Absence of magnetic resonance imaging evidence of pontine abnormality in infantile autism

In vivo studies involving magnetic resonance imaging and studies of neuropathologic specimens have shown that autism is most consistently associated with developmental hypoplasia of the neocerebellum. We investigated whether the cerebellar hypoplasia was accompanied by gross structural abnormalities in the major input (cerebrocerebellar) and output (cerebrorubral) pathways to the cerebellum by measuring the area of the ventral pons (including the pontine nuclei and the transverse fibers) and the midbrain on midsagittal magnetic resonance images in 34 autistic and 44 subjects. The area of the entire pons and several regions of interest within the midbrain (including the superior and inferior colliculi) were also determined with midsagittal magnetic resonance images. We found no significant difference between measurements of the pons and midbrain in autistic and control subjects. Our data show no evidence of gross anatomic abnormalities in the input and output pathways to the cerebellum in autism, a finding that is consistent with previous studies of neuropathologic specimens; rather, the reduced size of the neocerebellum in autism appears to be the result of maldevelopment within the cerebellum itself.

Emergence and propagation of interictal spikes in the subcortically denervated hippocampus

Spontaneous and evoked field potentials and cellular discharges of the subcortically denervated dorsal hippocampus were studied by multisite recordings in the freely behaving rat. Characteristic short-duration (< 100 ms), large-amplitude (up to 10 mV) transients, termed interictal spikes (IIS), were seen after fimbria-fornix (FF) lesion. Both pyramidal cells and putative interneurons fired maximally during IIS, with some interneurons sustaining long bursts (up to 400 ms) of high-frequency discharges (400-600 Hz) after the IIS. The speed of propagation of IIS along the longitudinal axis of the hippocampus varied from 0.2 m/s to > 3 m/s. The majority of IIS (type 1) could be accounted for by an enhanced activity of the intrahippocampal associational systems; a second class of IIS (type 2) had positive polarities in the stratum radiatum of CA1 and CA3 and propagated very rapidly (> 1.5 m/s). The authors propose that type 2 IIS reflect somatic depolarization and discharge of pyramidal neurons due to nonsynaptic (probably ephaptic) effects. Ephaptic interactions may also explain the longitudinal propagation of IIS at speeds higher than the conduction velocities (0.5 m/s) of hippocampal fiber systems. IIS emerged during the first 3 weeks after fimbria-fornix lesion, their incidence reaching a plateau of 2/min thereafter. During the same time period, paired-pulse suppression increased in the dentate gyrus. The amplitude of test responses to angular bundle stimulation was potentiated by small-amplitude IIS but suppressed by large-amplitude IIS. The incidence of IIS was significantly suppressed during walking relative to standing still. Tetanic stimulation of the angular bundle or handling-induced stress resulted in a 10- to 20-fold increase in the incidence of IIS that lasted for about 30 minutes. There was a negative correlation between evoked field PSP slope and population spike amplitude in the dentate gyrus of FF-lesioned rats; this correlation was positive in intact rats. The authors attribute the above pathophysiological changes to sprouting of both excitatory and inhibitory GABAergic pathways as a result of denervation of the intrahippocampal circuitry. They hypothesize that the majority of the observed physiological alterations can be traced to a weakening of feedforward inhibition coupled with an enhancement of feedback inhibition and excitation.

Alkaline reflux gastritis

Alkaline reflux gastritis and the symptoms associated with alkaline reflux gastritis have been reported in the medical literature since shortly after Billroth successfully performed his first gastrectomy in the 1880s. The disease process is produced by, or at least is associated with, the reflux of alkaline secretions into the gastric remnant. Although it occurs after any procedure that ablates the pylorus including pyloroplasty, it would appear to be most common after a Billroth II gastrojejunostomy. How the alkaline secretions cause the gastritis is still controversial. Clearly, the most effective therapy is to reroute the secretions from the biliary tract, pancreas, and duodenum so that they will not reflux into the gastric remnant. This is most effectively accomplished by a Roux-en-Y gastrojejunostomy with the afferent limb measuring at least 18 inches (40 cm). The surgeon and the patient should be aware that the construction of such a gastric outlet channel is associated with delayed gastric emptying. The etiology of this impaired emptying is also controversial. If the patient has symptoms of dumping (either early or late), these symptoms may also be abated using the Roux limb. At least 40% of patients will have gastric outlet obstruction. Supportive therapy is appropriate in the majority of these patients.

Analysis of DNA restriction fragments greater than 5.7 Mb in size from the centromeric region of human chromosomes

Pulsed electrophoresis was used to study the organization of the human centromeric region. Genomic DNA was digested with rare-cutting enzymes. DNA fragments from 0.2 to greater than 5.7 Mb were separated by electrophoresis and hybridized with alphoid and simple DNA repeats. Rare-cutting enzymes (Mlu I, Nar I, Not I, Nru I, Sal I, Sfi I, Sst II) demonstrated fewer restriction sites at centromeric regions than elsewhere in the genome. The enzyme Not I had the fewest restriction sites at centromeric regions. As much as 70% of these sequences from the centromeric region are present in Not I DNA fragments greater than 5.7 and estimated to be as large as 10 Mb in size. Other repetitive sequences such as short interspersed repeated segments (SINEs), long interspersed repeated segments (LINEs), ribosomal DNA, and mini-satellite DNA that are not enriched at the centromeric region, are not enriched in Not I fragments of greater than 5.7 Mb in size.

Cancerous colonic polyps. "Hands on" or "hands off?"

Management of the malignant colonic polyp remains a subject for debate even after almost two decades of experience. Some researchers believe all patients should have a colonic resection; others argue that only certain cases call for laparotomy, while still others hold for a selective approach but with varying criteria. Therefore, a survey has been made of current practice and opinion from the time colonoscopic polypectomy was introduced in 1969 to the present. The authors have reviewed a sizable segment of their experience, dividing cases of malignant polyps into two broad categories: those in which complete polypectomy was followed by bowel resection; and those undergoing polypectomy alone. The determinants leading to one course or the other were analyzed, as were the results.

Seasonal energetics of opossums (Didelphis virginiana) in Ohio

1. Female opossums acclimatized to each of the four seasons were not significantly different (P greater than 0.05) in oxygen consumption at a Ta of 0 degrees C; the overall average was 0.66 +/- 0.1 ml O2/g-hr. 2. Body weight decreased by 27% from autumn to spring; pelage density increased in winter, but thermal conductance changed very little between seasons. 3. Respirometry revealed no evidence of thermoregulatory adjustments in opossums acclimatized to winter in Ohio.

Human T cell clones express functional homing receptors required for normal lymphocyte trafficking

To function efficiently in vivo, lymphocytes must circulate from the blood into lymphoid tissues and other sites of immune reaction. Herein, we show that human cytotoxic and helper T cell clones and lines, maintained in vitro with IL-2, express the functional capacity to recognize and bind to high endothelial venules (HEV), a capacity essential for lymphocyte exit from the blood, and hence for normal lymphocyte trafficking. The expression of functional homing receptors distinguishes human T cell clones from their murine counterparts, which uniformly lack receptors for HEV and are unable to migrate normally from the blood in vivo. The results raise the possibility that human T cell clones may be more effective in mediating in vivo immune responses than is suggested by murine models.

Analysis of Sendai virus mRNAs with cDNA clones of viral genes and sequences of biologically important regions of the fusion protein

cDNA clones representing five of the genes of Sendai virus (P, HN, NP, F, and M) were isolated and used to identify the viral mRNAs by hybridization. Five mRNAs that were monocistronic transcripts of these genes were identified. A sixth transcript, which was identified on the basis of size and of hybridization to viral RNA but not to the cDNA of the other five genes, is thought to represent the message for the L protein. In addition, polycistronic transcripts of the NP and P genes and of the M and F genes were also found. The latter establishes the position of the F gene adjacent to the M gene; these results confirm and extend the previously reported partial gene order of the virus. Nucleotide sequences and derived amino acid sequences of two biologically important regions of the F protein--approximately 25% of F proximal to its COOH terminus and the region spanning the site of the proteolytic cleavage that activates the fusion activity of the protein--are presented. The F protein has an unusually large "cytoplasmic domain" of 42 amino acids beyond the hydrophobic region by which it is anchored in the viral membrane. A single possible trypsin cleavage site was found at the junction of the F1 and F2 polypeptides, and 26 hydrophobic amino acids extend from this cleavage site at the NH2 terminus of the F1 polypeptide.

The use of rotating gratings for the treatment of amblyopia: a clinical trial

The use of rotating gratings for the treatment of amblyopia was subjected to a controlled clinical trial. A treatment group (N = 19) observed rotating gratings for 15 min per week for 10 weeks and a control group (N = 19) observed a blank rotating disk for the same period. Both groups of amblyopes performed visually guided tasks to maintain their interest during treatment. Data were acquired in a double-masked manner. A second control group (N = 4) underwent weekly acuity evaluation without any form of treatment. Visual acuity was evaluated before and after each session and analyzed with a linear regression fit to a probit transform by a minicomputer. By using a criterion change in acuity of 10% Snell Sterling, we found no significant change of acuity in any group or between groups. These results demonstrate that rotating gratings are an insignificant variable in the treatment of amblyopia.

Activation of the Sendai virus fusion protein (f) involves a conformational change with exposure of a new hydrophobic region

The F protein of paramyxoviruses is actively involved in the induction of membrane fusion. This fusion may be between viral and cellular membranes, as in the initiation of infection or in virus-induced lysis of erythrocytes, or between the plasma membranes of different cells. The F protein is activated by proteolytic cleavage to yield two disulfide-linked polypeptides (F1 and F2); however, its mechanism of action is not clear. In the present study, the conformations of the inactive, uncleaved precursor of glycoprotein (F0), and the active, cleaved form (F1,2) have been compared. The UV circular dichroism spectra of the two forms of the F protein indicate that cleavage results in a conformational change. Detergent-binding studies by velocity sedimentation analysis of Triton X-100-protein complexes revealed an increase in exposed hydrophobic surface of the protein on cleavage. The inactive F0 bound an estimated 27 molecules of Triton X-100/F polypeptide; these molecules are presumably bound to the hydrophobic region of the glycoprotein that anchors the spike-like protein in the virus membrane and that is common to both forms of F. The active form, F1,2, bound 67 molecules of Triton X-100. This increase in the number of detergent binding sites upon F protein activation indicates the presence of a hydrophobic region that is peculiar to the active form, and that may be of functional significance in the membrane fusion reaction.

Role of paramyxovirus glycoproteins in the interactions between viral and cell membranes

Interactions of paramyxoviruses with cell membranes are mediated by two virus-coded glycoproteins of the virus membrane: HN and F. The HN protein is responsible for the attachment of virions to the membrane of the target cell. The F protein mediates fusion between the virus membrane and the cell membrane, and this step is essential for the infection process as well as for the expression of other biological activities of paramyxoviruses, i.e., cell fusion and hemolysis. The activity of F is dependent on the proteolytic processing of a precursor (F0) to yield two disulfide-linked subunits (F1 and F2), and unless this cleavage occurs, the virions are inactive and not infectious. Viruses differ in their susceptibility to specific proteases, as demonstrated with Sendai virus and its protease activation (pa) mutants. Findings with these viruses indicate that the host range, tissue tropism, and the ability of paramyxoviruses to spread within a host and to cause disease are dependent on the availability of an appropriate protease capable of cleaving the viral glycoprotein. Experiments with reconstituted particles that contain purified F protein and phosphatidylcholine indicate that to be active the F protein must be inserted in a lipid bilayer, and that no other viral function is needed for the membrane fusion process. Attachment of the F-protein-containing particles to the target membrane is a prerequisite for fusion; however, this function can be supplied by wheat germ agglutinin as well as by the virus protein responsible for attachment of intact virus, i.e., HN. Studies on the structure of the paramyxovirus glycoproteins indicate that they are inserted with a hydrophobic region of the molecule in the lipid bilayer of the virus membrane. Analysis of the primary structure of the F protein at the cleavage site revealed striking sequence homology among three paramyxoviruses, indicating a requirement for cleavage at a sharply defined site and the importance of a specific primary sequence for biological activity. This region is highly hydrophobic, suggesting that it may interact with the lipid biylayer of the target cell membrane during virus penetration, cell fusion, or hemolysis. Further studies of this system should provide knowledge regarding the mechanisms involved in viral penetration and in membrane fusion in general.

Altering the specificity of restriction endonuclease: effect of replacing Mg2+ with Mn2+

In the presence of 100 mM Tris buffer (pH 7.5) and 1-10 mM Mg2+ EcoRI endonuclease cleaves DNA at a specific nucleotide sequence and in a characteristic way: -GAATTC-. But if Mg2+ is replaced by Mn2+, the specificity of the cleavage is relaxed and cleavages occur at many other sites; moreover, there appears to be a hierarchy of cleavage rates at the pseudo-EcoRI restriction sites. For example, SV40 DNA is cleaved only once in the usual digestion conditions, but with Mn2+ more than ten cleavages are made; the five most rapidly cleaved SV40 DNA map locations are 0/1.0 larger than 0.93 larger than 0.33 approximately equal to 0.42 larger than 0.29 approximately equal to 0.40 larger than 0.25. Mn2+ also alters the restriction specificity of HindIII but not HpaII endonuclease.

Prognosis of nasopharyngeal carcinoma by Epstein-Barr virus antibody titer

A total of 433 samples of serum were collected from 305 patients with histopathologically proved anaplastic nasopharyngeal carcinoma (NPC). Antibodies against viral capsid antigens (VCA) of Epstein-Barr (EB) virus were titrated by means of indirect fluorescent antibody technique, using P3HR-1 cells as the target. High anti-VCA antibody titer in patients with NPC was found beginning to decline at the end of radiotherapy. Most (66.7%) of the patients were found to have a detectable reduction in antibody titer within six months after radiotherapy. Persistent high antibody titer after treatment correlates to high risk of the recurrence of the disease. This prognostic importance of anti-VCA titer becomes apparent at the end of radiotherapy, significant (P less than .05) within one year after treatment, and highly significant (P less than .0005) over one year after treatment.