Principal neuron spiking: neither necessary nor sufficient for cerebral blood flow in rat cerebellum

Neuronal activity, cerebral blood flow, and metabolic responses are all strongly coupled, although the mechanisms behind the coupling remain unclear. One of the key questions is whether or not increases in spiking activity in the stimulated neurons are sufficient to drive the activity-dependent rises in cerebral blood flow (CBF) that form the basis of the signals used in functional neuroimaging such as the blood oxygen level-dependent (BOLD) signal. To this end the present study examined the effect of enhanced spike activity per se on CBF in rat cerebellar cortex under conditions of disinhibition, achieved by blocking GABA_A receptors using either bicuculline or picrotoxin. Purkinje cell spiking activity and local field potentials were recorded by glass microelectrodes, and laser Doppler flowmetry was used to monitor CBF. Disinhibition increased Purkinje cell spiking rate to 200–300% of control without incurring any increase in basal CBF. This demonstrates that increased spike activity per se is not sufficient to affect basal CBF. The neurovascular coupling between excitatory synaptic activity and CBF responses evoked by inferior olive (climbing fibre) stimulation was preserved during disinhibition. Thus, the unchanged basal CBF in the presence of the dramatic rise in Purkinje cell spiking rate was not explained by impaired synaptic activity–CBF coupling. On the basis of our previous and the present studies, we conclude that increased spiking activity of principal neurons is neither sufficient nor necessary to elicit CBF responses and in turn BOLD signals, and that activation-dependent vascular signals reflect excitatory synaptic activity.     

Atypical maternal behavior,maternal representations,and infant disorganized attachment

The data for 197 mother-infant pairs from two longitudinal studies were analyzed to assess relations between maternal attachment representations; atypical maternal behavior, coded with a new tool. Atypical Maternal Behavior Instrument for Assessment and Classification (AMBIANCE), and infant attachment. Both maternal and infant attachment were systematically related to atypical maternal behavior: mothers who were Unresolved on the Adult Attachment Interview and those whose infants were disorganized in the Strange Situation Procedure engaged in more atypical behaviors than those who were not Unresolved and whose infants showed organized patterns of attachment, respectively. Regression analyses indicated that when tested as a mediator, atypical maternal behavior as measured on the AMBIANCE did not reduce the association between maternal Unresolved status and infant disorganized attachment. This may, in part, reflect the fact that our low-risk sample did not include enough cases in the risk categories. These data provide preliminary empirical validation for the AMBIANCE and strengthen the evidence for links between atypical maternal behavior and disorganized attachment but indicate that in addition to maternal attachment representations, other factors must contribute to atypical maternal behavior.     

An HLA study in 74 Danish haemochromatosis patients and in 21 of their families

HLA-A and -B alleles in 74 Danish patients and 21 homozygous relatives with idiopathic haemochromatosis (IH) were compared with those in a sample of 1719 chromosomes from healthy Danish control subjects. The following alleles occurred with higher frequencies in IH compared to controls: A3: 53.6% vs. 15.1% (Pc less than 0.001); B7: 33.1% vs. 15.6% (Pc less than 0.001); B14: 6.9% vs. 3.0% (Pc greater than 0.05); B38: 5% vs. 0.9% (Pc greater than 0.05); B47: 4.0% vs. 0.4% (Pc greater than 0.05). Pedigree analyses disclosed 19 different haplotypes in IH subjects, compared to 286 haplotypes in controls. The following haplotypes occurred with higher frequency in IH compared to controls: A3,B5: 10.3% vs. 0.3% (Pc less than 0.001); A3,B7: 25.6% vs. 6.6% (Pc = 0.001); A3,B14: 3.4% vs. 0.6% (Pc greater than 0.05); A3,B47: 6.9% vs. 0.2% (Pc greater than 0.05). The major IH marker HLA-A3 was found in 56% of the haplotypes. The patterns of HLA-alleles associated with IH in Denmark show similarities to those in Central Europe, Australia, USA and Canada, being A3,B7 dominated and those in Central Sweden, England and Ireland, being A3,B14 dominated.     

Peptide motifs of closely related HLA class I molecules encompass substantial differences.

The peptides presented by major histocompatibility complex class I molecules adhere to strict rules concerning peptide length and occupancy by certain amino acid residues at anchor positions. Peptides presented by HLA-A*0201 molecules, for example, are generally nonapeptides requiring Leu or Met at position 2 and an aliphatic residue, predominantly Val, at position 9. A closely related molecule, HLA-A*0205, differing from the former at four amino acid residues, has a related but substantially different peptide motif. A*0205-presented peptides are still nonapeptides, and position 9 is still aliphatic, although it is preferentially occupied by Leu instead of Val. Position 2 not only allows aliphatic residues but also polar ones. Occupancy at position 6, considered as an auxiliary anchor in A*0201, as well as non-anchor residues at positions 3, 4, and 8 are relatively well conserved between the two peptide motifs. Thus, although a number of the T cell epitopes presented by the two HLA-A2 forms is expected to be identical, a considerable number of epitopes should be different.     

Increase of cytochromes a and a3 in rat kidney mitochondria in response to administration of aldosterone in vivo

Summary The influence of aldosterone in vivo on cytochromes in rat kidney mitochondria is studied, comparing rats in normal state, adrenalectomized state, and adrenalectomized rats 2 hours after administration of adlosterone (7.5 g per 100 g rat as single dose plus infusion of 0.125 g per hour and 100 g rat).No significant changes between these states are observed of either cytochrome b, cytochrome c₁, or cytochrome c content.Cytochrome a, as estimated from the 605 m band of the difference spectrum (reduced vs. oxidized), decreases from 508±51 nanomoles per g protein (n=12) in the controls to 273±65 (n=12) nanomoles per g protein in the adrenalectomized state.After administration of aldosterone to adrenalectomized rats the concentration of cytochrome a increased to 464±38 nanomoles per g protein (n=12).The difference spectrum (anaerob vs aerob+Antimycin A) shows that the absorbancy maximum at 444 m (more specific for cytochrome a₃) is also considerably decreased after adrenalectomy, and increased after administration of aldosterone to adrenalectomized rats. Hence the contents of both compounds of cytochrome oxidase, cytochrome a and cytochrome a₃, appear to be controlled by aldosterone.The molar ratio of cytochrome c to cytochrome a is 1.1 in the controls, 1.8 after adrenalectomy, and 1.1 after administration of aldosterone to adrenalectomized rats.Possible relations of this effect to the previously observed increase of tricarboxylic acid cycle enzyme activities under aldosterone are discussed.The 46% decrease of the cytochrome a content in mitochondria from the whole kidney of adrenalectomized rats, which is restored to the normal level in response to aldosterone, is difficult to reconcile with the concept that the hormone acts on distal tubules only, as these constitute only about 10% of the material used. Therefore, the present result is considered to support the concept that the hormone acts on both distal and proximal tubules.     

Diminished neo-antigen response to keyhole limpet hemocyanin (KLH) vaccines in patients after treatment with chemotherapy or hematopoietic cell transplantation

Relapse is the most common cause of treatment failure for advanced cancer, even those treated with autologous hematopoietic cell transplantation (HCT). Effective tumor-specific immunotherapy may decrease relapse, however, this will fail if the immune system is unable to respond. We developed a strategy to test immune responses with a single injection of the bona fide neo-antigen KLH. The model was first tested in 37 normal volunteers using three KLH vaccines: Intracel KLH, Biosyn KLH, and Biosyn KLH + adjuvant. Despite finding the immunogenic epitope conserved in both products, intact Intracel KLH induced a better response compared to a purified 350/390 kDA subunit of KLH contained in the Biosyn KLH product. Addition of a synthetic oil adjuvant (Montanide ISA51) restored the response to a single injection of Biosyn KLH. A quantitative readout measured by a KLH-specific cellular and humoral response with isotype switching 1 month after KLH vaccination was established. To test the integrity of the adaptive immune response in cancer patients, we vaccinated 14 patients post-HCT and 19 patients with advanced cancer with KLH vaccines that elicited a 100% response rate in normal volunteers. In marked contrast to normal subjects, both responses were significantly impaired up to 16 months after autologous HCT with an intermediate response in advanced cancer patients. KLH vaccines are safe and require only a single injection to test neo-antigen responses providing an optimal platform for definitive testing of strategies to improve diminished immune recovery after chemotherapy or post-HCT.     

A monoclonal antibody against a new differentiation antigen of thymocytes

B14-2-14 is a monoclonal cytotoxic IgM antibody which reacts with thymocytes of all mouse strains tested. The fraction of positive cells (by visual immunofluorescence) varies between strains from about 25-45% in A.CA to 65-85% in C57BL/6, and high levels are dominant in F1 hybrids. In the periphery, the antigen is found on a few percent of lymph node and not on splenic T cells, and it is absent in nude mice. Among thymocytes, the distribution of the B14 determinant largely overlaps with that of the TL antigen and of molecules binding peanut agglutinin. The B14 antibody reacts only minimally with hydrocortisone-resistant thymus cells. Biochemical analysis shows that B14 antibody, anti-TL antibody and peanut agglutinin bind to separate molecules. The target of the B14 antibody may be either an immature, thymic form of Thy-1, or another molecule associated with it. Two polypeptides, of 40 and 35 kDa are precipitated by both B14 and anti-Thy-1 antibodies from biosynthetically labeled thymus cell lysates, and two others, of 27 and 17 kDa, from surface-iodinated thymus cell preparations. B14-2-14 offers an additional method for identification and selection of thymocytes at different stages of differentiation, and should also be useful for studies of the Thy-1 antigen.