Identification of human erythrocyte blood group antigens on decay-accelerating factor (DAF) and an erythrocyte phenotype negative for DAF.

Decay accelerating factor (DAF) is a glycoprotein present on the surfaces of many types ofcells in contact with plasma, including erythrocytes, leukocytes, and platelets (reviewed in reference 1). A small amount of DAF is also present in serum. Numerous investigators have demonstrated that DAF inhibits the action of C3 convertases on cell surfaces, and its absence has been shown to be at least partially responsible for the abnormal sensitivity to lysis by complement exhibited by erythrocytes of patients with the acquired stem cell disorder paroxysmal nocturnal hemoglobinuria (PNH) (2). Hereditary absence of DAF has not been previously described. Tc(a) and Cr(a) are high-frequency human erythrocyte antigens . These antigens are part of a family of blood group antigens, designated Cromer related, which are all absent from the null phenotype cell IFC(-) , or Inab (3). Recently, Spring and colleagues (4) have identified two monoclonal antibodies which bound to high frequency red cell antigens absent from the Inab phenotype. They also demonstrated that these antibodies, as well as several human antisera to Cromer-related antigens, bound to a 70-kD glycoprotein when used to stain immunoblots of human erythrocyte membrane proteins . Because the wide tissue distribution of mAb reactivity, along with some of the biochemical characterization and immunoblotting data, was similar to that of DAF, we investigated whether the Cromer-related antigens Cr(a) and Tc(a) resided on the DAF molecule.

A chromosomal region promoting outcrossing in a conifer.

Prefertilization mechanisms influencing selfing rates are thought to be absent in conifers. Outcrossing in conifers is promoted via an embryo-lethal system, but the genetic mechanism is poorly understood. This study is the first experimental profile of the genetic mechanism promoting outcrossing in conifers. Molecular dissection of a Pinus taeda L. selfed pedigree detected a chromosomal region identified as PtTX3020-RPtest9. Within this region, a semilethal factor was tightly linked (r = 0.0076) to a polymorphic expressed sequence tag (EST). The linkage group flanking the lethal factor showed strong heterozygote advantage. Using genotypic frequencies for the linkage group, three hypotheses about the semilethal factor could be tested: (1) the presence of a balanced lethal system, i.e., a lethal factor present in each of the two marker intervals; (2) gametic selection operative prior to fertilization; and (3) a stage-specific lethal factor. Selection acted via the embryo-lethal system. No support for a genetic mechanism operating prior to fertilization was found. The semilethal factor exerted no effect after embryo maturity. The genetic mechanism promoting outcrossing in P. taeda L. appears to have a balancing selection system due to either pseudo-overdominance or true overdominance.

D-Ala-D-X ligases: evaluation of D-alanyl phosphate intermediate by MIX, PIX and rapid quench studies.

BACKGROUND: The D-alanyl-D-lactate (D-Ala-D-Lac) ligase is required for synthesis of altered peptidoglycan (PG) termini in the VanA phenotype of vancomycin-resistant enterococci (VRE), and the D-alanyl-D-serine (D-Ala-D-Ser) ligase is required for the VanC phenotype of VRE. Here we have compared these with the Escherichia coli D-Ala-D-Ala ligase DdlB for formation of the enzyme-bound D-alanyl phosphate, D-Ala(1)-PO(3)(2-) (D-Ala(1)-P), intermediate. RESULTS: The VanC2 ligase catalyzes a molecular isotope exchange (MIX) partial reaction, incorporating radioactivity from (14)C-D-Ser into D-Ala-(14)C-D-Ser at a rate of 0.7 min(-1), which approaches kinetic competence for the reversible D-Ala(1)-P formation from the back direction. A positional isotope exchange (PIX) study with the VanC2 and VanA ligases displayed a D-Ala(1)-dependent bridge to nonbridge exchange of the oxygen-18 label of [gamma-(18)O(4)]-ATP at rates of up to 0.6 min(-1); this exchange was completely suppressed by the addition of the second substrate D-Ser or D-Lac, respectively, as the D-Ala(1)-P intermediate was swept in the forward direction. As a third criterion for formation of bound D-Ala(1)-P, we conducted rapid quench studies to detect bursts of ADP formation in the first turnover of DdlB and VanA. With E. coli DdlB, there was a burst amplitude of ADP corresponding to 26-30% of the DdlB active sites, followed by the expected steady-state rate of 620-650 min(-1). For D-Ala-D-Lac and D-Ala-D-Ala synthesis by VanA, we measured a burst of 25-30% or 51% of active enzyme, respectively. CONCLUSIONS: These three approaches support the rapid (more than 1000 min(-1)), reversible formation of the enzyme intermediate D-Ala(1)-P by members of the D-Ala-D-X (where X is Ala, Ser or Lac) ligase superfamily.

The effect of bran on glucose kinetics and plasma insulin in non-insulin-dependent diabetes mellitus.

Experiments were carried out on two groups of diabetic patients treated (1) by diet alone (group A) and (2) by diet and oral agents (group B), the latter being discontinued 3 days before each test. All patients were tested twice. To measure rates of glucose metabolism, 3H-3-glucose was infused before and during a standard 3-h 50-g oral glucose tolerance test. 14C-1-glucose was added to the glucose solution and the percentage of ingested glucose that appeared in peripheral blood was calculated. Bran improved glucose tolerance only in group B patients by delaying the peripheral appearance of ingested glucose but had no effect on glucose absorption in group A. In contrast, patients in group A showed a marked reduction in their insulin response when bran was mixed with the glucose. Despite this reduction, glucose tolerance, the metabolic clearance rate (MCR) of glucose, and all other rates measured were unaffected by bran. Thus we conclude that in patients adequately controlled by diet alone, the effect of insulin was potentiated when bran was ingested, but the mechanism involved remains obscure.

Cortisol levels predict cognitive impairment induced by electroconvulsive therapy.

BACKGROUND: Elevated glucocorticoids may increase the vulnerability of the brain to the adverse effects of repeated seizures. This study tested the hypothesis that higher ambient cortisol levels would predict increased cognitive impairment in depressed patients subsequent to receiving electroconvulsive therapy (ECT) for major depression. METHODS: Sixteen subjects provided three samples of saliva the day before receiving unilateral nondominant ECT. Measures of mood, global cognitive functioning, attention, executive function, verbal and visuospatial memory, and visuospatial processing speed were obtained 1 day before the first ECT and 1 day after the sixth ECT treatment. The relationship between basal salivary cortisol obtained before the first ECT treatment and the change score of each cognitive measure after the sixth ECT treatment was examined and tested with Pearson correlation coefficients. RESULTS: Electroconvulsive therapy treatments delivered over 2 weeks resulted in a significant improvement in mood and a decline in most measures of cognitive performance. Elevated basal cortisol was associated with a greater decline in performance of executive function, visuospatial processing speed, and verbal memory. CONCLUSIONS: Although this study is limited by the small number of subjects and the high number of comparisons, all significant correlations were consistent with the hypothesis that elevated cortisol predicts a greater degree of ECT-induced cognitive impairment.

9,11-Epoxy-9-homo-14-oxaprosta-5-enoic acid derivatives. Novel inhibitors of fatty acid cyclooxygenase.

A novel bicyclic prostaglandin analogue, [1R-[l alpha,2 beta (5Z),3 beta,4 alpha]]-7-[3-[(hexyloxy)methyl]- 7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid (1), and cogeners were found to be potent inhibitors of fatty acid cyclooxygenase. Compound 1 was the only stereoisomer out of eight possible structures that was active. Ether 1 was 20 times more potent than indomethacin (IND) in inhibiting arachidonic acid (AA) induced aggregation of human platelet-rich plasma. Compound 1 was also more potent than IND in several in vivo assays, AA-induced sudden death in the conscious mouse (2 times) and AA-induced bronchoconstriction in the anesthetized guinea pig (16-45 times).

9,11-Epoxy-9-homo-14-thiaprost-5-enoic acid derivatives: potent thromboxane A2 antagonists.

A novel bicyclic prostaglandin analogue, (1S)-[1 alpha,2 alpha(Z),3 alpha,4 alpha]-7-[3-[(hexylthio)methyl]-7- oxabicyclo [2.2.1]hept-2-yl]-5-heptenoic acid ((-)-10), and its cogeners were found to be potent antagonists at the TxA2 receptor. Compound (-)-10 was the only stereoisomer out of eight possible structures that was active. Thioether (-)-10 was 30-40-fold more potent than another TxA2 antagonist, BM 13.177, in inhibiting arachidonic acid (AA) induced aggregation of human platelet-rich plasma. Compound (-)-10 was effective (I50 = 0.5 +/- 0.4 microM) in inhibiting 9,11-azo-PGH2-induced (0.1 microgram/mL) contraction of guinea pig tracheal spirals. The bronchoconstriction in anesthetized guinea pigs induced by AA was also effectively antagonized by (-)-10 (1 mg/kg, iv); however, in this assay (-)-10 exhibited some direct agonist activity. Radioligand binding studies in washed (human) platelets revealed that (-)-10 is one of the most potent ligands for the PGH2/TxA2 receptor yet described (Kd = 1.6 +/- 0.4 nM).

Interphenylene 7-oxabicyclo[2.2.1]heptane thromboxane A2 antagonists. Semicarbazone omega-chains.

A series of chiral interphenylene 7-oxabicyclo[2.2.1]heptane semicarbazones 19-26 were prepared and evaluated for their in vitro thromboxane (TxA2) antagonistic activity and in vivo duration of action. The potency of 19-26 was found to highly dependent on the substitution pattern of the interphenylene ring and decreased in the order ortho greater than meta much greater than para. SQ 35,091 (25), [1S-(1 alpha,2 alpha,3 alpha,4 alpha)]-2-[[3-[[[(phenylamino) carbonyl]hydrazono]methyl]-7-oxabicyclo[2.2.1]hept-2-yl]methyl] benzenepropanoic acid, was identified as a potent and long-acting TxA2 antagonist. In human platelet rich plasma SQ 35,091 inhibited arachidonic acid (800 microM) and U-46,619 (10 microM) induced aggregation with I50 values of 3 and 12 nM, respectively. In contrast, no inhibition of ADP (20 microM) induced aggregation was observed at greater than 1000 microM. Receptor binding studies with [3H]-SQ 29,548 showed SQ 35,091 was a competitive antagonist with a Kd value of 1.0 +/- 0.1 nM in human platelet membranes. In vivo SQ 35,091 (0.2 mg/kg po) showed extended protection (T50 = 16 h) from U-46,619 (2 mg/kg iv) induced death in mice. These compounds have for the first time demonstrated that a metabolically stable interphenylene alpha-sidechain can be introduced into a prostanoid-like series of TxA2 antagonists with the maintainance of potent antagonistic activity.

Interphenylene 7-oxabicyclo[2.2.1]heptane oxazoles. Highly potent, selective, and long-acting thromboxane A2 receptor antagonists.

A series of interphenylene 7-oxabicyclo[2.2.1]heptane oxazoles (2) were prepared and evaluated for their thromboxane (TxA2) antagonistic activity in vitro and duration of action in vivo. Examination of the carboxyl side chain indicated that the interphenylene ring substitution pattern and, to a lesser extent, chain length were important factors in determining TxA2 antagonistic potency. For the carboxyl side chain, ortho substitution, a single methylene spacer between the interphenylene and oxabicycloheptane rings, and a propionic acid side-chain length were determined to be optimal. With respect to the oxazole side chain a wide range of amide substituents with diverse structures and lipophilicities were compatible with potent antagonistic activity. Finally, an acidic functional group on the alpha-chain and a hydrogen bond acceptor on the 4-position of the oxazole ring were critical for potent activity. From the analogs prepared 42 (BMS-180,291: [(+)-1S-(1 alpha, 2 alpha, 3 alpha, 4 alpha)-2-[[3-[4-[(n- pentylamino)carbonyl]-2-oxazolyl]-7-oxabicyclo[2.2.1]hept-2- yl]methyl]benzenepropanoic acid) was found to be a potent, selective, and orally-active TxA2 antagonist with a long duration of action and has been selected as a candidate for clinical development. In human platelet-rich plasma, 42 inhibited arachidonic acid (800 microM) and U-46,-619 (10 microM) induced aggregation with I50 values of 7 and 21 nM, respectively. Radioligand binding studies of 42 with [3H]-SQ 29,548 showed a Kd value of 4.0 +/- 1.0 nM in human platelet membranes. Both in vitro and in vivo studies indicated 42 was devoid of direct agonistic activity. In vivo 42 (0.2 mg/kg, po) showed extended protection (T50 = 14.4 h) from U-46,619 (2 mg/kg, iv) induced death in mice, and a single oral dose of 42 (3 mg/kg) abolished U46,619-induced platelet aggregation ex vivo in African green monkeys for > 24 h.

Synthesis and protein kinase C inhibitory activities of balanol analogs with replacement of the perhydroazepine moiety.

Balanol is a potent protein kinase C (PKC) inhibitor that is structurally composed of a benzophenone diacid, a 4-hydroxybenzamide, and a perhydroazepine ring. A number of balanol analogs in which the perhydroazepine moiety is replaced have been synthesized and their biological activities evaluated against both PKC and cAMP-dependent kinase (PKA). The results suggested that the activity and the isozyme/kinase selectivity of these compounds are largely related to the conformation about this nonaromatic structural element of the molecules.

9,11-epoxy-9-homoprosta-5-enoic acid analogues as thromboxane A2 receptor antagonists.

A novel bicyclic prostaglandin analogue, (1S)-[1 alpha, 2 alpha(Z),3 alpha(1E,3S*,4R*),4 alpha]-7-[3-(3-hydroxy-4-phenyl-1-pentenyl)-7- oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid (4), was found to be a potent and selective thromboxane A2 (TxA2) receptor antagonist. Alcohol 4 was the only member in a series of allylic alcohols which did not display direct contractile activity in the rat stomach strip model. Alcohol 4 was effective in the inhibition of (a) arachidonic acid induced platelet aggregation of human platelet-rich plasma (I50 = 0.65 +/- 0.1 microM); (b) 11,9-epoxymethano-PGH2 induced contraction of guinea pig trachea (pA2 = 8.0 +/- 0.2) or rat aorta (pA2 = 8.1 +/- 0.2); and (c) arachidonic acid induced bronchoconstriction in the anesthetized guinea pig (1 mg/kg iv). A radioiodinated analogue of 4 bound in a specific and saturable manner to human platelet membranes with a Kd = 2.3 +/- 0.9 nM. Modification of the alpha-chain, in an attempt to minimize in vivo metabolism, resulted in TxA2 receptor antagonists of reduced in vitro potency.

(S)-13-[(dimethylamino)methyl]-10,11,14,15-tetrahydro-4,9:16, 21-dimetheno-1H, 13H-dibenzo[e,k]pyrrolo[3,4-h][1,4,13]oxadiazacyclohexadecene-1,3(2H)-d ione (LY333531) and related analogues: isozyme selective inhibitors of protein kinase C beta.

Protein kinase C (PKC) is a family of closely related serine and threonine kinases. Overactivation of some PKC isozymes has been postulated to occur in several diseases states, including diabetic complications. Selective inhibition of overactivated PKC isozymes may offer a unique therapeutic approach to disease states such as diabetic retinopathy. A novel series of 14-membered macrocycles containing a N-N'-bridged bisindolylmaleimide moiety is described. A panel of eight cloned human PKC isozymes (alpha, beta I, beta II, gamma, delta, epsilon, sigma, eta) was used to identify the series and optimize the structure and associated activity relationship. The dimethylamine analogue LY333531 (1), (S)-13-[(dimethylamino)methyl]-10,11,14,15-tetrahydro-4,9:16, 21-dimetheno-1H, 13H-dibenzo[e,k]pyrrolo[3,4-h][1,4,13]oxadiazacyclohexadecene++ +-1,3(2H)-dione, inhibits the PKC beta I (IC50 = 4.7 nM) and PKC beta II (IC50 = 5.9 nM) isozymes and was 76- and 61-fold selective for inhibition of PKC beta I and PKC beta II in comparison to PKC alpha, respectively. The additional analogues described in the series are also selective inhibitors of PKC beta. LY333531 (1) exhibits ATP dependent competitive inhibition of PKC beta I and is selective for PKC in comparison to other ATP dependent kinases (protein kinase A, calcium calmodulin, caesin kinase, src tyrosine kinase). The cellular activity of the series was assessed using bovine retinal capillary endothelial cells. Retinal endothelial cell dysfunction has been implicated in the development of diabetic retinopathy. Plasminogen activator activity stimulated by a phorbol ester (4 beta-phorbol 12,13-dibutyrate) in endothelial cells was inhibited by the compounds in the series with ED50 values ranging from 7.5 to 0.21 microM. A comparison of the PKC isozyme and related ATP dependent kinase inhibition profiles is provided for the series and compared to the profile for staurosporine, a nonselective PKC inhibitor. The cellular activity of the series is compared with that of the kinase inhibitor staurosporine.

Synthesis and protein kinase C inhibitory activities of acyclic balanol analogs that are highly selective for protein kinase C over protein kinase A.

A series of balanol analogs in which the perhydroazepine ring and the p-hydroxybenzamide moiety were combined into an acyclic linked unit have been prepared and evaluated for their inhibitory properties against the serine/threonine kinase PKC. Several low-micromolar to low-nanomolar inhibitors of the alpha, beta I, beta II, gamma, delta, epsilon and eta PKC isozymes were prepared. In general, these acyclic balanol analogs were found to be highly selective for PKC over the serine/threonine kinase PKA. The type and number of atoms linking the benzophenone ester to the p-hydroxyphenyl group necessary for optimal PKC inhibition were investigated. The most potent compounds contained a three-carbon linker in which the carboxamide moiety of balanol had been replaced by a methylene group. The effect of placing substituents on the three-carbon chain was also investigated. The preferred compounds contained either a 2-benzenesulfonamido (6b) or a 1-methyl (21b) substituent. The preferred compounds 6b and 21b were tested against a panel of serine/threonine kinases and found to be highly selective for PKC. The more active enantiomer of 6b, (S)-12b, was 3-10-fold more active than the R-enantiomer against the PKC isozymes. The effect of making the analogs more rigid by making the three-carbon chain part of a five-membered ring, but with retention of the methylene replacement for the carboxamide moiety, led to potent PKC inhibitors including anti-substituted pyrrolidine analog 35b and the most potent PKC inhibitor in the series, anti-substituted cyclopentane analog 29b. The anti cyclopentane analog 29b, was a low-micromolar inhibitor of the PMA-induced superoxide burst in neutrophils, and its carboxylic ester was a high-nanomolar inhibitor of neutrophils. Finally esterification of 21b, (S)-12b, and 35b turned these potent PKC inhibitors into low-micromolar inhibitors of neutrophils.

1,2-Dibenzamidobenzene inhibitors of human factor Xa.

High-throughput screening of a combinatorial library of diamidophenols yielded lead compounds with the ability to inhibit human factor Xa (fXa) at micromolar concentrations (e.g. compound 4, fXa apparent K(ass) = 0.64 x 10(6) L/mol). SAR studies in this novel structural series of fXa inhibitors showed that the phenolic hydroxyl group was not essential for activity. The best activity was found in substituted 1,2-dibenzamidobenzenes in which the phenyl group of one benzoyl group (A-ring) was substituted in the 4-position with relatively small lipophilic or polarizable groups such as methoxy, vinyl, or chloro and the phenyl group of the other benzoyl group (B-ring) was substituted in the 4-position with larger lipophilic groups such as tert-butyl or dimethylamino. The central phenyl ring (C-ring) tolerated a wide variety of substituents, but methoxy, methanesulfonamido, hydroxyl, and carboxyl substitution produced slightly higher levels of activity than other substituents when present in combination with favorable B-ring substitution. Methylation of the amide nitrogen atoms was found to greatly decrease activity. Compound 12 is the highest affinity fXa inhibitor in this group of compounds, having fXa apparent K(ass) = 25.5 x 10(6) L/mol, about 40x more active than the original lead. This lead series does not show potent inhibition of human thrombin. A model for the binding of these ligands to the fXa active site is proposed. The model is consistent with the observed SAR and can serve to guide future SAR studies.

Pediatric acquired immunodeficiency syndrome with negative human immunodeficiency virus antibody response by enzyme-linked immunosorbent assay and Western blot.

A 5-month-old white girl having persistent oral candidiasis was brought to medical attention because of acute respiratory distress, pneumonia, and hypoxia that worsened despite supportive care and antibiotics. Bronchial lavage fluid yielded Pneumocystis carinii. The diagnosis of acquired immunodeficiency syndrome (AIDS) was suspected, although enzyme-linked immunosorbent assay (ELISA) and Western blot tests were both negative for human immunodeficiency virus (HIV) antibody. Immunologic evaluation included the following results: a low normal CD4/CD8 ratio 0.88, CD4 lymphocytes 493/microL, and elevated IgA 539 mg/dL and IgM 175 mg/dL with normal IgG 492 mg/dL. Lymphocyte stimulation study results were depressed. Lymphocytes sent for culture were subsequently positive for HIV. The mother was HIV antibody positive by enzyme-linked immunosorbent assay and Western blot but belonged to no high-risk group and was asymptomatic except for chronic diarrhea. The father was HIV antibody negative. The patient was treated with pentamidine and IV gamma-globulin with good clinical response and a rapid decrease of IgM and IgA toward normal values. Subsequent candidal pneumonia and candidal esophagitis were treated successfully with amphotericin B. The patient has received prophylactic IV gamma-globulin infusions for 6 months and remains HIV negative by enzyme-linked immunosorbent assay and Western blot. This case of pediatric AIDS highlights the need to consider HIV infection in the differential diagnosis of any child with physical findings or illnesses suggestive of AIDS-related complex or AIDS, even when HIV serologic findings are negative and parents belong to no high-risk group. Parental testing for HIV antibody is suggested in such cases.

Cytotoxic T-cell abundance and virus load in human immunodeficiency virus type 1 and human T-cell leukaemia virus type 1.

The correlation between virus load and specific cytotoxic T-lymphocyte (CTL) frequency during the chronic phase in human immunodeficiency virus type 1 (HIV-1) infection has been found to be negative in cross-sectional studies. We report here that, in infection with the related retrovirus human T-cell leukaemia virus type 1 (HTLV-1), the correlation is positive in asymptomatic carriers and zero in patients with the associated inflammatory disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). We demonstrate that the direction of the correlation may depend on the efficacy of the CTL response using mathematical models. We conclude that the CTL response is effective in asymptomatic carriers of HTLV-1, but ineffective in patients with HAM/TSP. Virus-mediated impairment of specific CTL production in HIV-1 infection can account for the negative correlation observed.

Purification of the human blood platelet thromboxane A2/prostaglandin H2 receptor protein.

The human platelet thromboxane A2/prostaglandin H2 receptor has been purified 6100-fold to apparent homogeneity by a three-step chromatographic procedure with an overall yield of 6%. A 6-fold purification of the receptor was first achieved by chromatography of 3-[(3-cholamidopropyl)dimethyl-ammonio]-1-propanesulfonate (CHAPS)-solubilized membrane proteins from human platelets on a diethylaminoethyl (DEAE)-Sepharose column. The DEAE eluate fractions containing receptor activity were then applied to a newly developed affinity column using the cyclohexyl derivative of SQ30,741 (SQ31,491) as the immobilized ligand. Elution of the receptor from the affinity column with BM13.177 yielded a further purification of 1700-fold. An additional 4-fold receptor purification from the affinity column eluate was achieved by HPLC using GPC 500 and GPC 100 columns connected in tandem. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining of the HPLC eluate containing purified receptor revealed a single, distinct band with a molecular weight of 55,000. The receptor binding activity was detected with [3H]SQ29,548 using a newly developed binding assay which involved immobilization of the receptor on polyethyleneimine-treated glass fiber filters. The binding of [3H]SQ29,548 to the purified receptor was time dependent, saturable, reversible and highly specific. Unlabeled SQ29,548, BM13.505, and U46619 (but not thromboxane B2 or 6-keto prostaglandin F1 alpha) competed for [3H]SQ29,548 binding to the purified receptor in a concentration-dependent manner. Scatchard analysis of [3H]SQ29,548 binding to the purified receptor revealed the presence of a single class of high-affinity binding sites, with a Kd of 4 nM and a Bmax of 17 nmol/mg protein.

Solid-phase synthesis of 1,2,3, 4-tetrahydro-beta-carboline-containing peptidomimetics.

A solid-phase method for the synthesis of 1,2,3, 4-tetrahydro-beta-carboline-containing peptidomimetics has been developed. The key step in the strategy is the Pictet-Spengler condensation of a resin-bound tryptophan-containing fragment with an Fmoc-amino aldehyde.

Grating acuity of cats measured with detection and discrimination tasks.

In order to help resolve the widely discrepant claims for the grating acuity of the cat, behavioral measurements were made of the acuities of two normal adult cats using two different tasks. In one, a conventional detection task, the cats were required to discriminate between high contrast vertical gratings and a uniform field of the same space-averaged luminance. The second, less commonly-used task, required the cats to discriminate between vertical and horizontal gratings of the same spatial frequency. Both cats obtained thresholds of between 8.5 and 9 cycles/degree, with no difference between tasks. These results suggest that detection of aliased patterns is not a likely factor contributing to the wide range of published acuities, and they provide support for one of two competing models of beta-ganglion cell sampling in the retina.

The laminar distributions and postnatal development of neurotransmitter and neuromodulator receptors in cat visual cortex.

We review efforts to further understand the development and nature of sensory processing mechanisms in the cat visual cortex. In vitro autoradiographic and homogenate assay techniques have been employed to determine the laminar distribution and characteristics of various neurotransmitter and neuromodulator receptor populations during postnatal development. Each receptor population shows a distinct laminar-specific pattern of binding, which, in most cases, is age-dependent. Changes in receptor number and affinity are also observed during postnatal development. These findings indicate that major alterations in the basic chemical circuitry of cat visual cortex are a normal feature of postnatal maturation and may play a role in plasticity mechanisms.