflexes was studied. In awake intact rats, forelimb, hindlimb and tail reflexes were recorded on videotape. In decerebrate spinal rats, electromyography (EMG) was used to record nociceptive withdrawal reflexes in musculi extensor digitorum longus (EDL), peronei, gastrocnemius-soleus (G-S) and biceps posterior-semitendinosus (BP-ST). Thermal (short-lasting CO2 laser pulses) and mechanical stimulation were used. 2. In adults, nociceptive withdrawal reflexes were typically well directed and reflex pathways to single hindlimb muscles had functionally adapted receptive fields. By contrast, at postnatal day (P) 1-7, the nociceptive withdrawal reflexes were often inappropriate, sometimes producing movements towards the stimulation, and EMG recordings revealed unadapted variable receptive fields. With increasing age, the nociceptive withdrawal reflexes progressively became well directed, thus producing localized withdrawal. Both withdrawal movements and spatial organization of the receptive fields were adult-like at P20-25.3. Up to P25, reflex thresholds were more or less constant in both intact awake rats and spinal decerebrate rats, except in G-S in which no nociceptive withdrawal reflexes were evoked from P20 on. After P25, mechanical, but not thermal, thresholds increased dramatically. 4. EMG recordings revealed that during the first three postnatal weeks, the latency of the CO2 laser-evoked nociceptive withdrawal reflexes decreased significantly in peronei and BP-ST, but not in EDL, and thereafter increased significantly in peronei, BP-ST and EDL. The magnitude of the nociceptive withdrawal reflexes in these muscles increased markedly between P7 and P20 and showed little change thereafter. 5. Possible mechanisms underlying the postnatal tuning of the nociceptive withdrawal reflexes are discussed.
A multiplex PCR (mPCR) was developed for simultaneous detection of specific genes for Streptococcus pneumoniae (lytA), Mycoplasma pneumoniae (P1), Chlamydophila pneumoniae (ompA), and Haemophilus influenzae (16S rRNA, with verification PCR for P6). When the protocol was tested on 257 bacterial strains belonging to 37 different species, no false negatives and only one false positive were noted. One Streptococcus mitis out of thirty was positive for lytA. In a pilot application study of 81 sputum samples from different patients with suspected lower respiratory tract infection (LRTI), mPCR identified S. pneumoniae in 25 samples, H. influenzae in 29, M. pneumoniae in 3, and C. pneumoniae in 1. All samples culture positive for S. pneumoniae (n=15) and H. influenzae (n=15) were mPCR positive for the same bacteria. In a pilot control study with nasopharyngeal swabs and aspirates from 10 healthy adults, both culture and mPCR were negative. No PCR inhibition was found in any of the mPCR-negative sputum or nasopharyngeal samples. Whether all samples identified as positive by mPCR are truly positive in an aetiological perspective regarding LRTI remains to be evaluated in a well-defined patient material. In conclusion, the mPCR appears to be a promising tool in the aetiological diagnostics of LRTI.
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