Biomedical subjects
J Barker
Publications and source records attributed to J Barker.
Anesthesia for craniofacial osteotomies.
Management of major craniofacial deformities requires an interdisciplinary approach. The importance of the role of the anesthesiologist is often not appreciated by those outside that specialty. The experience of almost fifteen years of dealing with these very difficult cases is presented. Anesthetic techniques are discussed in general terms. Intraoperative and postoperative airway problems and solutions are stressed. An effort is made to describe how the anesthesiologist should work with the surgeon to prevent anesthetic emergencies and to ensure optimal patient management.
Studies of the biological effect and degradation of glucagon in the rat perifused isolated adipose cell.
The time relationships between glucagon-stimulated lipolysis and hormonal degradation are incompletely understood. These studies were designed to examine the rat adipocyte response to hormonal stimulation in the perifusion system. The perifused isolated adipocyte responded to glucagon concentrations as low as 10(-11) M, with maximum lipolysis at 10(-7) M glucagon. The lipolytic response corresponded in timing with exposure to glucagon. At lower concentrations, there was an appreciable lag between exposure to hormone and initiation of lipolytic response. Termination of response occurred with removal of hormone from the perifusion medium. The percentage of undegraded glucagon in the perifusate fractions (as determined by precipitability with trichloroacetic acid) remained above 80% until the point where free hormone was cleared from the system and lipolysis had ceased. The adipocytes continued to release both intact and degraded glucagon into the medium, the latter increasing with time. Release showed first order kinetics for both undegraded and degraded glucagon, with rate constants of 0.0656 +/- 0.0053 and 0.0716 +/- 0.0073 min-1, respectively. These perifusion studies provide a mechanism for assessing the time relationship between glucagon stimulation of lipolysis and its removal and degradation. Furthermore, the increased sensitivity of the fat cell to glucagon demonstrated herein with perifusion suggests that the importance of glucagon as a physiological regulator of lipolysis may have been underestimated by earlier researchers.
[Properties of membrane ionic currents in pituitary clone cells].
Membrane ionic currents of the GH3 pituitary cell line have been studied using voltage clamp techniques. The inward current is completely blocked by cobalt (Co2+) ions and appeared to be carried by calcium ions. Three outward currents can be differentiated on the ground of kinetics and pharmacological studies: a transient current blocked by 4-aminopyridine (4 AP) and two delayed outward current which are voltage dependent. One is blocked by tetraethylammonium (TEA); the second is blocked by Co2+ and represents a calcium-activated potassium conductance.
Selective antilipolytic effect of bacitracin in the isolated fat cell.
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Cerebral circulation, intracranial pressure, and the pharmacophysiology of anesthetic agents.
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Deoxyguanosine kinase of neonatal mouse skin tissue.
Deoxyguanosine kinase (ATP: deoxyguanosine 5'-phosphotransferase) activity has been identified in neonatal mouse skin tissue. This activity which has a molecular weight of 44 000 was shown to be highly specific for deoxyguanosine as a substrate. Unique to deoxynucleoside kinases was the observation that this enzyme possessed a pH optimum of 5.2. In dilute solutions catalytic activity is lost, however the enzymatic activity can be stabilized by the addition of 20 micrometer MgATP or ATP. Kinetic analysis gave an apparent Km for deoxyguanosine of 7 micrometer. Double-reciprocal plots of activity vs. MgATP concentration produced a broken line with the break occurring at 0.5 mM MgATP. Below this concentration an apparent Km for MgATP of 23 micrometer was measured; above 0.5 mM MgATP an apparent Km of 265 micrometer was calculated. Mouse skin deoxyguanosine kinase was strongly inhibited by dGTP, dGDP and UDp. dGTP was a competitive inhibitor of deoxyguanisine with an apparent Ki of 1.9 micrometer. UPD (K1,app = 3 micrometer), dGDP = 0.7 micrometer) (Ki,app = 0.07 micrometer] were competitive inhibitors of MgATP and dGTP ki,app = 0.07 micrometer) were competitive inhibitors of MGATP when the concentration of MgATRP was greater than 0.5 mM.
Effects of profound hypotension on cerebral blood flow during surgery for intracranial aneurysms.
The progression of changes in cerebral blood flow (CBF) and neurological status were measured in 12 patients in whom profound hypotension (mean arterial blood pressure (MABP): 30 to 40 mm Hg) was used during intracranial aneurysm surgery. Nine patients (Group I) showed autoregulation of CBF to an MABP of 40 to 50 mm Hg during surgery. None of these patients had arterial spasm preoperatively. Postoperatively, mild flow disturbances were noted at the site of retraction. Three Group I patients developed arterial spasm postoperatively, but there was no associated neurological deterioration. The remaining three patients (Group II) had impaired autoregulation during surgery, and CBF decreased by 35% to 65% at an MABP of 50 mm Hg. Two of these patients had angiography immediately before surgery, and both showed moderate to severe arterial spasm. Relatively severe flow disturbances were noted postoperatively at the site of retraction, and two patients developed ischemic deficits of late onset. Brain retractor pressure and the degree and duration of hypotension were equivalent in the two patient groups. There was no correlation between intraoperative reductions in CBF (to as low as 20 ml/100 gm/min in the unretracted hemisphere) and immediate postoperative neurological deficits. The use of halothane and mannitol and the relatively short duration of the flow reductions were suggested as factors contributing to the protection from ischemia that was observed. Arterial spasm was found to produce hemodynamic instability and reduced CBF, although neurological status was unaffected in the majority of patients. Patients with impaired autoregulation during surgery were at increased risk of delayed ischemic complications postoperatively, and showed characteristic flow disturbances at all three stages of their clinical course.
An enteric coronavirus infection of cats and its relationship to feline infectious peritonitis.
An enteric coronavirus that is antigenically closely related to feline infectious peritonitis virus (FIPV) is ubiquitous in the cat population. This virus has been designated feline enteric coronavirus to differentiate it from FIPV. The virus is shed in the feces by many seropositive cats; in catteries it is a cause of inapparent to mildly severe enteritis in kittens 6 to 12 weeks of age. The virus may produce a more severe enteritis in young specific-pathogen-free kittens. Feline enteric coronavirus selectively infects the apical columnar epithelium of the intestinal villi, from the caudal part of the duodenum to the cecum. In severe infections, there are sloughing of the tips of the villi and villous atrophy. Many cats recovering from the disease remain carriers of the virus. Recovered cats, observed for 3 to 24 months, remained healthy and did not develop peritonitis, pleuritis, or granulomatous disease. The relationship of feline enteric coronavirus and FIPV was studied. Although the viruses were antigenically similar, they were distinctly different in their pathogenicities. The enteric coronavirus did not cause feline infectious peritonitis in coronavirus antibody-negative cats inoculated orally or intraperitoneally nor in coronavirus antibody-positive cats inoculated intraperitoneally or intratracheally. Serologic tests, using FIPV, canine coronavirus, and transmissible gastroenteritis virus of swine as substrate antigens in fluorescent antibody procedures may not accurately identify FIPV infection. These tests do not appear to distinguish between FIPV and this feline enteric coronavirus.
Specific receptor sites for alpha-tocopherol in purified isolated adrenocortical cell membrane.
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The carbon dioxide requirement of Klebsiellae.
The growth of 95 strains of Klebsiella cultured in air with added CO2 is described. Twenty-two strains of K. ozaenae required CO2 for characteristic growth when cultured at 37 degrees C and growth was promoted by co-trimoxazole, tetracycline and sodium barbitone. Four strains of K. pneumoniae, two of K. edwardsii var. atlantae and one of K. edwardsii var. edwardsii gave increased viable counts after incubation in CO2. None of the 40 strains of K. aerogenes tested required CO2 for growth.
A progressive axonopathy of Boxer dogs affecting the central and peripheral nervous systems.
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Anaesthesia or catalepsia for neurosurgery?
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Carbon dioxide-dependent klebsiellae.
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Stability of the individual globin genes during erythroid differentiation.
The genes of sheep betaA, betaC, and gamma globin were all present in DNA from erythroid cells which synthesized only betaC globin. Similarly, selective excision of non-expressed genes was shown not to occur during human erythroid differentiation. In contrast, evolutionary deletion of the betaC gene accounts for the inability of many sheep to make this globin.
Postoperative care of the neurosurgical patient.
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Measurement of jugular venous blood gases for prediction of brain ischaemia following carotid ligation. A comparison with direct measurements of cerebral blood flow.
Measurements of various indices derived from arterial and jugular venous blood gas and pH values during temporary carotid clamping have been compared with measurements of cerebral blood flow and internal carotid artery pressure in 15 patients referred for carotid ligation. Cerebral venous blood gas measurements did not provide a reliable index of cerebral ischaemia.
Cholesterol masses in association with spinal cord infarction due to intervertebral disc emboli.
The clinical and autopsy findings are presented from three dogs with spinal cord infarction. At autopsy firm gritty masses and cystic areas were present within the spinal cord. The masses contained numerous cholesterol clefts, collagen and reticulin fibres and were accompanied by a macrophage, giant cell and lymphocytic response. The cholesterol masses were present mainly in white matter. The ventral spinal artery or its branches as well as pial arteries contained fibrillary masses often covered by endothelial cells. The staining characteristics of these emboli suggested that they were fibro-cartilagenous and probably derived from the intervertebral discs. It is assumed that the cholesterol masses were formed from myelin breakdown products within infarcted areas.