Testis size,epididymis weight,and sperm competition in rhesus macaques

The intensity of sperm competition is often measured using the gonadosomatic index (testes/body weight). But sperm competition could be mediated more by size of the epididymis than by size of the testicles, and little information is available on the relationship between testicular and epididymal size. We found that both organs were positively correlated in size among male rhesus macaques. Body weight accounted for over 70% of the variance in testicle size and volumetric estimates of testicle size accurately reflected testicle weight. We conclude that methods for ascertaining testicle size are accurate, but the covariation in size between testicles and epididymis will hamper understanding of the physiological mechanisms involved in sperm competition in primates. © 1993 Wiley-Liss, Inc.     

Effects of isoproterenol,theophylline and carbachol on cyclic nucleotide levels and relaxation of bovine tracheal smooth muscle

The effect of theophylline and isoproterenol on bovine tracheal smooth muscle tension and cyclic AMP levels was investigated. Concentrations of isoproterenol (4 × 10^?6 M) and theophylline (10 mM) that relaxed carbachol-contracted tracheal muscle by 85–95% did not significantly elevate control levels of cyclic AMP. In the absence of carbachol, several-fold increases in cyclic AMP were caused by isoproterenol although no elevations by theophylline were measurable. However, when isoproterenol and theophylline were administered together, theophylline potentiated the rise in cyclic AMP caused by isoproterenol. Phosphodiesterase studies in tracheal muscle showed the presence of a high and a low K_m enzyme which were inhibited by theophylline. Cyclic GMP levels were elevated in muscles contracted by carbachol as well as in carbachol-contracted muscles that had been relaxed by theophylline. In non-tension studies, in which the tracheal muscle was not under isometric tension, carbachol or theophylline alone increased cyclic GMP and together they synergistically elevated cyclic GMP. Atropine blocked the elevation caused by carbachol but not that caused by theophylline. In contrast to theophylline, isoproterenol did not elevate cyclic GMP, and in carbachol-contracted muscles that had been relaxed by isoproterenol, cyclic GMP levels were no different from control. Also, in non-tension studies, isoproterenol decreased basal cyclic GMP and antagonized the increase in cyclic GMP due to carbachol.The results indicate that whole-tissue levels of cyclic AMP and cyclic GMP do not correlate with the state of tracheal smooth muscle tension. Cyclic GMP levels do not clearly correlate with either contraction or relaxation. The inhibition by carbachol of increases in cyclic AMP due to isoproterenol and the inhibition by isoproterenol of increases in cyclic GMP due to carbachol provide evidence for a reciprocal cholinergic-adrenergic antagonism of cyclic AMP and cyclic GMP levels. The antagonism did not appear to be due to either cyclic nucleotide affecting the elevation of the other since the levels of both cyclic nucleotides were depressed.     

Site-directed mutagenesis to determine essential residues of ribulose-bisphosphate carboxylase ofRhodospirillum rubrum

Both Lys-166 and His-291 of ribulosebisphosphate carboxylase/oxygenase fromRhodospirillum rubrum have been implicated as the active-site residue that initiates catalysis. To decide between these two candidates, we resorted to site-directed mutagenesis to replace Lys-166 and His-291 with several amino acids. All 7 of the position-166 mutants tested are severely deficient in carboxylase activity, whereas the alanine and serine mutants at position 291 are ∼40% and ∼18% as active as the native carboxylase, essentially ruling out His-291 in theRhodospirillum rubrum carboxylase (and by inference His-298 in the spinach enzyme) as a catalytically essential residue. The ability of some of the mutant proteins to undergo carbamate formation or to bind either ribulosebisphosphate or a transition-state analogue remains largely unimpaired. This implies that Lys-166 is not required for substrate binding; rather, the results corroborate the earlier postulate that Lys-166 functions as an acid-base group in catalysis or in stabilizing a transition state in the reaction pathway.     

Regulation of inositol phospholipid and inositol phosphate metabolism in chemoattractant-activated human polymorphonuclear leukocytes

Binding of chemoattractants to specific cell surface receptors on polymorphonuclear leukocytes (PMNs) initiates a series of biochemical responses leading to cellular activation. A critical early biochemical event in chemoattractant (CTX) receptor-mediated signal transduction is the phosphodiesteric cleavage of plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP2), with concomitant production of the calcium mobilizing inositol-1,4,5-trisphosphate (IP3) isomer, and the protein kinase C activator, 1,2-diacylglycerol (DAG). The following lines of experimental evidence collectively suggest that CTX receptors are coupled to phospholipase C via a guanine nucleotide binding (G) protein. Receptor-mediated hydrolysis of PIP2 in PMN plasma membrane preparations requires both fMet-Leu-Phe and GTP, and incubation of intact PMNs with pertussis toxin (which ADP ribosylates and inactivates some G proteins) eliminates the ability of fMet-Leu-Phe plus GTP to promote PIP2 breakdown in isolated plasma membranes. Studies with both PMN particulate fractions and with partially purified fMet-Leu-Phe receptor preparations indicate that guanine nucleotides regulate CTX receptor affinity. Finally, fMet-Leu-Phe stimulates high-affinity binding of GTP gamma S to PMN membranes as well as GTPase activity. A G alpha subunit has been identified in phagocyte membranes which is different from other G alpha subunits on the basis of molecular weight and differential sensitivity to ribosylation by bacterial toxins. Thus, a novel G protein may be involved in coupling CTX receptors to phospholipase C. Studies in intact and sonicated PMNs demonstrate that metabolism of 1,4,5-IP3 proceeds via two distinct pathways: 1) sequential dephosphorylation to 1,4-IP2, 4-IP1 and inositol, or 2) ATP-dependent conversion to inositol 1,3,4,5-tetrakisphosphate (IP4) followed by sequential dephosphorylation to 1,3,4-IP3, 3,4-IP2, 3-IP1 and inositol. Receptor-mediated hydrolysis of PIP2 occurs at ambient intracellular Ca2+ levels; but metabolism of 1,4,5-IP3 via the IP4 pathway requires elevated cytosolic Ca2+ levels associated with cellular activation. Thus, the two pathways for 1,4,5-IP3 metabolism may serve different metabolic functions. Additionally, inositol phosphate production appears to be controlled by protein kinase C, as phorbol myristate acetate (PMA) abrogates PIP2 hydrolysis by interfering with the ability of the activated G protein to stimulate phospholipase C. This implies a physiologic mechanism for terminating biologic responses via protein kinase C mediated feedback inhibition of PIP2 hydrolysis.     

Compatability of Metarhizium anisopliae var. anisopliae with chemical pesticides

The effects of various insecticides on the mycelial growth, sporulation and conidial germination of Metarhizium anisopliae var. anisopliae isolate E₉ were studied in the laboratory. Chlorpyrifos was the most toxic organophosphate to mycelial growth and sporulation at all concentrations. Temephos, malathion and leptophos were highly toxic to sporulation while malathion was the most inhibitory to germination. The carbamates, carbofuran, methomyl and oxamyl were moderately toxic to mycelial growth and sporulation while oxamyl had an adverse effect on germination. The pyrethroids (pyrethrin, permethrin and resmethrin) and the insect growth regulators (diflubenzuron and methoprene) were not inhibitory to the various developmental stages of isolate E₉. The chlorinated hydrocarbons (chlordane, lindane and toxaphene) were more deleterious than all other insecticide groups tested. Among the fungicides, benomyl and maneb produced the greatest inhibition.     

ReducedS-adenosylmethionine: Protein-lysineN-methyltransferase activity (protein methylase III) in shiverer mutant mouse brain

Mice with the dysmyelinating mutation shiverer were studied by measuring the activity of two protein methylases and myelin marker enzymes in the brain. It was observed thatS-adenosylmethionine: protein-lysineN-methyltransferase (protein methylase III, EC. 2.1.1.43) activity is significantly reduced in phenotypically affected homozygous shiverer (shi/shi) mutant mouse brain compared to the unaffected heterozygous littermate brain. This reduction in enzyme activity is manifested mainly by reduced formation of trimethyllysine during the in vitro methylation of histone. In contrast, myelin marker enzymes such as 2,3-cyclic nucleotide 3-phosphohydrolase and 5-nucleotidase as well asS-adenosyl-methionine: protein-carboxylO-methyltransferase (protein methylase II, EC. 2.1.1.24) activities were not significantly affected in these strains of mice.     

Rapid determination of antimicrobial susceptibility patterns ofListeria monocytogenes isolates by the autobac AIS and MIC procedures

A total of 34 isolates ofListeria monocytogenes were tested against ampicillin, cephalothin, chloramphenicol, erythromycin, tetracycline, and penicillin-G using the Autobac 3-h AIS and the Autobac 5-h MIC procedures. The results were compared to susceptibility category interpretations and MICs determined using the Sceptor system. With the Sceptor System, all isolates were interpreted to be moderately susceptible to ampicillin and penicillin-G, and susceptible to the four other antibiotics. With the Autobac AIS, all isolates were interpreted to be susceptible to all the antibiotics except penicillin-G. All but one of the 34 isolates were interpreted to be resistant to penicillin-G with the Autobac AIS test. The remaining isolate was interpreted to be indeterminant. The Autobac AIS test was unsatisfactory for determining the susceptibility ofL. monocytogenes isolates to penicillin-G. The Autobac MIC results correlated well with the MIC results of the Sceptor system provided that the Autobac was programmed as though it were testing enterococci. The Autobac MIC reported penicillin-G MICs in units per milliliter and required the use of a conversion factor to obtain micrograms per milliliter, and did not allow for the testing of erythromycin. The Autobac MIC susceptibility category interpretations must not be used, as they were derived from an outdated susceptibility standard. The Autobac MIC test may be used if the limitations given above are observed.     

Dynamics of Imbibition in Phaseolus vulgaris L. in Relation to Initial Seed Moisture Content

The seed moisture level marking the onset of imbibitional injury (breakpoint) was determined for two cultivars of Phaseolus vulgaris L. cvs `Tendercrop' (TC) and `Kinghorn Wax' (KW). At 20°C the breakpoints were 0.15 gram H₂O/gram dry weight (gram per gram) for TC and 0.11 gram per gram for KW. When seeds were imbibed at 5°C, the breakpoints were 0.19 gram per gram (TC) and 0.16 gram per gram (KW). Below the breakpoint germination changed 4.6%/0.01 gram per gram for all treatments. Imbibition rates were maximal at 0.07 gram per gram and 0.33 gram per gram after 20 minutes imbibition. Rates of electrolyte leakage were correlated with the imbibition rate maximum at 0.07 gram per gram but were unaffected by the maximum at 0.33 gram per gram. The transition from tightly bound to semibound water occurred at 0.09 gram per gram and 0.11 gram per gram for KW and TC, respectively. T1 values increased exponentially as seed moisture decreased from 0.47 gram per gram to 0.05 gram per gram. ¹³C-NMR sugar signals increased at moisture levels above 0.14 gram per gram and plateaued at approximately 0.33 gram per gram seed moisture. These results suggest that the breakpoint moisture level for imbibitional damage is a function of temperature while the injury process is similar at both 5 and 20°C. Imbibition and leakage rate maxima reflect transitions in the states of seed water. NMR data support the application of the Water Replacement Hypothesis to seeds. Thus, imbibitional injury may be related to specific, temperature dependent moisture levels that are determined by water binding characteristics in the seed tissue.