Cortical blindness in toxaemia of pregnancy: findings on computed tomography

Two patients with toxaemia of pregnancy presented with cortical blindness. Immediate cranial computed tomography (CT) demonstrated bilateral hypodense areas in the occipital lobes. Both patients underwent Caesarean section for delivery. There was gradual and complete recovery of vision, together with CT documentation of resolution of the cerebral changes, indicative of the reversible nature of the ischaemic lesion.

Claude's syndrome: clinical and computed tomography correlations

A patient with Claude's syndrome (ipsilateral fascicular third nerve palsy with contralateral ataxia) in whom computed tomography demonstrated a discrete infarct in the paramedian rostral mesencephalic tegmentum is reported. The vascular supply of the rostral mesencephalon is discussed.

Prizidilol. Metabolism by cytochrome P-450 and acetyltransferase

The hepatic microsomal cytochrome P-450 enzyme system bound and metabolized the experimental drug prizidilol. Prizidilol bound to two distinct sites on cytochrome P-450. At low concentrations (less than ca 20 microM), prizidilol bound to the substrate binding site of the enzyme and produced a Type I difference spectrum. At higher concentrations (25-190 microM), prizidilol bound to the oxygen binding site of the enzyme and produced a type II difference spectrum. Prizidilol stimulated hepatic microsomal CO-inhibitable NADPH oxidation. Prizidilol metabolism by hepatic microsomes assessed by prizidilol disappearance was inhibited by CO:O2 (80:20; v/v), SKF 525-A and metyrapone. Prizidilol disappearance was monitored using a newly developed TLC assay for prizidilol following derivatization with quinolin-3-al. The apparent binding constants (Ks), maximum extents of binding (delta Amax), Michaelis constants (Km) and maximum velocities (Vmax) for the interaction of prizidilol with hepatic microsomal cytochrome P-450 were assessed in rats pretreated or not with the inducing agents phenobarbital, beta-naphthoflavone and pregnenolone-16 alpha-carbonitrile. For the differently pretreated rats the apparent Ks values for the type I site and the type II site and the apparent Km were ca 3 microM, 150 microM and 2 microM, respectively. Apparent Vmax values varied from 20 to 70 pmol per min per mg microsomal protein. The observed effects of induction on the apparent equilibrium constants and maximum extents of binding and metabolism of prizidilol indicate that the forms of cytochrome P-450 induced by phenobarbital, pregnenolone-16 alpha-carbonitrile or beta-naphthoflavone do not play a major role in the metabolism of prizidilol. Prizidilol was also metabolized by hepatic cytosolic N-acetyltransferase. The apparent Km values for prizidilol and acetyl CoA were 0.8 and 22 microM. Apparent Vmax values were 50 and ca 2 pmol per min per mg protein for partially purified transferase and cytosol, respectively. It is concluded that the rates of oxidation and acetylation of this drug would be expected to be relatively low, being limited by low apparent Vmax values for both oxidation and acetylation.

Herpes zoster and its neurological complications

Ninety-three Chinese patients with cutaneous herpes zoster were seen during a 4-year period. Thoracic zoster occurred most commonly, followed by ophthalmic, cervical and lumbosacral zoster. Neurological complications were present in eleven patients (11.8%), the commonest being Ramsay-Hunt syndrome and segmental limb paresis. The clinical picture, pathogenesis, treatment and outcome of segmental limb paresis, myelitis and delayed contralateral hemiparesis following zoster ophthalmicus are discussed. Nine immunocompromised patients received intravenous adenine arabinoside (vidarabine) or acycloguanosine (acyclovir), and no cutaneous or visceral spread occurred in these patients.

High dose ketoconazole in the treatment of cerebral aspergilloma

A 32-year-old Chinese woman with bilateral occipital aspergilloma was treated successfully with high dose ketoconazole (1200 mg/day) for six months in conjunction with amphotericin B and 5-fluorocytosine. No unacceptable side effects occurred. The use of high dose ketoconazole could be considered in CNS aspergillosis unresponsive to conventional anti-fungal therapy.

Apoplectic intracerebral hemorrhage: an unusual complication of cerebral radiation necrosis

A patient with apoplectic intracerebral hemorrhage from delayed cerebral radionecrosis is reported. The histological changes of abnormal telangiectatic vessels account for the unusual clinical presentation. The pathogenesis and treatment of radionecrosis are discussed, and massive hemorrhage as a complication is emphasized.

Spinal cord compression in multiple myeloma: who gets it?

Of 97 Chinese patients with multiple myeloma seen over a 12-year period, 23.7% were found to have cauda equina or spinal cord compression (SCC). Predictive features for SCC include paraprotein type, hemoglobin level, and the extent of bone lesion at initial hematological diagnosis. A discriminant function derived from this analysis can be used to predict the likelihood of SCC with 79% accuracy. It is postulated that when the cortex is more involved than the medulla in a vertebra, it will predispose to SCC while hemopoiesis is relatively preserved. Our patients presented late with advanced neurological deficit so that treatment was unsatisfactory. It is emphasised that early recognition of back pain and neurological symptoms is essential, as any delay would jeopardize the chance of neurological recovery.

Tuberculous meningitis associated with meningeal tuberculoma

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Cerebral haemorrhage in a urban Chinese population

A prospective study of Chinese patients aged 20-70 years reveals that at least 30.5% of all strokes are due to cerebral haemorrhage. Compared to previous studies in Caucasians, there is both a proportional and absolute increase in cerebral haemorrhage amongst all strokes, alert strokes, or those who presented with just a lacunar syndrome. The cause for this increase is unclear but genetic, dietary, and other environmental factors may be involved.

Reexamination of the activation of yeast proteinase B at pH 5: loss of inhibition effect of proteinase B inhibitors

The activation of yeast proteinase B at pH 5 has been suggested to be due to the degradation of a specific inhibitor for the enzyme, IB, by proteinase A. However, we found that when pepstatin, which completely inhibits proteinase A, was included in the pH 5 activation mixture, the same time-dependent activation of proteinase B was observed. Furthermore, proteinase B preparations that were void of proteinase A activity were still activated by incubation at pH 5. We found that the activation of proteinase B at pH 5 was due primarily to the irreversible loss of inhibitory effect of IB, which can be resolved by isoelectrofocusing into four distinct bands with isoelectric points of 4.6, 6.1, 6.8 and 7.6. These four forms of IB showed varying degrees of stability at pH 5, which may explain some of the differing observations reported in the past.

Interaction between carbamazepine and dextropropoxyphene

Serious side effects may result from the concurrent administration of the usual dosage of carbamazepine and dextropropoxyphene. Three cases are reported and the mechanisms and implications discussed.

Interaction between L-aspartic acid and L-asparaginase from Escherichia coli: binding and inhibition studies

Experiments using equilibrium dialysis and fluorescence quenching provided direct evidence that approximately four moles of L-aspartic acid were bound per mole of tetrameric L-asparaginase from Escherichia coli, with a dissociation constant on the order of 60-160 microM. In addition, a set of weaker binding sites with a dissociation constant in the millimolar range were detected. Kinetic studies also revealed that L-aspartic acid inhibited L-asparaginase competitively, with an inhibition constant of 80 microM at micromolar concentrations of L-asparagine; at millimolar concentrations of the amide, an increase in maximal velocity but a decrease in affinity for L-asparagine were observed. L-Aspartic acid at millimolar levels again displayed competitive inhibition. These and other observations suggest that L-aspartic acid binds not only to the active site but also a second site with lower intrinsic affinity for it. The observed "substrate activation" is most likely attributable to the binding of a second molecule of L-asparagine rather than negative cooperativity among the tight sites of the subunits of this tetrameric enzyme. Further support for L-aspartic acid binding to the active site comes from experiments in which the enzyme, when exposed to various group-specific reagents suffered parallel loss of catalytic activity and in its ability to bind L-aspartic acid. Different commercial preparations of Escherichia coli L-asparaginase were found to contain approximately 2-4 moles of L-aspartic acid; these were incompletely removed by dialysis, but could be removed by transamination or decarboxylation. Efficiency of dialysis increased with increasing pH. Taken together, this set of results is consistent with the existence of a covalent beta-aspartyl enzyme intermediate.

Wilson's disease in a patient presenting with skeletal abnormalities

We present a case with extensive bone and joint involvement in the form of bone fragmentation and osteochondritis dessecans. The case was subsequently documented to be that of Wilson's disease. Biochemical screening was also carried out on the family members and the results of the findings are presented.

Small cerebellar strokes may mimic labyrinthine lesions

Thirty nine cases of cerebellar infarct and haemorrhage were seen over a period of 3 years. Of these, 69% had no impairment of consciousness. Six cases had nystagmus and gait ataxia as their only abnormal signs. Small cerebellar strokes may present with only vertigo, unsteady gait, and unidirectional nystagmus, thus mimicking labyrinthine lesions. Care in managing vertigo attacks in patients with risk factors for cerebrovascular disease appears to be warranted.

Electronystagmogram is useful in the diagnosis of vertebrobasilar and carotid transient ischaemic attacks

Electronystagmogram examination of patients with transient ischaemic attacks or infarcts in the carotid and vertebrobasilar system revealed significantly increased number of patients with reduced caloric response, abnormal optokinetic nystagmus, saccadic dysmetria and presence of central nystagmus in patients with ischaemia of the posterior circulation. Using the presence of such abnormality as criterion for confirming posterior circulation ischaemia in suspected cases, we have correctly identified 67% of cases of vertebrobasilar infarct, 44% of the transient ischaemic attacks, 83% of carotid infarct and 96% of the carotid transient ischaemic attacks. Electronystagmogram findings of brainstem/cerebrallar system abnormality were found in 36% of transient ischaemic attacks with vertigo, and 50% of infarcts associated with vertigo. Thus Electronystagmogram studies are useful in localising the site of lesion in patients with suspected vertebrobasilar disease or with ischaemic attacks of undetermined territory, and in differentiation of vertigo due to definite cerebrovascular disease from peripheral causes of vertigo.

Pontine ataxic hemiparesis, a lateral penetrator syndrome?

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The calmodulin-dependent activation and deactivation of the phosphoprotein phosphatase, calcineurin, and the effect of nucleotides, pyrophosphate, and divalent metal ions. Identification of calcineurin as a Zn and Fe metalloenzyme

Studies on the interaction of calcineurin with its activator, calmodulin, showed that the 1:1 complex is the activated species. Concomitant with activation, a time-dependent deactivation of the phosphatase was observed. The process followed first order kinetics and was dependent on the presence of both Ca2+ and calmodulin. The deactivation rate constant at pH 7.6 and 30 degrees C was 0.06 min-1, which was increased by the substrate, p-nitrophenylphosphate (Km = 11 mM), to 0.47 min-1. PPi and nucleotides inhibited the enzyme competitively and accelerated the deactivation. The first order rate constant was increased to 2.3 min-1 by PPi (Ki = 55 microM) and to 8.0 min-1 by ADP (Ki = 0.94 mM). A theory dealing with the deactivation (applicable to chemical modification, etc.) of an enzyme in the absence and presence of various ligands is presented. The deactivated enzyme remained bound to calmodulin and was not reactivated by dissociation-reassociation of the calcineurin-calmodulin complex. Calcineurin was found to contain covalently bound phosphate; however, no difference in its content was detected upon deactivation, indicating that self-dephosphorylation was not involved. The deactivation could be reversed, as well as prevented, by divalent metal ions such as Ni2+ and Mn2+. Atomic absorption spectroscopy revealed nearly stoichiometric amounts of tightly bound Fe and Zn (but little other ions) on purified calcineurin, which remained bound during the calmodulin-dependent deactivation; removal of tightly bound metals is, therefore, not the cause of deactivation. Our results indicate that calcineurin is a metallophosphatase and not simply a Ca2+- and calmodulin-stimulated enzyme. In addition to the nondissociable Zn and Fe and the Ca2+ bound to the B subunit and calmodulin, the enzyme requires a divalent metal ion for structural stability and full activity.

Mammalian brain phosphoproteins as substrates for calcineurin

Calcineurin, a Ca2+/calmodulin-dependent phosphoprotein phosphatase found in several tissues, is highly concentrated in mammalian brain. In an attempt to identify endogenous brain substrates for calcineurin, kinetic analyses of the dephosphorylation of several well-characterized phosphoproteins purified from brain were performed. The proteins studied were: G-substrate, a substrate for cyclic GMP-dependent protein kinase; DARPP-32, a substrate for cyclic AMP-dependent protein kinase; Protein K.-F., a substrate for a cyclic nucleotide- and Ca2+-independent protein kinase; and synapsin I, a substrate for cyclic AMP-dependent (site I) and a Ca2+/calmodulin-dependent protein kinase (site II). Calcineurin dephosphorylated each of these proteins in a Ca2+/calmodulin-dependent manner. Similar Km values were obtained for each substrate: G-substrate, 3.8 microM; DARPP-32, 1.6 microM; Protein K.-F., approximately 3 microM (S0.5); synapsin I (site I), 7.0 microM; synapsin I (site II), 4.4 microM. However, significant differences were obtained for the maximal rates of dephosphorylation. The kcat values were: G-substrate, 0.41 s-1; DARPP-32, 0.20 s-1; Protein K.-F., 0.7 s-1; synapsin I (site I), 0.053 s-1; synapsin I (site II), 0.040 s-1. Comparisons of the catalytic efficiency (kcat/Km) for each substrate indicated that DARPP-32, G-substrate, and Protein K.-F. are all potential substrates for calcineurin in vivo.

Alternating skew deviation associated with Mandrax overdosage

Alternating skew deviation has been described in patients with pretectum and mesodiencephalon lesions. Total external ophthalmoplegia has been reported in patients consequent to oral or intravenous administration of diphenylhydantoin and amitriptyline. This case report presents a patient with alternating skew deviation as a result of Mandrax ingestion.

On the mechanism of activation of the ATP X Mg(II)-dependent phosphoprotein phosphatase by kinase FA

The mechanism of activation of the Mg(II) X ATP-dependent phosphatase by the kinase FA has been investigated. The inactive protein phosphatase can be represented as FC X M where FC is the inactive catalytic component and M is the heat-stable modulator protein (also known as inhibitor-2). Phosphorylation of the modulator protein is demonstrated during activation of FC X M. In addition, continuous ATP hydrolysis during the activation is observed. This suggests that a cyclic phosphorylation-dephosphorylation reaction is continuously occurring during the activation. It is proposed that phosphorylation of the modulator protein causes an isomerization in FC to generate an active phosphatase. The activated phosphatase is capable of dephosphorylating the phosphorylated modulator. Upon dephosphorylation of modulator, the active phosphatase returns to its inactive form via a slow isomerization.

An optimized continuous assay for cAMP phosphodiesterase and calmodulin

A continuous spectrophotometric assay for cAMP phosphodiesterase has been optimized and adopted for assaying calmodulin in biological samples. This method utilizes the coupled enzyme reactions of myokinase, pyruvate kinase, and lactic acid dehydrogenase. The effective molar extinction coefficient for this method is 1.25 X 10(4) at 340 nm. A point-assay method capable of handling a large number of samples has also been established. This same procedure can also be adopted for the assay of calcineurin and other calmodulin-binding proteins.

Ataxic-hemiparesis, localization and clinical features

Five additional cases of ataxic-hemiparesis are reported. In 3 cases, computed tomography showed an area of decreased attenuation in the posterior limb of the internal capsule, and in 1 case, 2 areas of attenuation in the corona radiata. A review of previously reported cases suggest that brainstem ataxic-hemiparesis may be separated from supratentorial forms of ataxic-hemiparesis by the presence of nystagmus, dysarthria, cranial neuropathy, and the absence of sensory abnormality.

Isolated facial palsy: a new lacunar syndrome

Three cases of sudden isolated upper motor neuron facial palsy and two with associated pseudobulbar palsy have been seen. All were without significant limb weakness. Computed tomography demonstrated small deep infarcts in the internal capsular/corona radiata regions. Pure upper motor neuron facial palsy may be another lacunar syndrome, due to a lesion in the internal capsule or corona radiata.

Uridine phosphorylase from Escherichia coli B.: kinetic studies on the mechanism of catalysis

Using a highly purified enzyme preparation of uridine phosphorylase from Escherichia coli B, we have performed detailed kinetic studies which include initial-velocity and product-inhibition experiments in the forward and reverse directions of the reaction. These studies indicate a rapid-equilibrium random mechanism for this enzyme with the formation of an enzyme . uracil phosphate abortive complex. Lack of formation of the enzyme . uridine . ribose-1-phosphate abortive complex suggests that the ribosyl moiety of the two ligands compete for the same binding site. The random mechanism is different from the ordered addition of substrates found for uridine phosphorylase from other sources. All the kinetic constants in the forward and reverse directions and the Keq of reaction for E. coli uridine phosphorylase are reported herein.

Meningitis caused by Flavobacterium meningosepticum after transsphenoidal hypophysectomy with recovery

Adult meningitis caused by Flavobacterium meningosepticum is rare. Five cases have been reported in the literature. The case reported herein developed in a woman after a transsphenoidal hypophysectomy. The isolate was resistant to erythromycin. Treatment with oral rifampicin combined with intravenous chloramphenicol and cefoperazone resulted in complete recovery.

Activation of calcineurin by nickel ions

Calcineurin, a Ca2+- and calmodulin-dependent phosphoprotein phosphatase, was dramatically activated by Ni2+ ions. Activation by Ni2+ was independent of calmodulin and was not reversed by high concentrations of chelators. With histone H1 as substrate, the Km's obtained with Ca2+ and Ni2+ were 2.2 and 4.2 microM, and the kcat's were 0.5 and 24.3 min-1, respectively. Similar to the Ca2+- and Mn2+-supported reactions, the presence of calmodulin caused a 20-fold activation of the Ni2+-activated calcineurin over the basal rate. Incubation of calcineurin with Ni2+ resulted in 30% quenching of its Trp-fluorescence. This effect also was independent of calmodulin and not reversed by chelators. The results suggest that the Ni2+ ions are tightly bound to calcineurin and the effects may be physiologically relevant.

Streptococcus suis meningitis. An important underdiagnosed disease in Hong Kong

Streptococcus suis has been identified as the most common cause of meningitis in adults in Hong Kong. The disease is characterized by occupational exposure to pigs or pork. It occurs in summer, and is associated with early, severe, sensory deafness, arthritis, uveitis, and loss of balance. Examination of the cerebrospinal fluid may show an elevated white cell count with a predominance of either polymorphs or lymphocytes. Misinterpretation of the microbiological findings by inexperienced staff members may lead to a failure to correctly diagnose this disease. This is the first report of a series of cases of Strept. suis meningitis outside western Europe. Health authorities are urged to be aware of this disease in pork-consuming countries.

Peripheral neuropathy in the elderly: a clinical and electrophysiologic study

Fifty-nine elderly patients with clinical and neurophysiologic evidence of peripheral neuropathy were reviewed. Diabetes, alcoholism and malignancy were the important etiologic factors, but other causes of acquired neuropathy such as drugs, autoimmune disease, and acute or chronic demyelinating neuropathy continue to warrant attention. Postural hypotension associated with neuropathy occurred in three patients with diabetes and one patient with lymphoma. Prognosis for the neuropathies did not seem to be adversely affected by age.

Mechanism of activation of cyclic nucleotide phosphodiesterase: requirement of the binding of four Ca2+ to calmodulin for activation

Kinetic studies on the activation of cyclic nucleotide phosphodiesterase (3',5'-cyclic-nucleotide 5'-nucleotidohydrolase, EC 3.1.4.17) as a function of calmodulin and Ca2+ concentrations have been carried out. A general approach to analyzing the mechanism of activation, which takes into consideration the various interactions among phosphodiesterase and calmodulin liganded with Ca2+ to differing degrees, is presented. The method is applicable to other calmodulin-regulated enzyme systems. Our kinetic analysis reveals that all four Ca2+ must be bound to calmodulin for the protein to form an activated complex with phosphodiesterase. The mechanistic and regulatory advantages of having four Ca2+ sites on calmodulin can be briefly stated as follows. (i) With the enzyme--calmodulin--Ca4(2+) complex as the dominant active species, the activation of phosphodiesterase as a function of Ca2+ concentration is highly cooperative. This phenomenon serves as an effective on/off switch for phosphodiesterase activation. (ii) At normal cellular levels of Ca2+ (less than 0.1 microM), phosphodiesterase and calmodulin do not form a complex. Thus, the distribution of calmodulin among its various target enzymes is reshuffled for each Ca2+ surge. (iii) The affinity between the enzyme and the fully liganded calmodulin (0.1-1 mM) is 10(4)-10(5) times better than that in the absence of Ca2+ (greater than or equal to 10 microM). The tremendous increase in affinity can be achieved rather easily through a 10- to 20-fold increase in the affinity of Ca2+ for the enzyme-calmodulin complex in each of the four binding steps.

Transient kinetic analysis of the catalytic cycle of alkaline phosphatase

Transient kinetic studies were carried out to elucidate the catalytic cycle of Escherichia coli alkaline phosphatase at ph 8.3, 10 degrees C, and to evaluate the rate constants for the individual steps. Using a rapid mixing cell, we were able to detect the burst phase of the reaction, which could not be obtained at alkaline ph values with conventional mixing devices. Analysis of the burst phase revealed that the equilibrium of the initial binding of the substrate, 4-methylumbelliferyl phosphate, to the enzyme is attained rapidly, and that the production of the alcohol, 4-methylumbelliferone, is fast. Analysis of the steady state phase of the reaction yielded a phosphate release rate constant which agrees very well with the kcat determined by initial rate studies. Dephosphorylation of the phosphoryl enzyme prepared at pH 5.7 was studied by the pH-jump technique, using a three-syringe stopped flow apparatus. The results showed that the dephosphorylation step is not rate-limiting in the catalytic cycle and that the presence of substrates or inhibitor has no effect on this step. The lack of effect of substrates on the rate of dephosphorylation and on the rate of phosphate dissociation indicates that the flip-flop mechanism, in which the product release is supposedly facilitated by the binding of a 2nd molecule of substrate, is not valid for alkaline phosphatase. Kinetic constants for various steps in the catalytic cycle of alkaline phosphatase at pH 8.3, 10 degrees C, are reported and a reaction scheme which is in harmony with previous observations from other laboratories is described.

Confirmatory evidence for the association of hepatitis B surface antigen with antigenic determinants reactive with antibodies present in some anti-HBe-positive sera

Spherical 20 nm diam. particles of hepatitis B surface antigen (HBsAg), purified from some sera positive for hepatitis B e-antigen (HBeAg), are associated with antigenic determinants reacting with antibodies frequently present in sera containing anti-HBe. Treatment of HBsAg with the detergent Sarcosyl increased the exposure of these determinants which could be differentiated from HBeAg on the basis of immunological specificity and sensitivity to reduction and alkylation. The presence of these determinants appeared to be restricted to a subpopulation of HBsAg associated with IgG and albumin.

Studies on the mechanism of the glutamine-dependent reaction catalyzed by asparagine synthetase from mouse pancreas

Initial velocity and product inhibition studies were conducted with the glutamine-dependent reaction of asparagine synthetase from mouse pancreas. Double reciprocal plots of glutamine versus either aspartate or ATP were parallel, while aspartate versus ATP gave intersecting patterns. These patterns are indicative of a hybrid ping-pong mechanism consisting of a glutaminase partial reaction and a sequential catalysis involving aspartate and ATP. Inhibition patterns of the four products, glutamate, AMP, PPi, and asparagine, versus each of the three substrates are consistent with a hybrid Uni Uni Bi Ter Ping Pong Theorell-Chance mechanism where the glutaminase reaction occurs first and aspartate binds to the enzyme before ATP in the sequential segment. PPi is the first product released in the Theorell-Chance reaction, which is followed by the ordered release of AMP and asparagine. Product inhibition patterns also indicate the formation of E . NH3 . Asn and E . NH3 . Asp . AMP abortive complexes. Although an amide site (for glutamine and asparagine), presumably responsible for the glutaminase reaction, an acid site (for glutamate and aspartate), and a nucleotide site are involved in the overall catalysis, the "two-site" ping-pong mechanism is incompatible with the experimentally observed product inhibition patterns.

Isolation and characterization of the nuclear matrix in Friend erythroleukemia cells: chromatin and hnRNA interactions with the nuclear matrix

Nuclear matrices from undifferentiated and differentiated Friend erythroleukemia cells have been obtained by a method which removes DNA in a physiological buffer. These matrices preserved the characteristic topographical distribution of condensed and diffuse "chromatin" regions, as do nuclei in situ or isolated nuclei. Histone H1 was released from the nuclear matrix of undifferentiated cells by 0.3 M KCl; inner core histones were released by 1 M KCl. Nuclear matrix from differentiated cells did not maintain H1, and histone cores were fully released in 0.7 M KCl. KCl removed the core histones as an octameric structure with no evidence of preferential release of any single histone. Electron microscopy of KCl-treated matrix revealed no condensed regions but rather a network of fibrils in the whole DNA-depleted nuclei. When nuclear matrices from both types of cell were exposed to conditions of very low ionic strength, inner core histones and condensed regions remained. These observations support the contention that inner core histones are bound to matrix through natural ionic bonds or saline-labile elements, and that these interactions are implicated in chromatin condensation. hnRNA remained undegraded and tenaciously associated to the matrix fibrils, and was released only by chemical means which, by breaking hydrophobic and hydrogen bonds, produced matrix lysis. Very few nonhistone proteins were released upon complete digestion of DNA from either type of nuclei. The remaining nonhistone proteins represent a large number of species of which the majority may be matrix components. The molecular architecture in both condensed and diffuse regions of interphase nuclei appears to be constructed of two distinct kinds of fibers; the thicker chromatin fibers are interwoven with the thinner matrix fibers. The latter are formed by a heteropolymer of many different proteins.

Spinal cord tumours in the elderly

Spinal cord tumours in patients over 65 years of age are mostly due to metastatic lesions when maximum deficit occurs within eight weeks. Benign tumours have a more chronic progressing course, are mostly in the thoracic region and, unlike younger patients, are overwhelmingly meningiomas. Although uncommon, benign spinal cord tumours should be recognised as a cause of gait deterioration in the elderly patient, as they responde well to surgery.