Distributional characterizations and testing for differences of relatedness and inbreeding of a subpopulation of American Hereford bulls.

Beta distributions are characterized by two determining parameters and a parameter space from 0 to 1, and may be useful for examining population genetic parameters such as the relationship or inbreeding coefficients. Often subpopulations exist within breeds that are congregated around particular lineages of cattle or ancestors that breeders value. These subpopulations are more related to each other than to the majority of other animals; they may have higher inbreeding as well. Value may be added to these subpopulations because of their relatedness with important or renowned ancestors. The objectives of this work were to compare the relatedness and inbreeding of a group of 26 modern bulls from a subpopulation of the American Hereford breed relative to 1) 30 males with the most descendants present in the pedigree, 2) 15 renowned American Hereford bulls considered important individuals in the breed's history, and 3) 19 prominent subpopulation male ancestors. Conformance of the mean relationship coefficients of the bulls with the three groups and the mean inbreeding coefficient with all pedigree animals to beta distributions was assessed by 1) visually determining the parameters of the beta distributions based on the entire pedigree, 2) testing the mean relationship coefficient or inbreeding coefficient of the group of subpopulation bulls for its positional inclusion in those distributions, and 3) bootstrap sampling methodology. The mean relationship coefficients of the 26 Trask bulls with the 30 bulls with the most descendants, the 15 renowned ancestors, and the 19 Trask male ancestors were 0.15, 0.132, and 0.208, respectively. Testing of these means in beta distributions indicated that the group of 26 Trask bulls were no more related to the three groups of bulls than all of the animals in the pedigree (0.06 < P < 0.25). Bootstrap sampling indicated that the 26 bulls were more related to the three groups of male ancestors than the remainder of the animals in the pedigree (P < 0.0001). The mean inbreeding coefficient of the 26 bulls (0.13) did not differ from the overall inbreeding coefficient (0.056) when tested using a beta distribution; however, bootstrap sampling indicated otherwise (P < 0.0001). Results may indicate the inadequacy of visually parameterizing a beta distribution. Quantification of pedigree relatedness of a group of animals to key ancestors, especially with no DNA available, may add value to that group and individuals.

Localization and function of NK(3) subtype tachykinin receptors of layer V pyramidal neurons of the guinea-pig medial prefrontal cortex.

The NK(3) subtype of tachykinin receptor has been implicated as a modulator of synaptic transmission in several brain regions, including the cerebral cortex. The localization and expression of NK(3) receptors within the brain vary from species to species. In addition, the pharmacology of NK(3) receptor-specific antagonists shows significant species variability. Among commonly used animal models, the pharmacology of the guinea-pig NK(3) receptor most closely resembles that of the human NK(3) receptor. Here, we provide anatomical localization studies, receptor binding studies, and studies of the electrophysiological effects of NK(3) receptor ligands of guinea-pig cortex using two commercially available ligands, the NK(3) receptor peptide analog agonist senktide, and the quinolinecarboxamide NK(3) receptor antagonist SB-222,200. Saturation binding studies with membranes isolated from guinea-pig cerebral cortex showed saturable binding consistent with a single high affinity site. Autoradiographic studies revealed dense specific binding in layers II/III and layer V of the cerebral cortex. For electrophysiological studies, brain slices were prepared from prefrontal cortex of 3- to 14-day-old guinea pigs. Whole cell recordings were made from layer V pyramidal neurons. In current clamp mode with a K(+)-containing pipette solution, senktide depolarized the pyramidal neurons and led to repetitive firing of action potentials. In voltage clamp mode with a Cs(+)-containing pipette solution, senktide application produced an inward current and a concentration-dependent enhancement of the amplitude and the frequency of spontaneous excitatory postsynaptic potentials. The glutamatergic nature of these events was demonstrated by block by glutamate receptor antagonists. The effects of senktide were blocked by SB-222,200, an NK(3) receptor antagonist. Taken together, these results are consistent with a functional role for NK(3) receptors located on neurons in the cerebral cortex. In layer V pyramidal neurons of the medial prefrontal cortex, activation of the NK(3) receptor system plays an excitatory role in modulating synaptic transmission.

Otorhinolaryngological manifestations of the mucopolysaccharidoses.

The mucopolysaccharidoses (MPS) are a family of related inherited metabolic disorders where, due to specific lysosomal enzyme deficiencies, partially degraded glycosaminoglycans (GAGs) accumulate in the body's cells. Due to the ubiquitous nature of GAGs in the body this deposition can occur in many tissue types and may interfere with cellular function. Although these conditions are rare, there is a propensity for the disease process to cause problems with the function of the ears, noses and throats of affected patients. In this review, we present an overview of the clinical manifestations of MPS in general and highlight the problems specifically presenting in the field of otorhinolaryngology.

Neurokinin-1 receptor resensitization precedes receptor recycling.

Following agonist binding, neurokinin-1 receptors undergo rapid desensitization followed by internalization and recycling. Desensitization requires receptor phosphorylation but does not require internalization, whereas resensitization is thought to require internalization and recycling. Our previous data, however, have suggested that, following activation and desensitization, the return of responsiveness to the neurokinin-1 agonist substance P (termed "resensitization") occurs hours before internalized receptors are recycled back to the plasma membrane. To further investigate this novel mechanism of neurokinin-1 receptor resensitization, we have studied the time courses of neurokinin-1 receptor responsiveness, recycling, and dephosphorylation by measuring cellular Ca(2+) responses, ligand-receptor binding, and receptor phosphorylation, respectively. Concentration-response curves and competition binding curves were obtained at various times following desensitization. The effects of the nonhydrolyzable GTP analog Gpp(NH)p on substance P binding were also studied to assess receptor-G protein coupling. After receptor activation and desensitization, Ca(2+) signaling in response to substance P occurred within 90 min, whereas the return of receptor binding required 240 min. Receptor dephosphorylation was greater than 90% complete 20 min after agonist washout. In addition, the return of substance P responsiveness coincided with a return in sensitivity of substance P binding to Gpp(NH)p, indicating a return in receptor-G protein coupling. These data show that the resensitization of responsiveness to substance P precedes receptor recycling. This may result from a conversion of nonfunctional neurokinin-1 receptors to functional receptors at the plasma membrane.

Tachykinin peptide-induced activation and desensitization of neurokinin 1 receptors.

The actions of four tachykinins on inhibition and desensitization of the M-current of bullfrog sympathetic neurons have been characterized. Radioligand binding parameters of the tachykinins were determined at a neurokinin receptor in a heterologous expression system. The correlation between binding, signaling and receptor regulation was investigated. A correlation between receptor binding and signaling was found between the peptides; however, their ability to produce desensitization was not correlated with binding and signaling. These results show that the ability of a tachykinin peptide to induce signal activation is not indicative of its ability to induce receptor regulation.

A novel mechanism of neurokinin-1 receptor resensitization.

Prolonged or repeated activation of many G protein-coupled receptors induces rapid desensitization followed by a period during which receptors are resensitized. In this study, concanavalin A (Con A) and monensin were used to investigate the mechanisms of desensitization and resensitization of the neurokinin-1 receptor. Con A inhibits internalization, whereas monensin prevents receptor recycling. The effects of Con A and monensin on desensitization, resensitization, receptor phosphorylation, endocytosis, and recycling of the neurokinin-1 receptor were assessed. Desensitization was defined as the decrease in the ability of substance P (SP) to elicit an intracellular Ca2+ response after a prolonged SP exposure. Resensitization was characterized as the return of SP responsiveness. Under control conditions, desensitization occurred after a 5-min exposure to agonist. Resensitization was evident 30 min after agonist washout. Neither monensin nor Con A prevented desensitization. Monensin completely inhibited resensitization, whereas Con A decreased but did not completely block resensitization. Receptor phosphorylation was increased after agonist activation and returned to basal levels after a recovery period. Neither Con A nor monensin altered the amount of agonist-specific receptor phosphorylation. Receptor binding analysis showed that plasma membrane receptors were internalized after a 5-min agonist exposure. Receptor recycling was not observed after a 1-h recovery period; however, resensitization was apparent. Taken together, these results suggest that rapid neurokinin-1 receptor desensitization can occur without receptor internalization and that resensitization occurs before receptor recycling.

'Horseshoe-shaped' post-operative alopecia following lengthy head and neck surgery.

We report a case of 'horseshoe-shaped' pressure-induced post-operative alopecia following a lengthy head and neck procedure. Post-operative hair loss is rare and to our knowledge has only previously been found in fields of surgery where careful head positioning is not an inherent part of the procedure. In these cases there has been a single area of hair loss from the central occipital area and per-operative pressure effects of the head resting on the operating table have been postulated as the likely cause. The case presented shows an area of hair loss closely corresponding to the shape of the head rest used during a long procedure. This strongly supports the theory that prolonged pressure is the likely cause. The mechanism of pathogenesis is discussed together with a suggested strategy for its avoidance. The single most important aspect of prevention of this complication of surgery is the knowledge of its existence and aetiology.

Changes of the responses of single sympathetic ganglionic neurones to substance P following desensitization.

1. The neuropeptide substance P (SP) exerts an excitatory effect on sympathetic neurones by inhibiting a time- and voltage-dependent potassium current. During prolonged application of SP, the response desensitizes. The changes in kinetics of the SP response in single neurones after desensitization have been studied in an attempt to gain some insight as to the molecular mechanism of desensitization in live, functioning neurones. 2. Desensitization to SP resulted in subsequent SP responses being smaller, but the time course was unchanged in desensitized cells compared with non-desensitized cells. 3. Experimental manipulations were performed to decrease receptor and G protein function for comparison to desensitization. Intracellular application of GDPbetaS, to decrease G protein function, led to successive responses to agonist becoming smaller and slower. When functional muscarinic receptors were decreased by extracellular application of propylbenzilylcholine mustard (PrBCM), the response to muscarine became smaller, but the time course was unchanged compared with the change in time course produced by PrBCM vehicle alone. 4. The results have also been compared with simulations from a mathematical model of drug-receptor-G protein interactions. Under a constrained set of conditions, the model predicts that decreasing the size of the G protein pool will decrease both the magnitude and the time course of the response to agonist. Decreasing receptor levels results in a more efficient decrease in the magnitude of the response but no change in the time course of the response. 5. These data provide evidence that desensitization of the response to SP in single neurones results from a decrease in functional receptors.

Peripheral primitive neuroectodermal tumour (pPNET) of the cerebellopontine angle presenting in adult life.

We report a case of a peripheral neuroectodermal tumour (pPNET) of the cerebellopontine angle of a 67-year-old woman. The patient's age at presentation was highly unusual. This case highlights the difficulties encountered, both clinically and pathologically, in securing the correct diagnosis of such a rare condition presenting in this relatively inaccessible area. The development of the nomenclature and classification of neuroectodermal tumours is traced. Recent advances in immunohistochemistry and genetic typing have shown the close relationship between pPNET and the previously difficult to classify Ewing's sarcoma and Askin's tumour.

Solution structures in SDS micelles and functional activity at the bullfrog substance P receptor of ranatachykinin peptides.

A set of novel tachykinin-like peptides has been isolated from bullfrog brain and gut. These compounds, ranatachykinin A (RTKA), ranatachykinin B (RTKB), and ranatachykinin C (RTKC), were named for their source, Rana catesbeiana, and their homology to the tachykinin peptide family. We present the first report of the micelle-bound structures and pharmacological actions of the RTKs. Generation of three-dimensional structures of the RTKs in a membrane-model environment using (1)H NMR chemical shift assignments, two-dimensional NMR techniques, and molecular dynamics and simulated annealing procedures allowed for the determination of possible prebinding ligand conformations. RTKA, RTKB, and RTKC were determined to be helical from the midregion to the C-terminus (residues 4-10), with a large degree of flexibility in the N-terminus and minor dynamic fraying at the end of the C-terminus. The pharmacological effects of the RTKs were studied by measuring the elevation of intracellular Ca(2+) in Chinese hamster ovarian cells stably transfected with the bullfrog substance P receptor (bfSPR). All of the RTKs tested elicited Ca(2+) elevations with a rank order of maximal effect of RTKA >/= SP > RTKC >/= RTKB. A high concentration (1 microM) of the neuropeptides produced varying degrees of desensitization to a subsequent challenge with the same or different peptide, while a low concentration (1 pM) produced sensitization at the bfSPR. Our data suggest differences in amino acid side chains and their charged states at the C-terminal sequence or differences in secondary structure at the N-terminus, which do not overlap according to the findings in this paper, may explain the differing degree and type of receptor activation seen at the bfSPR.

Marjolin's ulcer presenting in the neck.

'Marjolin's ulcer' is a term that has come to be used for epidermal squamous cell carcinomas that have developed in areas of chronic inflammation. To our knowledge this is the first ever report of a Marjolin's ulcer developing following long-term irritation of the skin of the neck. The history of the eponym is traced and reveals that Marjolin probably never actually described this pathological process.

Regulation of M-type potassium current by intracellular nucleotide phosphates.

The effects of intracellular application of various concentrations of adenine nucleoside phosphates and nucleotide analogs on the M-type K current (IM) of single neurons isolated from sympathetic ganglia were studied. With 1 mM MgATP intracellularly IM decreased to 25% of its initial level 39 min after the start of whole-cell recording. In the absence of ATP the current decreased more rapidly. Addition of glucose and pyruvate extracellularly was equivalent to adding 1 mM MgATP intracellularly. AMP-PNP, a nonhydrolyzable ATP analog, at a concentration of 1 or 3 mM was unable to maintain IM in the absence of ATP. When ATP and AMP-PNP were combined in the pipette, however, the maintenance of IM was prolonged. A series of nucleotides and analogs have been combined with ATP to test for their ability to maintain IM and to alter calcineurin phosphatase activity. There was a positive correlation between the ability of a nucleotide to prevent the rundown of IM and its ability to inhibit calcineurin phosphatase activity. These findings show that the amplitude of IM is dually regulated by cellular levels of adenine nucleotide diphosphates and triphosphates. A hydrolyzable form of ATP is necessary to maintain the M current. The maintenance of IM is further enhanced by the simultaneous presence of ADP or other adenine nucleotides that alter calcineurin activity, but not by higher concentrations of ATP alone. These results are consistent with regulation of IM by phosphorylation events that maintain IM and dephosphorylation events that lead to current rundown.

Molecular characterization and functional expression of a substance P receptor from the sympathetic ganglion of Rana catesbeiana.

Substance P is an important neuropeptide neurotransmitter in the central, autonomic and enteric nervous systems. In sympathetic ganglia, substance P is thought to play a role in modulating synaptic transmission. Release of substance P by neuronal stimulation or direct application of substance P to ganglionic neurons increases neuronal excitability. An amphibian substance P receptor complementary DNA has been cloned and characterized from bullfrog, Rana catesbeiana, sympathetic ganglion complementary DNA libraries. The deduced primary structure contains features indicative of a seven transmembrane domain G-protein-coupled receptor. The deduced protein sequence shows 69% identity to previously cloned mammalian substance P receptors. In situ hybridization analysis performed on bullfrog sympathetic ganglia using digoxigenin-labelled complementary RNA probe demonstrated that approximately 75% of the principal neurons displayed reaction product above background levels. Radioligand binding studies were performed on stably transfected cells with [(125)I]Tyr-1-substance P as the ligand. Substance P had an IC50 of 16 nM and the agonist potency profile was substance P>neurokinin A >> neurokinin B. The order of potency for three tachykinins to increase intracellular calcium when applied to a stably transfected clonal cell line was substance P>neurokinin A >> neurokinin B. This order of agonist potency also held for inhibition of the M-type potassium current in intact bullfrog sympathetic neurons. The non-peptide substance P antagonists CP-96345 and RP-67580 at concentrations that block mammalian substance P receptors had little or no effect on the responses to substance P at the bullfrog receptor. Overall, these results demonstrate that the cloned sequence has the features consistent with and characteristic of a substance P receptor. The results are discussed with reference to the established pharmacology of the bullfrog substance P receptor and known structure activity relationships of mammalian tachykinin receptors.

Hyperpolarizing shift of the M-current activation curve after washout of muscarine in bullfrog sympathetic neurons.

The mechanism underlying the over-recovery of an M-type potassium current following the washout of muscarine (20 microM) has been examined. Whole-cell recordings were made from single neurons dissociated from bullfrog sympathetic ganglia. During over-recovery, the maximum M-conductance decreased by about 2.8 nS while the steady-state M-current activation curve was displaced in the hyperpolarizing direction by about 13 mV. These data suggest that a hyperpolarizing shift in the kinetics of M-current causes over-recovery in amphibian autonomic neurons.

Inhibition by wortmannin of M-current in bullfrog sympathetic neurones.

1. The actions of wortmannin, an inhibitor of myosin light chain kinase (MLCK), on M-type potassium current of dissociated bullfrog sympathetic neurones have been examined. 2. The amplitude of M-current was measured by whole cell recordings from cells pretreated with wortmannin (0.01-10 microM) or the wortmannin vehicle, dimethylsulphoxide (0.0001-0.1 vol%), for 30 min. Internal (recording pipette) solutions having three different pCa values (6, 7 and 8) were used for the measurements. 3. Irrespective of the pCa, M-current was not detectable when the cells were pretreated with 10 microM wortmannin. Wortmannin, 3 microM, produced 85-95% inhibition of the M-current. Pretreatment with 10-30 nM wortmannin was without effect on M-current. 4. The M-current inhibition by wortmannin at concentrations of 0.1-1 microM depended on the pCa of the internal solution. Inhibition occurred only when the calcium-rich (pCa = 6) internal solution was used. 5. Pre-treatment of the cells with wortmannin (10 microM) did not affect rapidly-inactivating A-type or delayed rectifier-type potassium currents not did it alter inwardly rectifying sodium-potassium current (IH). 6. These observations show that M-current inhibition by wortmannin has two pharmacological profiles. One is calcium-dependent and occurs at lower concentrations (0.1-1 microM), and is attributed to inhibition of MLCK by wortmannin. At higher concentrations (3-10 microM), wortmannin has an additional, calcium-independent action, inhibiting the M-current by an unknown mechanism.

gamma-Aminobutyric acidA receptor function is modulated by cyclic GMP.

Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the vertebrate nervous system. Modulatory effects of intracellular ATP on the GABA response in isolated bullfrog dorsal root ganglion neurons were examined using whole-cell voltage clamp. Investigation of the plausible mechanisms ATP might utilize to regulate the GABA response led to the discovery that intracellular cyclic GMP may play an important role in modulating inhibitory neurotransmission. This modulatory effect of cyclic GMP is likely to be mediated via a cyclic GMP-dependent protein kinase.

Regulation of the responses to gonadotropin-releasing hormone, muscarine and substance P in sympathetic neurons by changes in cellular constituents and intracellular application of peptide fragments of the substance P receptor.

The effects of alterations of intracellular constituents on the actions of three agonists [gonadotropin-releasing hormone, muscarine and substance P (SP)] on the M-type potassium current in bullfrog sympathetic neurons were examined. Application of maximal concentrations of each agonist resulted in inhibition of M-current followed by desensitization. Desensitization was greatest during SP application, less with gonadotropin-releasing hormone and least after muscarine. Recovery after agonist washout was greatest for SP, less for muscarine and least for gonadotropin-releasing hormone. The effects of varying intrapipette pH, [ATP], Ca buffer and free Ca on inhibition by each of the agonists, desensitization and recovery were tested. Comparison of the effects of different intracellular constituents showed that desensitization and recovery are distinct phenomena. Desensitization was greatest with 3 mM ATP in the pipette and was enhanced when pyruvate and glucose were added extracellularly. Two synthetic peptides, comprising amino acids 325-360 and 361-375, respectively, of the carboxyl tail of the rat SP receptor inhibited desensitization to SP, but not to the other agonists. A third peptide homologous to residues 376-407 and a peptide from the extracellular portion of the receptor (residues 168-179) did not affect desensitization. This suggests that the portion of the carboxyl tail of the SP receptor from amino acids 325-375 is involved in desensitization.

Myosin light chain kinase occurs in bullfrog sympathetic neurons and may modulate voltage-dependent potassium currents.

A polyclonal antibody against myosin light chain kinase (MLCK) of chicken gizzard recognized a 130 kd peptide of bullfrog sympathetic ganglia as MLCK. MLCK immunoreactivity was confined to the neuronal cell body. A synthetic peptide corresponding to an inhibitory domain of MLCK (Ala783-Gly804) was applied intracellularly to isolated sympathetic neurons during whole-cell recordings of ionic currents. The peptide inhibitor reversibly decreased M-type potassium current (IM) while not affecting A-type of delayed rectifier-type potassium currents. Intracellular application of an active fragment of MLCK enhanced IM, whereas application of an inactive MLCK fragment did not. The results suggest that IM can be modulated by MLCK-catalyzed phosphorylation.

Amyloid beta peptides act directly on single neurons.

A peptide consisting of residues 25-35 of the amyloid beta protein was applied to single neurons while monitoring membrane current by whole cell voltage clamp recording. Within minutes of direct exposure of a neuron to the amyloid beta peptide, a paroxysmal increase in neuronal membrane conductance was observed. This conductance does not resemble previously described ionic conductances in terms of its time-dependence, voltage-dependence or sensitivity to changes in extracellular or intracellular ionic constituents. The effect of the amyloid beta peptide was not mimicked or blocked by substance P nor was it prevented by low intracellular or extracellular Ca. The increased membrane permeability elicited by the peptides may lead to the neuropathology observed in Alzheimer's disease.