The effects of hyponatraemia and subarachnoid haemorrhage on the cerebral vasomotor responses of the rabbit

Impairment of cerebral autoregulation and development of hyponatraemia are both implicated in the pathogenesis of delayed cerebral ischaemia and infarction following subarachnoid haemorrhage (SAH) but the pathophysiology and interactions involved are not fully understood. We have studied the effects of hyponatraemia and SAH on the cerebral vasomotor responses of the rabbit. Cerebrovascular reactivity to hypercapnia and cerebral autoregulation to trimetaphan-induced hypotension were determined in normal and hyponatraemic rabbits before and 6 days after experimental SAH produced by two intracisternal injections of autologous blood. Hyponatraemia (mean plasma sodium of 119 mM) was induced gradually over 48 h by administration of Desmopressin and intraperitoneal 5% dextrose. Sham animals received normal saline. The cerebrovascular reactivity (% change +/- SD in cortical CBF/mm Hg PaCO2, measured by hydrogen clearance) of hyponatraemic (4.8 +/- 3.0%) and SAH (1.3 +/- 2.0%) animals was significantly less (p less than 0.05) than control (11.6 +/- 4.0%) and sham (8 +/- 2.0%) animals, whereas the reactivity of hyponatraemic-SAH animals was preserved (9.8 +/- 6.0%). Hyponatraemia and SAH alone each significantly impaired CBF autoregulation but their combined effects were not additive. Systemic hyponatraemia impairs normal cerebral vasomotor responses but does not augment the effects of experimental SAH in the rabbit.     

The effect of age, sex, weight and height on the plasma concentrations in healthy subjects of the acidic metabolites of some biogenic monoamines involved in psychiatric and neurological disorders.

1. The plasma concentrations of unconjugated phenylacetic acid and m-hydroxyphenylacetic acid are lower in male than in female subjects. 2. The plasma concentrations of unconjugated phenylacetic acid and mandelic acid decrease with increasing weight and height for all subjects combined. The same relationships apply for both males and females but are significant only for males. 3. Homovanillic and vanillylmandelic acid concentrations in plasma increase with age. 4. The importance of using age, sex, weight and height matched groups in studies involving the plasma concentrations of some of the trace amine metabolites in psychiatric disorders has been demonstrated. This is particularly the case for phenylacetic acid, the major metabolite of phenylethylamine which is now thought to be a neuromodulator of catecholaminergic neurotransmission.     

Relationships of plasma viscosity, coagulation and fibrinolysis to coronary risk factors and angina

Plasma viscosity, molecular markers of activated coagulation and fibrinolysis (fibrinopeptides A and B beta 15-42), coagulation factors (fibrinogen and factor VII) and antiplasmins were measured in 529 men aged 35-54 years and related to new angina pectoris (n = 117) and to coronary risk factors in controls without angina (n = 412). Five major risk factors (cigarette-smoking, blood pressure, cholesterol, triglyceride and body mass index) were each associated with increases in plasma viscosity, coagulation factors, and imbalance of coagulation over fibrinolysis (increased ratio of fibrinopeptide A/fibrinopeptide B beta 15-42). Increased viscosity and fibrinogen in smokers were partly reversed in ex-smokers, but the imbalance of coagulation and fibrinolysis persisted. Cholesterol and triglyceride were also associated with increased antiplasmin activity. In men with angina, only fibrinogen was elevated compared to controls. We suggest that increased plasma viscosity and an imbalance of coagulation over fibrinolysis may be mechanisms by which known risk factors promote arterial thrombosis, but are not present in stable angina.     

Familial association of intracranial aneurysms and cervical artery dissections.

BACKGROUND AND PURPOSE: The familial occurrence of intracranial aneurysms and cervical artery dissections has been described in different families and supports the hypothesis that a primary arteriopathy may play a role in the pathogenesis of these disorders. Although the basis for this arteriopathy is generally not believed to be similar among cases of intracranial aneurysms and cervical artery dissections, several similarities exist in the epidemiology of these disorders and a common underlying arterial abnormality may be suspected. SUMMARY OF REPORTS: The medical records of all 175 patients with spontaneous dissections of the cervical arteries who were seen at the Mayo Clinic between 1970 and 1989 were reviewed to identify families in which intracranial aneurysms and cervical dissections coexisted. Three families were identified in which intracranial aneurysms and cervical artery dissections were observed among siblings. These families are described in detail. CONCLUSIONS: The familial occurrence of intracranial aneurysms and cervical artery dissections within the same families provides support to the importance of a common underlying arteriopathy in the pathogenesis of both these disorders. The underlying vascular defect may, at least in some cases, be inherited.     

Simulated home treatment of depression with nortriptyline

1. Twenty-two patients hospitalized for treatment of depression were treated under conditions simulating those of home treatment. 2. Full doses of nortriptyline, from 100 to 150 mg/day, were started after baseline observations were made. 3. Two patients were dropped from the study, one for orthostatic hypotension, one for an aberrant response to nortriptyline. Two additional patients developed orthostasis which was easily managed. Otherwise no unusual side effects were noted. 4. After six days of treatment, 9 of 20 patients showed significant improvement with an overall reduction in scores on the Hamilton Depression Scale of 49% for the entire group. 5. Using the weight-adjusted dosage schedule, 18 of the 21 patients attained plasma concentrations of nortriptyline within the presumed therapeutic range; however, no clear relationship could be established between plasma concentrations and clinical response. 6. With proper selection of patients, it should be possible to treat at home some patients who currently are considered to require hospitalization.     

Folding and function of the myelin proteins from primary sequence data.

To explain how the myelin proteins are involved in the organization and function of the myelin sheath requires knowing their molecular structures. Except for P2 basic protein of PNS myelin, however, their structures are not yet known. As an aid to predicting their molecular folding and possible functions, we have developed a FORTRAN program to analyze the primary sequence data for proteins, and have applied this to the myelin proteins in particular. In this program, propensities for the secondary structure conformations as well as physical-chemical parameters are assigned to the amino acids and the pattern of these parameters is examined by calculating their average values, autocorrelation functions and Fourier transforms. To compare two proteins, their sequences are aligned using a unitary scoring matrix, and homologies are searched by plotting a two-dimensional map of the correlation coefficients. Comparison of the corresponding myelin basic proteins (MBP) and P0 glycoproteins (P0) for rodent and shark showed that the conserved residues included most of the amino acids which were predicted to form the alpha or beta conformations, while the altered residues were mainly in the hydrophilic and turn or coil regions. In both rodent and shark the putative extracellular domain of P0 glycoprotein displayed consecutive peaks of beta propensity similar to that for the immunoglobulins, while the cytoplasmic domain showed alpha-beta-alpha folding. To trace the immunoglobulin fold along the P0 sequence, we compared the beta propensity curve of P0 with that of the immunoglobulin M603, whose three-dimensional structure has been determined. We propose that the flat beta-sheets of P0 are orientated parallel to the membrane surface to facilitate their homotypic interaction in the extracellular space. An extra beta-fold in the extracellular domain of shark P0 compared with rodent P0 was found, and this may result in a greater attraction between the apposed extracellular surfaces and may account for a smaller extracellular space as measured by x-ray diffraction. A computer search of the myelin protein sequences for functional motifs revealed sites for N-glycosylation, phosphorylation, nucleotide binding, and certain enzyme activities. We note especially that there are potential nucleotide binding sites in proteolipid protein (PLP), MBP and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP). This is consistent with the experimental observations that PLP acts like an ionophore or proton channel when reconstituted into planar lipid bilayers, MBP binds GTP, and CNP catalyzes in vitro the hydrolysis of 2',3'-nucleotides into corresponding 2'-nucleotides.     

Difficulties in using animal data to predict pharmacological response in man

Variation among species in their response to xenobiotic agents depends upon two sets of factors: pharmacokinetic and pharmacodynamic. Pharmacokinetic factors, of which the rate of metabolic transformation is the most important, determine the concentration of the agent in plasma and tissues as a function of time after it is administered, while pharmacodynamic factors define the tissue response to a given concentration. Both are subject to considerable uncertainty when dealing with a new compound, so that it is not in general possible to predict reliably the response of human subjects to a new compound solely from studies on experimental animals. This uncertainty can be reduced substantially by understanding its mechanisms of action. Greater accuracy in predicting the metabolism of foreign compounds in man is also likely to be achieved by studies of the species variation of cytochrome P450s, and by the use of human hepatocytes and other cell lines to study xenobiotic metabolism.     

Genetic factors for the span of apprehension test: a study of normal twins.

The Partial Report Span of Apprehension test has been found to detect cognitive deficits in some first degree relatives of schizophrenic patients. To assess the relative contribution of genetic vs. environmental factors on this measure, 19 monozygotic and 14 dizygotic female twin pairs, selected from a normal population, were tested on the Span of Apprehension test and an IQ test. Both Span of Apprehension test performance and IQ score had high heritabilities: 0.65 and 0.71, respectively. The mode of transmission for performance on the Span of Apprehension test appears to operate in a nonadditive manner. A multivariate behavioral-genetic model applied to the Span of Apprehension and IQ measures indicated that slightly less than half of the genetic effects important for the Span of Apprehension test are found in common with the genetic factors important for IQ. The phenotypic correlation between the Span of Apprehension and IQ measures can be attributed entirely to genetic factors. The influence of unique genetic components in the performance of the Span of Apprehension test in the general population heightens the promise of this measure as a genetic marker for schizophrenia.     

Immediate effects of intravenous clomipramine on sleep and sleep-related secretion in depressed patients

An i.v. challenge dose of clomipramine (12.5 mg) was given to eight outpatients with major depression. The procedure facilitated the examination of all-night sleep and sleep-related neuroendocrine changes (cortisol, growth hormone, and prolactin). In comparison to baseline saline nights, the patients experienced a profound suppression of rapid eye movement (REM) sleep throughout the night with no rebound recovery in the second half of the night. Furthermore, REM-suppressing effects were noted on the following no-drug night. In contrast, little effect on delta wave sleep was found, except for increased consolidation of delta waves within stage 3 and 4 sleep. Delta sleep measures were significantly correlated with levels of cortisol and growth hormone.     

Surgical implications of cerebral dysgenesis

Cerebral dysgenesis encompasses varied disorders of brain development. Based on the understanding of these conditions provided by histopathologists, embryologists, radiologists and developmental pediatricians, surgeons are able to appropriately assist in the care of these patients. The surgeon can offer assessment of the ventriculomegaly that commonly accompanies cerebral dysgenesis in addition to providing methods to control hydrocephalus, to reconstruct cranial and facial malformations and to remove dysfunctional tissue. For most patients, surgical intervention is only one of the many factors that determine developmental prognosis. Based on the foundation built by other specialists, this review discusses cerebral dysgenesis from the perspective of historical and current surgical interventions.