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Biomedical subjects

J Majkowski

Publications and source records attributed to J Majkowski.

At least 19 recordsLinked to original sources
PubMed1996

A new route of transmission for Escherichia coli: infection from dry fermented salami.

OBJECTIVES: This study evaluated the production of dry fermented salami associated with an outbreak of Escherichia coli O157.H7 infection in Washington State and California. METHODS: Facility inspections, review of plant monitoring data, food handler interviews, and microbiological testing of salami products were conducted. RESULTS: Production methods complied with federal requirements and industry-developed good manufacturing practices. No evidence suggested that postprocessing contamination occurred. Calculations suggested that the infectious dose was smaller than 50 E. coli O157:H7 bacteria. CONCLUSIONS: Dry fermented salami can serve as a vehicle of transmission for O157:H7 strains. Our investigation and prior laboratory studies suggest that E. coli O157:H7 can survive currently accepted processing methods.

Adult↗
PubMed1989

Effect of after-discharge EEG patterns on performance and latency of the conditioned avoidance response in hippocampally kindled cats.

The relation between different EEG after-discharge patterns and memory retrieval of the conditioned avoidance response was studied in 8 hippocampally kindled cats. The after-discharge patterns were classified into 5 basic EEG types. The relation was analyzed in three different situations: A, at the conditioning stimulation onset, B, at the conditioning stimulus termination, and C, when conditioning stimulus onset and termination were studied within the same type of EEG pattern of after-discharge. The moment of presentation of the conditioning stimulus was determined by the type of EEG after-discharge pattern. Significant relation was observed between reflex performance and type II and III EEG AD types. The type II (4.5-12/s spiking activity) was associated with a greater proportion of positive responses if presented on the uniform background of EEG after-discharge patterns. During the type III pattern (EEG dysrhythmia), there were more negative than positive responses in all the three experimental situations, especially if the type III EEG pattern was observed at the time of conditioned stimulus termination. The latency of reflex performance measured in the experimental condition C (the same pattern of EEG during conditioning stimulus onset and termination) was longer during the type II EEG pattern of after-discharges than the latencies found during type III EEG activity and in the control group. During type III pattern associated with greatest proportion of response failures there was, however, no increase of reflex latencies. The results suggest differential effect of different EEG after-discharge patterns on memory retrieval of the well established conditioned avoidance response in cats.

Animals↗
PubMed1989

EEG afterdischarge patterns and performance of the avoidance response in hippocampally kindled cats.

The relation between EEG limbic afterdischarge patterns and the performance of avoidance response was studied in eight hippocampally kindled cats. Five basic types of EEG afterdischarge patterns were identified in the hippocampal formation: (i) continuous 2-4/s high amplitude spikes or spike and wave complexes; (ii) continuous, 4.5-12/s high amplitude spikes or spike and wave complexes; (iii) dysrhythmic pattern: disorganized irregular spiking, mixed with slow waves at 3-20/s frequency; (iv) continuous, 20-30/s comb-like shaped spiking of moderate amplitude, and (v) trains of high amplitude and frequency irregular spikes, lasting for 0.2-1 s. followed by EEG depression lasting 0.3-1 s. The performance of conditioned response was tested during first 10 s. of afterdischarge development after kindling electrical stimulation of the hippocampus. A statistically significant relation was observed between the EEG afterdischarge patterns seen at the beginning of afterdischarge formation (basically types I, II and III) and the performance of avoidance response, with greatest probability of the response failure with type III of afterdischarge pattern. Latencies of the avoidance responses were prolonged during afterdischarges, in comparison to latencies observed before and after kindling hippocampal stimulation.

Action Potentials↗
PubMed1988

Effects of hippocampal kindled afterdischarges and complex partial seizures on previously established avoidance response in cats.

The performance of well established avoidance response was tested in cats with developed, kindled, bioelectric hippocampal epileptic focus and complex partial and secondarily generalized seizures. The animals were trained before kindling to perform foreleg movement in response to clicks (conditioning stimulus) in order to avoid an unconditioned stimulus - electric shocks, applied to the same forepaw. In addition, two animals were trained to differentiate between different frequencies of clicks. There was no deficit in reflex performance and differentiatimon if the conditioning stimulus was presented during intensive uni- or bilateral spontaneous interictal limbic spiking, occurring before or after hippocampal afterdischarges and complex partial seizures. After repeated secondary generalized tonic-clonic seizures the performance was, however, completely abolished. Presentation of the conditioning stimulus during afterdischarges and partial seizures resulted in 75 percent correct responses during afterdischarges shorter than 10s and 25 percent correct responses during afterdischarges longer than 10 s. Correct responses were observed in cases when conditioning stimulus was applied not later than 6 s after the termination of hippocampal electrical stimulation. The results suggest that the functional integrity of the hippocampal formation is of no critical importance for the retrieval and for performance of the previously established avoidance response and differentiation. A deficit in memory retrieval and/or performance of the avoidance response during afterdischarges and partial seizures may be related to indirect effects caused by the afterdischarges in remote, other than limbic structures.

Animals↗
PubMed1988

Influence of hippocampal kindling on avoidance learning in cats.

The formation of avoidance response and differentiation was studied in 13 control and 7 kindled cats with developed hippocampal epileptic focus and complex partial or secondary generalized tonic-clonic seizures. Conditioning sessions lasted from 15 to 20 min in a period following afterdischarges and seizures resulting from electrical stimulation of the hippocampal formation. In two out of seven kindled cats the conditioned reflex was established within time limits (9 and 20 days) comparable to the control cats. These two animals had relatively short-lasting afterdischarges (mean values: 17 and 19 s). In cats with longer-lasting afterdischarges and complex partial seizures (mean duration: 32 to 65 s, in different animals) criterion was not reached during parallel kindling-conditioning stage of 10 to 30 days. The level of correct responses was low and variable (0-70 percent), despite typical reactions to the unconditioned stimuli and clear orienting responses to the conditioning stimuli on more advanced stages of training. Four kindled animals entered the stage of secondary generalization of seizures after hippocampal stimulation. Reflex performance after tonic-clonic seizures was practically abolished. The termination of kindling resulted in acquisition of the conditioned reflex in all the animals. The results indicate, that in animals with long-lasting complex partial seizures the learning of the avoidance response is impaired. In contrast to the effects exerted by afterdischarges and complex partial seizures, intensive interictal hippocampal spiking did not seem to have a direct negative influence on, this particular type of learning.

Animals↗
PubMed1986

Differences in antiepileptic drug efficacy in hippocampally kindled normal and microcephalic rats.

The difference in antiepileptic drug efficacy was investigated in two groups of animals: 5 normal and 4 microcephalic rats. The latter were produced by a single i.p. injection of 30 mg/kg methylazoxymethanol acetate in the mother on the 15th day of gestation. Hippocampal kindling was performed to a seizure criterion in all animals followed by testing of the antiepileptic drugs vs placebo. Besides carbamazepine (CBZ), two new anticonvulsants were tested: (E)-2-[(alpha-amino)phenylmethylene]-benzo-[b]-thiophene-3(2H)-one (AF-CX 921) and its metabolite (E)-2-[alpha-amino)phenylmethylene]-benzo-[b]-thiophene-3(2H)-one- 1- oxide (AF-CX 1325). Frequency of occurrence and duration of afterdischarges and seizures were statistically examined. The duration of early afterdischarges (AD1) tended to be shorter in microcephalic than in normal animals in control and placebo periods. In contrast, during treatment with the antiepileptic drugs, AD1 durations were longer in microcephalic than in normal animals. This suggests that the drugs inhibited AD1 to a lesser extent in the microcephalics. Two other characteristics of EEG epileptic activity, focal spiking (FS) and late afterdischarges (AD2) also varied in the two groups. Both were significantly lower in occurrence in the microcephalic rats independent of treatment. Three types of behavioral manifestations were also examined: convulsive seizures (CS), epileptic behavior (EB) and quiet states (Q). The two groups of animals responded differently to the drugs with respect to Q and CS. In the microcephalics, AFCX 1325 and AFCX 921 were superior to CBZ, which in turn, was superior to placebo.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

EEG and seizure threshold in normal and lissencephalic ferrets.

Changes in EEG and susceptibility to electrically induced seizures were examined in the ferret with lissencephaly produced by exposure to a single injection of methylazoxymethanol acetate (MAM Ac) given to the pregnant jill on gestation day 32. Ten lissencephalic and 11 normal ferrets were chronically implanted with 14 cortical stainless steel electrodes. EEG records were sampled from various stages of the sleep/awake cycle. Six of each group were subjected to electrical stimulation for seizure threshold. Although the number of stimulations and the current intensity required to produce epileptiform afterdischarges (AD) and seizures were not different between the two groups, the lissencephalic ferrets had significantly longer AD and seizures, and a greater number of generalized seizures, indicating an enhanced seizure susceptibility. The EEG of the lissencephalic ferrets was characterized by increased slow wave activity within the low theta band range, extreme spindle activity, focal or multifocal slow and sharp waves, spikes, or spike and slow wave complexes. The differences in the EEG were more pronounced during drowsiness and sleep stages. The brains of all of the treated animals were lissencephalic and hydrocephalic, and weighed significantly less than those of the normals. The cerebral cortex was thin and flattened, with the parieto-occipital region most severely affected. Heterotopic foci were found in the cerebellum as well as in the cerebral cortex. Abnormalities in the configuration of the cerebellar folia were also seen. Comparison between the electrophysiological and neuropathological data suggests that the extent of the extreme spindle activity, and longer AD and seizure duration depended on the degree of cerebellar dysplasia, whereas the EEG focal abnormalities were related to lesions in the cerebral hemispheres.

Animals↗
PubMed1984

Electro-clinical studies of epileptic seizures in Mongolian gerbils.

In 26 seizure-prone gerbils, with chronically implanted electrodes, the electro-clinical relationship of seizures was studied. The results are based on 70 EEG recordings of fully developed seizures resulting from: (1) moving the animal from its home cage to the testing area, i.e., the naturally occurring environmentally precipitated seizures (EPS); (2) electrically induced by stimulation of cortical electrodes (ICS); and (3) electrically induced by stimulation of hippocampal electrodes (IHS). The EPS were categorized into 4 electro-clinical phases: myoclonic, clonic-tonic, tonic, and clonic movements; usually preceded by an incipient period and followed by a post-seizure period. Usually the EPS were preceded by focal single spiking in the posterior part of the hemisphere, during which the animal's behavior was normal. This spiking turned to generalized epileptic discharges (incipient period without epileptic behavior) which were followed by the 4 phases of generalized myoclonic and clonic-tonic seizures. Post-seizure coma-like behavior was associated with EEG depression. The ICS were very similar to the EPS, but of course lacking the incipient phase. In contrast to the EPS and ICS, the IHS were very different both in terms of EEG and clinical manifestations. Moreover, the post-seizure depression was absent or negligible. We concluded that in the EPS in gerbils, the cortex is of primary importance as to the site of origin of the seizure, while the hippocampal involvement is secondary to it.

Animals↗
PubMed1984

State-dependent variations in brainstem auditory evoked responses in human subjects.

BAERs from 16 subjects during 3 sessions varied in the latency or amplitude of some components depending upon level of arousal as indicated by EEG patterns. There was a general tendency for activation to produce the fastest responses with the largest amplitudes and for drowsiness to produce the slowest responses with the smallest amplitudes. The latency of P2 was significantly prolonged during drowsiness, relative to those during relaxation or activation. For right-ear stimulation, P5 latency was longest during drowsiness, and shortest during activation while for left-ear stimulation the shortest latency occurred during relaxation. The amplitudes of Wave II and Wave VII were significantly smaller during drowsiness than during activation. Although the differences were below the level of clinical significance, the data indicate a modification in the characteristics of brainstem transmission as a function of concurrent activity in other brain areas.

Adult↗
PubMed1983

Drug effects on afterdischarge and seizure threshold in lissencephalic ferrets: an epilepsy model for drug evaluation.

In normal and lissencephalic ferrets with chronically implanted electrodes, two antiepileptic drugs, (E)-2-[(amino)phenylmethylen]-benzo [b] thiophen-3(2H)-on (AF-CX 921 XX) and carbamazepine (CBZ), were compared. The variables included afterdischarges (AD) and seizures induced by cortical electrical stimulations (ES). Both drugs were given orally, 100 mg/kg of pure substance. ES was applied before and 1, 2, 3, 4, 5, and 24 h after drug administration. Lissencephaly was produced by a single intraperitoneal injection of 15 mg methylazoxymethanol acetate to pregnant animals. The administration of both drugs resulted in increases of the AD threshold current to 240% in the normal and to 170% in the lissencephalic ferrets, in comparison with control stimulations (the difference significant at p less than 0.001). Moreover, duration of the AD was shorter (p less than 0.01) than before the drugs. Seizure threshold also increased 170% after AF-CX 921 XX and 175% after CBZ in normal and 153% and 138% in lissencephalic ferrets, respectively. The difference between the two drugs was significant. However, in contrast to the threshold, duration of seizures during AF-CX 921 XX administration was significantly shorter (p less than 0.05) than during CBZ. In general, lissencephalic ferrets responded less than normal ferrets to both drugs, but AF-CX 921 XX had a greater inhibitory effect on the duration of seizures. The lissencephalic ferret is proposed as an animal model of epilepsy with diffuse developmental defects.

Animals↗