Marijuana: medical implications

Over 50 percent of people will use marijuana sometime in their life. While intoxication lasts two to three hours, the active ingredient in marijuana, delta-9-tetrahydro-cannabinol, can accumulate in fatty tissues, including the brain and testes. Adverse effects from marijuana use include decreased coordination, epithelial damage to the lungs, increased risk of infection, cardiovascular effects and cognitive deficits. Unexplained behavior changes, altered social relationships and poor performance at school or work can signify a drug problem. Treatment requires a combination of education, social support, drug monitoring and attention to comorbid medical and psychiatric conditions.

Expression of cannabinoid receptors and their gene transcripts in human blood cells

1. This study shows that the human cannabinoid receptors and their gene transcripts can be analyzed in blood samples when combined with polymerase chain reaction. The results also demonstrate that the expression of the cannabinoid receptors is dependent on gender and ethnic background. 2. Normal human volunteers who do not use marijuana have genes that encode for the marijuana (cannabinoid) receptor proteins. 3. Primer pairs from CB1 and CB2 cDNA coding region sequences showed identical amplified DNA band sizes in both DNA-PCR and reverse PCR, with human templates. This suggests that the CB1 and CB2 genes are intronless at least in their coding regions. 4. An advantage of the coding region being intronless may be that the expression of these genes will have one major RNA processing event to skip, thus making the conditions of their expression relatively quick and simple. This advantage may have implications related to the biological functions of these proteins. 5. We therefore concluded that the existence of human cannabinoid receptors and genes along with the discovery of endogenous cannabinoids (endocannabinoids) may be useful markers in elucidating the role(s) and mechanism(s) of action of cannabinoids.

Alcohol and drug abuse in patients with physical disabilities

Alcohol and other drugs of abuse (AODA) are of great medical and social concern. Patients with physical injury requiring rehabilitation may be at particular risk of AODA due to pain, physical handicaps, mood disturbances, vocational difficulties, and problems of self-image. Their access to AODA, however, is often temporarily or permanently limited. In this literature review, we have explored various aspects of AODA in physically disabled patients. Frequently, AODA are involved in the cause of physical injuries. The average use and abuse of alcohol prior to injury was high. Postinjury alcohol use and abuse frequently declined or remained unchanged. Some non-alcohol drug use and problems increased postinjury, particularly during initial periods. Postinjury abuse of AODA is particularly important with regard to the disruption of the rehabilitation process. Use of adequate control groups and analysis at multiple postinjury time points is recommended in future investigations.

The influence of stress intrusion on immunodepression in generalized anxiety disorder patients and controls

Previous work from our group has examined the relationship between stress and immunodepression in medical students taking National Boards, Part I, and has described a relationship between stress intrusion scores (SIS) and immunodepression. We have also shown that a high proportion of individuals with generalized anxiety disorders (GAD) and panic disorders (PD) exhibit enhanced stress intrusion (SI) and are more prone to upper respiratory infections (URI). In the present preliminary study, we sought to establish a model to evaluate further the role of SI level on the extent of immunodepression. This would serve to assess in further studies the mechanism(s) of stress-induced immunodepression, its relationship to morbidity, and the role of therapeutic interventions. In 14 GAD patients and 14 controls, we correlated the expression of interleukin-2 receptors (CD25) on T lymphocytes stimulated with anti-CD3 in short term cultures and the frequency of URI and the SIS to assess the relationships among these parameters. A decreased expression of CD25 correlates linearly with increasing SIS and with a higher number of sick days with URI. These results support our previous observations that GAD patients are more susceptible to URI. Moreover, they suggest that there may be a direct relationship between immunodepression and morbidity and between SIS and immunodepression.

Recognizing borderline personality disorder in the family practice setting

The first step in the management of borderline personality disorder is making the correct diagnosis. A clinical example illustrates symptoms of a patient with borderline personality disorder in a family practice setting. Major characteristics of borderline personality disorder include severe mood instability, fear of abandonment, chronic boredom, self-injury, unstable interpersonal relationships, "splitting," identity instability and borderline rage. Early diagnosis may help prevent potential management problems and possible doctor-patient conflicts.

Roles of sulfhydryl and disulfide groups in the binding of CP-55,940 to rat brain cannabinoid receptor

The roles of sulfhydryl and disulfide groups in the specific binding of synthetic cannabinoid CP-55,940 to the cannabinoid receptor in membrane preparations from the rat cerebral cortex have been examined. Various sulfhydryl blocking reagents including p-chloromercuribenzoic acid (p-CMB), N-ethylmaleimide (NEM), o-iodosobenzoic acid (o-ISB), and methyl methanethiosulfonate (MMTS) inhibited the specific binding of [3H]CP-55,940 to the cannabinoid receptor in a dose-dependent manner. About 80-95% inhibition was obtained at a 0.1 mM concentration of these reagents. Scatchard analysis of saturation experiments indicates that most of these sulfhydryl modifying reagents reduce both the binding affinity (Kd) and capacity (Bmax). On the other hand, DL-dithiothreitol (DTT), a disulfide reducing agent, also irreversibly inhibited the specific binding of [3H]CP-55,940 to the receptor and about 50% inhibition was obtained at a 5 mM concentration. Furthermore, 5 mM DTT was abelt to dissociate 50% of the bound ligand from the ligand-receptor complex. The marked inhibition of [3H]CP-55,940 binding by sulfhydryl reagents suggests that at least one free sulfhydryl group is essential to the binding of the ligand to the receptor. In addition, the inhibition of the binding by DTT implies that besides free sulfhydryl group(s), the integrity of a disulfide bridge is also important for [3H]CP-55,940 binding to the cannabinoid receptor.

Estimating left ventricular work by gated blood pool ventriculogram

Utilizing simplifying assumptions and a formula for ventricular radioactivity versus time, a method is presented for the estimation of systolic ventricular work. This value in MKS units is calculated from data available from the radionuclide blood pool ventriculogram.

Serosal mast cells maintain their viability and promote the metabolism of cartilage proteoglycans when cocultured with chondrocytes

OBJECTIVE

To determine the consequences of mast cell (MC)-chondrocyte interactions.

METHODS

Cocultured cells were analyzed histochemically, morphologically, biochemically, and functionally.

RESULTS

Cocultured MC adhered to the chondrocytes and remained viable. Chondrocytes cocultured with nonactivated MC produced more proteoglycans than did chondrocytes cultured alone, and these proteoglycans possessed an intact hyaluronic acid-binding region. In contrast, most of the proteoglycans produced by chondrocytes cocultured with activated MC were degraded.

CONCLUSION

These studies indicate that a complex interaction occurs in which the nonactivated MC stimulates biosynthesis and the activated MC degrades cartilage proteoglycans.

A functional model of the human cardiac ventricle

A quantitative model is presented which accurately reproduces the time activity curve of the human left ventricular blood pool. Four parameters receive numerical values and may be of clinical value.

Antibody to interleukin 1 inhibits the cartilage degradative and thymocyte proliferative actions of rheumatoid synovial culture medium

Cartilage breakdown in rheumatoid arthritis results from (a) lytic action by synovial enzymes, and (b) release of synovial catabolin, now believed to be a form of interleukin 1 (IL-1), causing chondrocytes to degrade their matrix. Rheumatoid synovial culture media were tested for their ability to stimulate cartilage degradation (proteoglycan release from bovine nasal cartilage discs) and thymocyte proliferation (3H-thymidine incorporation) in the absence or presence of anti-IL-1. Degradation of living cartilage, stimulated 2-fold by synovial culture media, was inhibited up to 80% by anti-IL-1. Residual breakdown in living cartilage and synovial culture media induced breakdown in dead cultures were of similar magnitude, and both were unaffected by antibody treatment. Proteoglycan products released from synovial culture media treated cartilage were of smaller average molecular weight (Sepharose CL-2B), and such size reduction was inhibited by anti-IL-1 treatment. Synovial culture media that stimulated cartilage degradation also stimulated thymocyte proliferation; the latter was fully suppressible by anti-IL-1. One of 8 synovial culture media contained an inhibitor(s) of thymocyte proliferation, removable by dialysis. We conclude (1) rheumatoid synovial catabolin activity is due to a form of IL-1. (2) A minor nonsuppressible component of synovial culture media stimulated breakdown, identical in living and killed cartilage, is due to passive transfer of enzymic activity. (3) Cultured rheumatoid synovium releases both IL-1 and an inhibitor(s) of IL-1 action.

Effect of steroid hormones on endotoxin-mediated cartilage degradation

Cartilage degradation is a characteristic feature of various types of human arthritis, notably rheumatoid arthritis and osteoarthritis. The influence of glucocorticoid and other steroid hormones on cartilage proteoglycan breakdown was examined in a model system in which breakdown is readily quantified by the release of proteoglycan from cultured bovine nasal cartilage discs. Endotoxin (bacterial lipopolysaccharides) treatment enhanced the depletion of cartilage proteoglycan by 2-3 fold. This was inhibited in a concentration-dependent manner by hydrocortisone (10(-9) to 10(-5) M) or other glucocorticoid hormones (dexamethasone, prednisolone, cortisone). Inhibition required the continued presence of the steroid. Removal of hydrocortisone (3 x 10(-7) M) after 4 days from endotoxin-treated cultures resulted in the rapid restoration of an endotoxin response, so that proteoglycan release approached maximum levels during a second 4-day culture period. Other C-21 steroid hormones (progesterone, aldosterone) were also inhibitory at 10(-5) M, but testosterone and beta-estradiol showed little influence on endotoxin action. Proteoglycan products of smaller average mol wt (Sepharose CL-2B chromatography), consistent with core protein cleavages, were released from endotoxin-treated cartilage. Cleavage was unaffected by beta-estradiol, partially blocked by aldosterone and largely prevented by hydrocortisone administration.

Effect of purified human interleukin-1 on cartilage degradation

The effects of highly purified human monocyte-derived interleukin-1 (IL-1) on bovine nasal cartilage breakdown were investigated. Cartilage degradation was determined by quantifying the fraction of total proteoglycan released from cartilage during 8 days of culture. The response appeared to be chondrocyte-dependent, for IL-1 stimulated proteoglycan (PG) release from living but not from dead (frozen-thawed) cartilage. IL-1 action on living cartilage was heat labile and concentration dependent, with significant effect at 5 U/ml and maximal effect at 10-20 U/ml. Kinetic studies showed significant stimulation of PG release by 3 days of incubation with 10 U/ml IL-1. Studies in which IL-1 was removed on day 1 or day 4 showed that the cartilage-degrading effect of this monokine was reversible. Although IL-1 caused little change in the Sepharose CL-2B chromatographic profile of released PGs using an associative elution buffer, a significant shift to lower mol wt was observed under dissociative conditions. To probe the mechanism of IL-1 action, cartilage samples were incubated with IL-1 in the presence of the protein synthesis inhibitor, cycloheximide, or the lysosomal membrane-stabilizing steroid, hydrocortisone. Cycloheximide at 5-10 micrograms/ml completely blocked IL-1-induced breakdown. One the other hand, 3 x 10(-7) M hydrocortisone had little or no effect on IL-1 action. IL-1 was also shown to stimulate the degradation of human articular cartilage.

Cyclic AMP-regulating agents inhibit endotoxin-mediated cartilage degradation

The influence of cyclic AMP on cartilage degradation was investigated by using phosphodiesterase inhibitors [theophylline and 3-isobutyl-1-methylxanthine (IBMX)], forskolin (which activates the catalytic subunit of adenylate cyclase) and cyclic AMP analogues (dibutyryl and 8-bromo). Breakdown was assessed by quantification of proteoglycans released into the media of 8-day bovine nasal-septum cartilage cultures. Theophylline (1-20 mM), IBMX (0.01-2 mM) and dibutyryl cyclic AMP (0.1-2 mM) had little or no influence on the rate of proteoglycan release from unstimulated (no-endotoxin) cartilages. A small but detectable increase in breakdown was observed with 8-bromo cyclic AMP (0.5-2 mM) and forskolin (50-75 micrograms/ml). To examine potential inhibitory influences of these agents, the cyclic AMP modulators were added to cultures simultaneously treated with Salmonella typhosa endotoxin (12-25 micrograms/ml), a potent stimulator of cartilage degradation. The 3-4-fold stimulation of breakdown by endotoxin was strikingly inhibited by all three classes of cyclic AMP regulators. Optimal inhibition was found at 10-20 mM-theophylline, 1-2 mM-IBMX, 50-75 micrograms of forskolin/ml, 2 mM-dibutyryl cyclic AMP and 2 mM-8-bromo cyclic AMP. Inhibition was shown to be reversible, indicating that cartilages were viable after treatment. Sepharose CL-2B chromatography of proteoglycan products released from treated cartilages showed that the endotoxin-stimulated shift to lower average Mr was significantly prevented by cyclic AMP analogues and phosphodiesterase inhibitors. Together, these results show that agents which increase cyclic AMP inhibit both quantitative and qualitative aspects of endotoxin-mediated cartilage degradation.

Chondrocyte-mediated breakdown of cartilage

Chondrocyte-mediated degradation of cartilage was studied using bovine nasal cartilage discs cultured for up to 8 days in the presence or absence of chemically defined agents. Breakdown, assessed quantitatively as proteoglycan released into culture medium and qualitatively by gel filtration of (medium and cartilage) products, was potently stimulated by highly purified interleukin-1 (IL-1), bacterial lipopolysaccharides, and prostaglandin F2 alpha. IL-1 action was abolished by anti-IL-1 antibodies but unaffected by hydrocortisone. LPS-stimulated breakdown was reversibly inhibited by glucocorticoid hormones, indomethacin, and cAMP. In addition to their usefulness in probing chondrocyte degradative pathways, several of these agents may be of pathogenetic and clinical significance.

Glucocorticoid regulation of hepatic cytosolic glucocorticoid receptors in vivo and its relationship to induction of tyrosine aminotransferase

Regulation of rat hepatic cytosolic glucocorticoid receptors was studied using our newly developed exchange assay. Injecting 1 mg of dexamethasone or corticosterone into 150-250 g adrenalectomized rats caused a rapid decline in glucocorticoid receptor binding. Glucocorticoid receptor levels were depressed 80-90% in less than 15 min after hormone treatment, and remained low for about 24-48 h after glucocorticoid administration. 80-90% of glucocorticoid receptor binding was regenerated by 48 h, and complete binding was recovered by 72 h. Regenerated glucocorticoid receptor binding (48-72 h after first hormone injection) could be re-depressed by a second injection of the hormone. Similar results were obtained using normal (intact) rats. Optimum induction of tyrosine aminotransferase activity was obtained within 2 h following the first hormonal injection. Induction of tyrosine aminotransferase activity (measured 2 h after a second injection of the glucocorticoid) correlated with glucocorticoid receptor levels. Thus, 1 mg of dexamethasone or corticosterone greatly enhanced the liver tyrosine aminotransferase activity in the adrenalectomized rats (not previously hormone treated) and in adrenalectomized rats previously injected (48-72 h) with 1 mg of the glucocorticoid hormone. Enhancement of tyrosine aminotransferase activity was lowest 16-24 h after the first hormone injection (when receptor levels were extremely low). These results indicate that the induction of liver tyrosine aminotransferase activity by glucocorticoid hormones is correlated with cytosolic glucocorticoid receptor levels.

Rapid, high temperature exchange assay for the hepatic glucocorticoid receptor

Liver cytosol from adrenalectomized rats was prebound for 2 hr at 4 degrees C with unlabeled 10(-5) M corticosterone. After treatment of cytosol with dextran-coated charcoal to remove free steroid, samples were incubated at 15-25 degrees C in the presence of 10 mM molybdate plus 5 mM dithiothreitol (followed by a 60 min incubation at 4 degrees C). Essentially, complete exchange of [3H] dexamethasone for receptor-bound unlabeled steroid was observed after 120 min at 15 degrees C, and near complete (80-95%) exchange occurred within 60 min at 25 degrees C using these conditions. However in control, 5 mM dithiothreitol (alone) and 10 mM molybdate (alone) treated samples, less than 50% exchange was found. Using a similar protocol, only partial exchange was found in brain and kidney cytosols, suggesting at least partial specificity for the hepatic system. We have used this rapid, high temperature exchange assay to study the regulation of hepatic cytoplasmic glucocorticoid receptors under some experimental conditions.

Interaction of the hepatic glucocorticoid-receptor complex with Affigel blue

Unlike the unactivated glucocorticoid-receptor complex, the thermally activated glucocorticoid-receptor complex was able to bind to Affigel blue (a matrix previously shown to bind proteins containing a dinucleotide fold region) under low ionic conditions (0.05 M K C1). Glucocorticoid-receptor complex binding capacity to Affigel blue was enhanced by increasing salt concentration. Optimal binding was obtained at 0.15 M K C1 and remained at a plateau level up to 0.4 M K C1. In contrast to Affigel blue binding, glucocorticoid-receptor complex binding to nuclei was optimum at low ionic strength buffer, declined at 0.15 M K C1 and became negligible at 0.4 M K C1. Interestingly, at physiological ionic strength (0.15 M K C1) both nuclei and Affigel blue bound to the glucocorticoid-receptor complex with almost identical capacity. Glucocorticoid-receptor complexes incubated 45 min at 25 degrees C (activation conditions) in the presence of 10 mM molybdate were unable to bind to Affigel blue (or isolated nuclei) as expected. The results obtained suggest that Affigel blue mimics isolated nuclei in the binding of activated glucocorticoid-receptor complexes under physiological (0.15 M K C1) conditions. In addition, Affigel blue may provide a rapid and easy method to study glucocorticoid-receptor complex activation and interaction with nuclear acceptor sites.

Tosyl-lysyl chloromethane alters glucocorticoid-receptor complex nuclear binding and physical properties

We have investigated the effect of tosyl-lysyl chloromethane (a serine proteinase inhibitor) on rat liver cytosolic glucocorticoid-receptor complex binding to isolated nuclei. Tosyl-lysyl chloromethane (1-2 mM) significantly blocked nuclear binding when added before (but not after) thermal activation. Fifty percent inhibition occurred at about 1 mM tosyl-lysyl chloromethane. Interestingly, several other serine proteinase inhibitors (tosyl-phenylalanyl chloromethane, phenylmethyl sulphonylfluoride, and diisopropyl fluorophosphate) also depressed glucocorticoid-receptor complex nuclear binding. Tosyl-lysyl chloromethane, like molybdate, inhibited dilution-induced nuclear binding at low temperature, altered the DEAE-cellulose binding characteristics of heat-treated glucocorticoid-receptor complexes, and caused glucocorticoid-receptor complexes to sediment at about 9-10S (control complexes sedimented at 7-8S) in low salt-sucrose density gradients. Overall, these results suggest that tosyl-lysyl chloromethane modulates several properties of the glucocorticoid-receptor complex, that tosyl-lysyl chloromethane effects resemble those of molybdate, and that a serine proteinase(s) could be involved in the mechanism of glucocorticoid-receptor complex activation into a nuclear binding form.

Influence of proteinase inhibitors on glucocorticoid receptor binding

The influence of several proteinase inhibitors on rat liver cytosolic glucocorticoid receptor binding to [3H]triamcinolone acetonide has been investigated. E-64 (36 microM), an active-site directed cysteine proteinase inhibitor, significantly (about 40%) inhibited receptor binding. Tos-Lys-CH2Cl (1-2 mM) and Tos-Phe-CH2Cl (1-2 mM) also depressed receptor binding (20-67%). Interestingly, 5 mM dithiothreitol was able to prevent Tos-Lys-CH2Cl and Tos-Phe-CH2Cl effects, but had no apparent influence on E-64 action. A degree of proteinase inhibitor specificity was indicated by the lack of effect of several other proteinase inhibitors such as diisopropylfluorophosphate (1 mM), phenylmethylsulfonyl fluoride (1-2 mM), soybean trypsin inhibitor (1-2 mg/ml), tissue inhibitor of metalloproteinase (3.8 U/ml), cystatin (4-8 microM), and phosphoramidon (20-40 microM). These results suggest that thiol reactive proteinase inhibitors block glucocorticoid receptor binding, and that E-64 may prove to be a useful chemical probe in studying glucocorticoid receptor interaction.

Development of an exchange assay for cytosolic glucocorticoid receptors using the synergistic effects of molybdate plus dithiothreitol

A glucocorticoid receptor exchange assay has been developed for the accurate quantification of both free and steroid-bound receptors in rat liver cytosol. Hepatic cytosol from adrenalectomized rats was saturated in vitro with unlabeled corticosterone. Cytosol was subsequently treated with [3H]dexamethasone (with and without 1000-fold cold dexamethasone) for 2-28 h at 4 C in the presence of 10 mM molybdate plus 5 mM dithiothreitol (DTT). Complete exchange occurred between 16-28 h in the presence of molybdate plus DTT. In control and 10 mM molybdate (alone) treated samples only about 50% exchange was achieved. In the presence of 5 mM DTT (alone) approximately 60-70% exchange was observed. The exchange assay (utilizing molybdate plus DTT) was also applied to hepatic cytosol of adrenalectomized rats injected with corticosterone in vivo and to samples prebound with unlabeled dexamethasone.

Differential effects of chelating agents on cytosolic glucocorticoid receptor stability and nuclear binding in vitro

The effect of several metal chelators (EDTA, EGTA, and 1,10 phenanthroline) on rat liver glucocorticoid receptor properties in vitro was investigated. At 4 degrees C 10 mM EDTA (unlike 10 mM EGTA and 10 mM 1,10 phenanthroline) had a significant stabilizing effect on unbound hepatic glucocorticoid receptors. At higher temperature (25 degrees C) 10 mM EGTA appeared to act as a chemical stabilizer of unbound receptors. 1,10 Phenanthroline had no stabilizing effect at either temperature. Scatchard analysis indicated that the alteration in receptor binding after incubation at 4 and 25 degrees C in the presence and absence of chelating agents was due to a change in the number of steroid binding sites rather than perturbation of receptor affinity. Unlike results obtained with unbound receptors, all three chelating agents appeared to enhance prebound glucocorticoid-receptor complex inactivation. Interestingly these chelating reagents also significantly altered glucocorticoid-receptor complex binding to isolated nuclei.

Chloroquine stabilizes hepatic glucocorticoid receptors

Chloroquine (an antiarthritic, antimalarial, lysosomotropic amine) was found to significantly stabilize rat unbound hepatic glucocorticoid receptors in vitro for 2 h at 25 degrees C. Chloroquine stabilization was concentration dependent with statistically significant protection at 0.3 mM concentration and optimal effectiveness at approximately 3 mM. KC1 (0.3 M) induced unbound receptor inactivation at low temperature was also markedly reduced in the presence of 3 mM chloroquine. In addition, steroid prebound complexes were significantly stabilized at 4 degrees C and 25 degrees C by 3 mM chloroquine. Unlike molybdate (perhaps the most commonly used glucocorticoid receptor stabilizing reagent), chloroquine did not alter the sedimentation of glucocorticoid-receptor complexes in sucrose-density gradients. These results suggest that chloroquine may have useful application in glucocorticoid receptor quantitation, characterization and purification and may have interesting implications into the biological and pharmacological effects of chloroquine.

Inactivation of hepatic glucocorticoid receptors by heparin

Heparin dramatically enhanced the rate of unbound glucocorticoid receptor inactivation in vitro in a concentration, time and temperature-dependent manner. Control specific binding decreased only about 25% after incubation for 6 h at 4 degrees C. However in the presence of heparin (40 micrograms per ml cytosol) receptor binding decreased about 75%. At 25 degrees C liver receptor specific binding was found to have a half-life of about 60 min in control cytosol. However, in the presence of heparin (40 micrograms per ml cytosol) the glucocorticoid receptor had a half-life of only 15 min at 25 degrees C. Interestingly, 10 mM molybdate (with or without 5 mM dithiothreitol) greatly inhibited heparin-dependent receptor inactivation at 4 degrees C. Dithiothreitol (alone) significantly stabilized receptor binding in control samples at 4 degrees C, but provided no protection from heparin-dependent receptor inactivation. Heparin had no apparent inactivating effect on prebound glucocorticoid receptor complexes at 4 degrees C. Interestingly however, heparin altered the sedimentation coefficient of prebound hepatic glucocorticoid-receptor complexes in low salt gradients from 7-8 S to about 3-4 S. When molybdate plus dithiothreitol were added with heparin, the sedimentation coefficient was found to be approx. 6-7 S. These results demonstrate that heparin, which is often used pharmacologically and which occurs naturally in animal tissues, has significant effects on liver glucocorticoid receptors in vitro.

Regulation of cartilage acid hydrolases by growth hormone

The in vivo regulation of three acid hydrolases, namely cathepsin D, cathepsin B, and acid phosphatase, by GH was investigated. The costal cartilage cathepsin D and acid phosphatase activities of hypophysectomized rats were reduced relative to those found in normal controls. Treatment of hypophysectomized animals with GH enhanced rat growth rate and increased these two enzyme activities toward normal levels. Results of pepstatin experiments suggested that the elevated cartilage cathepsin D activity corresponded to an increase in enzyme concentration. A degree of specificity in this regulation was apparent because cartilage cathepsin B, unlike cathepsin D and acid phosphatase, was refractory to hypophysectomy and GH treatment. In contradistinction to cartilage, none of these hepatic enzymes responded to GH, and only cathepsin B activity was diminished by hypophysectomy. Centrifugational and detergent studies indicated that changes in enzyme activities induced by GH treatment were not due to the differential release of acid hydrolases from subcellular compartments. Overall, our results suggest that costal cartilage cathepsin D and acid phosphatase activities are GH dependent and may be related to cartilage growth. These observations may provide insight into the mechanism of GH action and, derivatively, skeletal growth.

Enhancement of cartilage protease activity during age and growth hormone-dependent growth

We wish to report an intriguing relationship between cartilage protease activity and rat growth rate. This was demonstrated by comparing protease activities of rats having different growth rates, i.e., normal rats of different ages, hypophysectomized and growth hormone-treated hypophysectomized rats. Protease activity, assessed by hydrolysis of a gelatin film by cartilage microtome slices, at pH 4.0, was time and temperature dependent. Preincubation of cartilage tissue at various temperatures resulted in an increase of protease activity from 4 degrees C to 37 degrees C and a decrease in activity from 37 degrees C to 100 degrees C. The activity of younger (4 week old) more rapidly growing rats, was greater than that of older, less rapidly growing animals. Hypophysectomy reduced protease activity to approximately one-third normal levels. However, injection of bovine growth hormone into hypophysectomized rats restored the activity. These results suggest that a positive correlation exists between cartilage protease activity and growth rate. Our results support the novel hypothesis that cartilage growth could be mediated, at least in part, via growth hormone-dependent proteolytic activity.

Somatomedin-like bioactivities of a growth hormone fragment on embryonic chick cartilage and cultured human fibroblasts

Somatomedins are growth hormone-dependent peptides which appear to mediate many of the effects of growth hormone in vivo. These peptides are commonly assayed by their enhancement of proteoglycan sulfation in cartilage (or fibroblasts). We now report that fragment A-II (bovine growth hormone, 96--133) stimulates sulfation in chick embryonic cartilage and cultured fibroblasts. Enhancement of fibroblast proteoglycan sulfation by fragment A-II was log-dose dependent with maximal stimulation at 10(-8) M. The 25--100% maximal enhancement by fragment A-II was similar to that reported with a preparation of somatomedin A (Wasteson, A., Uthne, K., Westermark, B. (1973) Biochem. J. 136, 1069--1074). Sulfation of chick cartilage, in the presence of both serum (hypopituitary human) and fragment A-II was greater than the sum of the effects of each substance tested separately. Fragment A-II was tested between 10(-12) and 10(-8) M; maximal stimulation occurred at 5 . 10(-11) M. To our knowledge, no other growth hormone fragment has yet been shown to possess these somatomedin-like bioactivities. Our results suggest that fragment A-II may be very useful as a model peptide to study the actions and mechanism of naturally occurring sometomedins.

The bonded alumina crown. 2. Construction using the twin foil technique

A technique has been developed for making aluminous procelain crowns bonded to thin tin oxide coatings on platinum foil. These crowns require only very thin metal linings of less than 0.05 mm, thus reducing metal costs and considerably improving aesthetics. In addition, by using the "twin foil" technique, porcelain butt fits may be obtained without loss of fit.