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Biomedical subjects

K Hogan

Publications and source records attributed to K Hogan.

At least 73 records · Page 4Linked to original sources
PubMed1992

Effects of hypocapnia on canine spinal, subcortical, and cortical somatosensory-evoked potentials during isoflurane anesthesia.

Although hyperventilation with hypocapnia is frequently used in the management of neurosurgical patients in whom sensory-evoked potentials may be monitored, the effects of hypocapnia on evoked potentials have not been described with precision. In the present experiment, the effects of randomized arterial carbon dioxide tensions of 20, 25, 30, and 35 mm Hg on spinal, subcortical, and cortical somatosensory-evoked potentials (SEPs) were measured in dogs anesthetized with 1.40% isoflurane. Other variables known to affect the SEP (temperature, blood pressure, and arterial oxygen tension) were stable throughout the experiment. Hypocapnia caused reductions in the latencies of the early peaks of the spinal and subcortical SEPs. These differences were small, consisting of a 2% shortening of latency at 20 mm Hg carbon dioxide tension when compared with 35 mm Hg. No changes were detected in the later subcortical and cortical latencies. SEP amplitudes were also unchanged. These results in a controlled animal study corroborate the direction and magnitude of changes due to hypocapnia observed by other investigators in surgical patients. The magnitude of the changes indicates that SEP monitoring sensitivity is not compromised by clinically useful levels of induced hypocapnia during isoflurane anesthesia. Because hypocapnia may produce small SEP changes, baseline recordings should be acquired prior to initiation of hyperventilation. It is not warranted, however, to impute a severe deterioration of the SEP to hypocapnia alone, and causes must be sought elsewhere in a patient's status and management.

Analysis of Variance↗
PubMed1992

A cysteine-for-arginine substitution (R614C) in the human skeletal muscle calcium release channel cosegregates with malignant hyperthermia.

A point mutation in the human gene for the skeletal muscle calcium release channel (ryanodine receptor [RYR1]) correlates with inheritance of malignant hyperthermia in a family of Northern European descent. The substitution of thymine for cytosine at position 1840 of the RYR1 transcript results in a cysteine-for-arginine substitution at position 614 (R614C) of the amino acid sequence. The mutation was absent in 59 normal individuals from the general population, in 61 additional unrelated malignant hyperthermia-susceptible patients, and in 18 patients with malignant hyperthermia associated with other inherited or congenital diseases. Together with reports of an equivalent mutation in six susceptible pig strains and an identical mutation in one other human pedigree, these findings suggest that the cysteine-for-arginine mutation represents a shared calcium release channel pathogenesis between porcine malignant hyperthermia and a subset of mutations responsible for the human malignant hyperthermia syndrome.

Adult↗
PubMed1991

Waisman syndrome, a human X-linked recessive basal ganglia disorder with mental retardation: localization to Xq27.3-qter.

Linkage of the gene responsible for an X-linked early onset parkinsonism disorder with mental retardation (McKusick 311510) to DNA probes that detect restriction fragment length polymorphisms is described. The disease gene is linked to the F8C gene, and to DNA probes detecting polymorphic loci DXS52, DXS15, DXS134, and DXS374 with maximum lod scores at theta = 0 of 5.08, 5.19, 5.00, 5.03, and 4.46, respectively. Multipoint linkage analysis gives a maximum multipoint lod score of 6.75 at the F8C gene. This places the disease gene in chromosomal region Xq27.3-qter.

Basal Ganglia Diseases↗
PubMed1991

Assignment of the human gene for the alpha 1 subunit of the cardiac DHP-sensitive Ca2+ channel (CCHL1A1) to chromosome 12p12-pter.

A human clone corresponding to the gene encoding the alpha 1 subunit of the cardiac dihydropyridine-sensitive calcium channel (CCHL1A1) has been isolated and partially sequenced. Oligonucleotides based on the human sequence were constructed and used in the polymerase chain reaction to amplify specifically this human gene in human-rodent somatic cell hybrids. Using somatic cell hybrids that contained defined regions of human chromosome 12, the human alpha 1 subunit of the cardiac dihydropyridine-sensitive calcium channel has been assigned to the short arm of chromosome 12 in the interval 12p12-pter.

Amino Acid Sequence↗
PubMed1991

Altered binding site for Ca2+ in the ryanodine receptor of human malignant hyperthermia.

The binding properties of [3H]ryanodine, a specific ligand of the receptor complex that forms the Ca2+ release channel of sarcoplasmic reticulum, were studied in normal (N) and malignant hyperthermia-susceptible (MH) human skeletal muscle. Integrity of the solubilized ryanodine receptor was demonstrated by single-channel recordings in planar bilayers and by the changes produced by activators and inhibitors of the Ca2+ release channel on the binding properties of [3H]ryanodine. N and MH receptors were capable of binding [3H]ryanodine in a Ca(2+)-dependent manner. Scatchard analysis showed that a single binding site for [3H]ryanodine was present in either N or MH muscle. Binding affinity was approximately the same in N and MH (Kd approximately 7 nM), when the Ca2+ concentration was greater than 30 microM. At 0.3 microM Ca2+, MH receptors displayed a higher affinity for [3H]ryanodine (Kd = 4.1 +/- 1.0 nM) than N receptors (Kd = 7.1 +/- 0.8 nM). The presence of a single Kd for [3H]ryanodine in MH muscle, distinct from that of N muscle, indicated that MH muscle does not have detectable levels of N receptors. Ca2+ dependence of [3H]ryanodine binding further suggested that MH receptors had a higher affinity for Ca2+ (Kd[Ca2+] = 120 +/- 50 nM) than N receptors (Kd[Ca2+] = 250 +/- 80 nM). Caffeine increased [3H]ryanodine binding at submicromolar [Ca2+], and the effect was larger in MH. Apparent affinity constants for caffeine were 13 +/- 1.8 mM in N and 6 +/- 0.8 mM in MH receptors. Evidently, the ryanodine receptor of MH-susceptible human skeletal muscle has an unusually high sensitivity to Ca2+ which is augmented by caffeine.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1988

The cerebral origin of the alpha rhythm.

The EEG alpha rhythm was recorded from 8 isolated canine brains in the absence of orbital contents, drug effect, or pulsatile cerebral blood flow. Abrupt shift to hypoxic perfusion, with maintenance of other perfusion variables, resulted in a loss of alpha coincident with a fall in CMRO2 and rise in oxygen deficit. It is concluded that the alpha rhythm reflects neural electrical activity, and that sources in the eye muscles or in cardiac-induced electromechanical properties of the brain may be rejected.

Alpha Rhythm↗
PubMed1988

Effects of halothane dose and stimulus rate on canine spinal, far-field and near-field somatosensory evoked potentials.

Evidence that canine spinal, far-field and near-field somatosensory evoked potentials resemble those recorded in humans and other species has been presented, and the vulnerability of each component to varying depths of halothane anesthesia is reported. Lumbar spinal peak latencies are not affected by halothane dose, but the negative peak is significantly prolonged by rapid rates of stimulation. Elevated stimulus rates and halothane doses reduce lumbar spinal cord potential amplitudes. Early far-field cephalic components are refractory to halothane. Late far-field components and near-field cortical potentials are substantially altered by increments in halothane dose. Both near-field and far-field responses are more readily identified in vertex-neck than vertex-brow derivations. Early far-field somatosensory evoked potentials recorded from vertex to neck, together with lumbar spinal cord potentials, may be the preferred monitoring technique when the use of halothane anesthesia is desired. Rapid rates of stimulation may facilitate earlier recognition of cord dysfunction, but supplement rather than replace baseline recordings at slow stimulus rates.

Animals↗
PubMed1988

Difficult laryngoscopy and diabetes mellitus.

The incidence of difficult laryngoscopy was determined retrospectively in 40 diabetic patients having pancreas transplantations and in 75 diabetic and 112 nondiabetic patients having kidney transplantations. Diabetes was associated with a significant increase in the proportion of patients having difficult laryngoscopies in patients having renal transplants: 0.027 in patients without diabetes; 0.320 in patients with diabetes. The incidence of difficult laryngoscopy in diabetic recipients of cadaveric kidneys (0.419) was not significantly different from that in diabetic recipients of pancreas transplants (0.40), but significantly higher than that in diabetics given kidneys from living donors (0.187). Although cadaveric recipients were older than recipients of kidneys from living donors (40.8 v. 31.6 years), age at the time of transplantation was not a significant predictor of difficulty in laryngoscopy. Groups were otherwise matched for clinical, morphologic, hematologic, and biochemical indices. Diabetic stiff joint syndrome (SJS), which predisposes a subset of Type I diabetic patients to rapidly progressive microvascular disease and subsequent need for renal and/or pancreas transplantation, may lead to difficult laryngoscopy because of involvement of the atlanto-occipital joint.

Diabetes Mellitus↗
PubMed1986

Whirlpool-associated folliculitis caused by Pseudomonas aeruginosa: report of an outbreak and review.

An outbreak of folliculitis caused by Pseudomonas aeruginosa serotype O:7 occurred among the guests of a hotel in St. John's, Newfoundland, Canada, and the source of the infection was traced to the hotel whirlpool. Of 36 persons who used the whirlpool, 26 (72%) developed folliculitis within 1 to 5 days after exposure; the attack rate was significantly higher for children (90%) than for adults (50%). The rash characteristics were consistent with those of Pseudomonas folliculitis previously described (T. L. Gustafson, J. D. Band, R. H. Hutcheson, Jr., and W. Schaffner, Rev. Infect. Dis. 5:1-8, 1983). This is considered to be the first outbreak in which P. aeruginosa serotype O:7 has been incriminated. Published reports to date of outbreaks of Pseudomonas folliculitis associated with the use of whirlpools, hot tubs, swimming pools, etc., were reviewed.

Adolescent↗
PubMed1985

An X-linked recessive basal ganglia disorder with mental retardation.

We report a previously apparently undescribed, X-linked recessive basal ganglia disorder segregating in three generations of one family. The affected patients were variably mentally retarded, although some showed strengths in oral reading and memory. Most affected males had frontal bossing and increased head circumference with large calvaria in relation to facial bones. Their height and weight did not differ from that of other relatives; testicular size was average, chromosomes were normal, and results of laboratory investigations for known metabolic disorders were normal. All patients examined had neurological impairment, including persistent frontal lobe reflexes, cogwheel rigidity, postural changes, and Parkinsonian-type tremors. Some had strabismus; several had seizures. Although carriers of the condition were not consistently abnormal, two had suggestive signs. No definitive indication of the disorder was documented in infancy in any affected male, and it is possible that this could be due to lack of careful prospective clinical evaluation rather than to the absence of symptoms in early life.

Basal Ganglia Diseases↗
PubMed1984

Use of a pharyngeal guide to aid intubation with the fibreoptic laryngoscope.

The fibreoptic laryngoscope is a difficult instrument to master in anaesthetised patients, and reasons for this are discussed. The use of a pharyngeal guide was shown to provide an acceptable success rate in patients without anatomical deformity. These guides may also be beneficial to those with such deformities.

Humans↗