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Biomedical subjects

M D Kirk

Publications and source records attributed to M D Kirk.

At least 19 recordsLinked to original sources
PubMed2006

Salmonella Mississippi infections in Tasmania: the role of native Australian animals and untreated drinking water.

Salmonella Mississippi infections are very common in Australia's island state - Tasmania - with an annual rate of 17 cases/100000 population. A case-control study conducted during 2001-2002 found single variable associations with indirect exposure to many native animal species, untreated drinking water, travelling within the state, hand-mouth behaviours and contact with pet faeces. No associations were detected with farm animal or pet species or with any food. Indirect contact with native birds, untreated drinking water and travel within the state remained significant predictors of infection in the final model with population attributable fractions of 0.57 and 0.54 for native animals and untreated drinking water respectively. In Tasmania, Australian wildlife species are the likely reservoir for S. Mississippi, contaminating land and water environments. To decrease infection rates requires treatment of water supplies, particularly private rainwater collection systems and advising people to wash their hands after being outdoors and prior to eating.

Animals↗
PubMed2006

Frequency of infectious gastrointestinal illness in Australia, 2002: regional, seasonal and demographic variation.

To estimate the frequency of infectious gastroenteritis across Australia, and to identify risk factors, we conducted a national telephone survey of 6087 randomly selected respondents in 2001-2002. The case definition was three or more loose stools and/or two or more vomits in a 24-hour period in the last 4 weeks, with adjustment to exclude non-infectious causes and symptoms secondary to a respiratory infection. Frequency data were weighted to the Australian population. Multivariate logistic regression was used to assess potential risk factors including season, region, demographic and socioeconomic status. Among contacted individuals, 67% responded. The case definition applied to 7% of respondents (450/6087) which extrapolates to 17.2 million (95% CI 14.5-19.9 million) cases of gastroenteritis in Australia in one year, or 0.92 (95% CI 0.77-1.06) cases/person per year. In the multivariate model, the odds of having gastroenteritis were increased in summer and in the warmest state, in young children, females, those with higher socioeconomic status and those without health insurance.

Adolescent↗
PubMed2004

An outbreak due to peanuts in their shell caused by Salmonella enterica serotypes Stanley and Newport--sharing molecular information to solve international outbreaks.

Salmonellosis is a global problem caused by the international movement of foods and high incidence in exporting countries. In September 2001, in an outbreak investigation Australia isolated Salmonella Stanley from imported peanuts, which resulted in a wider investigation in Canada, England & Wales and Scotland. Patients infected with Salmonella serotypes known to be isolated from peanuts and reported to surveillance systems were interviewed to determine exposure histories. Tagged image file format (TIFF) images of pulsed-field gel electrophoresis (PFGE) patterns of Salmonella isolates were shared electronically amongst laboratories. Laboratories tested packets of 'Brand X' peanuts from various lots and product lines. In total, 97 cases of S. Stanley and 12 cases of S. Newport infection were found. Seventy-three per cent (71/97) of S. Stanley cases were in persons of Asian ethnicity. Twenty-eight per cent of cases recalled eating Brand X peanuts and a further 13% had peanuts in their house in the previous month or had eaten Asian-style peanuts. Laboratories isolated S. Stanley, S. Newport, S. Kottbus, S. Lexington and S. Unnamed from Brand X peanuts. Isolates of S. Stanley from peanuts and human patients were indistinguishable by PFGE. This international outbreak resulted from a product originating from one country affecting several others. Rapid sharing of electronic DNA images was a crucial factor in delineating the outbreak; multinational investigations would benefit from a harmonized approach.

Adolescent↗
PubMed2001

Dichotomy in phasic-tonic neuromuscular structure of crayfish inhibitory axons.

Crustacean muscles are unique in their innervation by both excitatory and inhibitory neurons; therefore, they exhibit polyneuronal and multiterminal innervation. Because excitatory motoneurons are broadly divided into phasic and tonic types, we hypothesized that inhibitory neurons would follow a similar dichotomy. The abdominal extensor muscles in crayfish are separated into parallel deep and superficial bundles; the former has fast muscle fibers innervated by phasic excitatory motoneurons, and the latter has slow fibers supplied by tonic excitatory motoneurons. Each muscle also is innervated by a single, separate inhibitory neuron that uses gamma-aminobutyric acid (GABA) as the inhibitory neurotransmitter. The pattern of axonal branching by the separate inhibitory axons in phasic and tonic abdominal extensor muscles was visualized with confocal microscopy in preparations labeled for GABA-like immunoreactivity. Initial observations indicated that the phasic muscle was covered by extensive GABAergic, filiform axon terminals, whereas innervation of the tonic muscle was comprised of more localized and varicose terminals. With quantitative analyses, we found that the phasic axon has a more highly branched nature than the tonic in first- and second-order branches. The phasic axon branches also were significantly longer than the tonic branches in the second- and third-order branches. Synaptic varicosities in the phasic branches were smaller and less frequent than those in the tonic branches. The fine structure of the inhibitory nerve terminals near synaptic contacts examined with thin-serial-section electron microscopy revealed distinct differences between the phasic system and the tonic system. The phasic terminals were smaller in cross-sectional area than the tonic terminals, and they had smaller synapses and fewer mitochondria. The presynaptic active zone dense bodies were similar in length and number between phasic and tonic synapses. However, their number per synaptic area was two-fold higher in phasic synapses compared with tonic synapses because of the smaller size of the phasic synapses. Thus, within the same neuromuscular system, inhibitory synaptic terminals revealed unique phasic and tonic identities similar to those observed for the excitatory axons.

Animals↗
PubMed2001

Cerebral-buccal pathways in Aplysia californica: synaptic connections, cooperative interneuronal effects and feedback during buccal motor programs.

Ingestion of seaweed by Aplysia is in part mediated by cerebral-buccal interneurons that drive rhythmic motor output from the buccal ganglia and in some cases cerebral-buccal interneurons act as members of the feeding central pattern generator. Here we document cooperative interactions between cerebral-buccal interneuron 2 and cerebral-buccal interneuron 12, characterize synaptic input to cerebral-buccal interneuron 2 and cerebral-buccal interneuron 12 from buccal peripheral nerve 2,3, describe a synaptic connection between cerebral-buccal interneuron 1 and buccal neuron B34, further characterize connections made by cerebral-buccal interneurons 2 and -12 with B34 and B61/62, and describe a novel, inhibitory connection made by cerebral-buccal interneuron 2 with a buccal neuron. When cerebral-buccal interneurons 2 and 12 were driven synchronously at low frequencies, ingestion-like buccal motor programs were elicited, and if either was driven alone, indirect synaptic input was recruited in the other cerebral-buccal interneuron. Stimulation of BN2,3 recruited both ingestion and rejection-like motor programs without firing in cerebral-buccal interneurons 2 or 12. During motor programs elicited by cerebral-buccal interneurons 2 or 12, high-voltage stimulation of BN2,3 inhibited firing in both cerebral-buccal interneurons. Our results suggest that cerebral-buccal interneurons 2 and 12 use cooperative interactions to modulate buccal motor programs, yet firing in cerebral-buccal interneurons 2 or 12 is not necessary for recruiting motor programs by buccal peripheral nerve BN2,3, even in preparations with intact cerebral-buccal pathways.

Animals↗
PubMed2000

Short-term synaptic enhancement modulates ingestion motor programs of aplysia.

Activity-dependent synaptic plasticity regulates the flow of information in neuronal networks and has important implications for the expression of behavior. We find a functional role for short-term synaptic enhancement (STE) such as facilitation, augmentation, and post-tetanic potentiation at central synapses in the sea slug Aplysia californica. Consummatory feeding in Aplysia such as rhythmic biting is controlled by command-like cerebral-buccal interneurons (CBIs) that drive rhythmic motor output in the buccal ganglia. CBI interneuron-2 (CBI-2) makes monosynaptic connections onto buccal neurons, including premotor neurons B31/32 and B34 and motor neurons B61/62. Stimulating CBI-2 at a physiological firing frequency of 10 Hz for 30 sec causes these synapses to increase their EPSP amplitude by approximately 200%. This STE persists for nearly 2 min, during which time there is an increased cycle frequency of rhythmic ingestion buccal motor programs (iBMPs) elicited by CBI-2. This increase does not occur if the contralateral CBI-2 is trained and the test is performed with the ipsilateral CBI-2; therefore, the effect on motor programs only occurs in CBI-2 pathways in which STE is elicited. Furthermore, we find that STE elicited at CBI-2 buccal synapses permits iBMPs to be initiated at lower firing frequencies. Thus, STE of CBI-2 synapses appears to contribute to the initiation or modulation, or both, of buccal motor programs for rhythmic ingestion in Aplysia.

Action Potentials↗
PubMed2000

An outbreak of cryptosporidiosis in an urban swimming pool: why are such outbreaks difficult to detect?

OBJECTIVE: To describe an outbreak of Cryptosporidium gastroenteritis in a swimming pool in Melbourne in early 1998 that was not detected through routine surveillance, and discuss difficulties in identifying such outbreaks. METHODS: The Water Quality Study (WQS) was a large community-based study of gastroenteritis. Following suspicion of an outbreak of cryptosporidiosis within the study group, due to pool "X", a nested case control study was performed. Each case of Cryptosporidium gastroenteritis was matched with six controls and data from weekly Health Diaries from the WQS were reviewed. The Department of Human Services also instigated active surveillance among patrons at pool "X" using a systematic sample of 50 people from the pool's swim-school enrollment list. RESULTS: There were seven cases of Cryptosporidium gastroenteritis in the case control study. Five cases and eight controls swam at pool "X" during the outbreak period. The adjusted odds of developing cryptosporidial diarrhoea if an individual swam at pool "X" was 34.5 (CI 2.3-2548). DHS identified another 11 laboratory confirmed cases associated with pool "X" as well as cases not linked to pool "X". 125 cases were identified throughout Melbourne with the suspected involvement of seven swimming pools. CONCLUSIONS: Despite a high odds ratio of developing cryptosporidiosis this outbreak was not detected by routine surveillance methods. Current outbreak detection methods lack sensitivity, specificity or timeliness. IMPLICATIONS: Improved surveillance systems are required if outbreaks of gastroenteritis are to be detected early so an intervention can be instigated to reduce the amount of subsequent illness.

Animals↗
PubMed2000

Regeneration of cerebral-buccal interneurons and recovery of ingestion buccal motor programs in Aplysia after CNS lesions.

In the sea slug Aplysia, rhythmic biting is eliminated after bilateral cerebral-buccal connective (CBC) crushes and recovers within 14 days postlesion (dpl). The ability of cerebral-buccal interneuron-2 (CBI-2) to elicit ingestion buccal motor programs (iBMPs; i.e., fictive rhythmic ingestion) and to regenerate synaptic connections with target buccal neurons was assessed with intracellular recordings and dye injections. Isolated central ganglia were obtained from control animals and from lesioned animals at selected times after bilateral CBC crushes. Within 3 wk postlesion, transected CBI-2 axons sprouted at least 10 fine neurites confined to the core of the CBC that projected across the crush site toward the buccal ganglia. When fired with depolarizing current steps, CBI-2 was not observed to elicit iBMPs in preparations until 14 dpl. Thereafter a progressive enhancement in CBI-2's ability to elicit iBMPs was observed with time postlesion. By 40 dpl, CBI-2-elicited iBMPs were indistinguishable from those of controls. CBI-2 regenerated monosynaptic connections with appropriate buccal premotor- and motorneurons by 14 dpl, and the strength of these connections increased with time postlesion. Dramatic frequency facilitation was exhibited by the regenerating CBI-2 buccal synapses; for instance, at early postlesion times, no observable excitatory postsynaptic potentials (EPSPs) were obtained with 1- Hz stimulation of CBI-2, while at 7 Hz, a dramatic increase in EPSP amplitude was obtained with successive spikes. The present study shows that the time course of axonal and synaptic regeneration by command-like interneuron CBI-2 is correlated with the recovery of ingestion buccal motor programs elicited by CBI-2. These results parallel our previous findings of functional neural regeneration in the feeding system and suggest that functional neural regeneration is at least in part mediated by regeneration of specific synaptic pathways.

Animals↗
PubMed1999

Axonal regeneration in the central nervous system of aplysia californica determined by anterograde transport of biocytin.

Rhythmic biting, a component of consummatory feeding behavior in the sea hare Aplysia californica, is eliminated following bilateral cerebral-buccal connective (CBC) crushes and recovers within 14 days postlesion. To assess axonal regeneration after CBC lesions, we used biocytin backfills of CBCs followed by fluorescence labeling with streptavidin-lissamine rhodamine. Anterograde transport of biocytin showed up to 1 mm of outgrowth by regenerating axons at 3 days postlesion. At 7 days postlesion, the regenerated axons approached or had entered the ipsilateral buccal neuropil and exhibited numerous varicosities; the average rate of axonal growth was 326 microm/day for the longest, most rapidly growing axons labeled in the CBC. The number of varicosities on labeled axons, suggestive of intercellular interactions, was increased dramatically at all times postlesion. At 14 and 20 days postlesion, regenerated axons branched extensively in the ipsilateral buccal neuropil, entered the contralateral buccal neuropil, and entered peripheral nerves on both sides of the midline. At these later times postlesion, some labeled axons encircled unlabeled buccal cell bodies and exhibited branches containing numerous varicosities, indicative of axosomatic contacts. Some regenerating axons were observed in the sheath of the CBC, but the vast majority of labeled axons remained confined to the connective core, as in control preparations. The bilateral projections within the buccal ganglia of labeled cerebral-to-buccal axons and the large number of varicosities present on these processes are indicative of regenerating axons and synapses that likely contribute to the functional recovery of rhythmic biting.

Animals↗
PubMed1999

Timeliness of Salmonella notifications in South Australia.

OBJECTIVE: To evaluate the timeliness of Salmonella serotype and phage type notifications in South Australia. METHOD: We surveyed all notifications of Salmonella to the South Australian Department of Human Services between July 1995 and June 1996. We entered data onto an Epi Info 6.02 database and calculated the time interval between various stages of typing notification. RESULTS: The median time taken between collection of a faecal specimen and receipt of serotype notification was 10 days (range, 5-38), while phage type notification took a further seven days (range 0-40). The time interval between collection of a specimen and notification of a Salmonella final identity was 14 days (range 6-49). The internal mail system of the Department of Human Services delayed notification a median of two days. Environmental Health Officers supplied reports for 224 (58%) of 384 cases, 71% of which occurred before the final Salmonella isolate was known. CONCLUSIONS: We found that the internal departmental mail system delayed the notification of Salmonella. In South Australia, investigations should focus on clusters of cases of known Salmonella identity, rather than all notified cases. IMPLICATIONS: To improve communicable disease investigations, health agencies should evaluate the timeliness of surveillance systems and examine the feasibility of transferring laboratory data electronically.

Cluster Analysis↗
PubMed1997

Morphological correlates of neural regeneration in the feeding system of Aplysia californica after central nervous system lesions.

Morphological techniques were used to study regeneration of central neural pathways involved in feeding behavior following bilateral crushes of the cerebral-buccal connectives (CBCs). Electron microscopic analysis revealed that CBC crushes completely transect axons within the nerve core while leaving a remnant of the nerve sheath intact. Changes in the ultrastructure of the CBCs at the crush site were determined for 1, 7, 14, 21, and 50 days postlesion. At 1 day postlesion, the crush site was no longer compressed, and the nerve core had assumed a circular shape. In addition, several small axon profiles were evident, and large areas of tissue debris and prominent microglial cells were observed. Membranous debris and hemocytes were also present in sinuses that appeared in the sheath adjacent to the crush site. From 7 to 50 days postlesion, the core of the nerve at the crush site increased in size due to the addition of small diameter axons. Initially, the sheath surrounding the crush site exhibited hyperplasia and contained a few small bundles of processes, apparently due to newly sprouted axons that had strayed from the nerve core. By 50 days postlesion, the crush site appeared nearly normal; the nerve core was reacquiring the normal radial pattern of axon profiles with some medium-sized axon profiles covered with glial sheath and exhibiting invaginations typical of the intact CBC. However, there was still a distinct lack of large diameter axons. Cobalt backfills across the crush site revealed neurons in the cerebral ganglion by postlesion day 9. Positions of stained cell bodies were consistent with those observed in controls, although the numbers of stained neurons did not recover to control levels even by postlesion day 63. The changes in the crush site and return of cell body staining with time postlesion are correlated with the recovery of consummatory feeding.

Animals↗
PubMed1996

Locally acquired Brachylaima sp. (Digenea: Brachylaimidae) intestinal fluke infection in two South Australian infants.

Eggs of a small intestinal trematode were found in the faeces of two 21-month-old children from the same rural district of South Australia who presented 18 months apart with mild abdominal pain and diarrhoea. Treatment with praziquantel resulted in egg clearance and resolution of gastrointestinal symptoms. A brachylaimid intestinal trematode involving the common house mouse, poultry and introduced European helicid snails is well established in South Australia. Both infants had been seen eating raw snails, and snails from their environment were found to be infected with metacercariae of a brachylaimid trematode.

Animals↗
PubMed1995

rSec6 and rSec8, mammalian homologs of yeast proteins essential for secretion.

Many of the molecules necessary for neurotransmission are homologous to proteins involved in the Golgi-to-plasma membrane stage of the yeast secretory pathway. Of 15 genes known to be essential for the later stages of vesicle trafficking in yeast, 7 have no identified mammalian homologs. These include the yeast SEC6, SEC8, and SEC15 genes, whose products are constituents of a 19.5S particle that interacts with the GTP-binding protein Sec4p. Here we report the sequences of rSec6 and rSec8, rat homologs of Sec6p and Sec8p. The rSec6 cDNA is predicted to encode an 87-kDa protein with 22% amino acid identity to Sec6p, and the rSec8 cDNA is predicted to encode a 110-kDa protein which is 20% identical to Sec8p. Northern blot analysis indicates that rSec6 and rSec8 are expressed in similar tissues. Immunodetection reveals that rSec8 is part of a soluble 17S particle in brain. COS cell cotransfection studies demonstrate that rSec8 colocalizes with the GTP-binding protein Rab3a and syntaxin 1a, two proteins involved in synaptic vesicle docking and fusion at the presynaptic terminal. These data suggest that rSec8 is a component of a high molecular weight complex which may participate in the regulation of vesicle docking and fusion in brain.

Amino Acid Sequence↗
PubMed1995

Extracellular matrix synthesized by clonal osteogenic cells is osteoinductive in vivo and in vitro: role of transforming growth factor-beta 1 in osteoblast cell-matrix interaction.

ROB-C26 (C26) is a multipotential, clonal cell line known to express several members of the TGF-beta superfamily and to become more osteoblastic (e.g., express higher levels of alkaline phosphatase) upon treatment with 10(-6)M retinoic acid (RA). We hypothesize that the expression of this more osteoblastic phenotype subsequent to RA exposure is the result of the treated cell's extracellular matrix (ECM) becoming a repository and active source of putative osteoinductive growth factors including, specifically, select members of the TGF-beta superfamily. To test this hypothesis, we isolated the ECM from RA-treated and untreated C26 cells and assessed them for their ability to promote osteogenic differentiation in vivo and in vitro. We then explored whether the latter activities could be attributed specifically to TGF-beta 1. We found that the ECM of treated cells isolated by cell lysis and extensive washing induced endochondral bone formation in vivo when implanted into the thigh muscles of athymic nude mice and stimulated alkaline phosphatase (ALP) activity in vitro in freshly plated C26 cells. This latter stimulation was comparable to levels observed with direct RA treatment. This latter in vitro activity was only very partially mimicked by the ECM prepared from untreated cells and not duplicated at all by RA-treated collagen or the ECM from another RA-treated multipotential cell line. Moreover, the in vivo osteoinductive effect of the treated C26 cell ECM was not duplicated by comparable ECM prepared from untreated cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1995

Pathways mediating abdominal phasic flexor muscle activity in crayfish with chronically cut nerve cords.

1. Nerve cord transection abolishes the ability of crayfish (Procambarus clarkii) to produce tailflips in response to gradually applied tactile or proprioceptive stimulation of the abdomen, but this ability eventually returns. To determine the time-course of this return and to analyze its underlying neural pathways, we made behavioral observations, electromyographic recordings from abdominal phasic flexor muscles, and intracellular recordings from motoneurons in crayfish with cord lesions between the thorax and the abdomen. 2. Abdominal stimulation activated the phasic flexor muscles in the rostral 5 abdominal segments and their homologs in the 6th segment, the posterior telson flexor muscles. Nearly one-quarter of cord-transfected animals responded to the stimuli with phasic flexor muscle activity by one week after the lesion, and almost 90% were responsive by 3 weeks. 3. Regeneration of axons across the lesion played little or no role in the recovery of phasic flexor muscle responsiveness. In addition, the lateral giant axons were not activated by the gradually applied stimuli that triggered phasic flexor muscle contractions. These results suggest that non-giant pathways confined to the abdominal nervous system become functional following chronic cord transection. 4. Retransection of the nerve cord below the original lesion showed that smaller subsets of the abdominal cord, including a single ganglion, could develop the ability to generate phasic flexor muscle contractions in response to gradually applied stimuli. 5. Phasic flexor motoneurons in cord-transected animals could be excited by stimulation of afferents throughout the abdomen. The sensory pathways producing this activation appear to project through the nerve cord without much cross-over between left and right sides.

Abdominal Muscles↗
PubMed1995

Functional neural regeneration in the feeding system of Aplysia: behavioral recovery correlated with changes in buccal motor output.

1. We tested for functional neural regeneration in the feeding system of Aplysia after bilateral transections or crushes of the cerebral-buccal connectives (CBCs) with the use of behavioral analyses and electrophysiological recordings. 2. Both types of lesion selectively abolished rhythmic consummatory behavior, dramatically increasing bite latency and interbite interval, and decreasing bite magnitude. Appetitive feeding behavior was not affected. 3. About 2 wk after CBC crush, bite latency, bite magnitude, and interbite interval began to recover, as rhythmic biting reappeared; complete recovery of rhythmic biting occurred within 60 days. Rhythmic biting never recovered after transection of the CBCs. 4. The recovery of rhythmic biting was correlated with changes in buccal motor output, which were assessed with the use of in vivo recordings from buccal nerve 4 in freely moving Aplysia. Initially, some bursting in nerve 4 occurred without overt bites; with full recovery of biting, a 1:1 correspondence between bursts in nerve 4 and overt bites returned. 5. CBC lesions caused a functional separation between biting and swallowing; at early times postlesion, subjects displayed apparently normal rhythmic swallowing even though rhythmic biting had been eliminated. However, there was a disruption of the 1:1 correspondence between nerve 4 bursts and swallows, which persisted until consummatory feeding fully recovered. 6. Transection of the CBCs in animals that had fully recovered from a previous CBC crush again abolished rhythmic biting, suggesting that the recovery of consummatory feeding behavior was due to functional neural regeneration of cerebral-buccal connections.

Animals↗
PubMed1994

Neuromuscular regeneration by buccal motoneuron B15 after peripheral nerve crush in Aplysia californica.

1. We studied regeneration of neuromuscular connections by identified buccal motoneuron B15 after axotomy produced by crushing nerve 4; the intact contralateral nerve 4 served as control. Electrophysiological recordings, intracellular dye injections, and light and electron microscopy were used to characterize the nature and time course of neuromuscular reinnervation as well as the fate of the isolated distal stump of the motor axon. 2. Axonal outgrowth or sprouting in the form of numerous "regenerites" occurred from the proximal stump of the transected B15 axon, and these regenerites projected through the crush site along the length of the nerve to innervate target muscles at the periphery. 3. Reinnervation of one of the target muscles, the accessory radula closer (I5), was first detected 3 wk after nerve crush. Neuromuscular excitatory postsynaptic potentials measured in individual I5 muscle fibers were initially small and approached control amplitudes by 8 wk postlesion. Newly regenerated neuromuscular synapses displayed facilitation and depression to repeated B15 stimulation with properties similar to those of control synapses, even at early times postlesion. 4. Reinnervation of other buccal muscles by B15, such as I4, appeared slightly delayed relative to that observed for I5. No evidence of abnormal or enlarged fields of innervation were observed, and as in control preparations, regenerated neuromuscular connections were strictly limited to muscles ipsilateral to the B15 cell body. 5. Physiological evidence suggested that the distal axon stumps of B15, although isolated from their cell bodies, survive for several weeks after axotomy. In addition, several large axon profiles indicative of motor axons were seen in cross-sections of nerve 4 taken close to the muscle and distal to the crush site, indicating survival of distal axon stumps. 6. When B15 was selectively stimulated, the newly formed regenerites failed to fire the distal axon stump of B15, demonstrating that the regenerites do not reinnervate the distal stump. 7. Degeneration of axons in nerve 4 distal to the crush site was observed in cross-sections of the nerve at 8 wk postlesion; using ultrathin sections we found cellular debris in individual axon profiles as well as large acellular masses within nerve 4, the latter likely representing the concretion of many axons. Additional evidence for such degenerative changes appeared in the form of autofluorescing spherical bodies or "spheroids" both in individual axons and the nerve distal to the crush site.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗