Variations of Younger Dryas atmospheric radiocarbon explicable without ocean circulation changes

The concentration of radiocarbon, 14C, in the atmosphere depends on its production rate by cosmic rays, and on the intensity of carbon exchange between the atmosphere and other reservoirs, for example the deep oceans. For the Holocene (the past approximately 11,500 years), it has been shown that fluctuations in atmospheric radiocarbon concentrations have been caused mostly by variations in the solar magnetic field. Recent progress in extending the radiocarbon record backwards in time has indicated especially high atmospheric radiocarbon concentrations in the Younger Dryas cold period, between 12,700 and 11,500 years before the present. These high concentrations have been interpreted as a result of a reduced exchange with the deep-ocean reservoir, caused by a drastic weakening of the deep-ocean ventilation. Here we present a high-resolution reconstruction of atmospheric radiocarbon concentrations, derived from annually laminated sediments of two Polish lakes, Lake Gosciaz and Lake Perespilno. These records indicate that the maximum in atmospheric radiocarbon concentrations in the early Younger Dryas was smaller than previously believed, and might have been caused by variations in solar activity. If so, there is no indication that the deep-ocean ventilation in the Younger Dryas was significantly different from today's.

Pituitary gland: site of short-loop feedback for luteinizing hormone in the rabbit.

The development of a species specific radioimmunoassay for rabbit luteinizing hormone (LH) has permitted the direct demonstration of LH feedback control of LH secretion (short-loop feedback control). In previous studies we showed that small bolus injections of human LH (hLH) intravenously administered to castrate female rabbits suppressed rabbit LH for 20-30 min. Human LH had no effect on rabbit follicle-stimulating hormone secretion. This control system was responsive to amounts of hLH estimated to be present in blood of eugonadal men and women. These studies were designed to determine whether this feedback control was exerted at a pituitary or hypothalamic level. Two groups of studies were carried out: (a) in vivo studies: Rabbit LH was quantified in the blood of castrated female New Zealand White rabbits receiving either constant hLH perfusion (2.75 IU/min) or saline perfusion, plus a bolus injection of 0.5, 6, or 20 mug of gonadotropin-releasing hormone (GnRH). Human LH decreased the response to 6 and 20 mug of GnRH by 31 and 36%, respectively, and abolished the response to 0.5 mug, GnRH. (b) in vitro studies: Rabbit pituitary slices were incubated in the presence of medium alone, medium plus hLH (25 mIU/ml), medium plus GnRH (20 mug/ml), and medium plus both GnRH and hLH. hLH decreased basal rabbit LH release into the medium and abolished GnRH-stimulated rabbit LH release. hLH had no effect on rabbit follicle-stimulating hormone release. From these results we conclude that a direct and specific feedback control of LH on LH exists at a pituitary level.

Radiocarbon dating minute amounts of bone (3-60 mg) with ECHoMICADAS.

Because hard tissues can be radiocarbon dated, they are key to establishing the archaeological chronologies, palaeoenvironmental reconstructions and historical-biogeographical processes of the last 50,000 years. The advent of accelerator mass spectrometers (AMS) has revolutionized the field of archaeology but routine AMS dating still requires 60-200 mg of bone, which far exceeds that of small vertebrates or remains which hold a patrimonial value (e.g. hominid remains or worked bone artefacts). Here, we present the first radiocarbon dates obtained from minute amounts of bone (3-60 mg) using a MIni CArbon DAting System (MICADAS). An optimized protocol allowed us to extract enough material to produce between 0.2 and 1.0 mg of carbon for graphite targets. Our approach was tested on known-age samples dating back to 40,000 BP, and served as proof of concept. The method was then applied to two archaeological sites where reliable dates were obtained from the single bones of small mammals. These results open the way for the routine dating of small or key bone samples.

Prognosis of patients permanently paced for sick sinus syndrome.

In 39 patients (mean age, 66 years) treated for sick sinus syndrome (SSS) with pacemaker insertion, the long-term prognosis was studied. Fifteen patients (42%) died during the follow-up period of 6 to 59 months (mean, 25 months). Three patients were unavailable for follow-up. Eleven of the 15 deaths (73%) were cardiac-related, yet none could be associated with either an arrhythmia or pacemaker failure. Symptoms recurred or persisted after pacemaker insertion in 14 patients (mean age, 71 years), nine of whom died (31 deaths per 100 patient follow-up years). Twenty-two patients (mean age, 63 years) were asymptomatic after pacer insertion, six of whom died (11 deaths per 100 patient follow-up years). These follow-up results demonstrate a poor long-term prognosis in patients with SSS and persistent symptoms following permanent pacing.

Autoregulatory control of thyrotropin in rabbits.

Studies were designed to determine whether an autoregulation system exists for TSH in the rabbit. For this purpose, a species-specific RIA for rabbit TSH that does not cross-react with human (h) TSH was developed. Hypothyroid animals were studied at varying time periods up to 3 months after either surgical thyroidectomy or propylthiouracil (PTU) treatment. Highly purified hTSH was injected iv at doses of 0 (saline control), 0.1, 0.3, 1,3, and 10 micrograms into unanesthetized rabbits bearing chronically implanted Silastic catheters. Blood samples were obtained at -30, 0, 10, 20, 30, 60, 120, 180, 240, and 300 min and 24 h. Doses between 0.3 and 10 micrograms hTSH produced a prompt fall (10 min) in rabbit TSH in hypothyroid rabbits studied 8-21 days after thyroidectomy. The minimum dose of hTSH that significantly suppressed rabbit TSH was 0.3 micrograms. This dose produced a peak value of hTSH in rabbit serum of 1.3 +/- 0.1 (+/- SEM) ng/ml 10 min after injection, which translates into a bioassay potency of 2.0 microU/ml (close to the physiological level in humans). A dose-response relationship existed between the hTSH dose injected and the duration and magnitude of suppression of rabbit TSH. This response to TSH was specific; 10 micrograms hTSH produced no change in endogenous rabbit serum LH and, conversely, 10 IU hLH produced no change in rabbit serum TSH. In contrast to these striking effects in acute hypothyroid animals, hTSH produced no detectable suppression of rabbit TSH in animals that were hypothyroid for 2-3 months. The sensitivity of the autoregulatory system to the suppressive effects of exogenous hTSH decreased with increasing duration of hypothyroidism; a time-response relationship existed. We conclude that: 1) a sensitive and specific autoregulatory control system for TSH exists in the rabbit; and 2) as the duration of hypothyroidism increases, the sensitivity of the autoregulatory system to the suppressive effects of endogenous TSH changes.

Short loop feedback system for the control of follicle-stimulating hormone in the rabbit.

Studies were designed to assess whether a short loop feedback control for FSH existed in the rabbit. Castrated adult female animals bearing chronically implanted Silastic catheters to permit frequent blood sampling were studied without anesthesia. Ovine FSH was administered as an iv bolus in doses ranging between 0.1-500 micrograms. Endogenous rabbit FSH was quantified using a RIA that did not cross-react with ovine FSH. Blood samples were obtained before and 5, 10, 15, 30, 60, 120, 180, 240, and 300 min after the injection. Each animal was tested at two or more dose levels on different days. Ovine FSH produced suppression of rabbit FSH secretion within 5 min after injection. The minimum effective dose was 1 microgram; maximal suppression occurred with 50-100 micrograms ovine FSH. This short loop feedback control system was specific for FSH; ovine FSH, even at high doses, failed to suppress endogenous rabbit LH. This is the first direct demonstration of a negative short loop feedback control for FSH and the first entirely specific control for the FSH system to be described.

The secretion of progesterone during the periovulatory period in women with certified ovulation.

A pre-LH peak rise of progesterone in peripheral blood has been found in 13 normal cycling women whose ovulation was confirmed by biopsy of the corpus luteum through serial determination of progesterone and LH performed every 8 h during the periovulatory period. The progesterone rise began as an average 22 h (16-40 h) prior to the LH peak. The maximal preovulatory rise took place 9.6 h (0-24 h) before the LH zenith, remaining low for approximately 17 h when an abrupt rise of progesterone took place. The progesterone peak was detected in the morning samples in 11 of 13 patients studied. The progesterone rise was always followed by an LH peak and the highest peak of progesterone was trailed by the highest LH peak in all the patients except one.

Daily variations of FSH, LH and testosterone response to intravenous luteinizing hormone-releasing factor (LRF) in normal men.

The responses of FSH, LH and testosterone to acute stimulation with synthetic LRF were studied in 6 healthy, fertile men aged 33.4 plus or minus 1.6 yr (X plus or minus SE). Fifty mug of LRF were given, iv at 0600 h, 1200 h, 1800 h and 0000 h, at 1-week intervals, to all 6 volunteers simultaneously. Blood samples were collected by venipuncture before (-5 and 0 min) and 8, 16, 32, 64 and 128 min after LRF injection. Plasma levels of FSH, LH and testosterone were determined by double antibody radioimmunoassay techniques. The responses of FSH and LH to LRF injection showed a clear difference at the times studied. Maximal values were obtained at 0600 h and 1800 h while the response at noon was not significant for LH and absent for FSH. Testosterone secretion showed a clear-cut response to LRF in all the subjects. At three of the four studied times (0600 h, 1800 h, 000 h) plasma testosterone was already increased at 8 min reaching its maximum at 16 min and persisted high until the end of the study. The noon response reached its maximum at the end of the test period. The daily variations of FSH and LH responses to acute LRF stimulation should be taken into consideration in clinical practive and the increment in testosterone secretion makes this test a useful indicator for androgenic testicular reserve.

Immunocytochemical localization of epidermal growth factor in mouse kidney.

Epidermal growth factor (EGF) was originally isolated from mouse submandibular glands (SMG). However, SMG removal failed to lower circulating EGF, and large amounts of EGF have been found in mouse urine. In addition, the presence of pre-pro-EGF mRNA in mouse kidney has recently been reported by others. Kidneys may therefore represent an alternate source of EGF. In the present study, we investigated the immunocytochemical localization of EGF in mouse kidney. Male and female adult Swiss Webster mice were fixed by perfusion with 4% paraformaldehyde or Zamboni's fixative, the kidneys were frozen, and serial sections were obtained. Rabbit EGF antiserum was used for the primary incubation and the avidin-biotin complex immunoperoxidase procedure was utilized for immunostaining. EGF was immunolocalized in the apical portion of the cells lining the thick ascending limb of Henle (TALH) and the distal convoluted tubule (DCT). The macula densa, in contrast, lacked EGF immunoreactivity. No sex differences were observed in the distribution pattern or intensity of immunostaining. Infusion of EGF into sheep renal artery has been reported to induce changes in urine flow and ionic composition. Immunolocalization of EGF in the TALH and DCT documented here supports a regulatory role for EGF in the function of the mouse distal nephron.

Long-term results of valve replacement with the St. Jude Medical prosthesis.

To assess with truly long follow-up the long-term results of valve replacement with the St. Jude Medical prosthesis (St. Jude Medical, Inc., St. Paul, Minn.), we reviewed the case histories of the first 1112 patients undergoing 1244 valve replacements with this valve between June 12, 1978, and June 12, 1987: 690 male (62%) and 422 female patients, mean age 56 years. A total of 773 patients (69%) had the aortic valve replaced, 207 (19%) the mitral valve, and 132 (12%) the aortic and mitral valves. There were 42 hospital deaths (3.8%). Follow-up was 97.5% complete (8988 patient-years). There were 213 late deaths. Ninety-one (43%) were considered valve-related: sudden death, n = 27; anticoagulant-related hemorrhage, n = 22; thromboembolism, n = 19; prosthetic valve endocarditis, n = 13; valve thrombosis, n = 9; and noninfectious perivalvular leak, n = 1. Overall actuarial survival, including hospital mortality, was 68% +/- 6% (95% confidence limits) 14 years after the operation. Linearized rates of late valve-related events were as follows: thromboembolism, 1.09% per patient-year; anticoagulant-related hemorrhage, 0.94% per patient-year; prosthetic valve endocarditis, 0.32% per patient-year; valve thrombosis, 0.33% per patient-year; and perivalvular leak, 0.19% per patient-year. Actuarial freedom, at 14 years, from thromboembolism was 89% +/- 3%, anticoagulant-related hemorrhage 83% +/- 8%, valve thrombosis 97% +/- 1%, and reoperation 95% +/- 3%. Actuarial freedom from all valve-related deaths and valve-related morbidity and mortality, at 14 years, was 84% +/- 6% and 61% +/- 8%, respectively. We conclude that, because of its low thrombogenicity, low incidence of valve-related events, and low valve-related mortality, the St. Jude Medical valve is one of the best performing mechanical prosthesis currently available. Nevertheless, the late valve-related complications and deaths illustrate that the quest for a "perfect" prosthesis remains unfulfilled.

Isolation of the right subclavian artery.

Loss of continuity between subclavian artery and aorta with persistent connection to the homolateral pulmonary artery through a ductus arteriosus is an uncommon malformation, involving generally the left subclavian artery and associated with intracardiac or aortic arch anomalies. We report a case of right subclavian isolation with a left-sided aortic arch, presenting as a single anomaly and surgically corrected by aortic reimplantation.

Bronchial revascularization in double-lung transplantation: a series of 8 patients. Bordeaux Lung and Heart-Lung Transplant Group.

Donor airway ischemia is the main cause for defective tracheal or bronchial healing after double-lung transplantation. Anatomical studies and bronchial arteriograms have shown that the right intercostal bronchial artery is constant (95% of instances) and provides an important blood supply to the distal trachea, the carina, and the right bronchial tree as well as to the left side through a subcarinal and periadventitial anastomostic network. To maintain this important bilateral bronchial circulation, it is of capital importance not to mobilize the arteries individually and to avoid large dissections around the carina. Both bronchi can thus be revascularized by indirect aortic reimplantation using a bypass graft to a single aortic patch that includes the origin of the right intercostal bronchial artery. Furthermore, the origin of other vessels (a common trunk and left arteries) can be found within a short distance of the right intercostal bronchial artery and possibly be contained within the same aortic patch. From a series of 56 lung transplantations, 8 patients underwent restoration of the bronchial vascularization using a recipient saphenous vein graft between the donor bronchial arteries and the anterior aspect of the recipient's ascending aorta. A lower tracheal anastomosis was performed. Bronchial arterial blood supply was evaluated both by endoscopy and by arteriography at about the 15th postoperative day. The bronchial circulation was visualized at this time in five of seven arteriographies, and this was associated with excellent tracheal healing in all 8 patients.

Effects of short-term hyperprolactinemia on the endocrine reproductive system in male rabbits.

We have systematically studied the effects of short-term hyperprolactinemia on reproductive function in male rabbits. Purified ovine prolactin (PRL) was administered intravenously, as bolus injections or by constant infusion, to unanesthetized animals bearing two chronically implanted Silastic catheters; blood samples were obtained via the second catheter. Short-term hyperprolactinemia did not modify serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations in either castrated or intact rabbits. However, in spite of no changes in LH and FSH, short-term PRL administration lowered the serum testosterone (T) in intact animals. Furthermore, while PRL had no effect on the LH and FSH response to gonadotropin-releasing hormone, it did inhibit the testicular secretion of T in response to the increased endogenous LH. PRL also inhibited human chorionic gonadotropin-stimulated T secretion by the testes. All of these studies indicate that PRL interferes with the testicular response to LH. The fact that LH and FSH did not rise in response to the lowered T in intact animals suggested that PRL also altered the steroid feedback control of LH and FSH secretion. To assess this, PRL or saline was repeatedly injected after castration. PRL prevented the postcastration rise in LH and FSH. These studies indicate that PRL acts at at least two sites in the reproductive system in rabbits: (1) directly at a gonadal level by interfering with gonadotropin action and (2) at a hypothalamic-pituitary central level by preventing the expected rise in gonadotropins in response to low gonadal steroids.

Short-loop feedback of luteinizing hormone: dose-response relationships and specificity.

The short-loop feedback control of rabbit luteinizing hormone (rLH) was studied by using a highly specific radioimmunoassay (RIA) system for rLH which does not react with human LH. Permanent intravenous catheters were placed in adult female New Zealand White rabbits at the time of castration. Highly purified human luteinizing hormone (hLH) was injected intravenously at doses of 0.1, 0.3, 0.5, 1, 2, 3, 4, 10, 50, and 100 IU into unanesthetized animals 1 to 16 days following castration. Blood samples were obtained at -20, 0, 5, 10, 20, 30, 60, 120, and 180 minutes via catheter, and rLH and rabbit follicle-stimulating hormone (rFSH) levels were determined by RIA. Doses between 1 and 100 IU of hLH produced a prompt decrease in rLH (within 5 minutes); the maximal response occurred within 20 to 30 minutes. Calculated as integrated area of response between 0 and 180 minutes, a dose-response relationship existed between 0.5 and 4.0 IU of hLH. Human LH, even at high doses of 50 IU, produced no changes in endogeneous rFSH. This is the first description of an entirely specific control system for LH, separate from FSH. The short-loop feedback control system for LH is sensitive to levels of LH estimated to be present in eugonadal animals.

Prevention of the postcoital luteinizing hormone surge by ultrashortloop feedback control.

Studies were designed to determine whether the ultrashortloop feedback (USLF) system could prevent the gonadotropin-releasing hormone (GnRH) stimulation and postcoital rise of luteinizing hormone (LH). Unanesthetized castrated female rabbits bearing chronically-implanted venous catheters were subjected to the following: (1) GnRH stimulation. Ten animals received intravenous (IV) bolus injections of 30 microgram GnRH. Two hours prior to GnRH, animals received either 2000 IU human chorionic gonadotropin (hCG) or saline. A second group of ten animals received 20 microgram GnRH. One hour prior to GnRH, an infusion of human luteinizing hormone (hLH) at 2.75 IU/min or of saline was started and continued over 4 hours. (2) Coital stimulation. Ten rabbits were studied with the use of natural coital stimulus. They received either 2000 IU hCG 2 hours before mating or saline as a control group. Both hLH infusion and hCG injection inhibited GnRH stimulation of LH secretion but did not modify the follicle-stimulating hormone (FSH) response. hCG inhibited the coitus-induced LH surge and did not modify coitus-induced FSH secretion. These studies demonstrate that USLF control of LH can modulate LH secretion under both pharmacologic and physiologic conditions.

The effects of porcine follicular fluid in the postcastration rise of gonadotropins in the rabbit.

The effects of repeated administration of porcine follicular fluid (PFF) on the follicle stimulating hormone (FSH) and luteinizing hormone (LH) levels after castration were studied in rabbits. Steroid-free dextran-charcoal extracted PFF was administered to male and female adult rabbits at 0800 and 1600 h for four days immediately following castration. Serum levels of FSH and LH were measured before, during and after the PFF administration and compared to controls. A significant increase in FSH and LH was observed within 24 h following castration in the controls. In the PFF-treated group, a clear suppression of serum FSH levels was observed during PFF administration in both males and females. FSH concentrations returned to the control levels within 24 h after PFF withdrawal. Even through LH levels showed no differences during PFF injection, compared to controls, a significant increase was observed following discontinuation of PFF administration.

Surgical experience of coronary artery-right ventricular fistula in a heart transplant patient.

Routine follow-up catheterization 4 years after heart transplantation in a 55-year-old revealed a fistula from the main left anterior descending artery (LAD) to the right ventricle. The left anterior descending artery was dilated and tortuous because of this fistula. As he had effort dyspnea and fatigue 3 months after this catheterization, we decided to operate on the fistula, and direct closure of this through the LAD and coronary artery bypass grafting from the proximal to distal LAD were performed. Surgery and the postoperative course were uneventful. We discuss the surgical indication and technique for coronary artery fistula acquired as a result of endomyocardial biopsy after heart transplantation.

Should circulatory arrest with deep hypothermia be revised in aortic arch surgery?

Our experience (January 1982-May 1987) concerns 41 patients, operated upon for aortic dissection (30 patients) or aneurysm (11 patients) using circulatory arrest with deep hypothermia. There were 24 male and 17 female patients (mean age: 55 years 9 months, range 32-73 years). The mean circulatory arrest time in minutes was 41 +/- 3 (mean rectal temperature before circulatory arrest was 18.4 degrees C +/- 0.3 degrees C). Total (24 patients) or partial (16 patients) replacement of the aortic arch was performed. One patient with a sacciform aneurysm had the aortic wall defect closed. Hospital mortality was 22% +/- 7% (9 patients): 8 of 30 patients with aortic dissection (26.6%) and 1 of 11 patients with aortic aneurysm (9%). Neurological complications occurred in 3 patients. These data lead us to prefer circulatory arrest with deep hypothermia as the method of choice for aortic arch surgery. However, when a short circulatory arrest time (less than 30 min) for the repair is foreseeable, mild hypothermia (20 degrees C-24 degrees C) may be preferred. In patients who will not tolerate excessive cardiopulmonary bypass times, expected difficulties with the repair should suggest mild hypothermia and short circulatory arrest in easier cases or moderate hypothermia with brachiocephalic perfusion in the others.

Lung transplantation with bronchial revascularisation. Surgical anatomy, operative technique and early results.

Ischaemic anastomotic complications are an important cause of mortality and morbidity after lung transplantation. Anatomical studies have demonstrated that the pattern of bronchial arterial supply is relatively constant and therefore amenable to attempts at revascularisation. From May 1990, 10 patients who had a double lung transplantation (tracheal anastomosis) and 1 patient who had a right lung transplantation underwent concomitant bronchial revascularisation. There were two early and one late deaths. There were no anastomotic complications. Regular endoscopic examination showed satisfactory healing in all patients. Early angiography showed patent grafts in 7 of 9 patients. At a mean follow-up of 11 months (range 6-17 months) 8 patients are well and leading a normal life. This report describes the anatomical basis, technical aspects and early results of a promising operative procedure in the field of lung transplantation.

A simple and sensitive solid-phase radioimmunoassay for the assay of human TSH antibody. Use in screening hybridoma cell lines.

A simple and sensitive radioimmunoassay procedure is described for the screening and detection of specific antibodies in hybridoma cell lines. The specific procedure was developed to screen for antibodies against human thyrotropin (hTSH), but the procedure is applicable to screening for any desired antibodies. The immunoglobulin G(IgG) fraction of goat anti-mouse IgG is used to coat wells of microtiter plates. Anti-hTSH antibodies are measured by incubating antiserum dilutions in the coated wells and detecting the bound IgG with radioiodinated hTSH. Unlabeled hTSH may also be detected by its ability to inhibit binding of 125I-hTSH to the coated wells. This assay technique meets the demands of simplicity, sensitivity, reproducibility, and rapidity as a screening assay of hybridoma cell lines capable of secreting anti h-TSH.