Biomedical subjects
Publications and source records attributed to A C Young.
A patient with spontaneous periodic hypothermia who had both a lipoma and agenesis of the corpus callosum is described. Spontaneous periodic hypothermia associated with corpus callosum abnormalities is a distinct entity and although the mechanism underlying the hypothermic episodes is unexplained, the term "diencephalic autonomic epilepsy" does not seem appropriate.
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The "anatomical" dead space is commonly measured by sampling an inert gas (N2) and volume in the exhalation following a large breath of oxygen (VD(F)). It may also be measured from an inert gas washout (VD(O)) that describes both volume and the delivery of VD(O) throughout the expiration. VD(O) is known to increase with age and is enlarged in some obstructive syndromes. VD(O) was appreciably larger than VD(F) in our normal subjects. Both measures increased with lung volume, the increase being entirely due to an increase in the volume of phase I. Physiological dead space (VD(p)) however, did not change significantly with lung volume, showing "alveolar" dead space to diminish as a result. An increase in VD(O) occurred with increasing respiratory frequency that was explained by the increase in volume of phase I. Although an increase in VD(F) occurred with frequency, this was significantly less than that seen by VD(O), i.e., VD(F) did not see the progressive increase in phase I volume with frequency. No lung volume or frequency changes, parasympatholytic or sympathomimetic drugs, or altered patterns of breathing simulated the late delivery of dead space seen in age and some obstructive syndromes.
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A description has been given of cerebrospinal fluid (CSF) immunoglobulins in 355 patients with demyelinating, infectious, neuropathic, and other neurological disorders. An increase in the CSF IgG/albumin quotient was observed in 19/36 (53%) cases of definite multiple sclerosis (MS), in 13/47 (28%) cases of probable or possible MS, in 6/9 (67%) cases of proven herpes simplex viral encephalitis (HSVE), in 3/4 (75%) cases of neurosyphilis, in 1/1 case of subacute sclerosing panencephalitis (SSPE), in 2/9 )22%) cases of other central nervous system infections, and in 2/12 (17%) cases of polyneuritis when compared with a group of 236 patients having other neurological disorders. In constrast, a relative increase in the CSF IgA of IgM was seen only in some of the patients with central nervous system infections. It was also found that the quotient CSF/serum IgG, expressed as a percentage of the CSF/serum albumin, was better in distinguishing patients with definite or suspected MS from those with other neurological disorders than the quotients IgG/albumin or IgG/total protein. The CSF K/lambda ratio and the CSF and serum complement-fixing antibody titre to measles and herpes simplex virus were measured in many of the patients. In general, abnormalities of these measurements were associated with raised IgG/albumin quotients. However, in eight patients with definite or suspected MS, a normal IgG/albumin quotient was found with abnormal CSF K/lambda ratios (6 cases) or abnormal CSF titres of measles antibody (7 cases). In addition, two patients, with HSVE had normal IgG/albumin ratios but detectable herpes antibody in the CSF. These findings suggest that the measurement of the relative concentration of CSF immunoglobulin in combination with the K/lambda ratio and antibody titre to various viruses may supplement each other in the endeavour to detect central nervous system immunglobulin sysnthesis in neurological diseases.
Five patients with mental change as a prominent and early feature of an illness which appeared to be multiple sclerosis are reported. All the patients had in addition clinical signs of predominant brain stem involvement and the cerebrospinal fluid findings were similar. It is emphasised that mental change may be an early feature of multiple sclerosis even in those patients in whom the onset of the disease is insidious.
Eighteen-breath nitrogen washouts were performed on eight subjects. Each washout could be simulated by a four-compartment model, each compartment with a different ventilation-to-volume ratio and a variable contribution to expiratory flow. In large breaths initiated near residual volume, a terminal nitrogen rise (TNR) was seen. To account for the TNR with this model, there were relatively small changes in flow from compartments with markedly different nitrogen concentration. Reasons are given for believing these compartments could not be the upper and lower lung. Three of these subjects were studied in the supine, seated, and head-down positions. The TNR was seen at the same lung volume in all positions. At routine bronchospirometry in a second group of subjects, sampling with small catheters during a nitrogen washout showed a TNR in the expirate of lungs, lobes, segments, and subsegments in the upright and supine positions. Apparently a large vertical hydrostatic gradient is unnecessary to produce a TNR. Finally, the TNR was shown to occur at that lung volume where transpulmonary pressure is very small and changing rapidly with volume. This TNR was often followed by a terminal nitrogen fall while the lung was continuing to empty. The TNR occurs when flow from a large poorly ventilated compartment increases relative to the flow from other compartments. A model of lung in which the poorly ventilated compartment develops high specific compliance at low lung volume explains these data.
This paper reports a retrospective study of the preoperative and postoperative management of 28 patients who underwent thymectomy between 1956 and 1973. Patients who received postoperative artificial ventilation were compared with the group who did not with respect to sex, age, severity of disease, preoperative vital capacity, and thymic histology. Evidence is presented that postoperative artificial ventilation is required when the preoperative vital capacity with the patient on optimum anticholinesterase treatment is less than 2 litres. Additional features associated with a probable need for artificial ventilation were the presence of a thymoma, bulbar symptoms, especially dysphagia, and age over 50 years. These should be taken into account in any patient whose vital capacity is close to the critical level of 2 litres. When postoperative ventilation was required it was usually necessary for 12 days or more, and tracheostomy should therefore be done at or before thymectomy. Most patients in this series received the same dose of anticholinesterases after operation as before it and no evidence was found of a sudden decrease in requirements for anticholinesterase therapy. Two patients did not, and in them a myasthenic crisis was precipitated. We propose that the preoperative drug regimen can be continued in the immediate postthymectomy period, allowing selection of patients for tracheostomy and artificial ventilation primarily on the basis of the preoperative vital capacity.
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The pulsed-gradient spin echo nuclear magnetic resonance (PGSENMR) technique was used to measure restricted diffusion of water in three types of animal tissue: human blood plasma and red cells; rat and rabbit heart; rat and rabbit liver. Characteristic lengths (L) for restriction of diffusion are estimated from dependence on the measuring time. Limitations on the range of observable restrictive lengths (1.5-15 mum) are discussed.The decrease in diffusivity due to 1 mum alumina powder (volume fraction = 0.18) in glycerin/water mixtures agrees with the Wang theory assuming spherical particles and no hydration. The characteristic length (L approximately 4 mum) is larger than the particle size (1 mum) or separation (1.8 mum). Comparison of the diffusivities in tissues at short diffusion times with the Wang theory indicates some bound or trapped water.For packed red blood cells, a restriction (L approximately 2.3 mum) was attributed tothe red cell membrane. A permeability p approximately 0.014 cm/s may be estimated from the decrease in diffusivity. Average values of diffusivity ratio in heart were: 0.36 +/- 0.02 for rat; and 0.26 +/- 0.03 for rabbit; and in liver: 0.25 +/- 0.01 for rat; 0.25 +/- .04 for 10-day old rabbit; and 0.195 +/- 0.03 for 2-yr old rabbit. A restriction (L approximately 2.7 mum) in rat liver probably results from the mitochondria.
Lung volumes in irreversible diffuse obstructive pulmonary syndromes (DOPS(I)) have been studied by using an analog of the lung that simulates an 18-breath nitrogen washout. The functional residual capacity (FRC), the dead space volume (Vd), the distribution of ventilation, as well as the pattern of lung emptying have been measured in normal subjects and those with obstructive syndromes. The Vd increased progressively with severity of the obstructive syndrome, as did FRC. For all subjects, both normal and obstructed, the ratio of Vd/FRC remained relatively fixed with the regression line of Vd upon FRC showing a minimal value for Vd of 67 cm(3). Vd increased by an average value of 33 cm(3) per liter of lung volume above this value. The increase in FRC resulted from the increased volume of the poorly ventilated compartment for the most part. X-ray evidence of emphysema was poorly correlated with the changes in Vd or FRC. A significant increase in anatomical Vd in DOPS(I) makes up an appreciable portion of the total Vd (physiological).
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